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Vintage amplifiers that could challenge or approach current state of the art amplifiers

sergeauckland

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Never heard of this before - very cool, and thanks for the link!

Two comments/questions from reading the spec sheet:

1. Feedback. It appears to be a high-feedback design, yes? It says it uses 80dB of feedback, and the voltage gain goes from 14dB all the way up to 30dB with "reduced feedback," suggesting that the feedback must be significant if it reduces the output that much. Thus feedback would seem to be a major factor in reducing the distortion, and goes against - or I would presume pre-dates - the audiophile distaste for feedback, especially among folks who would seek out tube-based gear. (To be clear, I'm not anti-feedback myself.) Very interesting.

2. Gain. The voltage gain figures are interesting, and I wonder if anyone more knowledgeable than me can translate them into more of an apples-to-apples comparison with modern gear. The stated gain is 14dB, which is very low, but that's into a 16 ohm speaker - would the voltage gain increase into a more typical 4 ohm or 8 ohm load?

1. Feedback.

Negative feedback when properly applied is always A Good Thing. It reduces distortion, widens bandwidth and reduces output impedance.
The anti-feedback sentiments I view with the same distaste as anti-vaccination sentiments, wilfully ignorant idiots who don't understand the science or technology, and what's worse, don't want to understand. Finger in ears, La La La......

2) Gain.
A Valve amplifier with transformer taps adjusts the output voltage to provide the rated power into the specified load. To provide 50 watts into 16 ohms takes 1.4x the voltage as 50 watts into 8 ohms. So, the gain would be 3dB less, but could be the same if the feedback is also changed to match.

14dB gain (5x) means a voltage sensitivity of 4V for 50 watts which is high by the standards of the time which were typically 1V or less, even as low as 150mV. However, sensitivity is switchable to 30dB , so the 50 watts output would be achieved with 630mV input.

Great amplifier!

S.
 

Adam Bernau

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kevinh

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Never heard of this before - very cool, and thanks for the link!

Two comments/questions from reading the spec sheet:

1. Feedback. It appears to be a high-feedback design, yes? It says it uses 80dB of feedback, and the voltage gain goes from 14dB all the way up to 30dB with "reduced feedback," suggesting that the feedback must be significant if it reduces the output that much. Thus feedback would seem to be a major factor in reducing the distortion, and goes against - or I would presume pre-dates - the audiophile distaste for feedback, especially among folks who would seek out tube-based gear. (To be clear, I'm not anti-feedback myself.) Very interesting.

2. Gain. The voltage gain figures are interesting, and I wonder if anyone more knowledgeable than me can translate them into more of an apples-to-apples comparison with modern gear. The stated gain is 14dB, which is very low, but that's into a 16 ohm speaker - would the voltage gain increase into a more typical 4 ohm or 8 ohm load?



Remember he is using a output transformer so the number as you change the tap for the speaker output, the number of wire turns on the secondary changes.

BTW Dick Burwen designed some of the origianl modules for the Mark Levinson LNP 2 Pre Amp and later the Cello Audio Pallette for Levinson, which was based on an EQ he build to adjust recording on his own systems. 20 years he Built a software version of the Audio Pallette, Since he is now ~90 he liscensed the software to Levinson who markets it though his Daniel Hertz company.
 

Sal1950

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Nice! I own a 535 and 5400 and enjoyed both for many years.

According to this Ken Rockwell review, which includes plenty of measurements, it's a killer unit:

https://www.kenrockwell.com/audio/adcom/gfa-555-ii.htm

He reviewed the MKII version, but it's likely the original (which has a more vaunted reputation) measures very similarly.

I was also struck that the 555 he reviewed measured notably better than the 545 and the two 535s he also measured.

Only issue I'm aware of with these old Adcom amps is that they lack speaker protection.

In fact, aside from a lack of speaker protection (and the mechanics of the power switch, which apparently has a habit of going south), I would think this amp would tick all the boxes for the subject of this thread - it provides gobs of low-distortion power and an argument can be made that in terms of specs it's close enough to modern state of the art to be similarly audibly transparent.

@restorer-john , I hesitate to even ask, but would you agree that this is one of those amps that "could challenge or approach current state of the art amplifiers"? It seems like it is, yes?

The only historical knock I've seen on this amp is a series of subjective reports that it sounds "dry," "etched," or "unrefined." But surely that kind of subjective claim wouldn't disqualify an amp at this forum, yes?

I've got 2 545 Mk2s & 1 5400, powering the base speakers of my 5.2.4 system and 2 535 Mk2's powering the 4 ceiling Atmos speakers.
They've been my "go-to" SS amps for 30 years and there's no audible reason at all (IMHO) to change to something else. Only negative thing I can say is to bring up the little crackling sound 535's make when you shut them off, I've had 4 different ones over the years and they all do it. LOL. I avoid any power switch failures by using a trigger cable switched power strip to control them and leave their power switches on. One of Nelson Pass's best designs ever, done before his brain and wallet went High End. LOL
 
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Vear

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My vote goes to my Sansui AU-X1 seen here with my other favorite amp. You would be amazed.


