Michael, it is indeed an impedance issue. You can try playing with different Hi-Z and Lo-Z connectors to get the right combo that works, but the other solution is an active switch.
From: Ruben Medrano [mailto:email@example.com]
2014-07-31 22:44 GMT+02:00 Michael Peters <firstname.lastname@example.org>:
non-loop related question:
I want to use either-or or both of two sound sources (guitar, and guitar controlled synth), so I plug them both into an y-switch feeding my amp.
That seems to work fine at first, I can switch between guitar and synth without problems, both are loud and clear, but when I set the switch to "both at once", the guitar is suddenly very low in volume while the keyboard is as loud as it was. Why is that? is there a remedy?