Whoa there! MusicMan amps were not full tube amps. They had solid state preamps and tube output sections.
Well, it might be in the wiring/schematic, but this looks like tube power and pre-amp to me (I know, I don't know what I'm talking about, but it won't be the first time!)
Here's the specs posted by the seller:
All Tube Operation (1 x 12ax7 / 4 x Telefunken EL34)
A LOUD 130 Watt RMS output at a switchable 4 or 8 ohms
Standby Switch
Ground Switch
Dual Hi/Lo Power Operation (65w/130w)
Normal Channel Features: Dual Inputs, Bright/Normal Switch, Volume, Treble, Mid, Bass
Bass Channel Features: Dual Inputs, Bright/Normal Switch, Volume, Treble, Mid, Bass, Master, Deep/Normal Switch
Sturdy Housing
Grounded Electrical Outlet
3-Prong Power Cord
Made in Anaheim, California, USA