Power Scale Footswitching

[Steve Ward]

Hi,

I have an SV2-M36 in a cathode-biased 4×EL84 Rocket-style amp. 
In this amp the Powerscaling delivers an exceptional Overdrive or distortion sound. 

I would like to implement a footswitchable OD function which, when engaged, reduces the Power Scale setting by a proportional amount while simultaneously increasing a Lar-Mar PPIMV setting. It would also need to simultaneously reduce the reverb level.

I’ve read the switching section in TUT4, where preset PS levels are selected using separate Power Scale controls/units. On the SV2-M36, is it practical to switch an additional resistor/network around the existing 1M PS control to lower the output voltage, or would you recommend a different method because of the DC voltage present on the PS control and any concerns around instant changes of power?
I also have an ERK available. Can ERK/JFET switching safely be used anywhere in the SV2 control network, or should the PS function be switched with a relay/MOSFET arrangement instead?
Current SV2 setup: 1M PS pot, R5 calibrated to about 262k effective, PS3 fixed at 164.2k, full-power regulator drop about 6V.


best

Steve