The Carver Challenge

Bob Carver challenged the audio industry to a sonic shoot out saying he knew how to make any amplifier sound the same. What happened?

[bluesky]

I met Bob Carver a number of of years ago. We were visiting my older brother, who lived off of Puget Sound in Washington state. I talked him into driving out to Woodinville to the Carver factory.

Upon arrival, we walked in and asked the receptionist if it would be possible to meet Bob and get a tour. She told us to hang on a second and then proceeded to yell across the room to the open office behind us, "Hey Bob, these guys would like to meet you!" We turned to see Bob in the office with his chief engineer. He waved us in and we sat for almost an hour chatting about amps, sonic holography, and everything else hifi.

I told him about some issues I was having with my C-4000 preamp. Bob said, "Send it back to us and we'll update it to the latest specs. We'll cover shipping both ways." After recovering from that, he had this chief engineer take us on a tour of the factory. We saw everything except Bob's private lab.

We finally left a couple hours later. I will never forget that day. Along with the C-4000, I had a couple of his amplifiers and his FM tuner. All sounded fantastic. I wish I still had them all.

[tristanjones]

good old bob carver. If he were stuck on an island, he could probably build an amp out of coconuts and wilson volleyballs.

[Shred_Rocket]

I met Bob years back at an audio show in Scottsdale, AZ. He took time from the rest of the crowd to chat with me about technology the way he saw it, a fascinating individual. I ended up purchasing a subwoofer that was being promoted and Bob happily signed it for me. I still have it to this day!

[spectrelayer]

PM: Always interesting to hear your take on various subjects. I too was "there". This stunning stroke of marketing brilliance was accomplished because Bob is an "agnostic audiophile". In other words, he doesn't believe in "ineffable magical hi-fi unicorns" nor the boasts of the “SnobbyOphile class”. He is a brilliant scientist and it is his broad background in PHYSICS that gives him the intellectual scope to see in his mind's eye what mere electrical engineers cannot (because electronics is a mere SUBSET of PHYSICS).
Carver essentially knew that ALL amplifiers color the sound in subtle ways due to their implementation of components which have traits that are always a bit more complex than their schematic symbols let on. Consider the number of capacitances & inductances exhibited internally by ANY FET, for example. Taken in aggregate, these nuances that affect a signal give an amplifier its unique, subtle sonic fingerprint - which Bob refers to as the amplifier’s "Transfer Function".
In the “Carver Challenge”, what Carver did IN HIS HOTEL ROOM, was to measure the TRANSFER FUNCTION of the amps he needed to duplicate the sound of. One amp was a $5000 Conrad Johnson tube model if memory serves. Once Carver had derived a behavior of the target amps transfer function, - he proceeded to build a line-level filter out of components that he had brought into his HOTEL ROOM & that filter had a number of variable components on it that he used to tweak it - in order to match, extremely closely, the transfer function signal dynamics that he needed to duplicate.
Testing the design consisted of NULL measurements at the output stage of his amp (out of phase) with the target amp. When the speakers went silent playing test signals – he knew that he had matched the transfer function of the target amp & then implemented that bread-boarded TF-filter into the signal path of his amp. The ultimate result is history & a stunning display of the “audiophile’s ultimate lesson in humility”. Carver won the challenge and it was published far & wide (which is why 4+ decades after the fact – we’re still talking about it)!
Then is a stroke of marketing brilliance, Carver designed the “spared no expense” SILVER SEVEN TUBE MONOBLOCK AMPLIFIER. This monster/masterpiece would set you back $12, 000 (& you needed 2 for stereo). Well, the reviews were stellar. “Audiophiles” were in near consensus that the Silver Seven was a triumph of audio engineering (And sadly [sniff] priced out of the reach of the masses). And then, Carver did the unthinkable to the SnobbyOphile, eh, audiophile elitist class (those better-thans who had $24 grand to drop on Carver’s Silver Seven): He duplicated its TRANSFER FUNCTION into his ultra-powerful, solid state “magnetic field power amp” design. Hence the Carver M 4.0t (the “t’ denotes ‘transfer function’) was born (for about $700 if memory serves)! And that $700 got you BOTH channels! And since Carver had already PROVEN that he could duplicate a transfer function of any audio amplifier in the infamous “Carver Challenge”; - he now could claim, with unchallenged confidence, that the M4.0t at $700 sounded INDISTINGUISHABLE from his $12, 000 (eh, stereo configured $24, 000) Silver Seven Tube amp! I can almost hear their hell-tormented, narcissistic screams as the SnobbyOphiles realized that Carver had completely OWNED them – not once, but twice (& that their boast of owning the most superior amplifier was now a boast that virtually anyone with $700 or a credit card could make)! And that, was poetry.
BTW: Bob Carver was MY inspiration also. He proved what understanding the nature of THE SIGNAL could accomplish. And today, my venture is using proprietary tech (such as AI) to demonstrate just what artfully manipulating an audio signal can accomplish. Interested? 5mash my !con.

[strayspark]

i worked at Carver for about 2 years right out of high school. it was one of my 1st jobs. i read all their material with all these null tests, the Carver Challenge. it is a strange feeling to hear all this stuff so many years later. i have stories but i dont think anyone is going to see this shall see....shadowban

[rbm]

I worked in Carvers design office for a summer in the early 90's. My drafting board was right next to gear room. Fun geeking out everyday surrounded by audio gear and doing my bit to support the engineers with testing prototype amps.

