This is a first generation Fet Valve amplifier wedged into the stripped chassis of a Dyna St-410 amplifier, before we had resorted to designing and building our own chassis.
Its not very pretty looking in there is it? However it has all the good guts, just spread over several boards to fit into that layout.
These amp can be significantly upgraded, but not all the way to new status. We can rebuild the audio board and re-do the circuit to use 12AT7 tubes instead of the original 12AX7 tubes for much better current drive into the output mos-fets. We can also install the new double die Exicon mos-fets which will provide a big boost in current and power handling capability for this old Fet Valve amp inasmuch as it could only hold four mos-fet outputs per channel.
The cost to do this (both audio and output mos-fets) would be about $800.
One thing in the write up I am a bit suspect about. They said they replaced one power supply diode. Normally if one ever fails, we always replace all four as usually the remaining ones have been overstressed even if they remain working for now.
Regards,
Frank Van Alstine
