Speakers crackling/popping after replacing potentiometer?

[Aguiluz]

I have this Radioshack speakers (specifically this one) that had this irritating potentiometer issue, where the left speaker would be lower than the right one. Placing a heavy book or object on the volume control equalizes the volume, showing that this is a pot issue. I then checked inside for loose connections, then I checked the pot. The pot had unequal resistance, that equalizes (with tolerance) when I press down the shaft. I decided the pot is broken.

I decided to replace the potentiometer (a regular analog one) with a new digital potentiometer. The MCP42010 digipot had the same value as the original potentiometer, and was wired in exactly to replace the broken analog potentiometer. I then programmed an Attiny45 to control the digipot.

After building, it sounded great on my workbench, with my smartphone as an audio source.

Then I placed it to where it was before, next to my PS3 and a TV.


Routing audio through the cable box, the audio still sounded as great.

Trying the PS3, however, the audio become a crackly, popping, noisy mess at all volumes.


Thinking that the PS3 somehow "overpowers" the digital potentiometer, I added 2.2KOhm resistors inline to the input where the PS3's audio out connects to. The issue vanished and sound quality was great again, though the audio was significantly lower than before.


More info:
The speakers I have do not have a volume control on the amplifier circuit board itself. The amplifier has fixed gain. The volume control just increases or decreases the resistance in the input line.



So a few questions:

1. I am thinking that the Microchip MCP42010 *isn't* designed for audio volume control. Has anyone have any recommendations for a good IC that controls volume?

2. I used Kynar wires to connect the digipot's terminals to the original potentiometer's terminals. Is using Kynar Wire for audio lines a potential source for popping and distortion?

3. Why did the smartphone and cable box work without issues?


Thanks for any replies!

 

[laingsoft]

Re: Speakers crackling/popping after replacing potentiometer

1. I am thinking that the Microchip MCP42010 *isn't* designed for audio volume control. Has anyone have any recommendations for a good IC that controls volume?

I can't answer this, and I don't have time to look up the spec sheets, someone else might be able to help you.

2. I used Kynar wires to connect the digipot's terminals to the original potentiometer's terminals. Is using Kynar Wire for audio lines a potential source for popping and distortion?

Probably, Kynar isn't shielded, so any RF emitted by pretty much anything electrical will cause distortion and popping.

3. Why did the smartphone and cable box work without issues?

Your smartphone is a much smaller source of RF, and the voltages are much "cleaner" coming out of a handheld thing. From the wall, the voltage is very unstable, it all depends on how well the voltage is controlled and regulated. Most of your problems are probably from the Kynar.

Did you make sure to match the resistance from the old pot when you replaced it?

 

[public-pervert]

Re: Speakers crackling/popping after replacing potentiometer

I've used DS1669 from Dallas Semiconductor before and works great. DS1669 is designed to replace mechanical pots. The only issue is that's a single channel.

 

[Aguiluz]

Re: Speakers crackling/popping after replacing potentiometer

Thanks for the suggestions, guys!

I'll switch out the Kynar wires for thicker wires and try to shield them first.

If it all fails, I have a Texas Instruments PGA2311 to try next, and it's designed for audio control.