Monday, December 6, 2010

Sometimes Banana Plugs Are Fine, but this time not

For the past few years, I've been using banana connectors to connect my speaker cables to the Acoustats.  It finally bugged me that, despite reasonable high quality bananas, with hefty solid metal connectors (it's the Radio Shack brand but identical to another well known audiophile brand) they just were not being held very well by 5-way binding posts on the Acoustats.  (The culprit, IMO, are the 20 year old 5 way binding posts on the Acoustats, not the Radio Shack plugs.)

Actually, I was listening to a classic recording on DVD-Audio when I thought to myself "this sounds grungy" so I looked around for something that might explain the grungy and noticed that one of the bananas in one speaker had come a bit loose and was sagging.  This was actually happening fairly often, but I just kept plugging the jacks.  But this time, because of anger at the grungy sound, I finally removed the plugs from the speaker wire and plugged the bare stranded 16ga speaker wire straight into the hole in the binding posts (not easy to do even with a bright original style Tensor light, no wonder I hadn't done this before).  The sonic improvement was astonishing, much cleaner and sweeter sound.

Another Equipment Upgrade Unit (EUU) in performance was achieved.

Many audiophiles do not realize that under good conditions, well fitting banana plugs and jacks are among the best available connectors.  But they have to be well fitting and inclined to stay that way...that is the point.

First consider the spade lug.  I do have some experience with spade lugs, and I do not like them for connecting to speaker binding posts.  Even when the binding post is tightened down with a wrench (I used to use pliers on the sturdy posts on my Macintosh ML-2 speakers) they eventually come loose.  When they come loose, they are among the worst possible connections, and you might not notice it for awhile.  Spade lugs work best when their rotation is constrained by the connector, such as with a binding strip.  When their rotation is not constrained, they can twist loose and loosen the binding post in the process.  Now it is also possible to constrain the cable itself so that it doesn't put any torque on the binding post, but that is generally possible only with low profile equipment such as amplifiers and not possible with speakers which have their binding posts a foot or more above the floor.

A well fitting banana does not have this problem, the spring tension of the plugs keeps it tight, and rotational torque cannot loosen the connection.  The main factor here is the proper design of the jack.  My Revel M20 speakers (bedroom and kitchen) have nice unbranded 5-way connectors which look like midline WBT's.  The inside hole is a straight cylinder (possibly with the outside being slightly smaller in diameter than the inside).  Any kind of banana, either the low curvature ones in the late Pomona style, or higher curvature ones which include the Radio Shack audiophile grade, will fit into this connector (though it takes considerable effort to get it in there, at first you may wonder if it's even intended) and stay tight. Only problem, if you consider it a problem, is that the heavy metal binding posts on the M20's are too far apart for double bananas, so you have to use single bananas.

The Acoustat binding posts, OTOH, seem to have a ridge somewhere inside the jack.  That might work for the low curvature plugs (haven't tried this), but it definitely does not work for the high curvature plugs I use.  What happens is that at the point where the ridge contacts the plug, the plug metal is still curving smaller rapidly as it goes inward.  That means there is constant outward mechanical force on the plug, and over time, given vibration, the plug will get pushed out.  In fact, I can and did feel that it wasn't gripping very well the first time I plugged my jacks into it, I just chose to ignore this detail to get right to the music listening.

Well, I'm not going to ignore this any more.

Two other kinds of connection deserve mention.  One is wires that are terminated in a post which can fit through the hole in the binding post.  This is a good solid connection, but it requires a post which is small enough, and binding posts that have a hole (the binding posts on my Krell amplifier do not).  Another connection is bare wire around the post (what I generally do with my Krell, despite their recommendation to use spade lugs).  Bare solid copper wire is relatively soft and can often hold such connections OK, but stranded wire is even better for this, as it has many degrees of freedom which provide extra springiness.  The problem with stranded wire is that you have to be careful that all strands are being held tight and do not come in contact with unintended metal surfaces.

Tuesday, November 9, 2010

Electrical upgrades: two more steps forward

Yesterday I had two important upgrades to my electrical system for audio.

 #1 my house is now actually grounded (the old ground rod had gotten disconnected decades ago) with a new ground rod connected with 4 gauge wire (twice the diameter of the previous 8 gauge wire which connected to nothing).

#2 I replaced the Oyaide purple/gold outlet with a NOS Pass & Seymore 5262A (the legendary outlet recommended by the late Bob Crump).  The 5262A has much more consistent grip, holds plugs straight into the wall, whereas the Oyaide would always let them sag a bit.

Since these were both done during the same visit by electrician, I can't separate the effects (though I think the outlet upgrade was less important, I had previously found a trick to maximize performance of the Oyade).  But combined, the effect was that a piece I had been listening to previously, the Bach 4 Organ Concertos by E Power Biggs on SACD, went from being rather unlistenable to satisfactory (though it's still pretty noisy).

In addition, I added a new whole-house surge protector.  This is a new Intermatic device which shunts across the power lines (not in series) through a 50A breaker.  I did not expect this to have any positive effects on audio sound quality, but hopefully it will help preserve all my electronic equipment, including amplifiers which I often plug straight-into-the-wall with no surge-protecting outlet strip.  I would certainly not plug my Krell into such a strip, it might blow up under the 20+ amp instantaneous draw of the Krell.  (Just because it's on a 20A line, doesn't mean instantenous draw is limited to 20A.)

At least the whole house surge protector did not have any negative affects on audio I had detected so far.

Monday, November 8, 2010

Big Electrical Upgrade Today!

Bigger than expected, it turns out.  But it's always that way, because the old stuff was always worse than you thought...  Often way worse.  Today, I discover, that my house is not actually grounded.  There was no actual connection to an 8 foot copper ground rod as the electrical code requires.  I was only "grounded" through the wiring from the power company.  That kind of indirect grounding is potentially hazardous, illegal, marginally effective, and electrically noisy.

There was a ground wire, coming out of the power box, but it wasn't actually connected to anything, it was just touching the ground.  Funny, I remember it has been that way since I've owned the house.  I didn't realize that the 10ga ground wire was THE ground wire.  I thought it was just an unnecessary ground for an old and long-since-canceled cable TV line.

The little outside corner where the electrical service connects has been re-fenced 3 times, re-landscaped about countless times, dug up endlessly by my late mother's dogs, etc.  And that's just since we've owned the property.  The old ground rod is probably there, somewhere, but nearly impossible to find without messing up the underground wiring for the cable companies, the phone company, and the electric utility.

I hate underground utilities!  My back yard is marked by a big power company transformer, and cable and phone company wiring is anywhere within a 10 foot easement along the back of my property.  Then there's another 5 foot easement along the back fence leading up to the small corner where the electrical and telecommunications services connect to my house.

As a result of this, whenever a new cable or phone company comes along, or whenever the power company decided they need to upgrade their lines or transformers (which happened a few years ago), or whenever some additional power or telecomm repair is needed, they need to tear up my back yard.  And they usually don't put it back together very well, often leaving big clumps of dirt and open seams that attract weeds and volunteer trees.  I've gotten better at complaining and demanding that they replace destroyed lawn with sod, but then I've got the problem of getting the sod to actually take root, which is nearly impossible in a hot Texas summer.

But despite that, I've had my cable service (now used exclusively for internet) go out many many times.  With the previous cable company this happened annually.  Now I understand why.  It's because the cable company line that actually runs to my house is only allowed to be 3 inches (!) deep so it doesn't interfere with the power company lines which are more than a foot deep.  And often after a heavy rainstorm or hot summer you can see the lines right on the surface, indicating that they didn't even really get it 3 inches deep.  Pull a few weeds and you can break your cable.  (That happened to me last year.)

Anyway, today I'm getting a new 8 foot copper ground rod connected with 4 gauge wire (much bigger than the old 8 gauge wire).  That was not planned, but clearly needed.

What I mainly wanted to do was install a new whole-house surge protector.  Unfortunately the Leviton unit I bought is for indoor use only, so electrician suggested a couple different kinds.  I asked for the best one, and asked that it be installed the best possible way.  (Never the cheapest, here, always the best!)

So he chose a unit, installed inside the existing service box.  That requires moving several breakers to a new sub-box.  The alternate and cheaper method would be to keep the old breakers and add the surge in a new sub-box, but then the surge wouldn't work quite as well.

I'm replacing the existing 20A breaker on my dedicated audio line with a GFCI unit to protect against getting electrically shocked.  My living room system is so complicated, far flung, and sometimes used to experimentally test equipment and modifications.  I'm careful, and haven't gotten shocked in 40 years, but you never know when something might go wrong, so a GFCI is a very good idea.  I wanted to add GFCI breakers to many other circuits (the new standard is to have GFCI on *all* household circuits along with AFI also) but that would require replacing all my electrical service panels because I now use mostly half width breakers and GFCI's are standard width.  Basically, there isn't any more room.

