Electronics > Projects, Designs, and Technical Stuff
Audio potentiometer replacement
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tooki:

--- Quote from: drummerdimitri on May 04, 2020, 09:29:50 pm ---I would like to switch out the potentiometer on my headphone amplifier as it is scratchy and doesn't have good channel balance at low volumes.

Here is the one I currently have installed which is the same as the original one which has been replaced for the same reason  :palm:

https://bit.ly/3dbzldq

I would like to switch to something better quality and maybe even get a stepped attenuator but I am not much of a fan of those as sometimes the lack of steps makes it hard to find just the right volume.

I know ALPS make a 900$ one just for audio but that's more than the cost of the amp (800$). Would like something more robust and high quality.

What do you recommend?

--- End quote ---
That was a link to your order summary, not the product. Obviously nobody else could see that, even with a login.

How about using either a volume control IC or a transconductance amplifier (or other amp with voltage-controlled gain)? Then you can use a decent linear pot, with zero channel tracking issues and overall lesser demands on the pot, since the audio signal isn’t actually passing through it.

Also, one thing to consider is that the circuit design itself can exacerbate pot scratchiness. I forget what characteristic causes that, but I saw it discussed on here some time ago. Maybe someone else here happens to know!
John B:

--- Quote from: drummerdimitri on May 06, 2020, 08:26:40 am ---Here's the full link : https://www.aliexpress.com/item/32847980540.html?spm=a2g0s.12269583.0.0.124f2c2ecCm1LQ

I had a long look at their website and could'nt find a 50 k Ohm dual gang pot that mounts to the chassis with a nut.

If you think it exists, please send me the link thanks!

--- End quote ---

I wouldn't purchase brand name pots from ebay/aliexpress. Pretty safe to assume they are fakes, counterfeits and imitations. I still get a laugh out of some "Burans" pots that I have.

Doesn't mean they wont work, just don't pay any more for them than regular cheap carbon pots.
pqass:
If audio-taper log pots are hard to find/expensive maybe you could substitute a linear-taper with a loading resistor at its output to produce a log-ish curve.

see: http://sound-au.com/project01.htm#s1
glentek:
What about a digital volume control? I've used this in my car amplifier with good results
https://www.aliexpress.com/item/4000429773300.html
Bassman59:

--- Quote from: tooki on May 06, 2020, 07:51:11 pm ---
--- Quote from: drummerdimitri on May 04, 2020, 09:29:50 pm ---I would like to switch out the potentiometer on my headphone amplifier as it is scratchy and doesn't have good channel balance at low volumes.

Here is the one I currently have installed which is the same as the original one which has been replaced for the same reason  :palm:

https://bit.ly/3dbzldq

I would like to switch to something better quality and maybe even get a stepped attenuator but I am not much of a fan of those as sometimes the lack of steps makes it hard to find just the right volume.

I know ALPS make a 900$ one just for audio but that's more than the cost of the amp (800$). Would like something more robust and high quality.

What do you recommend?

--- End quote ---
That was a link to your order summary, not the product. Obviously nobody else could see that, even with a login.

How about using either a volume control IC or a transconductance amplifier (or other amp with voltage-controlled gain)? Then you can use a decent linear pot, with zero channel tracking issues and overall lesser demands on the pot, since the audio signal isn’t actually passing through it.

Also, one thing to consider is that the circuit design itself can exacerbate pot scratchiness. I forget what characteristic causes that, but I saw it discussed on here some time ago. Maybe someone else here happens to know!

--- End quote ---

DC on the pot. That's why you will see largish (47 uF or 100 uF) caps in series with either the top of the pot or the wiper.

Since we know nothing about the circuit it's hard to guess why the pot is scratchy or why the resistance value matters (50k vs 100k).

It may be that the pot is simply an input attenuator, with the top connected to an RCA jack, the bottom to ground and the wiper to the input of the amplifier. In this case, the pot value probably doesn't matter. If there's a DC block the pot resistance does affect the LF response.
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