FET Audio Mixer


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This simple circuit mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consumes very little power. The mixer is shown with two inputs, but you can add as many as you want by just duplicating the "sections" which are clearly visible on the schematic.

Schematic

This is the schematic of the Mixer

Parts

Part
Total Qty.
Description
Substitutions
R1, R3210K Pot
R2, R42100K 1/4 W Resistor
R516.8K 1/4 W Resistor
C1, C2, C330.1uF Capacitor
Q112N3819 Junction FET
MISC1Wire, Shielded (Metal) Case, Phono Or Other Plug For Output

Notes

  1. As many or as few channels as are required can be added to the mixer. Do this by just duplicating the input "sections" which are shown on the schematic.
  2. A shielded case is probably needed to reduce hum and help stop oscillations.
  3. The circuit can be powered by a single 9 volt battery.

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Comments

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Alex
FET Audio Mixer
Wednesday, December 11, 2013 8:34:15 PM
Hello, can I feed the inputs of the mixer with synthetizer line out and also can I change the 9v to +15v? Do I have to canghe some value? Thanks
Crankcase
FET Audio Mixer
Thursday, March 07, 2013 9:51:10 PM
This circuit would not be ideal for guitars because the potentiometers will shunt the pickups, which defeats the object. A suitable design will have R1 and R3 replaced with fixed resistors 3Meg - 10Meg, the individual volume controls will need to be on the output of these input stages and then mixed into another stage, with the whole thing producing unity gain.
anonymous
FET Audio Mixer
Monday, March 19, 2012 10:13:08 AM
I just wanted to clarify. Me and my groupmates are trying to make a language laboratory so we need a 4-to-1 channel stereo mixers (which would mix four input from microphones) and a 1-to-4 audio splitters. about the possible noise or hum. is this good enough to produce very little hum? and do you have any idea for audio splitters?
anonymous
FET Audio Mixer
Wednesday, March 07, 2012 7:53:31 AM
can i use another transistor in place of 2N3819 Junction FET
anonymous
FET Audio Mixer
Wednesday, February 08, 2012 9:37:07 AM
Should the pot ideally be linear or logarithmic please?
anonymous
FET Audio Mixer
Saturday, March 05, 2011 12:14:36 AM
If you build this for guitar, the input impedance as shown is too low. I recommend replacing R1 and R3 with 10M resistors (instead of pots).
Clayton
FET Audio Mixer
Wednesday, October 13, 2010 12:57:56 PM
Would the FET audio mixer be recommended for running a midi sampler and a guitar into the same guitar amplifier input?
ciaran
FET Audio Mixer
Friday, September 03, 2010 7:55:30 PM
we are currently doing a very similar project in our school but instead of 2 inputs, we have 4...hope it works...
Nick
FET Audio Mixer
Friday, June 25, 2010 8:29:18 PM
Hey i was wondering if you put in more than 4 input sections would you need to put in a higer value R2/R4 because when all the pots are at zero there would be verry little resitance therefore shorting the FET For example If all the 10k pots are set a zero resitance to ground # of chans R2/R4 value 1 100 k ohm's 2 50 k ohm's 3 25 k ohm's 4 12.5 k ohm's And it goes on But as you can see. the restors in parallel rule defnetly comes into effect here So the question is do you have to put in a bigger restor to stop Q1 shorting I want to make shure befori go and build this Circuit Thanks
anonymous
FET Audio Mixer
Wednesday, June 23, 2010 8:02:20 AM
from where 2 inputs are caming from ?
anonymous
FET Audio Mixer
Wednesday, October 21, 2009 2:25:30 PM
to make make master control use choice switch with 3 positions.
prasath
FET Audio Mixer
Friday, September 25, 2009 5:12:17 AM
what is mean by 10k pot. need explanation
Mr. Fletcher
FET Audio Mixer
Friday, July 24, 2009 1:15:16 PM
How can i make this circuit with only one variable resistor so it changes them equaly?

(Editor's notes: Use a dual gang pot.)

