The Peak Detector

The peak detector stage is a transistor follower driven by a diode attached to the output of the SSM 2015 stage. While the input impedance of the follower is large and the output impedance of the SSM 2015 is low, the load on the SSM 2015 is nonlinear, and it is remotely possible that distortion could be introduced into the amplifier's output by this arrangement.

I personally do not require a peak detector, since I almost always have an analog to digital converter on the output of the SX202 that clips before the SX202 will. If you wish to disable the peak detector, remove diodes D20 and D21. This removes the nonlinear load and also disables the peak detector function. I have no opinion as to whether you or I could hear any benefit from this mod, but it seemed like a prudent thing to do, so the peak detector is gone. If you disable the peak detector in this way, it is very simple to reconnect should you decide you need it again.