And fixing an outdoor light.

And, replacing the outlet on my dedicated audio line with an even better outlet.  More about that in my next message.

Meanwhile, I suspect that having a new solid ground will make all my electrical lines quieter.  As well as safer.  Surge protectors require a really good ground.

Sunday, November 7, 2010

Nothing beats a live Symphony Orchestra !!!!!

Wow !!!  Saturday night I heard the most fantastic music, with the most fabulous sound.  My spine was tingling.  And it was all there in front of me, from my 2nd row center-left seat at the Majestic Theater in San Antonio, Texas for The San Antonio Symphony.

Actually, this happens to me 15 or so times a year because I have a full season subscription, now in its 11th year.  This is the one expenditure I am most proud of, to be both enjoying and supporting such a wonder!  No "affluenza" guilt here!  I think it's important to buy season subcriptions, otherwise you'll forget about it and not go often.  Even if you miss a few, it's still a good deal (and my symphony allows you to exchange subscription tickets for other dates).  Compared with what people like me spend on other things (such as oddball barely working tuners) it's incredibly cheap.  I can't understand why all my music loving friends don't subscribe; they're fools if they don't.  I wonder if some people have trouble justifying paying for just an experience instead of a piece of stuff they'll keep lugging around forever.  But in my experience, it's all experience, even a piece of stuff is really just the set of experiences you have with it (serious audiophiles know that, and treasure every moment, starting with unwrapping the box).  Another argument I hear is the whine that it's better to hear (or re-hear) a classic performance, which may be the best performance ever.  But each different performance has it's unique glories, and once the quality of performance reaches a certain level (which it has here) you don't need more to have a great joy.

There's also something very special about congregating with your friends and soon-to-be acquaintances to hear a live performance with real living musicians.  It's spiritual, like going to church.  In fact, the San Antonio Symphony is my church.  It's the one I attend the most, believe in the most, and proselytize for.

Now I happen to be very lucky in many ways, including living in a city with such a wonderful orchestra.  I'm not kidding or just boasting with tribal pride when I say it is one of the world's best.  Every guest performer, conductor, etc., says that, and they're right.  I've heard some of the greatest, such as the Berlin Philharmonic, which I heard last year in Chicago, ok, I admit, that was the very best performance I've ever heard live, in the best music hall I've been in.  But actually,  my local band is nearly as good.  I believe that global levels of musicianship have never been higher.  So probably the professional orchestra close to you is about as good too.  Did you know more people attend professional classical music performances than professional football?  It's usually a lot cheaper too (though my single ticket to hear the Berlin Philharmonic in Chicago was way up there, but that was a very special treat, once in a lifetime kind of thing, though hopefully not for me).

I've even heard from an insider that many of the musicians are there mainly for one reason: to hear that incredible, truly incredible sound themselves, from right in the middle of it.  Unfortunately, for many of them, the pay may not be all that great.  Considering what we and our stingy-to-arts (but not sports) city government pay, we really do not deserve to have such a wonderful orchestra, but there it is anyway.

Last night's performance feature three fabulous works of music, revealed through the kind of glorious sound no reproduction can match.  There was also a fourth (the first played) that I didn't much care for, but that's just part of the game.  It helps to hear what you don't like to understand what you like.  And eventually, you may like that also; our musical tastes are dynamic, and with music a little familiarity usually helps rather than hurting.

The performance began with Stravinsky's Symphony in C.  Now I'm a fan of Stravinsky's most famous works such as Rite of Spring.  But this piece just seemed way too austere.  I often feel that way about Prokofiev.  When I once made this criticism (wrt a work by Prokofiev) to a great music director, he didn't deny it was austere, but said to me "austerity is one of the essential facets of life we must explore in music".  I think austerity is fine for solo instruments (such as wailing in a cave or huge cathedral) or small groups, but not for an orchestra.  By it's nature, a Symphony Orchestra is over-the-top, larger-than-life, full of potential passion and power.  If it's not reaching the heights of passion, it's a waste.  My favorite composers are the ones who do that best, like Tchaikovsky and Rachmaninoff.

Funny that when I was a kid, I greatly preferred Bach and Mozart to Tchaikovsky.

But then followed the great Concerto for the Left Hand for Piano and Orchestra by Ravel.  The pianist was the incredible (and amazingly small) Ryo Yanagitani, who played with incredible power with just one hand.  That being the left had, it had command of most of the keyboard, but tended to focus on powerful lower mids and bass.

The second half of the concert featured the essential Gershwin pieces Rhapsody in Blue and American in Paris, with Yanagitani playing the piano in Rhapsody.  It was incredibly delightful to hear these pieces with the full power, spaciousness, thereness of a real symphony orchestra.  Gershwin is pure Bad Boy (see 20B review below) in these works, challenging us to give up all our preconceived ideas about rhythm.  He swings and swangs and the same time.

In addition, every time I hear these great Gershwin pieces, the motifs sound a bit different.  Like vocal accents, no two players or orchestras play them exactly alike.  So if you always hear a particular version the live will always sound slightly different, revealing different nuances in its composition.

I once heard a piano roll version which had been originally recorded by Gershwin himself.  (Yes, that was with the San Antonio Symphony a few years back.)  Then, it shocked me how different Gershwin's personal version was from the version in my mind (from some classic recording I can't remember the name of).  Yanagitani's version was closer to Gershwin's than the old classic recording I remember.  But it seems no two performances are exactly alike.  Which is one more reason you have got to be THERE.

Wednesday, November 3, 2010

My tuner collection with comments

Here is a list of tuners I have with comments about their performance (from a posting earlier this year at AudioKarma before I got Marantz 20B):

Sony XDR-F1HD (x3) one has full RadioXTuners analog output mod (original)
***** This is my current main tuner and the ONLY tuner in my supertuner collection which gets KPAC without a birdie. I pipe this everywhere in house with Sonos and use wireless remote extenders for control (tricky setup in high RFI environment). Main system gets direct feed. I have been thinking about advanced mods based on external tube-buffered passive filter.

McIntosh MR 78 with Modafferi mod (2000) Nice tuner for DX'ing, sound can be annoying (unforgiving).

Fisher MPX-100 multiplex purchased for use with MR78 and others to give more pleasant sound (purchased recently, not yet hooked up).

Sony 730ES very nice sounding tuner, just tested recently. Might be convertable to LA3450 MPX adapter...

Yamaha TX-1000U my previous reference tuner, possibly still sounds nicer than Sony XDR-F1HD sometimes. Very good DX'ing performance also.

Kenwood KT-8300 Nice sounding tuner, seems to have more "passion" than digital tuners, but also way more noise. Good DX'ing.

Kenwood 600T Very nice unflappable mellow and rich sound. Very useful in antenna tuning because it has strength meter calibrated in 10dB increments. This has held fort in my Kitchen for several years now, hope to replace with MR78+Fisher combo. Very impressive looking (you know you've arrived when you see this).

Yamaha T-85. Former bedroom tuner, now needs service. Nicer DX'ing features than TX-1000U, but otherwise similar performance. Mine doesn't sound as good and constantly drops computer lock.

Kenwood KT-7500 This was my reference from 78-90. Unfortunately I grew to hate it's not-quite-good-enough performance, but I can't seem to let go of it either.

Onkyo 9090 MkII. Main tuner from 91-'01. Never has sounded quite right to me, slightly muffled, though it performs very well and has good features, except you can't actual tune new stations on the remote (which has always bugged me).

Sumo Charlie (non-handled) OK, but not much more.

Sony 5000F Mine needs repair because meters are broken and have to tune by ear. Pleasant sound, decent performance for 1-bandwidth tuner. But I wouldn't say it outclasses everything else as some prices would suggest.

Sansui TU-9900. Similar to KT-8300, but nicer looking, possibly slightly better sound, mine needs repair.

Fisher KM-60/61 (x2) Very nice sound, amazingly sometimes sounds quieter than 600T. Local stations only.

Kenwood KT-1000 (1980) Nice sound, clunky controls, currently in donation pile.

What I'd like to try: Marantz 10B, 20B, 150, 2130, 19 receiver (but they always sell for more than I want to pay). Kenwood L-02T (dream), L-1000T, KT-6040 tuner (on the way soon). Sequerra with Panalyzer (Model One or D/S Reference, would prefer later D/S Reference model because I suspect it has better sound quality, but not worth buying w/o panalyzer).

I'm still operating with indoor antennas (sigh). I have APS-13 and others, but not installed. The outdoor construction project is mind boggling for me, though I have most everything picked out.

