I bought a used JVM1C from GC and it it didn't come with a footswitch. They gave me a single button Blackstar FS. It doesn't work. I think this amp uses a single button FS to switch channels. I can't believe I can't find anything on the internet to identify the replacement switch.
Hello Stephen,
The pedal you need for your JVM1C is PEDL-90003 1 way with no led, this can be purchased through a Marshall dealer.
Kind Regards
Marshall Support
