What Makes the Epiphone Constellation a Bass Amp?

[martin manning]

Lifted the ground on the treble control. MADE IT VERY VERY LOUD.
Overall, not nearly as tonally interesting as with treble control active. Shoot, overall it was worse. Crummy. It made it hard to play, at any volume or combination of settings. Just wrong.

Yes, you are overdriving the stage following the treble now. At the least there should be an attenuator there, a drive control or a fixed resistive divider to reduce the signal level by 5-10x. Alternatively, you could do a partial lift of the treble control by placing a resistance between the treble pot and ground.