As it looked like I might never get a Sequerra with Panalyzer, I instead bought RF Spectrum Analyzer cheap, has problems but actually works adequately. It's actually a cell phone tester, but has spectrum analyzer option, HP8922M. Scope barely functions (crooked ebay seller) but video out works. Just purchased recently and was helpful in debugging problems in 413Mhz remote extenders, also noticed small adjacent channel blip which may explain birdie for KPAC.

I also have nice Tektronix 465M (no fan) for use with tuners, but don't use it much. These are great (if you get a working one, mine is rock solid) and I shoulda got a bunch of them when they were cheep. Also have Tek 475, ST1000A, ST1700B, and PC-based sound analyzer with RightMark, SpectraPlus, and Juli@ 192Khz soundcard.

Marantz 20B Service Manual

Ordered 20B service manual from AG Tannenbaum with mail and email delivery.  Also ordered replacement bulb for the stereo indicator (2187D) from ATR lighting.  I've read that replacing the bulb is a big pain, and sometimes the driver transistor goes bad, probably best with changing out load resistor to higher value.

Meanwhile called electrician to install new Leviton whole house surge suppressor I bought from Smarthome.

Monday, November 1, 2010

Fixing Remote Extenders

The remote extender (partly to control my Sony XDR-F1HD tuner from all rooms in my house) saga continues.  I finally worked up the nerve to take apart one of these little quasi-pyramids (the Radio Shack version RF Receiver).  I had read elsewhere on the web that the circuit board is not directly connected to the antenna.  Some guy wired it straight to the antenna and range increased from 8 feet to 50 feet or whatever else he needed.

He was right, sort-of.  Actually, the antenna is connected through a very tiny capacitor, a few picofarads, but it doesn't look like a capacitor, it looks like a piece of zip cord, with one wire of the pair being connected to the circuit board, and the other wire being connected to the antenna, furthermore most of the rest of the zip cord was removed, leaving only about 1 inch in which the two wires overlap.  Thus there is no direct copper connection to the antenna, just a 1 inch stretch where the two wires are in proximity.  This forms a small capacitor, though also with self-inductance, possibly more significant than the capacitance.

It's not clear why they did it this way, but it's clear it's not a manufacturing mistake (as the other poster suspected), this was clearly done intentionally.  Hooking the antenna up with a straight piece of wire did seem to improve reception a little.  But the biggest improvement for me came from relocating the antenna to a very high position on the outside of a kitchen cabinet.   For temporary (which really won't last long) it is held in place with clear duct tape.  I need to nail it in place this week because the duct tape is now sagging after two weeks.  I can also staple the wires, and get the top fitted back on the remote extender with some modifications to the plastic case with a drill or dremel.

One possible reason why the antenna is hooked up indirectly is to minimize RFI emitted by the unit.  One can imagine that the original designer didn't factor that in well enough, but when they were trying to get FCC approval they added this little hack to the design to get it to pass inspection.  Remember that I am modifying the receiver and not the transmitter, but even receivers emit RFI from their superheterodyne oscillator.  Then they didn't bother to change the "100 foot" range claimed specification, even though it could not longer meet that.

Another alternative is the funky piece of zipcord is actually a "balun" which reduces standing waves in the antenna.  In this case, removing the balun and wiring the antenna directly should reduce range, not increase it.  In my case, it did seem like it did increase range slightly even keeping antenna in same place, though I could be mistaken.  But moving the antenna to a position I can't move the whole unit is better still.

I did pull out my 500khz-10Ghz RF meter to check it out.  The RF produced by the modified remote extender receiver is just barely above the background.  I can find much greater RFI generators in my house that are presumably within FCC specifications. So I think this modification is not likely to cause actual interference for anyone.

Friday, October 29, 2010

Marantz 20B Sweet Rockin' Bad Boy

My Marantz 20B definitely has more personality than the average tuner; it has a Bad Boy attitude.  But it does sound sweet, particularly on strong commercial Rock n' Roll stations which might seem unlistenable on a geeky tuner like McIntosh MR 78.

 It doesn't work for the local classical station, my favorite station, it suffers even more from subcarrier noise, or something like that, than most tuners, so it's somewhat too noisy for seated listening, in addition to projecting the usual birdie I get from this station on most tuners.   With the Marantz, the birdie is localized outside the speakers, out-of-phase.  Low compression classical music also exposes noise much better than highly compressed Rock.  The modified Sony XDR-F1HD is the only tuner I have which gets this station perfectly, though modern digital tuners like Yamaha TX-1000 suppress the noise and birdie so well you have to get up to the speaker to hear it.  Analog tuners always get this station with some noise, but the 20B may be the noisiest I've tried so far, not that it's super noisy, but just noisy enough not to be fully satisfying.  I could enjoy this station on a Kenwood KT-8300 despite its noise, but the 20B just goes a bit too noisy.  It will be interesting to compare it with tube tuners.  I would not be surprised if some tube tuners actually sound quieter.

It works much better for a slightly weaker college Jazz station (which ironically has an actual HD subcarrier which creates no birdie), but still does nothing special like it does for Rock.

It totally enhances rock stations with a nice bass which seems to go underground (is it boosted?) and liquid mids and highs.  In the mids and highs it sounds a lot like tube tuners (and also has a rather laid back sensitivity curve like they do, hence the noise level on weaker stations).  There's also a kind of loosey-gooseyness that seems to open up the sound on otherwise highly-processed commercial stations.  The over-processed sound seems less processed and predictable.  I sense there is a kind of over-arching transparency that comes from the very wide bandwidth, but other than that this tuner seems more "musical instrument" than "precision instrument", and may also achieve some of its enhancement of rock stations through selective coloration and obscurity rather than the highest transparency.  Whatever, it works on commercial rock stations.

Listening through the noise to the classical station, I think I can also hear a bit of distortion which is somehow not audible on rock stations.  This 40 year old 20B looks untouched and after that many years, it's amazing it works at all, and like any tuner of this age,  it certainly needs to be refurbished and aligned.  Perhaps that will make it cleaner and quieter?  No, undoubtedly alignment will make it cleaner and quieter, but how much?

Anyway, right now it's a tricked out low rider car with fancy hydraulics and squeaky springs, just what you need for Rockin'.  Let me count the ways it shows attitude:

(1) Electrical leakage.  First plugged in, I felt a tingling from fairly strong leakage from the faceplate, though probably not bad enough to cause injury.  So I reversed the plug, a procedure all audiophiles from the 1960's are familiar with.  At first, this seemed to kill the leakage completely.  Then I noticed it's still detectable if you rub your finger along the edge of the front panel.  If you hold your finger down, you feel nothing, so this is very small leakage, not dangerous, but noticeable.  This unit from 1970 has no grounding plug, if it were sold today it HAVE to be grounded, and then you wouldn't notice any leakage (but you would instead notice an annoying hum from the ground loop).  So, the Bad Boy gives you freedom from hum but leakage instead.

(2) Interstation WHAM!  Unfortunately, and in contradiction to what the eBay seller said, the muting on my unit does not work.  Between stations, there are noises strong enough to rattle and blow your woofers if you are not careful.  It's like the usual output voltage is 1V but the interstation noises are 7V.  (This is a guestimate based on the LED's on my Lavry, not an actual measurement yet.)  But if your system has tons of headroom, like mine, it's fun to twirl the dial and shake the whole room.  Who needs actual music?  There's no volume control on the front panel either.

(3) Ringy chassis.  The chassis is nicely made out of very solid metal.  It rings nicely when you hit it.  So don't hit it.  Or hit it with rhythm.

(4) No stinkin' meters, man.  Yeah it's got a scope.  Not really a big enough scope IMO, the 10B and Marantz 150 had larger scopes, but it's better than no scope.   The combination of scope and very wide IF bandwidth is a license to off-tune.  When you have meters, it's like you have a little geek telling you "tune here or else."  With a scope, even if not adjusted, you see what's happening in the IF, and you see where the ultimate detection limits are, but not so clearly where the exact center is.*  So you just tune it "in there" and it works.  By the way, since this is a very wideband tuner, perhaps the widest band tuner I own, the detection limits are waaaay out there.  And somehow they arranged it so the stereo decoder works all the way to the limits.  In fact, it may be broken in my unit, my unit never seems to go to mono (judging from the sound, actually my Stereo light never comes on, may be just burned out or something worse).

*That's the way the most useful scope display, "multipath" works.  Now unlike the earlier Marantz 10B, the 20B also has a "tuning" mode to the scope display.  That changes the line on the scope from horizontal to vertical and you tune so that the vertical scope line appears inside the bullseye.  That's an extremely boring display so I tend not to use it.  Also, it turns out it isn't accurate anyway unless you calibrate it first.  To calibrate (I discovered this without reading the manual) you run the dial pointer all the way past 108.  That seemingly forces the scope line to its intended center.  Then you adjust the vertical and horizontal controls as required.  That whole procedure seems Bad Boy to me, especially turning the dial past 108.

