Switchable Bass Boost for JCM900 Dual Reverb

[tattybob]

So i just got back off nights and reading a bit of stuff on this forum.

I came across this a while ago and decided to give it a go. http://web.aoct.org/marshall/jcm900-gain-mod.txt

Im looking forward to hearing the results, and if anyone else here has done this already. I found some report dotted about saying they liked the changes this brought.

I was reading and i got to thinking about adding switches to go to and from resistor values, or rotary switches to switch caps about in the tone stack.



Anyway... that MASTERPIECE is something i just threw togther in ms paint.
would something like that work? in theory, thats a 2 position switch going from the standard 100K value of R15, and what is meant to be the mod... only i replaced the 220K resistor with a 100K resister in series with a 100K pot (linear).

the document says 470K defining the boost makes the bass flabby. so i thought id stick in the 100K safety resistor, so you have a familar start point, and then a varible resistor for varible bass boost.

I could mount the pot on the front of the chassis (if it sounds good) and even add a pre-dist mid boost switch across R7 and a high-cut switch affecting R61 & C37. i could go switch mad and attach all the gain boost bits to a switch too. hopefully something pleasing to the eye.

Anyway. if that sounds totally stupid/interesting let me know. this isnt to make my JCM900 sounds like an SLO or anything. its more out of interest than anything else!

cheers!

[GunalORSEL]

Have you performed the change you mentioned above? Would you like share its result with us?