Mesa Boogie Mk. 1 PreampVerified

From the post

A verified layout by Sebastian, thanks mate! In his own words...

I forgot about this layout I did ages ago, built up (it works), and never got around to boxing up: a Mesa Boogie Mk.1 preamp. I'm personally partial to pre-gain tone stacks (e.g. '60s Fenders, Orange Graphic MkII), so I was disappointed with the Runoffgroove Uno having its gain control before the tone stack instead of after. So I knocked together the schematic below, which is basically a straight JFET emulation of the actual Mk.1 preamp if you plugged into Input 1 (i.e. the input with the extra gain stage). This gives the user both pre- and post-tone stack gain controls. I added a Marshall-style "treble peaker" bright cap between the input and 2nd gain stages, just for some extra clang, which can be engaged or disengaged with the "TP" switch. After the master volume control, there's a mu-amp output stage to mimic the push-pull amplification of the Boogie's phase inverter.

I used BF245A JFETs just because that's what I have the most of, but I tested it with PN4393s and J201s, and it worked just as well. The gain boost can be either a toggle or stomp switch; as the original boost was operated by footswitch, I opted for that in my build.

This thing's pretty fun. Like actual Boogies, it takes a bit to dial in a great tone—it's absolutely packed with bad tones, LOL—but it can do everything from crystaline Fender cleans to Weezer "blue album" growl to thrash grind. I hope other folks enjoy it!