anonymous
FET Audio Mixer
Monday, June 22, 2009 2:48:05 AM
i want to use this in a multiple cd-rom w/ play button to play and audio music. how make this 12v as a source coz i want this to be used in my vehicle.
anonymous
FET Audio Mixer
Wednesday, May 13, 2009 7:00:50 AM
Its a simple circiut. We can make a couple of this and have our own audio mixer stadium conferences... We can also practice our music instruments with the help of this..... Thank you very much...... jonjongregorio hobbiyist philippines
august
FET Audio Mixer
Sunday, March 15, 2009 8:19:40 PM
Mike- I plan on building one of these as a stereo to mono device, so what I am going to do to eliminate the pots is to replace R1 and R3 w/ fixed 10k resistors, the connect the 100k resistors to the junction of the 10k's and the 0.1uF caps. It's like having the volume pots stuck on full. I have enough level controls on all the other equipment that more volume pots would just get in my way. Hope this helps!
Mike
FET Audio Mixer
Friday, January 23, 2009 11:04:13 AM
Is there any way to not use potentiometers? I'm looking to make two of these: one with no potentiometers at all (completely even blend) and one with only one potentiometer and a switch on that channel (i.e., one main input and a second input that can be turned on or off and volume adjusted).
anonymous
FET Audio Mixer
Saturday, December 20, 2008 6:00:53 PM
is it possible to add another POT for the master volume control? and if so, where in the circuit would i place that?
jin
FET Audio Mixer
Monday, December 08, 2008 3:18:34 AM
hi i'll try to audio mixer. but I could't find JFET in my city (seuol.korea). So I changed the other components. R 2,4:33(ohrm),R1,3 B50(K ohrm) C1,2,3 : 104J100N Transister : K193 K57 Same voltage. but I don't know what type use R5. I can't find R5. plz respose this question.plz~~~~
anonymous
FET Audio Mixer
Monday, August 04, 2008 10:52:23 AM
what part of this circuit I will place my tone control circuit?
jane
FET Audio Mixer
Wednesday, July 23, 2008 7:23:49 AM
please how can i build an audio mixer with 6 inputs and 2 outputs.
Tende I vo
mixer
Sunday, July 20, 2008 3:42:47 PM
Wnhat you people have done good, but some biginners liuke me do not know how to use the FET TRANSISTOR. So please if you people can send me some other schematics that dose not have FET i will be very happy . THANKS. I want to be a DJ using my own circuits.
computablemind
FET Audio Mixer
Thursday, May 01, 2008 12:45:38 AM
hello thanks for the circuit schematic. can anybody mention any other fet's that could be used instead of the 2n3819. in fact, anything about transistor equivalencies (specially for mixer purposes) is welcomed,thank you
Audioguru
FET Audio Mixer
Thursday, January 17, 2008 10:50:09 AM
This mixer attenuates the input levels. With 2 inputs the levels are half. With 4 inputs the levels are 1/4. With 8 inputs the levels are 1/8th etc.
anonymous
FET Audio Mixer
Sunday, October 21, 2007 12:31:22 PM
can anybody tell me more about the description of the circuit any one plz.... and yes i woul dalso like ot know that how are you goin to provide the input and output ? any specifications? any about the frequency ? amplitude (voltage) minimum or maximum requirements... anything any info.. plz tell me.. and kindly plz .. if any can guide me on my e-mail
anonymous
FET Audio Mixer
Wednesday, October 10, 2007 6:57:49 PM
please i need a very powerfull mixer with 8 channel and that have bass, treble, and volume control. thanksmfor your support.
anonymous
FET Audio Mixer
Monday, October 08, 2007 5:09:49 AM
I'd like to built this. does anyone have a circuit diagram for PC board or Veroboard layout? Thanks
anonymous
FET Audio Mixer
Wednesday, October 03, 2007 1:56:03 AM
I'm pretty new at this game-- what other transistors could be uses as a substitute for the 2N3819?
Watson A.Name
FET Audio Mixer
Sunday, September 09, 2007 4:10:34 AM
Oops! I forgot something. If the blocking caps are put between the wipers and resistors, then the Gate of the FET must have a 1 meg resistor to ground.
Watson A.Name
FET Audio Mixer
Sunday, September 09, 2007 3:55:54 AM
The combination of the DC blocking capacitor C1, and the level control pot R1 make a high pass filter that causes frequencies below 159 Hz to roll off, so that the sound has a loss of bass frequencies. The problem is that C1 should be larger and/or R1 should be a higher value. I would increase the pots R1 and R3 and resistors R2 and R4 to ten times their values. Pots should be 100k, and resistors should be 1 meg. Notice that C1 doesn't have to be on the input. It could instead be between the pot wiper and R2. Also, C3 should be ten or more times larger, 1 uF or more. Connect the polarized cap with positive to S of the FET.
Antonioni
FET Audio Mixer
Wednesday, September 05, 2007 9:45:48 AM
What type of diode would you suggest to place where exactly to avoid signal flow into each other? Also, I would like to know whether it would be possible to use a power supply of 12 V without blowing the FET. Do I have to change/remove R5 and/or C3? I am too poor in electronics to tell by myself and would appreciate your help very much.
anonymous cabalfin joeri
FET Audio Mixer
Sunday, August 05, 2007 10:44:03 AM
FET AUDIO MIXER is really great when it comes to audio mixing it depends only to one who assembled this circuit.if you assembled it and it does not work then maybe the problem is with in you as the assembler of this fet audio mixer. if you have assembled the fet audio mixer the one with split supply its really incredibly good in performance. i say that because ive made it by myself. i mean its perfomance is superb.
nhadzki
FET Audio Mixer
Wednesday, June 27, 2007 9:18:13 PM
it didn't work when i built this project!!!!
Luis Salazar
FET Audio Mixer
Thursday, May 17, 2007 1:42:23 AM
you should bias a diode on each line in, to avoid signal from other line ins getting into each other.. or put buffers in each line.
CTP
FET Audio Mixer
Sunday, May 13, 2007 1:53:18 PM
I built this circuit and am extremely pleased with how well it works...many thanks!!!
Dj Ivan
FET Audio Mixer
Thursday, May 10, 2007 2:52:26 AM
what substitution can be apllied
anonymous
FET Audio Mixer
Friday, March 09, 2007 11:48:51 AM
What is the input and ouput inpedance of this circuit?
Logan
FET Audio Mixer
Friday, March 09, 2007 2:00:20 AM
After a bit of a google search, I found this, and it seems to be exactly what I'm looking for! Thanks for putting this up here - You really saved me a lot of trouble!
Moustafa Ismail
FET Audio Mixer
Monday, March 05, 2007 12:50:21 PM
Very good
Koen
FET Audio Mixer
Monday, March 05, 2007 10:41:44 AM
Before I start to put this little thing into practice: Did you actually build this circuit and found it works well?
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