As mentioned in another thread, I recently acquired a Pioneer A-400 amplifier which I am interested in modifying.
The amplifier already sounds very good in my opinion, but I would like to make it even better, although I am not willing to sacrifice reliability or functionality.
I gather that Tom Evans, the original designer of the A-400 used to offer an upgrade for this amplifier at great cost, but no longer offers this service. Does anyone know what these modification entailed?
My plan at present is as follows:
Replace main smoothing capacitors with better, audio quality types.
Possibly replace some coupling capacitors with polypropylene types.
Adjust output transistor bias so that the amp runs in Class A to about 5 watts per channel.
Possibly replace the Op-amp(s) in the Phono section, although I don't' use the Phono input much at present.
Replace the manky, corroded RCA sockets with gold plated types. (I have cleaned the RCA connectors with T-Cut, but they still don't provide a good enough connection in my view.)
I am also considering replacing the mains transformer with a toroidal type, although I will have to make sure there is enough space for it.
When I have done this I plan to make similar modifications to the A-300, which appears to be virtually identical to the A-400 save for the absence of a MC Phono stage and the less powerful output stage; although the output stage (and mains transformer) would probably be easy enough to upgrade.
If anyone has any knowledge or experience of such modifications I would be very pleased to hear.
Nigel.