Expression out jack for volume.

[VPIF]

Hi.

Are there any advantages to having an expression pedal jack for controlling the volume of a rack mounted mixer with an expression pedal, over running the audio signals to/from an ordinary volume pedal?

Ideally I want to control the volume of four (two stereo) of the mixers channels, and that means having eight jack cables between the rack and the volume pedals. Are there simple ways to wire switched jacks for expression pedals to control the volume that will save some cable and not lead to considerable signal loss/degrade?

Thanks.

[mth5044]

You can use the similar technology as on GEOFEX for remote wah's. I wouldn't run a ton of cables with audio, that is asking for problems. Is this a DIY mixer? If so, you can use an LED/LDR combo for the volume control. Use a switching jack so when there is nothing pluged in, a potentiometer on the mxier will control the voltage of the LED, thus changing the resistance of the LDR and the volume. When something gets plugged into the jack, the voltage is then routed to the expression pedal and the potentiometer inside the pedal controls the voltage. You could run, for example, a cable that has the sleeve as ground, the tip as the V+, then the ring as the resulting voltage back to the mixer. Now, that's three paths you'll need for one stand alone mixer channel. For four, you could use any number of cables, although MIDI type cables could be easy. I believe they have 8 or 9 pins. One for ground, one for V+, then four more for sending different voltages back to different mixers. Of course, you can't plug one midi cable into four different expression pedals, but you could build a tiny box that has a midi in, then split it out to four TRS jacks to four expression pedals. Or just use 4 TRS cables from the beginning.

[VPIF]

Thanks for your reply.

It is a DIY mixer, the GGG mini mixer - in fact two of them, handling four stereo lines. I had planned to use four dual ganged pots for volume controls for the mixer, but I guess that could complicate thing a bit with the expression pedal wiering?

I do not in fact want four expression pedals, but one to control one of the stereo mixer line volume, and another to control the overall volume. Of course an expression pedal A/B/C/D switch box into one expression pedal for the mixer channels + one expression pedal for the overall volume would be great, but I fear that could easily end with an overy complex rig with reliability issues.