# Where would be the best spot to put a logarithmic volume control on this TPA3122 audio amp?

I'd like to add a volume control to the following circuit (a 2x15W Class-D Stereo Power Amp Kit). The schematic below is an image clipped from a PDF I found describing it.

This'll be being driven almost exclusively from my PC soundcard in case that changes anything. (I'd rather not exclusively use software volume control; I prefer the preciseness of an analog potentiometer :P)

Using a rheostat circuit on the audio input vaguely comes to mind, and that might turn out to be all I need, but I thought I'd ask anyway since I'm not certain (I know precisely zero about electronics).

I'm not familiar with the TDA3122 but I was thinking maybe fiddling with the GAINA0/GAINA1 lines might produce the effect I'm looking for...? What might I alter here?

## 1 Answer

Hmmm the precision of an analogue pot eh? Compared to the digital nature of a 15 watt digital class D amplifier. So be it.

Lowest input impedance of the chip will be at max gain and this could be as low as 9kohm so use a 1, 2 or possibly 5k pot on the input - wiper to chip and pot low end (CCW) to 0V. Input from external input to pot CW pin. Stereo pot of course.

Here's the data sheet for reference.

• Admittedly, a friend who knows a bit more about electronics than I do built a few of these kits a while back and recently gave me one. I actually had no idea they were digital >.< lol... okay, so looking that the datasheet, you're saying I wire the wipers to LIN and RIN and put the CCW low end on AGND? Jun 6, 2015 at 22:05