There's also a Left Channel vs Right Channel vector mode to the scope display.  If you're wondering what your stereo separation actually looks like, there it is.  Now real bad boys keep their Marantz 4400 receiver scopes set to the vector mode, because it is also "light show mode".  I've seen blogs where no bad boy present actually understood the other scope modes.

Marantz has decided not to give you an intensity control for the scope.  They don't trust you quite that much.  Anyway, the intensity was just fine, I thought of turning it down a bit to preserve scope life, but couldn't.  A Bad Boy certainly wouldn't bother turning it down, only up.

Most analog tuners that I've come across have had malfunctioning center tune meter anyway.  They never seem to be tune best at the center of the meter because the meter itself is off.  So allowing (even forcing) you to calibrate your own scope meter allows you to make sure it's always right.  Or always wrong.  Who knows if you can really trust the "past 108" tuning calibration voltage?   Anyway, given this kind of functionality, you could also adjust the center tune to whatever you want, whatever works for you,  Bad Boy, even if it's a particular amount of off-tuning.

(5)  Don't mess with adapters, just cut the RF cable.  Now perhaps this can be excused since this is such an old tuner, but I've always been annoyed at tuners and receivers that don't give you a proper F connector for your 75 ohm coax.  Marantz kept up this for quite awhile, the Marantz 2270 receiver I bought in 1974 also had no F connector (and worse, that one had lousy spring terminals) .  I'm not quite sure when Marantz started putting F connectors on their equipment, I think the Model 2130 from 1976 had one, but it seems like Marantz was bucking the trend here for quite awhile.  Why?

Well possibly because it's actually cheaper and easier to do things this way, unless you're worried about re-using your cable later.  Bad boys don't sweat such details.  Run the cable in from your antenna, and then Marantz gives you license to cut the cable at the exact length required to reach your tuner.  Then get out your big old slotted screwdriver and screw it down.  This one has nice big screws.

Back in the 1970's I used to worry that kind of connection was not good for the 75 ohm characteristic impedance.  But it's probably doesn't make much difference for a half inch of bare wire.

Once you've done this, of course, you are not going to go back to that other geeky tuner with an F connector, like a McIntosh MR 78.  But you weren't planning to do that anyway, were you?

(6) Right on top, left on bottom.  Most audio equipment has adopted the convention of putting left channel on top, right channel on bottom.  Marantz puts right channel on top, left channel on bottom.  For decades my conspiratorial mind has been pondering if there is some kind of political significance to this.  But even if it wasn't an attempt at making a political statement, clearly Marantz was bucking another trend.  Also, annoyingly, the channels are labeled A and B on a big label.  You have to read a smaller label to see which is intended to be right and left.

Now there are lots of bad boys in audio.  Here's a short list:  Dick Sequerra, James Bongiorno,  John Curl,  Dan D'Agostino, Nelson Pass.  These are the kind of guys who give you want you want, even if it's over the top, ignoring the nannies who say you don't need it.

And now I can see I'm a Bad Boy too, and I like this Bad Boy tuner for what it does best.

[Disclaimer for geeks: this is a "first impression" review from my first night of listening.  No measurements or A/B tests were performed.]

Thursday, October 28, 2010

Marantz 20B Mystery Solved

Now that I've actually printed out the 20B schematic, I can see there
are only 4 filters, not 8 as I had previously thought.

The 20B schematic from MarantzPhillips included both Model 20 and Model 20B
schematics for the IF. Each shows 4 filters. I thought they were both part of
the 20B. The 20B version has the tap for AGC return to the front end, and a FET
replacing the first bipolar, but is otherwise the same.

So the mystery I proposed is solved. The Marantz 20 and 20B were clearly
designed as an audiophile tuner, with 4 filters (not uncommon in such) for a
single wide bandwidth. I believe that the 20/20B may have a wider bandwidth
than the 10B. Actually there was discussion previously here that Marantz 10B
does not have sufficiently wide band for lowest possible stereo distortion. 
Also, IIRC, the 10B has 6 filters, I need to go back to check my 10B schematic.

I don't know how this compares with other tuners, but each filter module in the
20/20B IF seems to have 8 reactive elements. So that would make 32 reactive
elements (poles?) in all.

WRT the 20/20B issue, I now admit that is an interesting question. It is quite
possible that either of these things in the 20B could have a slightly
detrimental effect:

1) RF amplification (could add noise and distortion)
2) AGC circuit (operates like slow feedback)

I'm not sure how fast the AGC circuit operates. I think it would be interesting
to replace AGC circuit with a switch that would either use normal AGC operation,
or set some fixed levels of amplification. And, having done that, remove the RF
attenuator too.

I think in my case, though, I'm going to need the RF amplification. My 20B
arrived this morning so I look forward to unpacking it tonight.

Wednesday, October 27, 2010

Marantz 20B from below

I found the above picture at ImageShack linked from AudioKarma showing all the stuff inside a Marantz 20B from the bottom.  This is someone else's unit; mine has been shipped but has not arrived yet.

This is just as impressive as the 13 page schematic.  There's lots of stuff visible here, and lots more inside boxes to the left and on top.

But while I'm high fiving myself over finally getting this tuner, a question arises.  Why isn't the 20B better than it is?  With all that stuff, you would think it could be one of the best of the best.  (Some people think the 20B is one of the best, but that's unusual, the 10B is more widely known and praised.)

OK it might be a good sounding tuner, but why isn't the selectivity one of the best since it has an outlandish 8 filters, and they are always active?

I wonder if there isn't some kind of design error here, as apparently there was with Marantz 120, though for different reasons probably.

I believe that the Marantz Model 20B was one of the last Marantz components designed by the legendary Marantz designers Sid Smith and Dick Sequerra.  It was intended to replace the 10B, and used a similar IF design with 8 LC filters always active (no wide/narrow switch).  It was manufactured in the USA at Woodside, NY and later at Sun Valley, CA.  Actually, the design was first used in the Model 18 receiver, then became the 20 and 20B tuners and 19 receiver.  The models 19 and 20B had a revised version which included a mosfet RF amp to improve sensitivity.

The 120 was the first high end Marantz model produced by Standard Radio of Japan, which had been purchased by Superscope to be the factory for the less expensive Marantz products.   It also uses an outlandish 8 filters, but this time they are ceramics, which are less expensive but can be very good.  But it appears there is a design error, the IF strip is not loaded properly, and it appears the 120 cannot be made good without completely replacing the IF.  (This is documented at FMTunerInfo.)  After the 120, Marantz temporarily switched back to an LC filter design for the models 125 and 150, then finally got the hang of ceramic filters with the Model 2130.

Though their pedigrees are entirely different, the 20B and 120 appear to both have 8 filters yet be lacking in selectivity.  It is known that the 120 has a design error.  So that makes me wonder about the 20B.  Though I find it hard to believe that Dick Sequerra would have made such a design error, if he was the 20B designer.

Another possibility goes like this.  It was hard to achieve the highly touted selectivity of the 10B using transistor circuits because the impedances of the transistors in common collector mode is too low.  Or perhaps the gain is too small, or they are not as linear.  But this design (actually a re-implementation of the 10B with transistors) worked reasonably well and sounded good.  Given the difficult transitional situation of Marantz (acquired by Superscope in 1964, moved to Sun Valley and outsourced most manufacturing to Japan in the late 1960's), they chose not to invest resources in an entirely new design to make the best of transistors.  Perhaps they were even able to use surplus 10B parts, such as the filter modules.  So they went with what they had, even though it would not have been cost-effective for an original design.

Surely Dick Sequerra would not have wanted to do things this way, but he was nearly (or already) out the door anyway, possibly even working on contract.  After Superscope acquired Marantz, the old staff stayed on for a few years but eventually got ticked off by the Tushinsky's and left.

For what it does, the 20B does not look like a cost-effective design, but perhaps it could be made much better with some new thought.

Smith and Sequerra did get another chance to make the best possible transistor tuner later with the Sequerra Model One.  That tuner is even more outlandish and expensively built than the 20B, and includes balanced circuitry in the RF and IF stages,  a high end design feature I've never seen in any other tuner.  Still, reports I've heard suggest that the Sequerra Model One isn't the best of the best either, in sonics and selectivity, though the cool panoramic analyzer is worth the price of admission (and may explain why the FCC bought most of them).

One thing is unarguable, and Sequerra has even admitted it himself.  He should have figured out how to make better equipment at lower prices.

Tuesday, October 26, 2010

Examining Marantz 20B schematic

This tuner is very impressive from the 13 pages of the official schematic, which I have now obtained from MarantzPhillips.  Unfortunately it can't be saved or printed properly, at least I can view it onscreen for now.

