Fender Performer 650 Tone Stack distortion

[Helmholtz]

Usually it's the classic tube amps that I have to use the inst. input and play with the tone controls.

I feed my signal to the PI input (before the coupling cap where there should be 0 VDC).
If there's a (MV or treble control) pot, it should be turned up to not load/short the signal.

In cases where there's no suitable 0 VDC insertion point, I add a DC blocking (coupling) cap, e.g. 0.1µ or 0.47µ depending on circuit impedance.

[Stratfordade]

Yes, I always try to use FX Return or Pwr Amp IN jacks if available. Usually it's the classic tube amps that I have to use the inst. input and play with the tone controls.

Yes I checked the output power using signal to FX return. Handy as I fixed the PA before the pre-amp!