Originally Posted by JensJ
Well if you do a spice-analysis, the amplifier has more than 3 dB deviation from the RIAA curve. The response peaks at 10 kHz and has its lowest value around 110 Hz (more than 3 dB), so no wonder there is too little bass.
Component values should be: (only one channel shown)
Unchanged:
R5 = 1M
R6 = 2.2k
R8 = 3,3k
Change:
R4 from 100k to 76.33k
C4 from 680pF to 1.06NF
C5 from 3.3n to 2.95nF
This will give a response within +/- 0.1 dB. You will have to find suitable parallel combinations for this yourself.
In my experience it is almost impossible to make a phono preamp with standard component values.
Thanks for running SPICE on this circuit. Next time I go to the parts store I'll pick up the suitable components to build the values you've listed and post my impressions.