Lowering highend in Randall MTS RM100

[BesaMoogie]

Hi guys, I have a Randall RM100 and I want to cut some high end in the amp. The NFB circuit is already modded.

The problem is, that the amp uses modules. So a big part of the preamp where this tweaks are done to is out of the equation. This basically leaves me with V1, the FX loop section and the whole powersection (minus the already modded NFB circuit) to do some work on.

V1 has a switch for different cathode bias values (a common mod on MTS amps). I already lowered some highs by adding a 250pf cap on the plate resistor. I could go higher there, but maybe there are orther options?
Did anyone ever added a small cap to the plate resistors of the PI or FX loop tube? The signal passes the FX loop tube as well, even when the FX is not engaged.

I did prowide some pictures with the schemitcs of the amp.

Cheers

 

[ilikehats]

Wish I could help. The cap across the plate load would be my suggestion. I looked at the schematic but not close enough to identify a good spot, but if you found a voltage divider, you could put a cap on the output to ground as another low pass option. If signal passes through the FX tube stage, you should be able to shape the frequencies there but I'm not entirely sure.