[Art Vandelay]

I've taken fft + square wave measurements as before with a Marantz SC11S1 preamp and a Krell KSP-7B preamp.

Both are mid priced preamps. The Marantz is designed to be a low distortion preamp - using HDAM modules and it's a fairly new design.

The Krell is old school from the late 90's, using a jfet input stage and high bias to drive low impedances.

Note that I was unable to perform the 100khz square wave test on the krell, because it wanted to oscillate.