Flat Balanced Input Moving Magnet Preamp and RIAA-EQ Construction Information

[mediatechnology]

4.7µF, the max available in PP, should be large enough since it moves the cutoff frequency down to about 2.4 Hz.
It varies a little bit as the gain jumper is moved from 10K to 14K3 to 20K for -3, 0, and +3 dB gain.

The RIAA path through the first input has two coupling caps - one at the input the second at the output - so the cutoff is about 1.6X higher IIRC.
With a FET op amp in the RIAA section you might be able to eliminate the one on the RIAA output.

[Gold]

The RIAA path through the first input has two coupling caps - one at the input the second at the output - so the cutoff is about 1.6X higher IIRC.
With a FET op amp in the RIAA section you might be able to eliminate the one on the RIAA output.

I always wondered whether it was better to drive the RIAA EQ with the opamp from the first input or directly from the 1200 in the second input, since the 1200 doesn’t have as much drive capability.

[mediatechnology]

Updated the RIAA EQ Assembly instructions and BOM to use 0.1% resistors in the RIAA EQ section. Added text about coupling capacitors regarding footprints, values and high-pass cutoff frequencies. viewtopic.php?t=753

[AnalogJoe]

I have a MATLAB program I developed to obtain component values for arbitrary low and high frequency corner frequencies for a single-opamp RIAA equalizer/preamp. There are far superior circuits, but If any one is interested, I can try converting it to Octave and post it. But first I have to make sense of what the hell I did in the code.