lowering the presence

[Chuck H]

I'll jump in with the speaker change too. As a custom builder I can attest that every amp will have a favorite speaker. That's why there so damn many guitar speaker brands and models available! The implication that there may be something "wrong" with one amp because another amp sounds fine with a particular speaker would seem to imply that the world only needs one guitar speaker. Or perhaps even just one amp for that matter. Maybe take the Marshall to a big music store like Guitar Center and just try the amp through as many different speakers as you can and see for yourself.

[cjenrick]

tack a .001 across C68 and see what happens, (parallel) if that works, adjust caps til you are happy.
can ot solder the .001 uf to the leads of the plastic square cap? you can go off the deep sw or R58 with a jumper wire to one end of caap and connect other end of cap to R92 or the top off the Presence pot.

nothing is worse than too much presence, resolution of the pot needs to be reasonable so you can dial your sound at any level.

[Valvehead]

how about a snubber cap , 10-33pf across 1 or more plate resistors?

agree on speaker swap....i like the Warehouse Guitar models