Nelson’s design of the 555 was just fine.
In production, how that was handled, in order to make for ’over the top reliability’, ease of build, ease of servicing, etc... and how all that was executed --- that is what resulted in a grainy amplifier.
Nelson’s job was the circuit design. The rest (AFAIK) was handled by whomever Adcom had do the rest. And that includes layout, fusing, chassis, etc. All of that had a major impact on Nelson’s supplied circuit.
Modding the 555 or the 5500 or any of the other adcoms... in a way that is centered around removing the built in obstacles to positive gains...generally has a very positive effect on the sound of the given Adcom. The individual modded amplifier will be fine, but as a production item (fully maxed out in all ways), as percentages of failures go...reliability would (and does) generally take a huge step backwards. So much of a step that it could easily make a company insolvent. And at times, it has happened. Extremism has its costs.
’Best sound quality’ and reliability in the long or sometimes even short term, do not normally fit together. Their demands for existing --are in opposite directions, in high end audio. I state it as an incontrovertible fact, in an imperial manner but there are a few exceptions.
The problem is that, if exception is given for that 2-3% of the best of the best, that actually DO exist... 110% of the companies out there will refer to themselves as the exception that is in that small few percent range.
Which is impossible, so +95% have to be full of it or ignorant of their own products limitations. Marketing, in all sensible guises and attempts, must never touch this, at any price.
Eg, ’CTC builders’, for Parasound, etc, each of the three people did a part of the final issued design, with aspects of all that controlled/directed by Parasound. CTC wanted performance, and Parasound wanted utter reliability, and reasonable projected price points being met. Which is why John Curl, afterward, supplied a huge amount of data to the DIY folks on turning the HCA-3500 into what CTC really wanted it to be. My guess is with Richard’s OK beforehand. So --much respect to Richard for allowing that.
In the end, it is the psychological positioning of the buyers that is at the heart of this scenario and how it has had to play out in the consumer marketplace for high end audio. The inability to understand the complexities that lie behind the curtain, and how they (the buyers and users) react to the given shadows on the wall...
