Monday, April 2, 2012

Phono player back up...the story

For two years I have not had a working phonograph player hooked up.  My #1 rig is a Sony PSX-800 linear tracking biotracer table (I see one on eBay right now listed for $2950 buy-it-now) with Dynavector D17 II diamond cantilever moving coil cartridge, Fulton mat, Michell clamp, dB systems HG phono preamp with teflon jacks and big upgraded power supply.  Back in 2010, just after a very bad power surge damaged my washing machine electronics (I've added whole house surge supressor since then) I started the Sony and thought I saw and smelled some smoke.  It was also responding, if at all, a bit sluggishly.  I decided it needed careful examination at minimum before any further use.  It was unplugged and hasn't been replugged since.

BTW, I'm not necessarily saying that the way I have any of my rigs set up is optimal, only that it is what I have come up with so far.  A friend says that felt makes a much better record mat than sorbothane (which I believe is what the Fulton mat either is or is similar to) and he has an even better material.  It's been almost 3 decades since I've done any record mat testing, and even back when I did what little I did, I did it very casually and largely based on the recommendations of people I trusted then.

So after my #1 system went down, I figured I'd just switch over (finally) to my #2 system.  My #2 rig was what I had purchased after the Sony turntable first stopped working for me and (at the time) I had little hope for repairing it.  That was around 1999.  I figured I'd buy something completely different, so I could compare the two, and because I had always wanted an audiophile belt drive turntable.  I really wanted a midline Rega, they had just introduced the P25 and I read a compelling review in Stereophile, so I figured I'd get that.  So I headed down to Concert Sound, a small audio specialist (who no longer exists) carrying Rega and a number of other high end brands.  When I got there, the dealer suggested that I get a Linn LP12 instead of a Rega.  (He may have been right about that...I sometimes do listen to loud music, for which Linn's may be more suited due to better isolation.)  And he just happened to have in a barely used Linn rig for $1350 including LP12 with Vallhalla power supply and Ittok arm, a $3500 value at original list price.  (Mind you, he made sure to warn me, this was a concession sale, though later he fixed the faulty Valhalla diodes for free.)  So I took that rig, and the dealer mounted the Panasonic Strain Gauge cartridge I had been using since a cartridge showdown in 1988.  The Linn dealer said the strain gauge cartridge was very good sounding and I would continue to be happy with it.

But after a few years, the #2 system went down because all both of my Panasonic 405 strain gauge preamps had stopped working properly.*  Meanwhile, I had gotten the Sony PSX-800 repaired by a very nice technician in Austin.  So I put my very nice Dynavector D17 II in a headshell and got a MC phono preamp, and didn't look back until my Sony broke again.

(*These units have a 35V input coupling cap that has gone bad on both of my units.  I figure it goes bad frequently because being at the front end, it picks up static electricity and other abuse coming down the wire from the turntable.  What's needed here is a 400V metalized polyprop cap.)

Well that's not entirely correct.  Around 2005 I obtained a tube based preamp for the strain gauge cartridge.  I tried it out, and it was very nice.  In fact I was blown away.  But after about a week of bliss, I determined that it was not accuracy that I was finding most pleasing.  It was bass boost, lots of bass boost, probably around 10dB or so I determined with a test.  I took apart the tube based preamp and determined that it did not use any EQ at all.  Some people *like* to operate their position sensitive strain gauge cartridges that way, but I do not believe it is correct, and I have done lots of measurements to show that it gives you 10dB of bass boost (or treble cut).  Actually, according to one authority, it requires exactly 12.6dB of treble increase from 500Hz to 2122 Hz.

This was back at the time I was showing off my then-main bedroom system to some friends.  I played Dark Side of the Moon, 30th anniversary LP release, first on my Sony/Dynavector system and they loved it.  Then I said you may like this even better.  Well, they didn't like it at all.  Far too much bass.  You can really tell when you compare an accurate system (like #1) with an inaccurate system.

So then I figured I'd figure out some way to modify the tube based preamp.  That went nowhere.  A few years ago, I figured I could use a Behringer DEQ 2496 to do the equalization, AND it would also convert the analog input to digital which is required for my bedroom system anyway, as the selector, equalization, and crossover all work in digital domain.  Since the analog-to-digital conversion needs to be done anyway, the EQ done in the digital domain is absolutely perfect, free of noise and distortion, etc.  The actual conversion to digital isn't quite perfect (the DEQ 2496 could use better input analog circuitry and power supply) but it is pretty good and better than the conversion done by my Tact 2.0 preamp.

So I obtained the Behringer, but it got immediately put into the slightly different task of simply converting the output from my audio disc player (then a Denon 2900, now a Denon 3910) from analog to digital for those discs (like HDCD or SACD) that have no full fidelity digital output.  In that job, it handled input, but didn't have to do any EQ.

Finally, last weekend, after spending a week thinking about and bidding on still other turntables, I decided to get my #2 rig going.  One of the biggest hangups was that I had placed the Linn on a low credenza, that goes half-way into my open closet, and I wanted to keep it there.  Unfortuntely, lots of stuff in the area would need to be moved somewhere else permanently, and there was no other place for the stuff.

What was needed was to blow past the mental hangups and do something different.  In this case, I simply decided to move the Sony out of the room, and move the Linn into the convenient location the Sony had been using.  I need to examine the Sony on my bench, but my bench is full of the stuff I was using to analyze the Koss 950 headphones, which is not yet finished.  So I could not put the Sony on my bench but temporarily put it on the living room coffee table.

In less than an hour, I had the Linn in the new location, along with strain gauge bias battery holder, strain gauge preamp, and DEQ 2496.  The DEQ 2496 sends a Toslink digital signal (24 bit 96 Khz) to my Tact preamp.  Finding a 30 foot toslink cable was about the hardest part...I took the one from the living room that had once connected keyboard to my system (but, since I hadn't been able to find the cable in years, it hadn't even been used for that), but I was able to untangle the required wire with the help of a flashlight.  I had panned to use coax cable, but I think toslink is nice in this application because it makes sure all the turntable stuff is totally electrically isolated.

That new level of electrical isolation from the rest of my system might or might not explain why now, for the first time ever, I am running system #2 without any hum.  Previously I just had to ignore the hum.  But now it just isn't there.

So I made the decision to go ahead at 11pm, and finished setting everything up by midnight.  It was a miracle, and also a miracle that it worked so well.  But the details that made that miracle possible will be described in another post.

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