Hey Mike, presence is probably anywhere between 2.5khz to 6kHz. In audio (mixer) land it's generally 5 or 6kHz, in mics (eg SM58) the presence hump is around 5kHz, and in guitar gear maybe a little lower (and varies on different gear), but 3kHz is definitely in the presence ball park (and hard on the ears when it squeals
).
@ Max, interesting results with loop send and headphone out with output off. So the loop send is before the chorus (IIRC after the eq, MJMP did post the signal flow a while ago), the headphone out is after the chorus (as is stereo) but before main outs (I think, or what you did wouldn't work), the headphone out also has rudimentary filters to reduce top end (similar to a cab sim). So if you have lowered your trim pots to minimum (means with MDRT the tube stage is running much hotter
), this could be overloading the eq or chorus input ? (a guess
).
@ herbyguitar, the bass trim pot mod lowers the bass cut/boost centre frequency down to (IIRC) around 80Hz (bottom E in concert pitch is around 82Hz) from (again IIRC) 127Hz, there's a post MJMP put up that lists the centre frequencies of the eq bands, they're not listed in my MP1 manual. But this is not low mid although harmonics (halving/doubling) happen. So 3kHz > 1.5kHz > 750Hz > 375Hz (375Hz is in the low mid/mud zone), or conversely 80Hz > 160Hz (always a problem frequency) > 320Hz. I don't recall that others who did this mod had any introduced "hum" issues, it should be a problem, check you install though, make sure all is good and no solder or component issues, maybe trim pot needs a clean
.
Interesting tit bit, when AKG D12 was made it was intended for male vocals and has a 80Hz boost (hence good on kick drum (add 2 or 3 kHz for click/cut), also the Bayer M88 was similar and a useful kick mic.