Taking in mind this circuit, how would I apply a high pass filter on lets say channel one of this circuit?
http://www.generalguitargadgets.com/pdf/ggg_mixer_lo.pdf (http://www.generalguitargadgets.com/pdf/ggg_mixer_lo.pdf)
The idea is to mix two channels, but I want to filter the lows from channel one.
Are you looking for something like a rumble filter?
How you do it depends on how much rolloff you need etc. If you can get what you want out of a first order filter it can be pretty simple since C1 and R5 are already setting up a first order HP filter. You would just need to reduce the cap size for C1 where the formula is f = 1/(2 π R5 C1).
If that isn't good enough, then you'll need to put an active circuit in before R5 and that'll probably need to be buffered.
Was thinking ofdoing it simle.Maybe, I'll try to reduce the input cap