No more 60 Hz hum in a PL2000 preamp.

Got the volume pot in. Was going to also use one of these for the balance pot, but it's too close to the toroid transformer. It fits, but too close.
So we know those original CTS pots are decent quality, silver plated, and have deposit issues on the wiper slip rings after all these years.
Going to rebuild the original CTS Dual balance pot to reuse. Think I have the proper colors of replacement wires.
 

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George S. said:
The pots in excellent condition except for the wiper slip rings that need cleaned and polished. I really like these old CTS pots.
Click to expand...
I used your posts a while back to convert the dual gang to a new single gang balance control in my S2. I kind of like that configuration, but all this potentiometer refreshing is interesting, George. Thanks for posting the pics of the guts. Looks like you're rebuilding a watch!
 
It's very easy to do Al! If you still have that dual pot, give it a try.
All the parts cleaned up nice and are ready for grease.
Note the resistance of the carbon tracks.
As Joe pointed out numerous times, this isn't a issue.
This isn't a issue because the pots are wired inverse to each other. The pot has wire pigtails and can be rotated. Simply adjust for equal channel output and lock it down with the knob indicator indexed.
Since this is my main preamp and I have extra balance pots, going to look and see if I can find a pair of better match carbon tracks, just because I can.
 

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Al, we'll see tomorrow. I do still have that single pot balance control with the wiring intact that I made way back when. I agree, I did like how that single pot performed
Have to wonder why they went from single to dual pots. Maybe lower crosstalk? We need a audio engineer to answer that. Maybe Joe knows why.
 
So, complications due to my inexperience. These pots are not as simple as I thought.
The carbon tracks are logarithmic. And, they are directional in regards to increasing resistance from lug to lug. That is, one version increases resistance clockwise, the other version increases resistance counter clockwise.
And I've been swapping tracks around without realizing this. Crap!
Lesson learned: Keep everything in order when disassembling these.
The ones on the right increase counter clockwise, the ones on the left increase clockwise .
 

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Three balance pots rebuilt properly in regards to carbon track matching and position.
Pulled a original out of the rooms system to use as a guide after measuring it. I'll rebuild it now as it's out and ditch the old wire.
Listening to the Allman Brothers on the Acurus L10 pre and a very old home built class A amp.
 

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Turned out great! Balance pot is snugged down very slightly off center to properly index the knob.
Now to hear what these ladder volume pots sound like.
 

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Hell yes, all that work was worthwhile and the system has climbed another rung!
Having equal channel output at all volumes is decidedly there now, makes a big difference.
The ladder volume pot turns with no clicks or pops, so I guess it's "make before break", which I thought only the much more expensive ones offered.
Been listening to electronica FLAC files. Higher details are evident in the music and I need to go into the MiniDsp and lower the subwoofer frequencies.
How can one ladder type volume control do that? Must be something to do with impedance that I'll never fully understand.
Freaking unreal the difference this has made.
 
Gene, a scope is not the best tool to see noise. What I was doing there was providing a equal signal to both channels and checking for equal output.
Next weekend I'll try to find time and measure it for distortion and noise on the QuantAsylum QA403.
I love test gear that allows me to see and measure the invisible.
 
When I went from new quality Alps pot to cheap stepped attenuator (cheapest I could find) in my headphone amp, it was like going from an old busted Walkman to a center seat in symphony hall.

It is crazy how drastic the difference is.
 
J!m said:
When I went from new quality Alps pot to cheap stepped attenuator (cheapest I could find) in my headphone amp, it was like going from an old busted Walkman to a center seat in symphony hall.

It is crazy how drastic the difference is.
Click to expand...
Jim, good to know. Going to do some reading this week and find out why. Think it has to do with impedance and frequency.
 
George - how do you switch power to the 2000-II ? The original power switch was on the back of the volume pot. Power strip or some external means to turn the preamp on/off?
 
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