IronSean said: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.
As much as I'd love for there to be a JH Mesa I'm inclined to agree with the prototype theory. Specifically, helping them determine the 'magical spot' for Vol 1 to go into either the V or the JP2C. I'm betting the JP given the V volume was lower than what James used to, and probably still does, set it to.
It's also no secret that Petrucci's goal sound is Metallica and Puppets album which he talks about when discussing his tonal options in the JP.
The manual also mentions polls from artists and c+ afficianados when determining some of the internally preset settings
.
Doubt there's anyone better to help them determine how to achieve it. Although, I'd love to be wrong on this.
The other knobs may be experimenting with the new pull presence and shred frequencies.