Sound of potentiometer materials?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Jen

Active member
Joined
Sep 26, 2018
Messages
37
Any opinions on the sonic aspects of conductive plastic as compared to Cermet? My application is the multitude of pots used in an EQ for boost-cut. If this might be better asked in another part of the forum, please also suggest where.
Thanks. Jennifer.
 
@Jen if you're asking what I think you are asking, I've had the same question: do the different materials that pots can be made of have different tonalities? Edit: meaning, would the composition of the resistive trace make any significant difference in sound?

Cermet vs Conductive Plastic points out that cermet has a much lower tempco, so I would imagine if the internal temperature within a housing varies significantly, that could change the curves in an EQ that uses conductive plastic pots. That's different of course.
 
Last edited:
they can only make noise when you are moving them...

JR
Well, thats not what I asked about.. Every material effects the 'sound' of the signal passing through it to some extent. I have a great deal of experience with conductive plastic pots, and non with cermet. Cermet offers lower tempco, and tighter specification linearity, meaning for a dual pot with each section covering L and R of a stereo signal, the channel matching would be tighter. In this case temperature coefficient is not a big concern, but matching of section to section, is about twice as good in cermet compared to plastic. I am trying to avoid buying duplicate parts in each material and listening to the sonic effect. I don't buy into the notion that "it all sounds the same so it does not matter" .. everthing matters in some way... sometimes it is trivial, sometimes its sufficient to drive making choices.
 
I have a great deal of experience with conductive plastic pots, and non with cermet. Cermet offers lower tempco, and tighter specification linearity,
Do they? Do you have links to documents that show it? What "linearity" do you mean? Is it tracking between sections or R vs. V?
meaning for a dual pot with each section covering L and R of a stereo signal, the channel matching would be tighter. In this case temperature coefficient is not a big concern, but matching of section to section, is about twice as good in cermet compared to plastic.
I believe there is some misunderstanding here. Since both wafers are in very close proximity, there is almost no temp gradient between them, hence no relative drift.
I am trying to avoid buying duplicate parts in each material and listening to the sonic effect. I don't buy into the notion that "it all sounds the same so it does not matter" .. everthing matters in some way... sometimes it is trivial, sometimes its sufficient to drive making choices.
Since your goal is to achieve a specific audible (or not) result, I'm afraid you'll have to do that anyway eventually.
 
Surely a huge old fashioned high value pot has tons of extra incidental capacitance compared to a modern sub mini part ,
into a high z grid it could easily make a sonic difference . Continiously variable pots have their place in sound equipment ,but where stereo channel balance is concerned its pretty rough at best ,
Switched resistances as we know provides much better matching in every respect .
 
If you don't believe us and why would you? :unsure: Perhaps swap out the pots on one or two channels of a small mixer, then sum the outputs into one bus to look for a null. If you don't have a polarity reverse capability you can invert the wiring on one input. Compare the depth of null that you get between two identical channels vs the one stock, one with fancy pots.

JR
 
Or use user 37518's upcoming Octave/Matlab scripts for a bigger picture...
It is not trivial to evaluate bench readings wrt to audibility. Using modern bench equipment I can measure things that I can't hear... Using a simple mixer null test we can listen to the null product to better evaluate what difference is present, or not.

JR
 
Surely a huge old fashioned high value pot has tons of extra incidental capacitance compared to a modern sub mini part ,
into a high z grid it could easily make a sonic difference . Continiously variable pots have their place in sound equipment ,but where stereo channel balance is concerned its pretty rough at best ,
Switched resistances as we know provides much better matching in every respect .

Yes. The detailed model of a pot' or fader in terms of stray impedances can get quite complex.
But the OP's question was specifically about CP vs Cermet conductive track.
So yes, it's possible that in some cases a CP pot might have a different result than a Cermet pot but that the difference is not due to the conductive track itself.
 
I can envision a heat source being oriented to a multi element potentiometer so that the element closest to the heat source acts as a heat shield to the next element, and so on.
One need only look at the JWST to see how much effect a closely spaced heat shield can have!
More likely a layout & design issue than a component selection issue, but taking temperature into account may be worth consideration in the pursuit of perfection.
IMHO, performance over time with use / non use is pertinent, here C/P is by far the best, carbon 2nd and cermet last
 
Cermet possibly scratchier and more issues/compromises with wiper wear.

Is there data that supports this? In practice I've have cermet pots wear our quicker with repeated use. But they were also in different mechanical packages so hard to conclude for sure the failure mechanism.

I avoid cermet unless it's a minimal use set and forget type application.
 
I used to have great discussions with an old friend (now RIP) who was also a console designer, about ergonomics or "human factors". Customers have difficultly discriminating between things like audio path linearity, and control laws (gain, or boost/cut), and control feel...

Back last century Alps tooled up inexpensive faders with the dual cylindrical metal guides (like P&Gs) because of the feel not the performance. It didn't hurt that Jung Poon a Korean company did it before they did and was getting designed in by majors. The Jung Poon faders were literally crapola (the plastic parts inside were brittle and would too easily break). Alps came to the rescue with inexpensive faders that didn't suck, for a price that didn't break the bank.

In my experience customers buy almost as much on how faders feel than what they sound like. Subtle things like control laws can dramatically affect user perception. An EQ that is too fast or too slow can make a bad impression.

JR
 

Latest posts

Back
Top