Regarding the High/Low level switches on the external amp & fx loop send/returns…
Is the ‘high-low’ selection like a +4/-10 type selection? If I was putting normal guitar pedals in the fx loop like an eq and delay, would it be set to ‘low’ and if I was putting another preamp in the external amp loop (Friedman IR-D), would that be set to high? The manual doesn’t really say anything about what settings should be used for interfacing different gear types.
From the PS Series manuals regarding the HI/LO level switches. The GPDI/IR manual is being updated. It is the same FX level description.
FX LEVEL – This sets the signal level inside the loop. Use the HI position for line level (+4 to 0dB) devices. Use the LO position for guitar level devices (-10 to -20dB) such as pedal delays, etc.