My Kenwood/Trio L-05M mono-blocks would get my second vote for this thread. I won't risk shipping my AU-X1 to @amirm but I would probably be willing to send him the L-05M's sometime later this year.

The L-05M are high speed/bandwidth and are basically the 100W versions of the L-07MII (which were 150W). The specs of the original L-07M were not as aggressive as the later L-05M or L-07MII.

 
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cjfrbw

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All these pages and no mention of Yamaha B2 VFET? Yes, it definitely challenges modern amps in sound quality, it is hypnotic to put a word on it.

My Sample, all original (except for VU meter LED), sounds amazing:
IMG_0522.jpeg


I have a Yamaha MX 600u, too, that is also all original, powers some surrounds speakers. It sounds OK, but nothing approaching the B2.
 

anmpr1

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All these pages and no mention of Yamaha B2 VFET? Yes, it definitely challenges modern amps in sound quality, it is hypnotic to put a word on it.
I recall the big splash these made in the hifi world. I also recall a brief demo with, I believe, a speaker known as the Ultralinear, whose drivers were supposed to be 'time aligned'. The dealer switched between the B2 and an SAE amplifier (don't remember the model, most likely post Bongiorno, I'm sure). FWIW the B2 sounded much clearer than the SAE. I don't however recall the other associated gear. Probably the companion Yamaha preamplifier.
 

Radixons

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Rated THD of 0.02% and Crosstalk at -60dB doesn't seem to challenge or approach current state of the art.
Agreed. Later versions such as the Hafler DH-220 or the Hafler LX280 fare better on paper. However, even the original DH-200 is a very musical sounding amp that can hold its own when the testing equipment of choice is our ears and real speakers rather than 'objective' figures obtained from testing equipment simulating perfect loads. All the Hafler amps are able to drive difficult real-world loads, the XL280 down to 1 ohm even. Listening to one as I am typing. The exact amp is presented here: https://eiaudio.de/gear-and-review/power-amplifiers/hafler-xl-280#share
 

Radixons

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You can't say "every single parameter" and then say "not zooming in on a singular measurement, but looking at the big picture" - that's sophistry. It's saying you will discount whatever you don't like by pointing to a single parameter - regardless of whether it's actually relevant to performance - but then on the other hand you will hold up whatever you do like by "looking at the big picture" and not focusing on any particular measurement.

The fact that Class D is measured with an ultrasonic filter is well-known and the reason is well-understood, including by you, and you know full well it has nothing to do with poor design, poor engineering, or audible issues. It's a feature of the design topology. If you don't like it, that's your prerogative. But your unending beating of this very dead horse is silly on a forum like this one.

And you are straw-horsing Class D proponents by claiming they say no measurement above 20kHz matters when you know full well that is not true. The ultrasonic noise is up around 400kHz in most cases. Amir and most others here would no doubt raise an eyebrow at an amp that had major noise at 30 or 40kHz.

Similarly, you know full well that Class D amps have smaller power supplies and usually smaller and lighter-weight casing because of the nature of the topology: they use switching supplies and they don't need the same kind of heat-sinking. You might not like their "toy" appearance and weight, but it doesn't mean they're unreliable or poorly engineered. A Radio Shack amp from the 1980s that was small and inexpensive was indeed a very low-power device with limited bandwidth and relatively high distortion and noise, because it used (as far as I know) a traditional Class AB topology and such a topology is difficult to impossible to make high quality in such a cheap, small, and light package. (Not ragging on Radio Shack - it's just that when I was growing up in the '80s their catalogue was the main place I saw little 12" wide, 10wpc Class AB amps for $129 - and I remember the specs were not what one would call hi-fi). But a different topology can perform well and be robust in such a package.

Now, where you are no doubt correct is that Class D amps cannot and do not produce their rated wattage in a fashion that you, I, or most others here (at least those of us of a certain age :) ) would call honest or what we expect from hi-fi equipment. A "400 watt" Purifi or Hypex module is rated that way into 4 ohms, whereas most vintage hi-fi gear of the '70s and '80s was sold based on watts into 8 ohms. And as tested by Amir, the Purifi module produces "only" 257 watts into 4 ohms and 131 watts into 8 ohms - at 0.0002% distortion! (And something like 275 and 170 respectively if one uses 0.01% as the distortion limit.)

If I showed you a Class AB amp that produced more than 125wpc of continuous, ultra-clean signal into 8 ohms at 0.0002% THD, and fully doubled its output to more than 250wpc into 4 ohms with the same ultra-low distortion, you'd be thrilled and declare it a superb design.

