Summing two guitar signals into one output

L

LeadPaint

New member
I'm looking for an easy solution to sum two signals from guitar effects into one output.

It would be great if this can be done passively. I don't need switches, send/returns or pots for blending or mixing, just two inputs and one output. I'll set levels with the effects' level control. I have lots of stuff laying around, enclosures, jacks, resistors etcetera. I guess something to sum signals can be made easily, I just don't have the skills to come up with something myself considering stuff like impedance.

Thanks for any advice :)
 
As long as:
A - The sources are relatively low-Z and non-reactive (like the output of most FX devices, unlike passive guitar pickups)
AND
2 - The load is comparatively high-Z and non-reactive (like most things you'll be plugging this into)
You can usually get away with passive mixing just by putting a resistor in series with each output and connecting them together at the input. This will involve a certain amount of insertion loss though. Both sources will be attenuated some, and the overall mix will be less than the sum of the two sources. If this is a problem, you'll need an active gain stage after the mixer.

If either A or 2 (or both) are questionable, or impossible to control, then you need active devices on one or the other (or both) sides of the passive mixing resistors so that you are basically taking control of those variables.
 
LeadPaint said:
I'm looking for an easy solution to sum two signals from guitar effects into one output.

It would be great if this can be done passively. I don't need switches, send/returns or pots for blending or mixing, just two inputs and one output. I'll set levels with the effects' level control. I have lots of stuff laying around, enclosures, jacks, resistors etcetera. I guess something to sum signals can be made easily, I just don't have the skills to come up with something myself considering stuff like impedance.

Thanks for any advice :)
Click to expand...

Do you mean you want to sum two OUTPUT signals into a single INPUT? If so, as Ashcat says, this can be done quite simple using resistors in each signal line.
With regard to loss, if the input Z was say 10k, about as low as it should ever be* if you used 10k feed R's you would get a 6dB loss but if both sources were the same level they would add to give a a total loss of only 3dB, not likely to be a problem?

But 10k is a bit high unless you can get the mixing resistors at the INPUT end because of HF loss in the cable. 2k2 should be ok since the common but feeble TL07X will see 4k4 and be happy!

*Mic inputs can be as low as 1k....Jusfort! Whenever you tie two devices together you run the risk of a hum loop. No harm but nuisance. If so come back, there are simple fixes.

Dave.
 
ecc83 said:
Do you mean you want to sum two OUTPUT signals into a single INPUT?
Click to expand...
I want to sum two output signals into two inputs and have one output, outputting the summed signals.
So my Ultimate Lead Paint Passive Summing Device will have two input jacks, getting signals from two stompboxes, and one output, to feed another stompbox or a guitar amplifier.

If you can recommend me resistors values which handle average stompbox impedance I'm a happy guy. You say one 2k2Ω resistor in series with each signal? A total loss of something like 3dB won't be a problem at all :)
 
LeadPaint said:
Ha nice, my mad technical skills :D

Resistors should both be 2k2Ω? Thanks for helping me out!
Click to expand...

You are very welcome. Note, that circuit will also serve to split one output to two inputs (guitar to two amps say). Technically you don't need the resistors for that but they will not hurt.

Dave.
 
I've made the summing device today and it works nice to mix effects. The volume drop is no problem. The only effect I've tried that gets really soft is the Big Muff, but only when used before the circuit. Boss distortion effects work well.
 
LeadPaint said:
I've made the summing device today and it works nice to mix effects. The volume drop is no problem. The only effect I've tried that gets really soft is the Big Muff, but only when used before the circuit. Boss distortion effects work well.
Click to expand...

Well done!
The level drop with the Big Muff is a consequence of the wrong headed design practice misnamed "true" bypass.

Dave.
 
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