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

Parts

Part	Total Qty.	Description	Substitutions
R1, R3	2	10K Pot
R2, R4	2	100K 1/4 W Resistor
R5	1	6.8K 1/4 W Resistor
C1, C2, C3	3	0.1uF Capacitor
Q1	1	2N3819 Junction FET
MISC	1	Wire, Shielded (Metal) Case, Phono Or Other Plug For Output

Notes

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.

A shielded case is probably needed to reduce hum and help stop oscillations.

The circuit can be powered by a single 9 volt battery.

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Comments

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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?

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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?