combining/bodging audio inputs

Using Arduino General Electronics
#1

I would like to hardwire one of my projects into a box, with a couple of (true bypass) guitar pedals effects in sequence after it.

I assume I can just omit the projects "audio out" and solder this directly into the first pedals "in" and then that pedal's out into the next pedal's "in", with the final audio coming out to a 1/4" jack?

My other question is:

is it then possible to wire an "in" jack in parallel to the input from my project, so that I can also add external audio sources to the "stream" (for want of a better word).

I don't need to mix between these sources as will have independent volume control. But I am not sure if there is an issue with doing this - cancellation of one sort or another? Do I need to add a resistor or diode somewhere to prevent an issue?

thanks in advance for any help!

#2

actually, sorry, I rushed to post this too fast. Last time I looked I obviously didn't google all that well, I think I found the answer to my Q.

As I can't delete, and in case this comes up in search for anyone else, I believe this answers the Q:

#3

I’m not really sure what you are asking, but mixing two audio signals can be as easy as using two
resistors, one for each audio source, and taking the output from the junction of the resistors.

It helps to know the output and input impedances of the pieces of kit. Typically audio gear as a low
output impedance (< 100 ohms) and high input impedance (> 10k ohms), in which case a couple of
1k (or so) resistors would be fine.

If you want different attenuation for the two signals you have to do the calculations and know the
impedances really.

Don’t delete a thread, document the solution and then others can benefit from it.

#4

yes, that was pretty much what I was asking! thank you

It seems that the simple resistor model can create some issues though... I think I need to go one step more at least.

And sorry - I suspect not being able to put it into the right words was why I struggled to google the answer last time, a real beginner at this stuff!

Don't delete a thread, document the solution and then others can benefit from it.

gotcha. In the spirit of that, this is pretty excellent on this subject:

Audio Mixing

need to work out if there are issues with low impedance sources going into guitar effects pedals...
essentially I want to stack a couple of kit guitar effects in series with a dub siren synth, but still leave the inputs to the effects open to send other sources to them as well.

I think a simple passive summing mixer for each input will do it by the looks of things.

#5