I'm looking to build something similar to a GigRig Wetter Box for my pedal board. I've assembled a simple buffered splitter (FuzzDog Spluffer) which will send the signal to two different pre-amps. I then want to create a pedal that allows me to select between Pre-amp A or Pre-Amp B or a blend of the two (100:0% to 0:100%), which can be adjusted with my feet. I've done a bit of research and put together the following schematic which contains the following stages:
1. A buffered input with a relatively small gain so that I can adjust/balance the level of each channel. I've used a schematic of a micro amp (https://www.electrosmash.com/mxr-microamp) as a starting point but made a few tweaks.
2. A phase inverter on one channel based on a RG Keen circuit on Geofex (http://www.geofex.com/article_folders/polarity_reverser/polarity_reverser.htm).
3. A cross fader (or Panner) again based on a RG Keen article on Geofex (http://www.geofex.com/Article_Folders/panner.pd). It's also used in my amp on the effect return input to combine the wet and dry signals.
4. A summing amplifier to blend the two signals.
5. Two footswitches, one that selects blend or single pre-amp, if the latter than the second footswitch selects which pre-amp, A or B.
I've worked through the calculations provided in the above resources to hopefully come up with some suitable values for resistors and capacitors, but I'm no electrical engineer and have only a basic understanding of the sizing and location of different capacitors in particular. As I understand it, the input stage will provide a gain of ~1.75 to 8. The x-fader should hopefully reduce this by a factor of 2 with the resistances selected (R13-R17).
I've breadboarded stages 1 to 3 for a single input and it seems to be doing something sensible but I haven't done the full schematic. Before I commit to building the whole thing, I thought I'd see if anyone was willing to point out any issues/blunders or propose any mods that might make it more robust, stable etc.
Any suggestions would be appreciated, but this is my first post so please be gentle!
If you need any further information just let me know.
Thanks!
(https://i.postimg.cc/sMv6Q9Gh/XFader.png) (https://postimg.cc/sMv6Q9Gh)
Welcome.
I don't see a problem. (Yet?)