I have made some progress (although I admit taking apart the old receiver is sure to be the easy part of the job. At present I am still trying to decide between the LM3886 and the TDA7293
We have removed all the circuit boards at this point, I was intending to keep the power supply but it was old and I didn’t trust it. I know that electrolytic capacitors do age so I will discard them. I will make a new power supply on veroboard and as a 35A chassis mount bridge as recommended for the power amplifier design.
The front panel turned out to be nice and flat and made out of good solid material. I intend to mount switches, volume, balance and inputs all on the front panel so that small signals are kept away from the amplifier outputs.
I should probably be able to fit 2 of these heatsinks, one for each chip amp. The power amplifier board would sit mount transversly underneath these. The heatsinks would be attached to aluminium angle mounted to the case with nylon bolts and washers so as I do not need to use mica washers. I originally thought the case would seem too large but these only just fit. Hopefully this will allow me to run the amplifier a quite high power.
The image opposite is planned rough layout. Not that I intend to place inputs on the front panel close to where the pre-amp is mounted. Hopefully this makes a good separation from the outputs. I also avoid having to use any form of extension for pots and switches or long runs of shield cable.