Author Options:

need help with audio mixer? Answered

Hello . im going to make this mixer circuit.Im not sure if it work fine or not.Can you please check it for me ? Thank!

In this schematic, i use R1=R2=47k Ohms , can i use a lower value like 10k or 4.7k ?

5 Replies

Jack A LopezBest Answer (author)2011-11-14

I think R1 and R2 are there to limit the current flowing into input1 and input2  respectively. 

Notice that it is possible to move the wipers on both those 10K pots to ground, and that is the case when the largest input current would be possible, and in that case only thing limiting current on input1 and input2 would be R1 and R2

That being said, I think 47K is more than enough resistance, and you could make R1 = R2 much smaller.  10K or 4.7K sounds good to me.

There are lots of possibilities for an signal adding network that will work.  Like that circuit you posted yesterday:
I thought that one was good too.

Select as Best AnswerUndo Best Answer

gmoon (author)2011-11-15

There's a serious problem with your schematic--the resistors that limit the interaction / crosstalk between the inputs (R1 & R2) need to be after the POTs.

Why? Because when either POT is turned all the way to GND, it will ground both inputs, silencing them.

Select as Best AnswerUndo Best Answer

login721 (author)gmoon2011-11-15

Thanks ! i have some mistake when draw this schematic :).
when making it, i put r1 and r2 after the pot, change the pot value to 50k,and change the input to pin of pot .

Select as Best AnswerUndo Best Answer

gmoon (author)login7212011-11-15

Maybe change it to something like the schematic steveastrouk posted.

I don't see any problems with your resistor and pot values. Ultimately that's dependent on the input impedance of the opamp (which should be plenty high enough to give you some flexibility here).

Although unlike steve's drawing, I personally I would move each capacitor to before the pots, where they would be in a typical high-pass filter configuration.

Select as Best AnswerUndo Best Answer

steveastrouk (author)2011-11-14

An inverting amplifier is the best way to do this. Here's a barebones mixer


Select as Best AnswerUndo Best Answer