[keithallsop]

What Carver was really doing was establishing that measurements define and characterize the sound, but doing it in a cute competitive way that subjectivists thought must fail. Very smart.

[stimpy]

I owned a phase linear 400 amplifier so many years ago and I was thrilled with the way it drove my Dahlquist speakers. Then one day I decided to buy an Audio Research D-76A. I never tried to compare the sound of the two against each other but there is no question to my ears that the audio research was a much more musical amplifier. Carver is a true genius in this industry and always has been and I tip my hat to him for everything that he’s given to our community.

[mddawson]

The first challenge amp was a Conrad-Johnson Premier Four which Bob successfully duplicated its sound and sold as the Carver M1.0t. The second challenge amp was a pair of Mark Levinson ML-2 mono blocks that Bob duplicated the sound in his Carver M1.5t.

[brucermarino]

Thanks, Paul. I remember following all the craziness around this. He did what he said and made his amp indistinguishable from others. It's just physics, engineering, and psychoacoustics. He put the litter to all the marketing nonsense about power cables (which can be pretty), the tube sound (which i like :), power conditioners (sorry Paul :(), etc. Most of all he was an economic threat to our beloved hobby. Good testing can go along easy to protect our sanity and wallet. That's why it is done so little. Thanks!

[billfarrell]

I was lucky enough to talk with Bob this past year and it was a pleasure, so friendly, I am a Carver fan and own his 350 watt tube mono blocks and a C11 preamp with sonic Holograph, if you never heard sonic holograph, you need to try it just so cool. Also his tube amplifiers will drive any speaker and the sound signature is so smooth and refined. Everyone has a different taste when it comes to sound that’s why it’s so hard to say one system is better than another. Hats off to Bob Carver, a legend in the audio world.

[stevec.]

Sorry Paul....that was a "cop out" of sorts. First: thank you for not trashing Carver....he IS a genius. Second: You truthfully gave the test didn't go on to say why someone would spend thousands of dollars on a "mega-amp", when very similar results could be had by a "mega-cheaper" Carver amp?? I had the "Carver Cube" amp for years (driving Shehannian Oblisks), and I was in sonic heaven ! I absolutely know that your products are state of the art they are so out of reach, price wise, for 99% of stereo consumers. P.S. LOVE your videos, your dedication to the art of sonic excellence, and to the education of the masses

[brucepyeatt]

I had a highly modded Carver TFM 45. Carver did the work. Great amp. Dead quiet. Tons of power. I wanted to try something different so I bought a pair of M 1200s from PS Audio. It was like a Vail was lifted. Way better. More clarity. More air. Very happy. Good work Paul.

[Reyfox]

Owned a Phase 400. Managed to blow one channel. Took it to high end repair store in Manhattan. Repaired and everything biased again, I took took it to my local hifi store in Queens for it to do battle with the Carver 1.5t. I was confident in the Phase 400. Lets just say, after the "battle", I took my Phase 400 home and sulked. A little while later, I bought the 1.5t. It drove my Acoustat 1+1's medallion mod electrostatic speakers. Front end was VPI HW19 (when they were made in Long Island City), Premiere tone arm, Koetsu Black Goldline, Counterpoint SA3 pre amp, SA2 head amp.
And it was magic in my listening room.
Eventually the 1.5t gave up the "ghost" after several years of hard use driving the Acoustats. Then I bought a Counterpoint SA220 amp, but I do miss that 1.5t.

[mr.b]

I have a 35 year old Carver Receiver that I don't use anymore. It's sitting in my closet wrapped up because I decided to modernize and take advantage of some of the newer audiophile offerings out there. I have a pair of Maggie LRS+. I connected that Carver a few months ago for kicks to hear how it sounded with the LRS+ and I'll have to say it kicked that more modern setup, an Outlaw RR 2160 MkII all over the place, it drove those speakers without breaking a sweat, quality of sound wise it sounded great. It's a different kind of sound. I preferred the Outlaw's openness a little more but that Carver pushed those speakers in a way the Outlaw does not and the Outlaw has a higher rating wattage wise.

[BeyondResolution]

The "problem" here is that he actually made a cheap amp sound as good as a expensive amp... That is a mind twister.. If a cheap amp can be made to sound that "good" you would think expensive amps are just rubbish.. :) If he did not touch the expensive amps to adjust them down he did prove something extraordinary.. :)

[dougg]

I bought his sub in 1998 ( Sunfire True Sub) and still use it today. Bought his EQ sub later and still use it. Beast of a thing

[gdownz]

I still have a Carver PM 1.5 amp I bought used for DJ work and it was a WORKHORSE! I used the hell out of it and it still sounds pretty good but really needs recap and capacitor replacements. Great Amp👍 Bob is another legend in the world of sound. 💯

[spentron]

I've tried the null test between the channels of several vintage amps and receivers, in the course of repair, sometimes finding bad switches and aging pots. I've yet to find one that completely nulls against itself, best null was maybe 40 dB down.

[doctormidnight]

I met Bob in Seattle a year or two after he released the Sunfire TruSub. I'll never forget the interview with him and his wife and her going on about "Musicus Interruptus" and him saying "the ceiling did not fall down..."