When pushed, many audio designers will tell you that the most critical component in a preamp, or anything with a volume pot in it..~IS~ the volume potentiometer.
In the Sony TA-2650, it is... a 23 step or 23 position Alps brand Stepped plastic film attenuator.
The kind of quality potentiometer you can't buy for under $100 in today's money. Better than an alps 'b lack beauty' potentiometer. Notably so. Alps does not make them any more, that I'm aware of, no market, no buyers.
Sony 'got it' and so did the buyer end up 'getting it'. :)