The Grinch Lost

 Since October, the Grinch has visited me many times.

Upon returning from vacation on October 31, I discovered the DEQ for the supertweeters had become dysfunctional.  Attempting to bypass, I then discovered the entire right channel of the supertweeter had died--they were shorted.  Some kind of catastrophic failure I hadn't noticed.  It appears the amplifier is still OK.

I managed to get a replacement for the nearly unobtainable D21AF right away.  Suprisingly, it has been much harder to replace the Vifa tweeter in back.

But then, I discovered that merely moving the supertweeter towers out of the center made the imaging far better.  It turns out there's a "central" rule: don't put stuff in between dipolar speakers.

So, the grinch lost that one.  While it may take a year (I've determined not to hurry it) to get a new supertweeter system in place again, it will be far different.  It will not be on a tower in between the speakers.  My current plan is to have the supertweeters behind the Acoustats, just above "interface" level.  More recent testing has revealed the Acoustats are nearly acoustically transparent, so little harm in putting the supertweeter behind and then compensating for the time difference digitally, as I always do.

The grinch has really determined to mess up my audio life in the past couple days.

In the previous week I figured out to hook up my modified QSC ABX switch box to switch speakers instead of amplifiers.  That seems to work fine (but I need to inspect if the amplifier is ever "shorted").  Only then was I able to nail down the difference in sound between my newest 2+2's and my original pair, with instantanous switching.  Then I learned a bunch of things:

1) Instantaneous switching is near essential for making audio comparisons

2) The new speakers sounded way louder, but measured softer.  They could sound more dynamic without any level compensation (and which way???) but had a glare that became objectionable quickly.  Possibly lowering HF level and changing to C mod would help.

I then started working on lowering the level.  It took sanding the variable resistance bar in the interface in the left channel.  I had disconnected the speaker wires during this time.  But the first time I plugged the speaker wires in it didn't work, and it took several more attempts of sanding to get it to work.  I also plugged the speaker in while it was connected to the amplifier (which I now think could be a no-no).

I had the channels reversed and messed with fixing that.  Somehow in the process of modifying the speaker and reversing the (complicated extended and automatically switched) connections I managed to kill my Hafler 9300.  One channel first became increasingly noisy (which at first I thought was the modified speaker, or the connections) and ultimately it went out completely.  It took some testing before I realized it was the 9300 that had failed, it was not a matter of the (now very complicated) speaker connections.

I'm now worried that it was actually the new 2+2 on the right side, which makes a very soft arcing sound about once per second, that had killed the amplifier.  Perhaps especially when I plugged in the speaker.

I can't blame the new speaker for certain, but I now think it's a risk not worth taking.  I'm not going to play that speaker with a non-expendable amplifier until the arcing has been fixed.

So the grinch blew up my favorite amplifier, killed my new pair of speakers, and killed my new speaker testing plans and even my imagined post-testing scenario: how I first planned to use the new Acoustats in bedroom if I couldn't get them to sound as good as the older ones (which of course had been the original hope).

Pretty bad.

But it gave a renewed purpose in life to my Aragon 8008 BB amplifier that's been waiting there in the living room all this time, as my backup and "alternative" amplifier to test to see how audible amplifier differences are (try as I might, in blind A/B testing, I've never been able to consistently identify which is which...which right now comes in handy...because I know I'm not 'missing' anything...I don't have to pine over the now dysfunctional Hafler).

In fact, I had spent the last month or more pondering the sale of the Aragon amplifier.  Though it's clearly the 'highest end' working amplifier I own, I just didn't need it.  If anything, I thought the Hafler sounded slightly better overall (though not being able to prove I could hear this difference).  My sighted listening impression is that the Hafler sounds 'sweeter' (less distortion) whereas the Aragon sounds 'punchier.'  

I didn't need a backup amplifier, I was thinking, because the Hafler (unlike the Krell FPB 300 before it) seemed totally reliable.  I'd never had one of my two Hafler 9300's fail.  I thought they were virtually indistructable.

And now that I'm leaving the Aragon on all day, I'm thinking I might like it better.  It's got at least twice as much power and current handling capability (it has two 1100VA toroidal transformers, that's a total of 2200VA--too much for one Insteon switch to handle btw).  I'm feeling the extra bass punch and solidity, exactly what I'd been hoping to get from the newer speakers (and sort of did, but also with listening fatigue).