The IF alone has the 8 LC filters, and of course they're all full time there is only one bandwidth.  Each filter looks to have about 8 primary reactive elements in addition to fairly complex power supply decoupling which includes chokes and capacitors everywhere.  Each of the 8 filters does appear from the schematic to be some kind of "filter module."

Funny, never has a tuner with so many filters been made so un-selective.  Legend has it the 20B is less selective than 10B, may have something to do with the gain or impedance of the active devices.  OTOH, some say the 10B bandwidth wasn't sufficiently wide for low stereo distortion, so maybe this is better for sound if not for receiving weak stations.

OK possibly it is less complex than more modern tuner because it's just brute force discrete circuitry instead of IC's.  But there is a lot of circuitry. There is also a 4 transistor circuit board "limiter".  I do not believe there are any IC's, so it's all discrete.

In the front end, there is indeed a dual gate mosfet in the first tuned circuit.  There's a jfet that appears to be part of the mixer.  3 caps one inductor in first stage, 6 caps two inductors (transformer) in second stage .  Mixer is not balanced.  BTW I think Sequerra Model One has balanced IF as well as mixer.

The MPX oscillator is quite complex, 10 transistors, one FET, one optocoupler.

I think detector is ratio detector.  Detector like most other blocks is in a shielded can.

The multiplex matrix is non trivial, 4 fets, 2 transistors, two optocouplers, and 4 diodes.  The diodes are shunted with caps and have cap+resistor loads.

About the only thing that looks a little unsophisticated is the power supply, though it is quite large.  Within the power supply itself, there are 2 unregulated voltages for scope and 3 regulated voltages for tuner.  The regulators are all shunt regulators, with 2 and 5 watt series resistors.  I notice that on the front end board itself there is an additional elaborate capacitance multiplier regulator, and there might be other sub regulators on other boards.  Most serious transistor tuners have had multiple series regulators, sometimes with active feedback.  Series regulators are far more efficient and can regulate better generally.  Shunt regulators may have lower noise.

The output stage is a flat two transistor cascade (all the countouring having already been done).  Seeing as it has a 110K input impedance it could be bypassed though capacitive coupling is required because it rides on the matrix +4.8v and -4.8v for other channel.  There is no input or interstage cap on this board, only the output 1uF cap.

A DVD-Audio winner

Finally got back to listening to discs, a nice previously unwrapped HDAD+ version of De Falla's The Three Cornered Hat.  This is a classic recording remastered from the original master tapes to produce a DVD-Audio with 24 bit resolution.  If you have a DVD-Audio player (like all my Denon's) you can play the DVD-Audio version with 192kHz sampling rate.  If you only have a DVD-Video player, you can still play the version with 96kHz sampling rate, still with 24 bits.  A CD (16 bit) is also included, I plan to copy that to the hard drive used by my Sonos system.  I think that all good music should be distributed like this, with both CD and "advanced resolution."  (Note while the disc includes some pictures, it is not a video disc, there is no reason to listen with monitor on.)

This disc is incredibly liquid, dynamic and theatrical, a treat to listen to.  The incredible dynamics do not seem to be weakened much by just a tiny bit of noise, probably coming more from the microphone amplifiers than the 35mm recording.  Other than the noise, it sounds so good, one wonders if maybe it sounds extra good because of the noise.  Often modern noise-free recordings just don't quite have the depth of this recording.

Classic Records makes these HDAD+ packages and also regular HDAD which do not include the CD.  Before coming up with the HDAD package, Classic Records made DADs which would play on all DVD video players at 96Khz, and I have quite a few of those.  (PULSE is one of their best, btw.)

My feeling is that 96Khz is all that's needed, 192Khz may even be generally inferior for technical reasons (see essay by Lavry).

In my system, I cannot play 192Khz as well as I can play 96khz, because my Denon 5900 cannot output 192Khz digital directly.  So if I need to play a 192Khz disc, I take the analog output of the Denon and convert it back to digital with a MSB PAD-1 analog-to-digital converter which operates at 96khz.  Either way, digital gets fed to my digital equalization preamp and digital crossover.  But no doubt some noise is added when I have to convert analog to digital, as I do with 192Khz discs, DVD-Audio discs in general (which usually suppress the digital output at the highest resolution, even if it's only 96khz), HDCD's, and SACD's.

So in the case of this disc, I could choose either the direct digital output at 96Khz (and 24 bits resolution), or the analog output at 192Khz converted back to 96/24 digital by the MSB PAD-1.  One would think bypassing the conversion would be the best, though sometimes I have liked the converted higher nominal resolution versions, which can reduce harshness a bit (useful for Red by King Crimson).  Last night I only bothered to listen to the direct digital at 96Khz.

The MSB is also connected to my preamp using AES/EBU over balanced wire instead of spdif.  But since my preamp has only one AES/EBU input, I need to make a connection change to switch from the Lavry (currently used for FM radio) and the MSB (currently used for high resolution discs).  I've decided the simplest and most effective way to switch XLR is to have short XLR cable that can connect to one of other cables that actually connect to the equipment in question.

Sunday, October 24, 2010

Finally I get what I want, a Marantz 20B

Not that I am expecting this to be my best performing or sounding tuner...  I do not expect it displace my modified Sony XDR-F1HD in that position as my #1 tuner in both weak station pulling power and sonics.  So perhaps, I shouldn't have bought this.  I am not a nostalga-phile.  I try to pursue the best possible sound using the latest technology (such as I can afford), not relax into some 50's or 70's sensibilities.

But I just had to because I've been studying them for nearly 40 years since I first saw one at a new high end stereo business (one of three) in my school age hometown, and I hope it's pretty good sounding tuner, fun to play, and a useful tool because of the oscilloscope.

I believe that business was the store whose cranky and outspoken owner later became famous on the internet, Sunshine Stereo, but during its very brief incarnation in California before moving to Florida.

Anyway, as a pimply faced high school sophmore I wandered into one of the back auditioning rooms, there on a shelf was the 20B.  It blew my mind.  It may have been playing and sounding elegant as I recall, or just quiet, but sitting there, with scope and blue face and white lights, it was so cool I thought.  The owner wandered in, quizzed me about what stations I wanted to listen to, decided I needed his most sensitive tuner, and showed me a Sansui, which kinda looked cheap I thought.  He also had an SAE, which he didn't think performed as well as the Sansui for picking up weak stations.  But I still lusted for the Marantz.

Later I saw a 10B, and was disappointed that it was not the same tuner.  I didn't warm to the appearance of the 10B at first.  Now, however, I admit I lust for the 10B more than the 20B.  I've bid on 10B's and lost.  I hope to get a good 10B eventually, but they are incredibly expensive and unpredictable.  They are the most legendary "good sounding" tuner in history, many people have reported fabulous sound from them, though just as often you find negative reviews of them.  They appear to need a lot of service only by apprentices of the original designers whose charges are astronomical, though sellers just as often claim their unit has never needed service and still works perfectly.   Advertised as never-needing-alignment, the actual history seems to read never-stops-needing-alignment.

Quite a number of people who as Marantz employees or audio salesman lived with both 10B and 20/20B like the 20/20B better. The 20B is said to be a transistorized version of the 10B, based on the same precision toroidal filters (or something very similar), which are often incorrectly described as Butterworth.  This tuner uses no ceramic filters which are used ubiquitously in other tuners, but some think are inherently inferior for sonics.  Both tuners were designed by the original genius Marantz designers Sid Smith and Dick Sequerra who also went on to design the original Sequerra tuner.  It is said to be one of the best sounding tuners, if not one of the best performing tuners (among online reviewers you can find many opinions including these: some think the 10B performs better than anything but sounds worse than the 20B, others think the 20B is better in all ways to 10B as well as being best sounding tuner but not as good performing as others like McIntosh MR78, many tuner fans think both these early Marantz tuners are a joke except in their mythological impact).

The 20B version is different from preceding 20 and 10B in an important way for people who use indoor antennas.  It has a dual gate MOSFET RF amplifier with AGC, and changes the first IF transistor from bipolar to FET.  That makes it more sensitive.  But also, it makes it potentially more subject to overload.  There is a switchable attenuator for that.  A modern design would use a more modern silicon device (they have gotten extremely good) as RF amplfier for better performance without needing bandaid attenuator.  But anyway, unless you have outdoor antenna, the 20B is clearly the one-of-these to get.  It should be more sensitive than even the legendary Marantz 10B, which feeds the incoming signal directly to a diode mixer with no RF amplifier.

But despite the boost in sensitivity, this is still not noted for weak station pulling by just about anyone.  It is noted for nice sound, interesting built-in scope, and cool looks.  A bargain solid state version of the legandary Marantz 10B, and notably more reliable than its predecessor.

