Seems to me the whole debate is about efficiency which clearly favors class D vs class AB. The much neglected class H and G is also more efficient than class AB but never gets any respect. I own several amps of this class great sound no reliability problems, I wish they could be tested by Amir's measurement standards ( I am too far away to send equipment).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"?
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Vintage amplifiers that could challenge or approach current state of the art amplifiers
- Thread starter restorer-john
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Even within the classes there are distinct variations... and substantially different efficiencies...
Well designed (!) low bias AB designs can be very efficient - high bias AB designs (called various things... Quasi Class A, New Class A, etc...) can be almost as inefficient as pure Class A designs (sort of Class A with some AB headroom!)
But yes as a category - class D are more energy efficient.
Still my Class D amps idle at around 35W.... my Quad 606 idles at around 55W ... that puts them into the same order of magnitude, albeit with the advantage to the Class D - if either class of amp has some sort of auto-standby circuit... the one with that circuit will end up having the advantage (neither of them do in this case!)
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.
Well, it took me a while to send one in for testing but better late than never.
https://www.audiosciencereview.com/...kenwood-l-05m-vintage-amplifier-review.43409/
SirPaulGerman
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I was able to get a vintage Crown D-150A for $40, works fine, very heavy, and sound good too.
There is a review, and the tech did a good job measurement the amp
The amp was released in D 150A (1975-1985)
Can someone tell me if the amp get good numbers after all ?
There is a review, and the tech did a good job measurement the amp
The amp was released in D 150A (1975-1985)
Can someone tell me if the amp get good numbers after all ?
mhardy6647
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Well, the A may (??) be better than the original, unsuffixed D150 -- they're bulletproof ("Built missionary tough!"
) but kind of dreadful for hifi. Probably less dreadful than the DC300, though, so there is that.It is less horrible than the original, unsuffixed IC150 preamp, though. So there is that, too.
Note that this is not an ASR-approved critique!
Difficult to tell, because, per the comments visible on the FFTs disclosed in this video, A weighting was applied during the measurements.
This type of weighting could mislead the evaluation of the noise or distorsion performance of an amplifier and, in any case, weighted measurements are not directly comparable with unweighted ones.
If you are going on a "for the money" deal, I would say "OK". & run mono would be better from a power perspective. But 13 bits is not even CD quality (my ACVENT 300's amps tested at that (but I only use it as a preamp for my NAD 2100's [whose specs we do not actually know].
If you want at least CD quality you need something that can do 16 bits of better.
Like my APT/Holman PREAMP's and my NAD 2200's.
SirPaulGerman
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THD+N is running around -80 dB or about 13 bits dynamic range at about full power. That is still pretty good, considering your speakers are likely adding much more distortion than that. SNR is a little better than 100 dB so reasonably quiet though not exceptional. The Hafler preamp shouldn't add significant noise or distortion so a good match. When these were made, <0.05% THD was pretty good, especially for a pro amp, so enjoy it.
Just after 16:20 in the video he states that the multi tone tests on the amp shows 13 bits of distortion free dynamic range and then say the same thing for the 2nd amp.
That MAY be enough if you are using a Turntable as a source. It is definitely not enough if you are using a CD (or most other digital stuff) as a source. For a CD, you need 16 bits of distortion free dynamic range to hear it all. So that is a minimum requirement.
That is not to say that it wont play good or sound good. It just means that you will not get the full dynamic range that the source is capable of.
My CD stuff using my ADVENT 300 still sounds good, but it sounds more immersive on my better system.
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I presume that It depends on the rest of your system as to whether you can hear that you are not getting the full dynamic range ( I could be wrong, I have been wrong before, just ask my wife)..
As with my ADVENT 300, it did not sound, in any way, BAD. But when I changed my amps from the internal amps to the NAD 2200's, I got more low BASS and it just sounded like there was more frequency range. It turns out that there is, with a more wide FR range
That was the impression that I dot from Amir's review of my ADVENT 300 (and I also changed to the APT/Holman Preamp)
Advent Model 300 Vintage Receiver Review
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DSJR
Major Contributor
Ken Rockwell measured a used Crown D-150A in mk2 guise and didn't find it wanting at all!!! My earlier D-150 is absolutely silent, low DC offsets still in spec, runs cool even after a good session and the once vaunted high 'damping factor' keeps old UK designed 'porty boomer' speakers (including window ratttling old IMF transmission lines) well under control
Crown D-150A Series II Review & Lab Measurements by Ken Rockwell
Crown D-150A Series II Review & Lab Measurements by Ken Rockwell
www.kenrockwell.com
Surely the sinad results on this nearly 50 year old design aren't bad at all? Only thing which dates it perhaps is that current limiting becomes intrusive at 4 ohm loads and below and a 'Choice' test on the slightly earlier satin finished 150A showed some IM components if pushed over 20kHz if I read it right, again I believe a factor of the limiting designed in against abuse professionally. The manuals were again an object lesson from times gone by and servicing is still easy should it be needed.