Your analysis here is motivated by your bias against Class D as a topology. Your knowledge is impressive (to say the least!), but your arguments here are just a fancy version of, "no amp that weighs just a few pounds and produces noise at 400kHz can be any good."

Finally, let me be clear - I love a good vintage amp. Give me an Adcom GFA-555 or 5800 and I'm happy. But the entire point of the subject you've devoted this thread to should be to identify which vintage amps actually deliver(ed) the goods in terms of specs to compete with high-performing amps of today. You keep saying such amps exist - and I certainly believe you - but you keep saying "they're scattered around the world," "I'll have to post some measurements," "some are great but not good candidates for this list," "xyz amp is essentially perfect except for its high noise," etc.

If it's this hard to actually identify a vintage amp that measures sufficiently well in "all the important parameters," doesn't that suggest that there are few if any commonly available, or easily/affordably purchased older amps that can "challenge or approach current state of the art"?
Similarly, you know full well that Class D amps have smaller power supplies and usually smaller and lighter-weight casing because of the nature of the topology: they use switching supplies and they don't need the same kind of heat-sinking.
To be honest, with me it is not about the weight or dimensions, but I am feeling a little troubled just reading the words 'switching power supply'. In my personal experience such technology has very little in common with an audiophile listening experience. For example, I had quite a bid of noise on the power grid despite running a dedicated power cord. It turned out that 50% of this came from the DAC's switching power supply. I replaced it with a 100 VA linear power supply and guess what... Switching power supplies might be good for shipping costs and for the energy bill, but they tend to mess up the sound.
 

Radixons

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Perhaps I will. Mint condition not as important as unmodified condition to me. Anytime I see a mod performed (or even a recap advertised bringing something back to original glory) - nope. A-717 flies under the radar.
One would think we can be grateful to people who respectfully restore vintage gear so that folks like me can have the pleasure of having them around. Not everyone has the means or skills to restore them on their own. In fact, most of the equipment I ordered used needed some help one way or another. Replacing or even upgrading old caps only has advantages as far as I can see, for as long as the people doing the repairs know their stuff.
 

Radixons

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What about B&K amps ? I've heard that some of their model are great like 4420 reference.
I am really happy with my B&K ST-140. They are not very well known here in Germany, and the specs do not reveal its virtues, however, on our Martin Logan SL3s the 105 watts revised version of the amp performs really well. If anything were to happen to it, I think I would look for it again. https://eiaudio.de/gear-and-review/power-amplifiers/bk-st140#share
 

Harmonie

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Before that Brinkmann started his own company, he was part of the team of company Audiolabor with reasonable mono blocks Schnell .
Audiolabor Schnell monoblocks.jpg
 

eddantes

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Haven't owned one - but this documentary makes a heck of a case for Perreaux

 
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LTig

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To be honest, with me it is not about the weight or dimensions, but I am feeling a little troubled just reading the words 'switching power supply'. In my personal experience such technology has very little in common with an audiophile listening experience. For example, I had quite a bid of noise on the power grid despite running a dedicated power cord. It turned out that 50% of this came from the DAC's switching power supply. I replaced it with a 100 VA linear power supply and guess what... Switching power supplies might be good for shipping costs and for the energy bill, but they tend to mess up the sound.
Nope. As long as power line noise does not creep into the analog electronics (filters prevent this) you need not worry about SPS.
And since more and more SPS are used in all kind of electronic units in ones household we all have to live with them and better get eqipment which is able to deal with power line noise.

OTOH transformers in big linear PS induce hum into the surrounding analog electronics. This is especially problematic in high gain preamps for MM and MC pickups.
 

Radixons

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Nope. As long as power line noise does not creep into the analog electronics (filters prevent this) you need not worry about SPS.
And since more and more SPS are used in all kind of electronic units in ones household we all have to live with them and better get eqipment which is able to deal with power line noise.

OTOH transformers in big linear PS induce hum into the surrounding analog electronics. This is especially problematic in high gain preamps for MM and MC pickups.
Yes, agreed. Hum from linear supplies can be problematic for phono, and this is 50% of my music. And meanwhile there are ways of lessening this effect, such as proper grounding, etc. When it comes to digital amps, I can only say that I have personally never heard one that could compare with a class A Mosfet in a clean setup. The deviation I could hear sounded like the noise from my DAC's switching power supply. My own experience is limited, of course. It is well possible that this has meanwhile been solved. Which amp would you recommend that I try?
 

Radixons

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How's about Crown D75/D75A? Aside from a bit of transformer buzz...

Then there was DB Systems: They were promoting measured performance before it became unfashionable. Never got to sample their wares but they still exist in some capacity:
https://www.dbsystemsaudio.com/
DB Systems is better known for their preamps, I believe. I am still very happy with my DB1 preamp + DB2 power supply combination. Of their large mono amp DB-6A-M even photos are hard to find.
 
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