How do the External Switching Jacks work on the Mark V?
On the Mark V's rear panel there are four jacks with an EXT SWITCHING label between them. These are provided so that you can control the Mark V's 3 Channels, the EQ and the SOLO feature with an external master Switching device (using the MARK V as part of a Midi rig where all sounds are called up via a Midi Foot controller and both amplifier and effects settings are stored under a midi program number). The logic used to trigger these ports is simple tip-to-ground, latching type and most Master switching systems incorporate several jacks dedicated to this logic. These External Switching jacks override the MARK V’s Foot controller. Once a Channel or Feature has been triggered “On” at the EXT. Switch ports, it may not be controlled or turned “Off” until the logic at the Switch Port is reversed.
These External Switching jacks can also be used with individual tip-to-ground, latching type footswitches to control each function, however, when channel switching you'll need to be aware of how the switching logic works to be able to easily get yourself from Channel to Channel. The default Channel for the amp is Channel 1 and when a switch is activated for a higher numbered channel, the Channel with the highest number will be selected (so the footswitch for Channel 3 will always override the footswitch for Channel 2). With the Channel Selector for the Mark V set to either FT SW (footswitch) or CH 1 (Channel 1), if the external triggers for Channels 2 or 3 aren’t activated, then the Mark V will automatically choose Channel 1 as the Channel in use. If you activate an external trigger for either Channel 2 or 3 and then and then turn that trigger off, the amp will switch back to Channel 1. If you switch to Channel 2 and then to Channel 3, when you deactivate the trigger for Channel 3, you’ll switch back to Channel 2. In order to return to Channel 1 from Channel 3, you need to make sure both triggers for Channels 2 and 3 are inactive, so you’ll have to turn off the trigger for Channel 2 before turning off the trigger for Channel 3.