A while ago I needed a very simple pasive miker to join one stereo and two mono signals together before amplifying them...
There is some mixed information on how to properly connect a mono signal to a stereo input, but most of it uses active mixing.
I looked at a few schematics, like Tomi Engdahl's simple line mixer, and combiner, and the All Electric Kitchen simple mixer.
For my needs I finally made this simple ciruit that mixes the signals and allows to ajust the levels of each channel independently, before the amplification stage.
 | |
|
 |
| mono/stereo passive mixer board 600dpi (aprox. 51x48.5mm) |
 |
| mono/stereo passive mixer component layout |
 |
| Picture of the actual board |
10K STEREO POT is like Pan?
ReplyDeleteNo, the stereo (double) pot is used to control the level (attenuation) of the stereo signal, in the same way as each mono pot controls the level of each mono signal.
Deleteare you sure you're not tapping the outcoming signal from the wiper, with the ends of the pots going between the incoming signal and ground? That'd be a standard divider circuit, whereas what you have in the schematic with a grounded wiper is.. well, actually I'm pretty sure that would result in no output.
ReplyDeleteYou are totally right!
DeleteThe schematic showed the pots in the wrong position (just changed it).
The board was right, though.
Thanks for the correction!
how can I add a second stereo channel to this?
ReplyDeleteJust add two additional 1k resistors and another stereo pot (or two pots one for L and one for R of the new stereo channel). Connect the each of the new L and R inputs through one of the new 1k resistors to the corresponding L and R ouputs. See as reference:
Deletehttp://www.epanorama.net/circuits/linemixer.html
http://www.instructables.com/id/Passive-Audio-Mixer-w-Channel-Volume-Control/
This comment has been removed by the author.
ReplyDeleteshall I do it vice versa? (to convert mono to stereo)?
ReplyDeletemono to stereo is straightforward: connect the same mono signal to both stereo channels
DeleteGreat inspiration, just what I've been looking for! Any idea how to add pan to the mono inputs? I guess it would need a stereo pot, but connected kind of reversed, so that when left gets turned louder right gets quiter. But I'm not quite sure about the details.
ReplyDeleteHmmm, how about if you put, before the stereo input, a regular mono pot, say 10k, plugging the new mono input to the center pin of the pot, one side's pin of the pot to the left stereo input of the mixer and the other side pin to the right stereo input?
DeleteThe higher value of the pot the more noticeable panning, but with more gain loss (you may try also with 1k and 100k).
Apologies for my lack of knowledge. I am new to this and playing around. The 1u caps, does it matter what voltage it is ?
ReplyDeleteAny voltage will work :)
DeleteThank you David.
DeleteIm actually trying to make a 3 channel mixer (cell in, landline in, pc in) 1 out to main headphones. I'm also trying to get one mic in from the headphones into the 3 devices. If listening to music and a call comes through I would like to be able to mute the music and take the call. (would be amazing if this could happen automatically - calls take preference and mutes the rest) Has anyone made anything like this before ?
I still did not have a chance to put it together and I still have question.
ReplyDeleteI assume this mixer accepts line level audio signal but I would like use with my modular synth setup which is modular audio level = 10v p-p.
Do I need to use different value for resistors on mono channels ? Thanks
As far as I understand, if all the modules use the same voltage the circuit should work. However, I'm not an expert in audio circuits an this is a very simple passive solution, there is no calculation of impedance maching, etc. My suggestion is that an experimental test may give you the answer: try mixing two signals by joining the wires through two resistors. Do the test with a low volume signal and see if increasing the volume saturates the module where the mixed signals come in. If so, double the resistors value and repeat the test...
Deletei'm building this without the pots.
ReplyDeleteso just as a combiner,
1 mono, 1 stereo, to stereo output.
i'm finding some of the stereo signal
is returning thru the mono wiring, ie,
the caps do not stop the stereo signal
from leaking thru mono, left to right etc.
am i making sense?
can anyone help?
Hmmm, actually never tested if the signals were leaking back.
DeleteWhat are the levels (volts) of each input signal?
https://www.sweetwater.com/insync/understanding-signal-levels-audio-gear/