After this last bit of tweaking, where Bob was able to reinstate his 70dB null while driving a very difficult load, we now had what sounded like two absolutely identical amplifiers. No matter what speakers we used, every "difference" we thought we had isolated turned out to be there, in equal quantity, when we swapped amplifiers.
This time, the listening went on through the whole afternoon and much of the evening, until all of us were listened out. More leisurely listening, refreshed by a good night's sleep, failed to turn up anything. As far as we could determine, through careful comparisons and nit-picking criticisms, the two amplifiers were, in fact, sonically identical. It is a gross understatement to say that we were flabbergasted!
The next morning, I told Dick Olsher over the phone what we had found. "Bull- shit!" was his reasoned response. "That just can't be." But it was, it was then that we started to realize that, in reporting the outcome of this Challenge, we were going to have more to contend with than outrage and wonderment. We were going to have to contend with incredulity.
On the face of it, what Bob Carver pulled off should be impossible. You can't make a silk purse from a sow's ear. What about the audible differences between transistors, capacitors, internal wiring—all the things that we know contribute to the superiority of no-holds barred amplifiers? What about all the things that amplifier designers have learned during the past 20 years, which enable them to build better amplifiers (at whatever price) than have ever been built before? How could all of these things have been factored into the relatively quick and painless transformation of an average amplifier into a world-beater? But, of course, the "factoring-in" was the key to all this.
You see, Bob didn't have to concern himself about quality capacitors, minimal internal wiring, gold connectors, or any of those things; all he needed to do was duplicate, at the output of his amplifier, the sum of their effects at the output of the reference amp. Once he had obtained the necessarily deep null between those amplifiers, it was his belief that ears were not going to pick up on what was left. To do this, he needed only (!!) to know how to change practically any parameter of his amplifier's performance—a knowledge which we must now acknowledge is his.