You can connect a normal two-way footswitch with a stereo jack to the footswitch jack of the AMP1 - in addition to the REMOTE1 and the MIDI1 adapter. The two switches on the external footswitch then take over the respective functions of the left and middle internal footswitches on the AMP1 in direct access mode, i.e. CLEAN/OVERDRIVE and BOOST on/off.

The solution: preset mode

In order to access all 4 channels of the AMP1, the three internal footswitches are assigned presets in preset mode, in which each of the three footswitches calls up a different overdrive channel, e.g. VINTAGE for the left, CLASSIC for the middle and MODERN for the right switch - also optionally with BOOST and/or REVERB on or off. With the double footswitch, you then also have access to the CLEAN channel - and thus to all 4 channels! With the second switch on the external double footswitch you can also switch BOOST on and off for each channel or preset.

More articles on the topic:

What are the switching options for the AMP1? ‍

Direct Access Mode and Preset Mode

AMP1 + external foot switch - Why don't all foot switches with LEDs work? ‍