Anyway, more fun, I hope, on the way.  I bought this one for a relatively high price because it appeared to be in excellent physical and working condition.  What happens on ebay is that some mint unit will sell for a huge price, and from then on all the rust bucket barely working units will try to be sold for the same high price.  Whatever the primo unit costs extra is often worth paying, but only if it is the primo unit and not some copycat seller.  This is about the best looking unit (with numerous high resolution photos) I've ever seen and is described as fully working by the long time audio guru who is selling it.

Symphony, 101dB

The San Antonio Symphony had a stirring rendition of Pines of Rome on Saturday night.  This is a big audiophile favorite going way back, but however many times I've heard it reproduced it was even more impressive live last night.  It was mind blowing!  Perhaps wrecking the mood, at the final climax I discretely pulled out my mobile device to measure peak dB.  I did see a 101dB average A weighted reading, pretty impressive in itself, but after I switched to peak I couldn't reproduce that again.  Immediately thereafter I was the first to rise in the unanimous standing ovation.  [Note: I tried to be discrete, and didn't disturbe anyone around me because there was none.  But I think I'll avoid doing this in the future, the symphony hall is my church.]

Wednesday, October 20, 2010

Cleaner Power, Lower Noise

I switched my line level components over to the dedicated amplifier circuit.  As a result, wideband amplifier noise dropped from 1.8mV to 1.7mV, and there was a similar small drop in A weighted noise.

More impressive was comparing the AC lines directly with my AudioPrism Noise Sniffer.  I can now give these reading quantitative values by holding an SPL meter directly above the widest part of the sniffer speaker.  For SPL meter, I used a very accurate mobile device SPL app.  The dedicated line got a measurement of 78dB.  The old household line got a measurement of 100dB (!) as it was buzzing like hell. I got that measurement after turning off the dimmer for the kitchen fluorescent lamp.  Strangely, with the dimmer on at 50% brightness level, the line noise level was lower.  The old household circuit is crazy, it goes from the the outside light in front of the garage to the outside light in back of the house which are both fluorescent with photosensors.  In between it goes to the entry light and outlet and the kitchen light/fan which is on a special fan-compatible dimmer.

It's hard to tell exactly how much the sound improved since I've been making so many changes that have improved signal-to-noise ratio over the past month or so.  The overall result is that the sound is very warm and imaging is very stable.

I think I'll keep the line level components connected to this circuit in the future.  In the past, I had used this line exclusively for the Krell FPB 300 amplifier, which draws current mightily sometimes.  But I think now it's worth keeping the line level components on this line also, and if the Krell lowers the line voltage significantly the new UPS will restore it, but I don't expect that to happen often.  If it turns out this line causes the UPS to make too much noise when the Krell is on it, then I'll have to move back to the old circuit.

The dedicated amplifier circuit has these specifications: 120V, 20A Breaker, 10ga wire, wired straight to main power entry box, insulated ground, oyade outlet.  Cost the better part of $1300 to install.

The reduction in noise could come from less noise on the hot, neutral, and ground wires.  But it could also come from putting both line level components and amplifier on the same AC circuit.  For the purposes of deciding how to do my connections, this answer to this question is unimportant.  But for audio science, the question is important, because reducing amplifier noise by using a quieter AC might be considered tweaky and not part of standard audio engineering.

To have a controlled experiment, I would have to try one or more additional comparisons.  For example, having all components, including the main amplifier (currently a Parasound HCA-1500A because the Krell is waiting for repair) on the noisy line.  Then I could compare the two cases:

1.  All components on noisy line
2.  All components on quiet line

which would single out the issue of noisy or quiet line, and remove the additional issue of having components on one or two lines.

Actually, because I had been operating on two lines before, I had previously ground-lifted the Parasound.  For some reason, every Parasound amplifier I've had has needed to be ground-lifted or connected to an otherwise ground-lifted system.  Perhaps now, with everything on the same line, I could operate the amplifier without being ground lifted, but I made the change internally.

But since I already ground lifted the amplifier, the issue regarding the previous operation of components across two different AC lines should have been relatively small.

I am interested in the scientific question, so I expect to go back and do some additional experiments, but I think that operating both line level components and amplifier from the dedicated circuit makes the best sense.

When doing the noise sniffing, I also tested the outlets of the Belkin PureAV AVU1500 when plugged into the quiet circuit.  In that condition, they measured the exact same "noise sniffer level" as the circuit itself, 78dB.  My interpretation is that 78dB is already as quiet as AC gets.  The other interpretation might be that the PureAV filtering doesn't do anything.  But I recall (no numbers) that when the PureAV was plugged into the noisy circuit, it was still quiet.  So that supports the idea that the Belkin filters power pretty well, but when you are already starting from fairly clean power, it may not do much.  And clean power may mean simply a dedicated circuit with insulated ground.

Tuesday, October 19, 2010

Air has noise, and other measurements

Unplugging my Parasound HCA-1500A amplifier from the Meguro noise meter, the meter immediately jumps up (not down) to a higher reading: 10.5 mV.  That is apparently the EMI/RF voltage in the air across a pair of banana jacks, in my room at this time.  (I've noticed a little variation over time, the range seems to be 9-11mV so far.)  The Meguro has a bandwidth of something like 1 Mhz, and an impedance of 1 Megohm.

It's particularly funny to remove an amplifier and see the voltage reading go up IN THIN AIR.  It's like the amplifier cables are shorting out the air around the banana jack.  Fortunately the air has a rather high impedance so the cables win.  But one can wonder what affect this has on amplifier circuitry.

BTW, with 6dB's of attenuation dialed in on its level control, but otherwise being fed by the noisy Behringer DCX 2496, I get 1.8mV wideband and 0.3mV "A" weighted noise from the Parasound amplifier.  The majority of that may still be from the Behringer itself.

Sunday, October 17, 2010

The total noise reduction was achieved through various means NOT

Update and Edit: Additional testing has cast doubt on the original claims of this post below.  It now does appear that 6dB of noise reduction in the supertweeter amplifier output was achieved by using a 6dB attenuator.  I now measure 21mV, 0.64mV (A weighted) with no attenuator and 9.7mV, 0.33mV (A) with attenuator.  Specifically re-measuring the change of putting most equipment (plugged into power conditioner/UPS) on dedicated amplifier circuit instead of regular (crazy!) household circuit, I have found that change makes zero measureable difference in noise level.  Surprise Surprise.  I have now switched from using a 3dB attenuator on midrange amplifier Parasound HCA-1500A to using its built-in level control to achieve 6dB attenuation.  The Harrison Labs 3dB attenuator I was using seemed to make the sound slightly funny sounding in the midrange probably because it presents 3K ohm load to the Behringer.  But the Harrison Labs 6dB attenuator on the supertweeter amplifier, which has no level controls, does not seem to have that effect, probably because ears can't hear it at such high frequencies.  I watched the voltage output on the tweeter amplifier for awhile, it seems it stays below 1 volt (!) which is much less than a watt output (on a 250 watt amplifier).  Based on that test, there should be no problem with 12dB attenuator which will be ordered today.  [End edit, now back to original erroneous post.]

Yesterday's noise reduction exercise (the supertweeter which used to make a rough fizz now only makes a barely audible background hiss as close as you can get to it) mainly focused on use of interstage attenuation.  Actually, only about half of the noise reduction came from attenuation.  The other half came from switching to short shielded equipment cords on 3 main pieces (UPS, Tact, DCX), which definitely made a measureable but small difference, switching the power conditioner to the dedicated amplifier circuit, and using some better shielded cables.  Unfortunately, my measurements of all this are incomplete, but the total noise reduction was from 21mV at the output of the tweeter amp (pretty hefty noise level) to 9mV at the amp, a greater than 6dB reduction.   The use of a 6dB attenuator didn't quite reduce noise 6dB, more like 4dB according to my measurements, likely due to other noise sources not yet fixed that are not being attenuated.

These noise measurements are wideband, made with my nice Meguro noise meter shown above.  I didn't do A weighted measurements consistently unfortunately.  The audible noise reduction seemed much greater than 6dB actually, which is possible because it's possible the audible noise has been reduced more than the inaudible noise.  In fact, that often happens.  The A weighted noise levels are much much lower.  I figured out that is how Behringer can meet their noise specifications for the DCX 2496.  The "A" weighting ignores a huge amount of high frequency whine from the Behringer's switching power supply.  A weighting is not a completely accurate weighting according to audibility, either.  I understand that the B weighting is better but nobody uses it.  I think noise is bad whether it's considered "audible" or not.  Even the "inaudible" noise modulates audibly with lower frequencies.  And it may well be that our hearing system is affected by tones we don't actually perceive; there is at least one peer reviewed research paper which suggests that.

