Wood tap stompbox with guitar mixer

[Julien911]

I have already build and wired a cabinet, built many wood instruments, wired mics of a guitar, but totally new to electronics.
My project is to build a wood tap stompbox to tap with the foot. It is pretty clear, I only have to wire a piezzo mic, a volume knob and a jack output (I found the schematic for that).
Now I want to add a guitar input to the pedal, mix the sound with the output of the stompbox and jack out to the amp, maintaining the level of signal of the guitar.
The only diagram I found is a passive mixer that will drastically reduce the volume of the guitar.
Could you help me or point me to anything that could help me? Similar projects? Video? Schematics? I'll been looking a lot around the web, without success.

Thanks!

[nocentelli]

You need a buffer circuit after the piezo output, and a buffer for the guitar input and then you can mix the buffered signals passively without too much loss. Here is a very basic example that uses transistors to buffer the two signals (guitar and mic in this case). Note that the mic input gets a big gain boost, whereas the guitar input just has a more moderate boost:


Also note this has two independent level controls, but a simple mix pot would also work (connect the two outputs to lugs 1 and 3 and the output to the wiper as in the opamp-based blend control below:



A better approach would be to use opamps for the two input buffers: You could then use either individual level pots on each instrument or a single mix pot to balance the signal levels into a third opamp mixer stage. If you use a quad opamp chip, the 4th opamp could be used to provide a nice stable vref the audio stages need. If you search for "opamp splitter", "opamp mixer", "opamp blend" etc you'll find lots of schematics you could adapt.

[r080]

Welcome to the forum! That seems like a cool idea.

There are a couple options I can think of right away - The blend side of the runoff groove splitter blend, and the general guitar gadgets mini mixer.

http://runoffgroove.com/splitter-blend.html
https://generalguitargadgets.com/effects-projects/boosters/mini-mixer/

I would consider adding some sort of bass control for the stompbox, as all the ones I have heard have a bit too much bass for most guitar amps.

[antonis]

Note that the mic input gets a big gain boost, whereas the guitar input just has a more moderate boost:

Audio in boost strongly depends on signal source output impedance..

P.S.
Can't figure out that outputs HPFs corner frequency huge difference..

[PRR]

You need a buffer circuit after the piezo output, and a buffer for the guitar input....

That was my reaction. But the product he wants to copy is "No battery or power supply needed; input & output  - only one channel needed" so totally passive?

https://ortegaguitars.com/en/products/annalog-m10807.html

EDIT-- today's reviews on Amazon do mention "tone suck" and "don't plug your guitar into it."

[Julien911]

not sure If I want to copy the internal mecanism, as some users report a much lower guitar level due to this pedal.
Might be active, not really an issue IMO.