I did for A810 in changing into tube (7119 mu stage) of the out-put stage, with a selector switch for compare to the original circuit in a very good result. also not too long ago I did for A80's record amp in changing the in-put and drive stage into tubes and transformer coupling, but kept the EQ section in because I want to use the same CCIR,NAB filter and adjustment pots.this one end up with big return than the stock in working with ribbon tube mic and tube mic pre amp of live recording.
Now I try to work with it's repro amp too, in stock design the first stage has gain and EQ, sec stage also has gain with all adjustment pots and cross talk too, If I still to keep those that mean I can only change the out-put section again. This days more people use separated tube or SS repro pre amp direct from head but with a simple EQ and frequency control design not like the A80 so complicate (maybe that is specially design for it's head and transport or that is the main factor of it's sound character presentation)
Although my favor is all tube and passive filter without feedback, but that is only experienced in RIAA phono stage none in tape playback, So What do you think ? a simple passive EQ and all tube is better or a Hybrid with it's own EQ filter and controls ? maybe in future I will have both to compare but now I have to pick one first
tony ma
