screamingdaisy wrote:Theory A: It's a blend knob.... channel 2/Recto, channel 3/Crunchberries, blend to taste.
That would be a highly impractical design. Those are two totally different amp schematics, needing a handful of preamp tubes each, and since I don't know of any tube amp that mixes two high gain signals inside it I assume it's a non-trivial problem to solve in a musical way. Plus half the magic of the Recto line is in the power amp, especially the Modern mode feedback removal thing.
screamingdaisy wrote:Theory B: it's a chorus knob.... they built the JC-120 chorus into the amp.
Seems unlikely, Mesa doesn't own Roland or the JC-120
screamingdaisy wrote:Theory C: it's a scoop knob.... they built James' parametric EQ into the amp.
Now this is getting more plausible, especially since there's no straight up boogie amp that's going to nail their studio tones because of the significant extra EQing.
screamingdaisy wrote:Theory D: it's a dummy amp.... having it in the background wasn't a mistake, they knowingly put it there to f*ck with people.
Possibly. Could also be a test amp or prototype. Maybe he was helping them tune an internal gain setting on the TC-50 before it released and they gave him one to find the sweet spot on a knob that would eventually become a fixed resistor. (same as the Mark V has the Volume knob on the lead channel fixed, at 7.5, or the JP-2C as 4 fixed values to choose between). Being a prototype/test amp would explain why it's larger than usual (more room to work inside) and have exctra knobs for things that aren't final. Then perhaps he kept it because he know it could make sounds no stock amp ever would.
Or I present Theory E: It's just the Volume knob(input gain), like older Mark series amps had, for adjusting both gain controls like you could on a IIC+-IV.