How to control the gain of more than one TDA2030/2050 IC with a single potentiometer?

Question

I am on a project of making a music system which will be able to output 6 speakers. I want to control the gain of each six TDA2030/50 ICs with a single potentiometer.

Here is a schematic example of 2 ICs controlling with a single potentiometer, I have tried but does not seem to work correctly.

^{simulate this circuit – Schematic created using CircuitLab}

When I tried this schematic, I get music sound but also with music, it offers some free noises.

Now some of you may think that this might be the answer I am looking for but, unfortunately, the answer schematic given here is not understandable to me as a beginner, and I don't want to use another TDA IC to generate a static voltage or something like that which may create difficulties for me to understand. I only want to use either BJTs (2N2222A) or MOSFETs (IRFZ44N), so if anyone here has a solution for me, please do me a favor by sharing it with a proper understandable schematic and pointing my mistakes respectively for a beginner like me.

Please avoid suggesting any kinds of ICs for performing this action till there are other ways left.

Answer 1

If we look at the functional schematic in the datasheet:

then it is easy to recognize the common non-inverting (opamp based) amplifier structure. I marked the feedback which sets the gain.

The TDA2030 does not have an input for adjusting the gain.

I do not "see" how your proposed circuit can even work as the transistors cannot "work like a resistor" in the way that would be needed for this. And even if it worked, the transistor will be somewhat non-linear and that will introduce distortion in the feedback circuit which really should be linear.

The solutions that I see are to use a different audio amplifier, one that does have a volume (or gain) control input.

If you want to keep using the TDA2030 or any other amplifier without a volume control input then for two channels, use a "stereo potmeter". For more channels, use a volume control IC, this is what is used in many commercial multi-channel amplifiers.

Answer 2

Don't dink around with the outputs. Use a volume control at the input. One potentiometer connected to the inputs of two amplifiers.

Like this:

^{simulate this circuit – Schematic created using CircuitLab}

Where C1 and C3 are the same as in your diagram. The gain of the 2030 is fixed - you can't change it. Just vary the amplitude of the input signal.

Most amplifiers work that way. The amplifier has a fixed gain, and the volume control varies the amplitude of the signal going into the amplifier.