Both amplifiers have impressively wide bandwidth, I know it's 300kHz for the Hafler, I thought the Aragon was much less than that but in fact Secrets of Hi Fi and Home Theater reported 550kHz for the Aragon.  There is no indication of any early rolloff in the frequency response shown by Stereophile for the 8008 (regular model), though there is a slow rise in the distortion floor above 1kHz, nevertheless the amp exceeds it's 0.07% THD spec.  The Hafler does have lower distortion, but it hardly matters at these levels.  The Aragon gets high praise in all the High End Audiophile magazines, even The Absolute Sound, meanwhile the Hafler got high praise in Audio magazine (it SHOULD have been noticed more IMO, it was a sleeper).  The Aragon has the basic "good" design standard by the 1990's for bipolar amplifiers: complementary symmetry DC coupled with servo, not unlike the GAS Ampzilla of 1973, but with much better parts down to the teflon coated wire and high end circuit boards.  And massive heatsinks so it doesn't need a fan.  And the high bandwidth plastic transistors were a special limited edition from Toshiba before with extra fat die for elevated ruggedness on top of high linearity.  They ran out of replacements in the 90's, all you can get now are the more conventional variety.  Mine was in the earliest series that was contract built by a manufacturer in Connecticut that really knew their stuff, the circuit boards and everything look instrumentation grade.  Later Aragon had their own factory in California.  Then they were absorbed by Klipsch, then spun off a separate company again today.  Always in the niche right below the insanely high end.  Back in the 80's they were distributed by the same people as Krell, perhaps that's how the rumor got stated that Dan D'Agostino himself designed the basic 8008 series of amplifiers.  If there's any truth to that, it would have to be the cocktail napkin kind of design, where D'Agostino sketched out the basic design, and an engineer named Robbii did the detailed design work, his name is on the circuit boards.  I think it's more or less textbook as far as the basic amplification circuit, except the bias is probably simpler than the textbook kind which I think would be more regulated.  I don't think it's as finely tuned as something by D'Agostino, Curl, Pass, or another of the amplifier designer legends might have created.  But if you're not cutting corners, by the 90's it was fairly easy to do a top notch Class AB+ amplifier that would blow everything from the 70's away.  So this is the "value" high end amplifier with over-the-top high end parts and build but without the fancy designer label (though nowadays Aragon is plenty fancy).  And that's good enough, it doesn't take a one in 10 million genius to design a good audio amplifier, pretty much all you have to do is copy the one of the transistor manufacturer design examples, with a bit of fine tuning.  And if you're not pushing things to the limit, it's probably going to last longer too.

I met the Mondial (Acurus and Aragon) co-founder named Tony.  He showed me the Aragon in a back room of an audio meeting (after the Meitner amps had failed spectacularly in an audio meeting playing Apogees...they weren't supposed to be doing that and the store owner was pissed).  Tony bragged about how could stack stuff on the amp without issues and he even "warmed it up" the sound by putting a blanket over it for 15 minutes.  He was absolutely fearless about it, but I was scared to leave it covered that long so I took the blanket off a bit earlier, but indeed the sound was already warmer.  I've discovered the bias supply is very "flexible."  As the amp warms up, the bias goes even higher.  But if you put the amp on tall feet, as I did, you then give it "too much" airflow and the amp cools down and the bias goes down too.  So with tall feet I had to re-adjust the bias higher.  I've set it so that with the tall feet and nothing on top it runs at a perfect 125F after one hour where it measures and sounds great.  Balancing the heat of the two channels is essential too, otherwise they "cycle" pushing each other up and down.  There is incredible thermal mass and it takes a long time to heat up or change.  And of course if it gets too hot, it shuts down, or at least is supposed to, well before anything breaks.

I guess you could say this is "old school biasing" before Nelson Pass patented 'optical bias' went mainstream (btw, it's what made most later era Krell amps with plateau biasing possible, and I'm pretty sure it's used in Levinson and most other high end class AB amps).  Old school biasing has it's "advantages" in being kind of self-limiting, but it really needs to be adjusted for your exact situation to perform perfectly.  But then it does really well.  It's fairly easy to access the Aragon controls but not easy to get them set just right, to avoid cycling, etc, and depending on the height of the feet under the unit.

The Mondial founders were not themselves engineers, they were audio marketing guys who felt there was a missing niche just below the very high end they could sell along with other brands (which originally included Krell, which was sold by the same distribution chain) and not compete with them, by having more basic designs.

I've owned the Aragon 8008 BB longer than any other amplifier without any failures, and the way it's conservatively designed and built you'd expect that (but often don't get as much durability from the more prestige brands, which are often more like race cars needing pit stops after every lap).  So on top of everything else, the Aragon is a survivor.  At this point in my life, my system is all survivors, and I honor survivors.  (Some things survive because it's easy for me to get them fixed, others like the Aragon just keep on working, and that's good because fixing it could be somewhere between very expensive and impossible.)

I know really don't have to continue the speaker test in earnest, which in a way is a kind of relief.  The plans I had for moving everything in the house around to make way for another major pair of speakers are for the time unimportant.  Now I merely need to plan for the somewhat simpler storage of all the new speakers, and keeping the arcing pair out in an accessible way so I can work on it.

So here are my wins:

1) My most high end working amplifier has renewed its purpose, and I'm liking it better than ever.

2) I don't have to sweat all the speaker moves I was planning.

3) I get to tear down an electrostat speaker with no worries since it's already broken (unlike the clocks I took apart as a kid and into my teens).

4) I've learned to love my original pair of Acoustat 2+2's better than ever before.  They've stood high even against another pair of 2+2's.  And it's clear my slightly attenuated HF helps.  The default position sounds way too bright and becomes fatiguing.

5) Failure after failure, and my living room stereo keeps working and sounding better all the time despite them.

6) I'm finding that indeed the higher power of the Aragon 8008 BB makes it possible to play louder than I felt like doing before, and then it's magic.  To really appreciate this at first it may help to be drunk, as I was on the evening of December 25.  I had to move the Mapleshade damper back on to the Hafler to stop the rattling.  And the right channel of even my older 2+2's has a rattle at louder levels, even with my 8th order linear phase crossover.  Eventually I'm going to have to rebuild that too...  (I was hoping to THIS time around, but the new pair aren't a suitable replacement yet.)

I plan to continue to test the one new 2+2 that is not arcing, to see how similar I can get it to sound to my originals, etc, so I can use at least that one as a backup unit for now.

I not only fear that an arcing speaker could destroy the amplifier driving it (by sending spikes of HV back to the amplifier) it probably cannot sound as good, because the uniform charge of the panels is disrupted, causing distortion.  So not really worth further sonic testing.  Once it's arcing, it's over.  I should have known that.