The mk1 amp I have is cap coupled on the input but the 'A' version isn't it seems. Also, mine has a solid metal shroud around the driver circuit rather than a 'mesh' type and bridging was done with wire links made and soldered in I recall). the official mk2 turned the existing 150A upside down and fitted a new front panel, but apart from that I don't think there was much difference apart from 5% resistors being used more I think where mine is mostly 10% carbon apart from critical feedback resistors which are 1% (mono switch on the back).
I think I posted it earlier, but here's my tatty looking one from the ad I bought it from (it's still online somewhere). It'll never win a beauty contest
, but it does the job so well when driven from the IC-150 (easy to hear different recording techniques)P.S. If anyone can find the originally optional front panel for the original D-150 I'd be very grateful as I prevaricated over the last one I saw on offer (fifty quid or so shipping from the US) and missed it
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SirPaulGerman
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Got another Crown gear to match the D-150AKen Rockwell measured a used Crown D-150A in mk2 guise and didn't find it wanting at all!!! My earlier D-150 is absolutely silent, low DC offsets still in spec, runs cool even after a good session and the once vaunted high 'damping factor' keeps old UK designed 'porty boomer' speakers (including window ratttling old IMF transmission lines) well under control
Crown D-150A Series II Review & Lab Measurements by Ken Rockwell
Crown D-150A Series II Review & Lab Measurements by Ken Rockwellwww.kenrockwell.com
Surely the sinad results on this nearly 50 year old design aren't bad at all? Only thing which dates it perhaps is that current limiting becomes intrusive at 4 ohm loads and below and a 'Choice' test on the slightly earlier satin finished 150A showed some IM components if pushed over 20kHz if I read it right, again I believe a factor of the limiting designed in against abuse professionally. The manuals were again an object lesson from times gone by and servicing is still easy should it be needed.
The mk1 amp I have is cap coupled on the input but the 'A' version isn't it seems. Also, mine has a solid metal shroud around the driver circuit rather than a 'mesh' type and bridging was done with wire links made and soldered in I recall). the official mk2 turned the existing 150A upside down and fitted a new front panel, but apart from that I don't think there was much difference apart from 5% resistors being used more I think where mine is mostly 10% carbon apart from critical feedback resistors which are 1% (mono switch on the back).
I think I posted it earlier, but here's my tatty looking one from the ad I bought it from (it's still online somewhere). It'll never win a beauty contest
View attachment 281982
View attachment 281983
P.S. If anyone can find the originally optional front panel for the original D-150 I'd be very grateful as I prevaricated over the last one I saw on offer (fifty quid or so shipping from the US) and missed it
A Straight Line One preamp for $75, is a op amp design with 5532 op amps
Crown Straight Line One Stereo Preamplifier Manual | HiFi Engine
Professional review of the original D-150 amp 1972, just for fun
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DSJR
Major Contributor
Well done for $75 - I'm green with envy The SL1 looked a bit too plain I think in the rise and rise of inferior ARC models which were catching the US enthusiast market's ears with their warm charing sound processing (the IC-150 was said to be fingers down a blackboard, yet mine is sonically transparent when inserted into a straight through chain). My IC-150's have 5532 op amps in and there were four 1uF tantalums on the input which were recommended to be replaced.
The SL1 looked a bit too plain I think in the rise and rise of inferior ARC models which were catching the US enthusiast market's ears with their warm charing sound processing (the IC-150 was said to be fingers down a blackboard, yet mine is sonically transparent when inserted into a straight through chain). My IC-150's have 5532 op amps in and there were four 1uF tantalums on the input which were recommended to be replaced.SirPaulGerman
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Do you have the https://www.hifiengine.com/manual_library/crown/ic-150.shtml / ?Well done for $75 - I'm green with envy
DSJR
Major Contributor
Yes thanks, including an original which came with one of mine
I'll need to slim it all down before to long as I have two bridged pairs of D-60's (lovely little amps these and the forerunner to the D-75), a straight stereo D-60 which makes for a deafening and devastating headphone amp, two and a half IC-150's (the half is a bitser) and my beloved tatty old D-150 in need of dressing up. Thanks for the reviews - I need to do work on the delayed muting which doesn't on one of mine for some reason. I have my beadies on a good order DC300A mk 1.5 I know (produced just before the restyled mk2 came out) and love it to bits but it may not be as good at lower volumes these days (no idea really)
I'll need to slim it all down before to long as I have two bridged pairs of D-60's (lovely little amps these and the forerunner to the D-75), a straight stereo D-60 which makes for a deafening and devastating headphone amp, two and a half IC-150's (the half is a bitser) and my beloved tatty old D-150 in need of dressing up. Thanks for the reviews - I need to do work on the delayed muting which doesn't on one of mine for some reason. I have my beadies on a good order DC300A mk 1.5 I know (produced just before the restyled mk2 came out) and love it to bits but it may not be as good at lower volumes these days (no idea really)
Hi i am impressed by the low number of active parts of this amp that fwiu sounds also very good indeed
I've always wondered why so many projects use so many transistors when very good results can be obtained with fewer parts
As far as features go I think low noise and distortion is always a good thing
Rather, we need to keep in mind that a loudspeaker can be a rather difficult load and undermine an amp that is not robust enough from an electrical point of view
A vintage amp that must have been exceptional (unheard unfortunately) is this one
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