I have the Sonic Port (not VX), running into an IPad Pro. I connect an electric guitar in the Sonic Port, and then another cable to monitor through a guitar amp.
When I go to record a track in Garageband, the input level slider must be all the way up to even register. The level of the drums tracks or other inbuilt material is fine, and must be reduced with the slider to avoid clipping, but the guitar input is barely audible.
I know the Sonic port is working, because when I use the Line6 app (Pod - the effects collection), the levels are fine, producing a strong input and output. When I select the Line6 app as the input device (rather than a straight feed from the Sonic Port), the input levels improve dramatically, but this also comes with some noise and latency.
It seems there is some problem with the interface between the Sonic Port and Garageband.
I have searched the forum, but I cannot find a thread that this has been addressed.
Thank you.