One funny thing in all this was that I didn't intend to go this way.  I had long figured the supertweeter noise was ground loop noise with all the lower harmonics filtered by the supertweeter's build-in crossover.  However, when I tested for ground loop noise by temporarily ground lifting the tweeter amp (using a grounding adapter) I discovered that made no difference.  To be sure I was hearing everything, I put a full range speaker on the amp instead of the supertweeter.

So then I got involved switching the line cords to the nice new ones (SJT shielded 14 gauge, much nicer than freebie SVT), etc., which wasn't making much difference, so I asked myself "Just where is this noise coming from."

I then put my meter on the Behringer itself, with no actual digital input, and the wideband noise level was an astoundingly high 0.7 mV.  So that's where the noise is coming from!  Then I immediately realized an attenuator would be a quick fix.

Now I'm a little worried about the 3dB attenuator on my midrange amp.  The voltage levels there are pretty high, and the Behringer may be getting distorted into the 10K load or less of the attenuator.  Now I'm thinking I may just use those volume controls on the back of my Parasound HCA-1500 after all.  They maintain a relatively high load impedance for the Behringer, and may sound better for that reason if not others.  In the end, I'd like to replace those volume controls with fixed resistor networks of the lowest noise resistors.

Another day, another twofold (6dB) reduction in noise

Actually this doesn't happen often, that I am able to improve my audio system by a factor of two in one day.  If it did, my system would already be astronomically good, two to the power of over ten thousand. But it is often possible to find improvements that can be made which are real, provably real because they are also measureable, and having an ability to do audio measurements can help find them.

The above picture shows a Harrison Labs 3dB attenuator like the one I am now using now on the output of my Behringer DCX 2496 digital crossover that feeds my midrange amplifier.  I'm using a similar 6dB attenuator on Behringer output that feeds my supertweeter amplifer, where I have achieved more than 6dB in total measureable noise reduction (also including some smaller noise reductions from other factors I'll discuss in future posts).  [Correction: In the following post, I give measurements showing that possibly the entire noise reduction came from attenuation, not from cord changes.]  I think the 3dB may be the optimal limit in improvement for the midrange amp, but I'm planing  to try a 12dB attenuator, when I can get one, on the supertweeter amplifier.

For some time, I have noticed a whiney high frequency noise from the supertweeters (like the right one shown above) when I put my ear right up to them.  I had figured the problem was ground looping (to be discussed in future posts) but ultimately found to my surprise and horror that the source of the problem was that the Behringer DCX is rather noisy for a hifi component.  (And this is after having spent months doing bench tests on the Behringer, which convinced me that it was fairly quiet.)   Since the Behringer both has excess noise and excess output capability for most hifi components, it makes sense to attenuate it for them.

I don't really notice any noise coming from my midrange speakers, the Acoustats.  But anyway I put a 3dB attenuator on the input to the midrange amplifier, so there is a 3dB noise reduction through the midrange as well, even if requires a listening session to hear, not just a quick listen.  As well as being less immediately obvious, the benefit in the midrange is uncertain.  In addition to being objectively quieter, there might also be a slight rise in distortion, which is much more noticeable in the midrange.  I sometimes think I hear a slight hardening of the sound, but it is superceded by a tremendous improvement in depth.  But because it may already be a mixed blessing, I'm not certain I'll precede to using a 6dB attenuator for the midrange once another one becomes available when I replace the tweeter attenuator with a 12dB one.  3dB attenuation in the midrange may be the best compromise option.

Actually, I have argued against using attenuators with the Behringer in a DIYAudio forum.  But that was when I was using a Krell FPB 300 as my midrange amplifier.  No attenuator is desireable for that combination, because the Krell can use the extended high output of the Behringer, and also because the Krell is less sensitive and already suppresses the excess noise of the Behringer.

But while I was making these arguments, I was overlooking the need for attenuation of my supertweeter amplifier.  Attenuation was clearly called for there.  And now that I am using a different midrange amplifier, a Parasound HCA-1500A, some attenuation is useful there also.

Under my loading conditions, the Krell requires 2.6dB more signal input to output the same level as the Parasound.  This means the Krell, relatively speaking, suppresses the noise of it's source by 2.6 dB compared to any THX approved amplifier.  So long as the preamp or source component can provide enough level (and the Krell requires about 5-8V input max) this can be an overall benefit.

Now why doesn't everyone play this game, make their amplifiers less sensitive to make better sounding systems (and sell more amplifiers)?  The answer is standards.  Currently, there is a defacto standard for audio amplifier sensitivity.  It is a proprietary standard, THX.  THX determines the "correct" level of amplifier sensitivity.  They have chose a comparatively high sensitivity level that tends to exaggerate the noise level of preamplifiers.  But anyone like Parasound who wants the THX seal of approval needs to use the THX sensitivity level (can't remember what it is offhand).  John Curl has complained about this, though his amplifiers do often (like my 1500A) have a volume pot on the back.  If I wanted to, I could lower the sensitivity using the volume pot.  I simply hate volume pots because of noise and other factors and will always use a fixed attenuator instead.

So anyway, the context of my old system was the Behringer crossover (with max output around 10V) and Krell amplifier (max input similar to that).  In that context, it makes no sense to attenuate the output of the Behringer, because if you do, you are limiting how much of the peak power of the Krell you can access.  And that peak power is a lot higher then the specified power of 300 watts, more like 550W into 8 ohms (and more into lower impedances).  So therefore don't calculate the max level from your preamp based on the amplifier power spec.  Based on that calculation, the Krell would need only about 4 volts to reach max output.  But if the preamp runs out of steam at 4V it will never access the ultimate peak power of the Krell.  It needs more like 8 volts for that.

In this context, not only was attenuation not good, it was not needed, because of the 2.6dB noise suppression from lower sensitivity.  Thus the Behringer and Krell are a good match without any attenuation.  Attenuating the Behringer in this context either reduces peak power or increases distortion.  In addition to being rather noisy, the Behringer gets slightly more distorted at the higher voltage levels above 4V output.

But the Behringer and Parasound are not a good match.  The Behringer puts out way more voltage than the Parasound will ever use, so that extra voltage is wasted.  And being more sensitive, the Parasound exposes the noise of Behringer much more loudly.  In this context, some level of attenuation is desireable, possibly 3-9dB.  I'm using 3dB now, and 6dB on my supertweeter amplifier, an Acurus A250, which has similar sensitivity.  The supertweeter generally only needs a few watts, so it's unnecessary to access the upper power ranges of the A250, so using lots of attenuation is not a problem.

Why use the noisy/distorted Behringer?  Because it is a miracle box, letting me build a fantastically complex speaker system that could not have worked 20 years ago.  It was designed to cheap semi professional standards, not audiophile standards, but the capabilities of the digital processing it offers is without peer (at least under $5K).  I plan to get my Behringer modified with new audiophile grade circuitry from Europe soon.  That will make it an audiophile grade unit.

I actually blame the THX standards somewhat also.  Given current technologies, the sensitivity and output levels of the Behringer and Krell work out better.  There is no sensible reason why amplifiers need to reach maximum output level with less than 2 volts input.  But historically, lower levels like that were common. In fact, for many years, amplifier sensitivies were around 1 volt.  Why?  I don't know, maybe just because it's an obvious number.

OK this is getting too long and I need to get to yard work before I post pictures, but there is more to come, and other tricks helped get lower noise levels also.

Friday, October 15, 2010

Ethan Winer

I stumbled across Ethan Winer's website while looking for info about power conditioners.  Interesing guy, mostly on the audio objectivist side of things, owned a studio but sold it to go with Cakewalk digital production exclusively, written lots of magazine articles in popular and recording engineer magazines.

He has a take on the use of various kinds of distortion to sweeten recordings.  He says the way recording engineers use tubes, transformers, etc., these days is not because of higher fidelity or the inherent superiority of analog.  It is because the addition of a tiny bit of distortion often makes things sound better.  This is not a stupid idea at all, and he proved it in a cello recording project.  He calls for the use of digital plug-ins to get these effects instead of often extremely expensive hardware.

Here is his article.

I think this is probably true, at least largely true.

And here is his discussion of power filtering (and dimmers)

he recommends the use of the Corcom Series R (inductor-capacitor) filters, which has got to be a more cost effective solution than using Monster, Belkin, Furman, or even APC filtering strips.

