Reducing noise from digital potentiometer (MCP41100)

I have replaced my speaker’s analog potentiometer with an MCP41100 digital potentiometer; however, now the output has static and a distorted sound.

Any ideas on why this is happening and how I can reduce / eliminate it?

I’ve attached the schematic, where the MCP41100 output pins 5,6,7 feed directly into the integrated circuit pins where the analog potentiometer was previously attached.

Breadboard.jpg

I've attached the schematic,

Sorry you haven’t, you have attached a physical layout diagram which is useless for seeing what a circuit does.

where the MCP41100 output pins 5,6,7 feed directly into the integrated circuit pins where the analog potentiometer was previously attached

It is not as simple as that.
First you need a common ground between the Arduino and the system that had the origional pot. Then the signals on the pot have to be within the power supply limits of the Arduino / digital pot.

Unless you know these parameters or you can measure them it is unlikely you can come up with a correct design. Normally what goes wrong is the negitave part of the signal is outside the range of voltages the digital pot can cope with.

If you want to replace a volume control in an original analog circuit, I think you’d be better starting with a dual rail digital volume control such as one of the Ti digital volume offerings. But they cost a lot more and need +/- 12-15v supplies.

My reasoning is that even if you fix up the signal to bias at 2.5v or so as suggested above, that only leaves best case of just over 2v peak before distorting. And that assumes the digital pot is linear right up to the rail voltage. It may be enough or maybe not. Without seeing the amp schematic it’s difficult to tell.

davetcc:
My reasoning is that even if you fix up the signal to bias at 2.5v or so as suggested above

Please read what I said. I never suggested this.

Apologies I did not mean to misquote and will correct the above text.