Here is what the chips mounted on the copper plate look like.
The amp had a hum and I just could not remove. I tried an external PS which worked. The Hum and the buzz went. I realised the external PS had a slightly lower PS by only five volts. Could this be the reason my amp hummed and buzzed???
Experimenting with different resistors, starting at 100ohms and going down to 0.22ohms that I could remove the hum and buzz by slightly lowering the B+\B-. In the end the best value was 6.8ohms. The PS sags slightly on heavy passages. I could stop this sag with extra 10,000uf filter caps but this gets away from the "Gain Clone" formula I wanted to follower.
The amp is up and working with 6.8ohm 5W resistors in the +\- power feeds. Note the 5W Rs on the rectifier board.
This has removed all the hum and buzz with only minimal power sagging at the chips. As you can see it is a compact build with the massive copper plate (3.6kg), minimal chip amp and dual 24V low profile toroid(s). The power cord has a ferrite choked and there is a power filter (top right-hand corner) installed. The diodes are Super Fast with soft recovery (3A) and are snubbed (0.01uf). Only 4.7uf caps provide a pre-filter at the PS and 1500uf caps (Panasonic and snubbed - 0.1uf) provide smoothing and storage right at the chips. All the signal path is silver soldered and silver wire (0.4mm) and silver plated copper wire is used in the signal path. No shieled wire or PCB are used! The earth to the input RCAs and for the speaker return is five-nines solid silver wire back to the star earth. The copper plated is suspended on two very small brass washers, above the bottom plate of the enclosure. This 1mm of separation is to ensure only the resonance from the copper plate is heard.
The Sound of Copper: I played a 24B\96K classical baritone piece to start with and warm-up the amp. I was not impressed. "Please give me the Silver Dragon(300BSE)". Then I played Claire Martin, Jenny Schliemann and Liz Springer (Australian local singer). WOW does this amp rock. All the things I hated in the classical piece I loved in these upbeat jazz and rock pieces. So how does copper sound with rock\pop\upbeat jazz: Blo**o#dy great!! It's bright, thump'n and pump'n. It's in your face, loud, gutsy and driv'n. I just need the wife to go out for, oh, I don't know, about 10 more hours so I can work through some raunchy pop and rock. The Dragon still holds court but this 9.6kg (21.12lb) bad boy needs some attention.