I note that he also has delt with ground loops in a way not recommended by electricians and institutions like UL.  He says:

In my studio I have ground lifters on everything except my main mixer. The entire system is grounded through the audio wire shields that connect to the mixer, but only the mixer is connected to the power line's ground through the third grounding pin of its power cord
BTW, for liability reasons, I won't recommend that anyone do this, it could cause death through electrical shock, it's against all electrical codes and may even be illegal.  However, this is similar to approaches I have used in some of my systems.  The idea is to "lift" all grounds except one (either power amp or preamp) using grounding plug adapters that are not sold to be used this way.  I know lots of audiophiles who do this, and I can see why, it's almost impossible to get a complex system hum-free any other way.

Now I have done lots of reading and research on this subject.  If equipment had been designed properly, this would not be required, but hardly anything actually is, it turns out.  There is a particular way of isolating signal and chassis ground that can be done with a diode bridge, but hardly any manufacturer actually takes the trouble and expense to do this.  They just connect signal ground to the chassis at some point, and this will cause hum if there is more than one piece of equipment connected.  I will discuss the grounding and hum issues more in a future post, but here I just wanted to show what somebody else says.  Here we have a well informed professional actually suggesting something against electrical codes and potentially deadly.

The First Remote Extender modifications

Already having a remote extender "transmitter" (which picks up infrared from the remote and transmits it on radio frequencies) in the bedroom, to add remote control to the modified Sony XDR-F1HD tuner in the living room I first put a remote extender "receiver" (which picks up the RF and converts it back to IR) in the living room next to the tuner.  That basically didn't work at all.

About the same time, I got my first RF spectrum analyzer, a used boat anchor, from an eBay seller.  This was a useful test.  I used a small antenna to probe the room background noise and signals at 413Mhz, the frequency that remote extenders use.

I discovered to my horror that my beloved Tact 2.0 Room Correction Preamp is for some reason pumping out as much noise at 413Mhz as the remote extenders produce signal at that frequency.  So obviously no remote extenders are going to work in the vicinity of the Tact.  And I have two Tact's, one in the living room and another in the bedroom.  (Somehow the one in the bedroom doesn't seem to interfere with remote extenders.)

So, obviously remote extenders aren't going to work in the vicinity of the Tact, which is located very close to the Sony tuner.  I tried putting the receiver in nearby locations and using the 6 foot extension wire that comes with them with an LED at the end.  That way I could locate the receiver as much as 6 feet away from the tuner (and the nearby Tact).

Well, it seemed to work.  Several times I got it working by finding some clever location for the receiver where it didn't get as much interference from the Tact.  I tended to get it working in the night time when I do most of my listening.  Then I tended to discover that it didn't work in the morning.  I still don't quite understand why it doesn't work in the morning.  Obviously there is more radio frequency interference in the morning.  But where is it coming from?  Is there some way I can block it?

Finally I got really fed up with this approach when the clever receiver locations I found at night didn't work on the following night.  It was almost OK if it didn't work during the day.  But not working on some nights was not acceptable and before long it seemed not to be working on any nights.

About this time I also tried a bunch of different brands of wireless remote control extenders.  I found they are all very similar, with similar sensitivity.  Actually at first I thought one new brand was better.  Then I found it was worse.

Ultimately, to make this reliable, I decided to make my own extension wire with an LED at the end.  I made it long enough so that I could plug it into the known working receiver in the Kitchen.  That took 50 feet of wire, and conveniently I had a 50 foot roll of cheap 18 gauge speaker wire.  The hardest part of this was running a wire through the kitchen doorway.  I ran the wire up and around the doorway as inconspicuously as possible (but you can imagine my non-WAF house already) using AV staples (one of the most useful things to have).

Then I discovered that while the receiver in the Kitchen continued to receive signals from the transmitter in the bedroom, it would not simultaneously send them down my new wire and control the components in the kitchen.  Either plugging in the wire switched off the internal LED's, or it simply soaked up so much power that the internal LED's were no longer bright enough.

So I had to put a second receiver in the kitchen just to power the 50 foot extension wire with LED going into the kitchen, and leave the first receiver, which controls my kitchen video components, untouched.

Then while all this seemed to be working for awhile, eventually it wasn't working any more again.  I tried moving the receiver in the kitchen around a bit, putting it in different locations to see if it could pick up the bedroom signal better.  This sometimes seemed to work, but only for awhile.

Finally I decided something even more radical was required.  I would need to take either the transmitter or receiver apart to see if I could somehow juice them up a bit.  I had read stories online about other people doing it.  It sounded like something I could do, I even have equipment to test that my modifications are working properly.

Remote Extenders and RFI

The topic of remote extenders is more "home theater" than "audiophile" according to audio stereotype.  The purist audiophile does not use remote controls, but prefers to get up and clean records before putting them on the 'table.  I've known some audiophiles who even eschewed volume and balance controls.  Their system was set up for the one correct volume that makes everything sound best, they said.  The only control is the power switch on the main amplifier.

I have a record cleaner and occasionally use it, but generally I AM the kind of guy who does like to use remote controls, especially with digital sources.  I have lots and lots of remote controls.  I like to use the factory remote for each gizmo, and I have mountains of gizmos that have remotes.  It always seems to me that "Universal" remotes leave out some of the obscure functionality that makes each unit special.  So I have big wood boxes for remote controls in every room.  And I have a whole house audio system called Sonos which lets me play music from my hard drive and internet services like Rhapsody and Pandora in any room in the house.  Sonos also lets me listen to non-digital sources.  Every Sonos box has an analog input as well digital and analog outputs.  In every room there is a preamp or other source selector which feeds the Sonos input in that room.  So I can listen to any source from any room in any other room or in all the rooms in my house at once.  My Sonos system is set not to use any form of audio compression, so it digitizes all analog inputs in 16 bit 44.1Khz digital ("CD Quality").  And Sonos has its own remote controls, but thankfully they're radio frequency wireless and in my experience provide 100% reliable transmission unless they lose their memories from power failure and need rebooting.

Contra audio stereotype, I like this kind of audio distribution system for automation and convenience.  Sometimes I set my system just to play music selections randomly.  That has actually allowed me to listen much more to the obscure pieces in my collection than I would otherwise do.  In fact, mainly it allows me simply to listen much more than I would otherwise do.  Not that I am always listening to audio, in fact it's less than half of the time.  I like silence some of the time also.  But if I didn't have an automated music system, I'd be getting more silence than I'd like, since it's actually quite a hassle to select music from your record collection, clean the record, clean the stylus, and put it on the turntable, etc.  Not much better with a CD.  Much easier to press a button and load songs from your hard drive (as it seems everyone but purist audiophiles has discovered).

Anyway, I started using remote control extenders long long ago.  Back when I had both Super Beta and VHS vcr's (hey, I still do!).  I had the Sony 900 Super Beta vcr in the living room, and the Panasonic VHS vcr in the bedroom.  But it always seemed I wanted to watch beta videos in the bedroom, and VHS videos in the living room.  Both video systems were wired on the same RF line from the cable company.  (Things were so simple back then, there weren't 10 different kinds of video interconnection to hassle with.  But then the quality wasn't as good either.)  With a remote extender, I could control the Super Beta box from the living room, etc., just as I wanted to.

Now as time has advanced, I got more and more remote extenders to bridge more and more needs for functional control across the house.  Now I have 4 video systems which interchange digital HDMI video through OWLink fiber optic cables.  I have 3 remote control extender "transmitters" in strategic locations, and I've forgotten how many receivers, they're all over.  I aim my remotes at one of the "transmitters" and the infrared remote signal gets transmitted to everything, so I have total control, everywhere, BWAHAHA.

But there is a fundamental problem with this approach to home entertainment.  The problem is that these wireless remote extenders use radio frequencies, and our home space is getting more and more saturated with radio frequencies.  So I'm finding that the range of wireless remote extenders is getting less and less as they are forced to compete against this background.  They advertise 50 or 100 foot range, but if you search online you can find people complaining that they don't go as far as 8 feet.  I've learned a lot from these postings how the units work and can be modified.

But for me, it seemed like all my remote control extenders were working perfectly until I needed to add just one new one for the modified Sony XDR-F1HD tuner which is now my "whole house tuner" that I listen to everywhere in the house through Sonos.  I like having it always available, but I can't listen to FM without having the ability to change the station at whim, otherwise, before too long, I simply have to turn the radio off.  The tuner is actually located in the living room where I have my best indoor FM antenna.  But it was hard, hard, hard to get the remote control extender working to there from the farthest location, the bedroom.  I struggled with this for months.  I even bought an RF Spectrum Analyzer to see if I could determine the nature of the problems (and for other reasons, mainly I just wanted it).  Wierdly, the remote extender tended to work in the night, but not during the daytime.  I figure that is because there is far more background radio frequency "noise" (that's someone else's signals) during the daytime.

This week I made one more upgrade to the remote control extender system which I hope will finally fix this problem,  so I can control the FM radio from the bedroom any time of the day.  I'll describe this upgrade and how I got there in a future post.