One of the tasks I have on my to do list is to increase the gain of my phono preamp v2.0 from 35 dB to 40 dB at 1 kHz. Before I update the design I wanted to benchmark the performance of the existing design. I read about an audio analyzer called the QuantAsylum QA401 Audio Analyzer in book by Jason Stoddard about the start-up of Schitt Audio entitled “Schiit Happened: The Story of the World's Most Improbable Start-Up” (an excellent book by the way). QuantAsylum QA401 Audio Analyzer is capable of measuring the noise, frequency response and distortion of the phono preamp.

So far I have been able to confirm that the preamp implements the RIAA equalization curve to +/- 0.025 dB from 20 Hz to 20 kHz. This is exceptionally accurate and is the result of using capacitor multipliers and fine tuning as described in my November 30th, 2018 post. The noise level is also very low with an output noise level of 18 uV with 100 Ω input source resistance (-94.9 dBV or - 92.7 dBu) again from 20 Hz to 20 kHz. The Spice simulation of the circuit reported 10 uV of output noise so I am still trying to track done any extraneous noise before recording a final measurement. I still need to complete the distortion measurement (THD).

I will post graphs of all this data once I complete the testing.