Graham Maynard said:Excellent investigation.
[...description of another phono preamp circuit...]
I would love to see your type of investigation cover something like that [in reference to circuit described above], maybe including noise performance as well as amplitude/frequency.
AndrewT said:why was this Neumann thing put there?
Does it give any advantage?
And that 20Hz roll off is balderdash (good english word from a Scotsman).
I support the toplogy of splitting the time constants and putting the 75uS last even without a final buffer, provided you keep the next stage impedance high (say>= 50k).
amplifierguru said:I don't see any point in adding the cost/complexity of extra active stages and noise/distortion input stages to something that can be achieved simply with one full RIAA feedback stage with a small added hf loop zero and following passive rolloff.
I have done this in a commercial preamp with a single op amp with the RIAA network declining at hf to about 2K2 ohms and a passive rollof immediately after. this way you have only one op amp noise/distortion source, retain full (maybe 40dB) overload margin, ....