Audio potentiometer replacement - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 04, 2020, 09:29:50 pm
content: 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 reasonhttps://bit.ly/3dbzldqI 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?

author: themadhippy
author_rank: Super Contributor
timestamp: May 04, 2020, 09:54:28 pm
content: if you want the best ,penny and gileshttps://www.cw-industrialgroup.com/Products/Legacy-Products/Faders/Rotary-Fader-RF15

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 04, 2020, 10:00:16 pm
content: Quote from: themadhippy on May 04, 2020, 09:54:28 pmThose are like 600$ newI need something reasonably priced (100$ or less) as the whole unit is 800$ so any more than that is quite a ridiculous amount to spend on a pot for such hardware.

author: John B
author_rank: Frequent Contributor
timestamp: May 04, 2020, 10:57:36 pm
content: Bourns makes some conductive plastic pots. I think there's audio spec ones, ie log taper, dual gang. Dual gang ones were more in the $20-30 range. Down to availability and demand I guess.

author: sam[PS]
author_rank: Contributor
timestamp: May 04, 2020, 11:37:44 pm
content: If you have more time than money and/or taste for diy electronic project, you may consider replacing the audio pot by LDR and use a 20cts generic pot as a control to a dimer for the LED's lighting the LDR. This method has made it's proof for audio circuit, it works very well, just it's not a drop in replacement part, you'll need to get your hands in it.Another well proofed method is to use a quality rotary switch and fixed resistors array. That's probably what's inside the 600$ gizmos that have been shown in previous post. That's also how the early REDD fader found in abbey road where made. That could probably be made for few 10's$. I've made some test that showed that for most mere mortal 16 position is enought, 32 is good and 64 is much more precise than what they could get with an analog pot.Just my 2cts...

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 05, 2020, 12:53:16 am
content: What about a PGA2311 along with a microcontroller and rotary encoder?

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 05, 2020, 11:12:43 am
content: Quote from: John B on May 04, 2020, 10:57:36 pmThey seem to all be 100kwhile mine is 50K.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 05, 2020, 11:13:16 am
content: Quote from: NiHaoMike on May 05, 2020, 12:53:16 amThe chassis is very small so I will need a drop in replacement without any additional modding

author: apblog
author_rank: Regular Contributor
timestamp: May 06, 2020, 02:40:03 am
content: Your link doesn't work for me.But any Bourns sealed conductive plastic audio taper pot will be fine.You said you can't get them in 50K, but I very much doubt that's the case.You don't need to spend any serious money on this part to get excellent quality.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 06, 2020, 08:26:40 am
content: Quote from: apblog on May 06, 2020, 02:40:03 amHere's the full link :https://www.aliexpress.com/item/32847980540.html?spm=a2g0s.12269583.0.0.124f2c2ecCm1LQI 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!

author: tooki
author_rank: Super Contributor
timestamp: May 06, 2020, 07:51:11 pm
content: Quote from: drummerdimitri on May 04, 2020, 09:29:50 pmThat 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!

author: John B
author_rank: Frequent Contributor
timestamp: May 06, 2020, 09:39:51 pm
content: Quote from: drummerdimitri on May 06, 2020, 08:26:40 amI 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.

author: pqass
author_rank: Super Contributor
timestamp: May 06, 2020, 09:54:33 pm
content: 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

author: glentek
author_rank: Regular Contributor
timestamp: May 08, 2020, 12:30:24 am
content: What about a digital volume control? I've used this in my car amplifier with good resultshttps://www.aliexpress.com/item/4000429773300.html

author: Bassman59
author_rank: Super Contributor
timestamp: May 08, 2020, 03:36:38 am
content: Quote from: tooki on May 06, 2020, 07:51:11 pmDC 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.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 09, 2020, 10:47:33 am
content: It's a scratchy pot since if I put upward pressure while increasing the volume, the scratchiness goes away.I found that the ALPS "blue" pot to be a worthy replacement as it is used in most mid-tier Hi-Fi equipment.Not sure if I need it to be linear or log. Any thoughts on that?

author: sam[PS]
author_rank: Contributor
timestamp: May 15, 2020, 10:56:29 am
content: For volume control the standard is using log pots, that's the reason why lot manufacturer call log pot "audio" pot. That's not the only solution but in doubt it's the safe bet.Just my 2cts ...

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 15, 2020, 01:39:29 pm
content: Quote from: pqass on May 06, 2020, 09:54:33 pmI also recommend this. There was a past thread dealing with this already.The resulting curve is usually good enough for audio purposes, and as I already mentioned earlier, there is an added benefit IME. The loading resistor allows to discharge static charge that tends to build up at the wiper - so that avoids the potential scratching sounds.OTOH, you need to consider the resulting input impedance and see if it can fit your requirements. Just my 2 cents.