Hi everybody, as the title indicates I'm new here although I've lurked around here for a while as this forum is an excellent resource for all things Boogie, especially for the Mark series amps. Anyways, I came up with a mod recently that I'd like to share with you all. This mod is designed for any Boogie with a single tone stack (passive EQ) that uses LDRs for channel switching. See here for schematic:
What this mod does is automatically reduce the amount of bass coming from the tone stack in the Lead Channel mode only. This mod addresses the problem that anyone with a Mark II/III knows all too well in that in order to have a tight lead sound, you must greatly reduce the bass at the cost of fullness on the rhythm/clean channel; what the added LDR and trim pot (or set value resistor) does is shunt across the .1 bass cap and .047 mid cap limiting how high the bass control can go in the Lead channel. On the Rhythm channel, the LDR is off and the trim pot has no effect on the function of the bass control. The primary benefit of this mod is that one could set the tone stack for a full sounding clean tone, then click on the Lead channel and adjust the internal trim pot to where the overdrive's bass content sounds comfortable to you.
Sorry, trying to get used to this board's format, how does one post pictures? Here's the link again: https://www.dropbox.com/s/kwy2qerlwh1l5ul/Mesa_Mark_Bass_Reduction_mod.jpg

Sorry, trying to get used to this board's format, how does one post pictures? Here's the link again: https://www.dropbox.com/s/kwy2qerlwh1l5ul/Mesa_Mark_Bass_Reduction_mod.jpg