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In the circuit below, where would I place an audio taper potentiometer to modulate the output volume level? Which of the resistors should get replaced with the pot and why?
If understand correctly, I should place the pot between the input decoupling capacitor and the buffer amp is this correct? Additionally, this circuit was designed for +-12V, if I am only capable of providing half of the +-12V, around +-6.2V, what effects will I observe, will the amp still function, just at a lower output?
Since this circuit requires both positive and negative power, you can place a pot either before of after capacitor. If you had a virtual ground (for example made using two resistors), you would want to place the pot before the capacitor.
Reduced power will reduce output, but halving the supply voltage will decrease the output power by more than 50%. Both devices are may operate from +5/-5V power supplies; however Figure 6 in TPA6120 datasheet shows that distortion-free power is 0.5W for +-15V, and 0.05W for +-5V (into 32ohm speaker).
There are a number of ways you could add a volume control to this circuit. The traditional volume control circuit is an audio taper pot with one end connected to the input, one end to ground and the wiper to the input of the actual amplifier. You would usually place this in front of C1 (and it would obviate the need for R1).
You could also alter the gain of either amplifier by varying R5 or R7.
The voltage of the power supply must exceed the maximum voltage of the output of either of the amplifier stages (plus a little extra because op amps generally don't do as well near the rails). If you don't do that, you'll get clipping on the output.
