There are (unfortunately) different methods for making a logarithmic scale on a potentiometer. Some volume pedal might act different even though the specs for both are i.e. 100 kOhm logarithmic scale. Besides that, we have seen that some volume pedals (i.e. the BOSS FV-300H) give a better response if you connect a jack plug (just an open plug, no cable) to the input of the pedal (technically speaking: the input of the pedal is shorted when no jack is inserted, if you insert a plug you will get the correct impedance response on the output of the pedal). You will naturally connect the output of the pedal to the G-Majors Ext.Control input.
At the moment it's not possible in the G-Major to set the response curve of your volume or expression pedal, for the volume parameters (Global Outlevel, Global Inlevel, and Preset Outlevel). The workaround would be to use the last active effect block's output level to control the overall output volume. F.i. if you have a preset with the REV block active, this will be the last block in the chain. If there's no reverb, DLY will be the last effect, if there's no delay, CHO/FLA is the last block, and so on.
The advantage of this is, that you can make a custom mapping of the M1 response - and thus compensate for the logarithmic scale, making it more linear. Unfortunately, it's not possible to do this with the input volume... So, REV or DLY spill-over after turning down the volume is not possible.
- Make sure the G-Major is set to serial routing.
- Assign your expression pedal to f.i. M1 by pressing MOD, and selecting "Learn" (push the dial to start the learning), then move the pedal.