Mesa Boogie Mk I input resistors
- Yazoo55
- Breadboard Brother
I am going to try to build the preamp section of the Mk I Mesa Boogie. I have found several schematics with some variations. I think I understand how all 4 stages of the 2 12ax7s are switched in for the high gain channel. The query I have is in some schematics Input 2 is shown with a 220k resistor hard-wired to ground. In another, the resistor is wired to connect only when Input 2 is not used, shown in the attached picture. Any ideas on which one is correct please?
- bmxguitarsbmx
- Cap Cooler
My guess would be that the 220k is NOT hardwired. It could be mesa did both at one time or another however. Mesa did switch it up a lot. You might try asking in the music electronics forum. There will be some techs there who have been inside one of these. I have never even played a MK1.