The Carver Amp Challenge and the 21st Century and it's Failure


Some of you may be old enough to remember this article from Stereophile. Bob Carver claimed he could make an amplifier audibly indistinguishable from some of the best from Conrad Johnson. A high efficiency (not class D), solid state linear amp vs. a linear tube amplifier.


https://www.stereophile.com/content/carver-challenge


Carver's approach was to feed a speaker via both amps at the same time using opposite terminals. The speaker itself was the measure of accuracy. Any difference in output between the two amplifiers would cause audible output.


What's super important here is Carver invented a new way to measure the relative difference of amplifiers with a real load.


That's kind of revolutionary from the standpoint of commonly published measurements of amplifiers before. Steady state, frequency sweeps, THD, IM and S/N all failed (to my ears) to express human experience and preference. I remember a reviewer for Audio, I think Julian Hiirsch, who claimed that these primitive measures were enough to tell you what an amplifier sounds like. The man had no ear at all, in my mind.  More here:


https://www.soundandvision.com/content/reconsidering-julian-hirsch

And here was Carver in 1985 cleverly showing that two amplifiers which measured reasonably well, sounded differently. We should also be in awe of Carver's ability to shape the transfer function on the fly. That's pretty remarkable too but not the scope of this post.


My point is, really, Carver showed us a revolutionary way to examine differences between gear in 1985 and yet ... it did  not become widespread.  << insert endless screaming here >>


As far as I know (and that is very little) no manufacturer of any bit of kit or cable took this technique up. We are still stuck in 1985 for specifications, measurements and lack of understanding of what measures cause what effects and end up cycling through cables and amps based on a great deal of uncertainty.


My points, in summary:

  • Most of what we consider state-of-the-art measurements are stuck in the 1970s.
  • There are a number of ways to improve upon them
  • No one has.
  • We should be a little more humble when asserting if it can't be measured it isn't audible because our measurements are not nearly comprehensive
  • I look forward to manufacturers or hobbyists taking modern equipment to pursue new measurement and new insights into our hobby.


Best,
E


erik_squires
lowrider57" I’ve read the stories where Bob was considered a showman or a barker. I can see how those in the industry resented that. Also, his history of company ownership raises concern about the future of his current highly regarded tube amps. Will there be any authorised service when he hangs it up?"

It is not likely that is why all of his companys have gone "belly up" as Americans say.
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The issue behind us hard nosed business types is that designing a reliable product, the real engineering work.. which is viewed as boring to many IS key to long term survival....

Bob and his now rather extensive lineage of products and companies in the wake, do not have a reputation for longevity or reliability.

as an aside, we were a very early PS Audio dealer - they offered quirky products, oversized power supplies, frequently great sound for $$$ and I remember only one amp and zero preamps in the service department.

i could set my watch for Tuesday morning Frat boys dropping off the Phase 400 for a weekly fix....

about a 2 week break even payback to switch to a Hafler DH-200 and 4 weeks for a DH-500

we sold a bunch of those....

no hate at all...

as I said, hope the 75 is a sweetheart !
Seriously the speaker null part of the test is essential IF you really want to move the ball, just don’t pick a lame easy load... back EMF, phase angle, reactive and reflective impedance.... none of that shows up in the “ Julian Hirsch “ testing.....

give that null test some thought...

start with an Apogee... pair of em....
And.... the humble LiL CC2 circa 1978 inspired by dr Ottala can drive the nasty 3 ohm stage......