Pan pot for a passive mini mixer

[PlamenValkov]

I am completely new to circuitry and am looking to build a passive mini mixer.
Basically, what I want is two 1/4'' mono inputs running to an 3.5mm stereo output. I want volume and pan controls for each input channel. So, for panning, that would mean splitting the mono signal so that it can be pushed either to the left or right on the stereo output.
I basically have everything figured out, except where to get or how to make a pan pot...
Could you guys please tell me what exactly I need and how to go about the process?..
Thanks in advance!

 

[JohnRoberts]

If you google pan pot circuits, you will invariably find lossy circuits with make up gain following because it is simpler and cheaper.

A common pan circuit will connect the wiper of a single pot to ground and use that to alternately shunt and attenuate sends to Left or Right sums to effect the pan.

You want to make a passive mixer, which usually involves loss and make up gain, with pans, that also typically involve loss.

You don't mention how many audio stems you want to combine, what kind of signals are on the 1/4" inputs, and what the 3.5mm stereo output must drive.

All things that will matter to the design.

I'd start by searching passive mixers and pan circuits right here to start...

JR

 

[PlamenValkov]

Thank you for the reply and here is exactly what I want to do with it:

Basically, what I want it to do is split the mono signals from the headphone and booth output on a DJ mixer and combine them into the 3.5mm stereo output. Both input channels need be pan-able and have individual volume control.
The 3.5mm stereo output will be driving a pair of in-ear monitors. : )

 

[PlamenValkov]

Haha, silly me :-[ I actually just saw that 'balance' potentiometers would serve my purpose just fine.
Since I'm splitting a mono signal anyway, I don't need to be able to move the entire 2 mono image, just regulate how much left and right I get through on the split signal.
Here's a schematic showing what I want to do.. aand sorry that it's drawn, I don't know how to make them on a computer
http://p.twimg.com/AinnqyrCEAANIin.jpg

My next question is: How many ohms do the balance pots need to be? Also, that final "master level" pot I have, how many ohms does that need to be for minimal loss?

 

[gemini86]

You're going to need a makeup stage/headphone driver just before that 3.5mm jack... I don't see a completely "passive" mixer fed straight into a set of buds working at all.

 

[PlamenValkov]

Could you please specify what you mean by "makeup stage/headphone driver"? I'm sorry, I really am a complete newb when it comes to these things.. :-[

 

[JohnRoberts]

The pan circuit will reduce the output level. You need an active gain stage (like a headphone amp) following that to get the level back up to normal to drive  headphones.

JR

 

[gemini86]

easiest would be to use the gyraf headphone amp.

http://www.gyraf.dk/gy_pd/hpamp/sch_small.GIF

 

[PlamenValkov]

Thanks, but the whole point of this is for it to be completely portable and an active mini mixer just doesn't serve my purpose..
Could we maybe look at how to make it as little 'lossy' as possible?

 

[PlamenValkov]

Actually, I could use a 9V battery to power this. Does anyone know what I could use as a gain before the master out? ???

 

[pyjaman]

You could use 2 9v batteries and use opamps.
Laurent.