Hi Jeppe

Hi. Do you know if there is a Highpass / Bandpass filter mod for the
MP4 Or is it possible to mod the Mono/Poly and install an extra filter
stage (like with the MS20)

I don't know any solution to implement a highpass with an SSM2044 (beside known halfhearted workarounds like mix the filtersignal with the phase inverted original signal).

An additional Filter shouldn't be a problem. The bigger problem might be the required additional Potentiometers.

perhaps it is a good idea to add an insert between VCF and VCA, so you could add an external filter.

Florian