Well done Bill, brought back a flood or memories, good, bad and downright ugly. Many thanks for these informative postings.
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Drove a friends Testarossa about 3 weeks ago. Soon learned that a greybeard and a Ferrari is not a good match. Forgot how things happen so quickly in a Ferrari, my reflexes at 67 now can't keep up with what it takes to own one now. But at least have good memories of the one I had and it was marvelous. Nothing sounds like a V12 a full song. High end audio pales in that comparison.
....Time it was, and what a time it was, it was
A time of innocence, a time of confidences
Long ago, it must be, I have a photograph
Preserve your memories, they're all that's left you
And a pair of A-25s still working perfectly.
The greed of audio industry forced music lovers to walk away. Hopefully, the greed of today's manufacturers of $500 throw away items will lure music lovers back.
What is needed is NEW audio industry, offering awesome products for fair prices, like Dynaco and Hafler did.
Well, you guys left out a few things and need a minor correction. Regarding the speakers, the A-25 did not vent internally; there is a horizontal vent at the bottom of the front panel. The A-50 was divided into two chambers and was internally vented. I don't know about the others. Supposedly, each A-25 was "stuffed" while the assembler was looking at something that measured the "back EMF" from the speaker. The idea was to minimize that value. In more modern terms, the impedence peak characteristic of all speakers was reduced. In yet another fit of misplaced zeal, JGH gooshed over the A-25, claiming that its bass went lower than the AR 3a -- the gold standard of the time -- claiming that the A-25 was "flat to 30 hz." The statement is utter nonesense. The A-25 doesn't have anything below 50 Hz. That said, it is a much better sounding speaker than the AR-3a, which, despite its superior performance at the frequency extremes, has a rather discontinuous sound. The A-25 is a great example of the design principle of "get the midrange right and the rest will take care of itself."
Among the tube classics produced by Dyna was the FM-3 vacuum tube stereo tuner. Using the "tuning eye" tube, the home builder could align and adjust the tuner to meet it's specs without a signal generator or a 'scope. The FM-3 wasn't the most sensitive tuner out there, but featured a very steep quieting curve, so in the typical urban or suburban environment, it was very quiet. Of course, it had the classic "tube sound" of soft bass and gentle highs . . . but it was very musical, like the rest of Dyna's tube gear.
Contemporary tests of the time showed that the Stereo 120 did meet its specs, in compliance with what would become the FTC standard (other than the 1/3 power thermal-stress preconditioning period). It had a fully regulated power supply. The Stereo 80 had an unregulated supply, so it would equal the stereo 120 on transients, but had a lower continuous power. Oddly, and perhaps because of the difference in power supply, the Stereo 80 sounded better.
Julian Hirsch's gaga review of the Phase Linear 700 was not based the AR-3a, but on AR's "LST" which used the same woofer as the 3a but multiple midrange and tweeters from the 3a on a faceted cabinet. It was even more inefficient than the 3a, but unlike with the 3a, the non-ferrofluid cooled tweeters and dome midranges would not blow up under higher power. Hirsch's comment at the end of the review (having discovered the virtues of avoiding the dynamic compression inherent in driving such an inefficent speaker with a modestly powered amp) was "I wonder if 700 watts is enough?!!"
Bob: whould've thought we'd reach the point where $500 constituted "throw-away" territory? Clearly, I'm gettin' old.
Bruce: I recall Hirsch's comment, and given those speakers, he probably could've used another kilowatt or two.
You are of course correct about the A-25's vent; late-night writing sometimes makes for stupid mistakes. Likewise, the LSTs: afraid my decades of Stereo Review copies disappeared a decade again. My bad.
Thanks for taking the time to comment,guys!
thanks again for a great series Mr Bill
Bruce: were the ST80 and ST120 basically the same amp with different power supplies? If true, it's not all that surprising to me the 80 sounded better, albeit a lower RMS power rating. I've always asserted that the output stage power supply should have as low impedance as possible, and that "enhancement" (via regulation) only serves to raise the supplies' output impedance, thus degrading the amp's sonic signature.
I've been playing with Dynacos since I first got into this hobby - having started with the venerable Dynaco 70. I've owned 'em all except for the Mark VI... tons of fun to modify and a great way to learn circuits.
As I type this, I'm listening to a refurbished Dynaco ST-80 being driven by a modified Dynaco PAT-4. State of the art? Hardly, but it still sounds better than I imagined they would! A nice system for the family to play with while I get the expensive toys - heh.