I think I found the answer for better or worse: clip out one RIAA feedback cap and substitute the other cap with a variable potentiometer in order to adjust gain down by lowering overall feedback resistance. That should allow gain to be dropped to 10-20db range by adjusting the potentiometer. I guess the value of the potentiometer is the question.
I might try it since I don't use this phono anyway. It would produce a flat ?? small signal VFET gain stage (linearity unknown).
I might try it since I don't use this phono anyway. It would produce a flat ?? small signal VFET gain stage (linearity unknown).
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DIY Sony VFET lottery discussion
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DIY Sony VFET lottery discussion
VFET-less round 3 details will come once the dust has settled from round 2.
Thanks to thing about..Just as a point of follow up, I energized the phono section of the TA4650 and snipped the capacitors in the feedback circuit. Didn't blow up.
Listening through a cell phone half turned up with music and keeping the volume of the main preamp at below 10 o'clock, the RIAA indeed turned back into a flat amp with a good bit of gain.
I connected the hi sensitivity headphones to the main preamp outputs so it was nonRIAA small signal VFET>4650 preamp section>headphones.
Surprisingly as long as it was kept within bounds, the sound was wonderful. Baby VFET in fact sounds like you put a little extra tube in there. I will isolate the outputs to bypass the preamp later and see how it works as a head amp for an MC cartridge fed into another RIAA MM phono amp.
Good Luck to Diyers 
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