I have to Fender Amps... One a Rumble bass amp - the other an Acoustisonic 30 DSP. When I plug into the line out, I still have speaker sound and there is no "mute" button on these. Is it possible to install a switch to the amp to turn off the speaker when so desired?
Combo Amp Line Out
Just plug a blank jack into the return of the amp and it'll cut off the speaker.
Looking at the two amps in question......why do you want the amps to mute?