The one I installed has conductive plastic track.
Benchmark DAC1 Volume Control replacement.
Currently I use Benchmark DAC3 HGC, but still keep DAC1 for the second system. I had static with volume pot on DAC1. I sprayed it inside with Deoxit F5 and it was OK for a while but static came back. Benchmark had problems with early pots and replaced them for $50, but I decided to do it myself. I unsoldered and removed old pot and measured it. It appears to be 10k linear characteristic, that are almost never used for volume control. I started searching on internet and found that Benchmark is using them purposely, because it is much easier to match tracks/gangs. I wonder if anybody encountered linear pot for volume control. I have to admit it was a little difficult to set low volume at night, but channel matching was pretty good. I didn’t want to guess the circuit Benchmark put it in, so I ordered similar pot, with exactly same dimensions (even looks identical) but with conductive plastic track. I ordered 3 and measured voltage at the wiper with 5V between pins for both gangs. Two of them were about 2x worse but one showed only 0.07V difference in the middle and about half of that at 1/4 turn. It would correspond to 20log(2.57V/2.5V)=0.24dB - pretty good, assuming pots are often specified as +/-3dB between gangs. New pot is smooth turning without "bumps" imitating steps in the original one, but that’s OK. If anybody is interested part number is: TT Electronics P092N-QC15BR10K and available at Mouser.
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this is plastic trackDon’t think so, looks like all pcb copper contacts with brass/copper wiper to me, far better than any conductive plastic, cermet or carbon. https://ibb.co/8M51znn click on the pic for a super closeup. Only one thing better for a passive volume control, is you know what. Cheers George |
George, thank you for the link. Looks very promising. It would have to be on the outside, since room inside is limited to standard 9mm pot while PCB is so close to the hole, that nothing else would fit inside. One option is to put it on the outside, but I will see if this plastic track is acceptable the way it is (it is a second system). Original pot was cermet, this is plastic track, but they come in different qualities/compositions. People claim that plastic tracks have distinctive sound. I used ALPS "Blue Beauty", also conductive plastic track, in headphone amp I built and it sounded great. I will save this link for the future projects/replacements. |
P092N-QC15BR10K That type aren’t the best https://www.mouser.com/images/ttelectronics/lrg/P0915.jpg Take it out, and use this 21 position switched smd resistor pot, in an external box if needed. https://www.ebay.com/itm/DACT-Type-SMD-Steeped-in-Attenuator-21-Step-Volume-Control-10-250K-Potentiometer/392817481761?hash=item5b75bf1821:g:wksAAOSwD4Je0LRB Cheers George |