What a difference a pot makes

[Bob-I]

I've used Alpha pots in many of my builds, mostly because of availability. In my guitars I use CTS, same reason.

So a few weeks ago the volume pot on my modded bassman was very scratchy, sprayed it, NG. The amp uses a TrainWreck Rocket pre, which has a 500KA volume. I didn't have one around but I had some guitar pots, CTS 500KA.

All I can say is holy S&*t what a difference. The taper is far better making it much easier to adjust the volume, but somehow the overall tone is dramatically better.

Thinking I did something else while I was in there, I bought a few 1MA CTS pots and swapped them into my Princeton reverb (almost) clone and Super reverb (almost) clone. SAME RESULTS.

The Princeton always had an issue where the distortion got ratty sounding above about #6 on the volume knob. With an OD pedal it was even worse at the upper ranges of volume. With the new volume pot I've run it wide open and it's got that really nice BF distortion. The OD pedal makes it really sing. The volume knob is now more even from 2-10 instead of all volume coming on below #6.

The Super had an issue where it would sound really thin with the volume at below about #3, and at that level it was insanely loud. With the CTS I can now get the volume very low but still that big fat Super reverb tone.

No more Alpha pots for me...

Just wanted to share.

[lumox0013]

what series of CTS and where are you buying from? thanxx

[eddie25]

Say it ain't so! I used these in one of my favorite amps I've built, but haven't used them since, due to cost. Gonna need to do an A/B soon.

[Bob-I]

I bought them from All Parts, they're EP-4989 $5 each.

[martin manning]

I'd like to understand this, and would be most interested in the results of any A-B testing. Do you think the CTS sound better when both are working properly? Something about the conductive properties of the element?

Taper is one thing, but a scratchy pot has poor contact between the wiper and element (assuming no DC on the pot). Correcting that would likely bring a noticable improvement in sound quality. The Alpha input volume pot on my ODS was a bit noisy out of the box, but it would clean up after being rotated back and forth. That happend a few times after the amp was left unused for a few days, but it doesn't seem to display that behavior anymore. There are definitely some quality control issues with these pots.

[Bob-I]

Yea Martin, I thought at first it was just a bad pot but the difference in overall tone was quite different. I'm thinking of the difference in composition. Like changing a key resistor from a poor quality MF to a quality CF changes the tone.

Who knows, but I like it.

[Jana]

Anybody from the '60s can tell you that quality matters.

[diagrammatiks]

if your willing to pay 5 bucks for an alpha or cts you might as well grab some mil-spec rv4's from steve at apexjr.

[sliberty]

I know what you mean. Went to see the Grateful Dead in 1974 at the Nassau Colliseum, and was straight through the first few songs. But then during Dark Star, the doobies got going and .... Oh wait .... You meant potentiometers?

Never mind.

[Structo]

My D'lite volume pot was occasionally scratchy which I attributed to having a bit of DC on it.

I've had pretty good luck with Alpha pots but I haven't done any direct comparisons.

I took efforts to source what I thought were good NOS parts for my 100w.
When I built the 100w ODS I used several NOS pots including two NOS 1M Allen Bradley pots which both turned out to be defective.
The volume pot would get to about 1/3 rotation and the go full volume.

And the Master volume would jump around.
I replaced them both with Alpha's and it worked fine.

Yes it is getting hard to find good quality without breaking the bank.


But hey, I'm willing to try a couple of these CTS pots just for grins.

[martin manning]

AES has CTS pots in the common values for $3.65; still twice the price of an Alpha. They are not exactly the same as the CTS AllParts sells, at least not in the pictures. The AES pots actually look more old-school, with brass bushings and stamped steel saddles instead of one-piece die-cast. I wonder would these use the same internal materials and construction?

[LeftyStrat]

I've always used Clarostat pots for "keeper" builds, and have always attributed the better sound to the fact I built a bunch of throw-aways before committing to a keeper.

But this is definitely something worth investigating.

[Gaz]

When I built the 100w ODS I used several NOS pots including two NOS 1M Allen Bradley pots which both turned out to be defective.

There is a chance you melted the track if you soldered at too high a temp or too long without a heat sink. The conductive plastic is more delicate than the typical carbon tracks.

[Structo]

Well I didn't think I did.

Soldered no different than I have many times before.

Are you saying the vintage AB pots have conductive plastic?
I would think the old ones would be carbon.

What I did do those was cut off the too long shafts.

They both had like 2 inch shafts which I cut off with a Dremel and cut off wheel.

Maybe the vibration did something? Dunno

Something we have discovered over the years is that any dealer that orders a large number of pots can have them custom made.
So they can specify the rotation resistance or torque, whether or not there is grease inside, bushing and shaft length.

There seems to be different appearances with CTS pots.
Nylon, aluminum, or brass shaft.
The ones with the smooth back and the ones with the dimple back where the shaft end protrudes.

That kind seems to be like the vintage CTS pots.

And also whether the top is cast or stamped.

[img:111:110]http://www.tubesandmore.com/cemirror/inv/R-VC-TH.GIF[/img]

[img:150:210]http://a248.e.akamai.net/origin-cdn.vol ... 000-2T.jpg[/img]

[img:335:336]http://a248.e.akamai.net/origin-cdn.vol ... -000-2.jpg[/img]

Then of course their higher end guitar pots, which I have never tried.
Anybody here try these?

[img:150:150]http://a248.e.akamai.net/origin-cdn.vol ... -000-1.jpg[/img]

[husky]

I've used Alpha pots in many of my builds, mostly because of availability. In my guitars I use CTS, same reason.

So a few weeks ago the volume pot on my modded bassman was very scratchy, sprayed it, NG. The amp uses a TrainWreck Rocket pre, which has a 500KA volume. I didn't have one around but I had some guitar pots, CTS 500KA.

All I can say is holy S&*t what a difference. The taper is far better making it much easier to adjust the volume, but somehow the overall tone is dramatically better.

Thinking I did something else while I was in there, I bought a few 1MA CTS pots and swapped them into my Princeton reverb (almost) clone and Super reverb (almost) clone. SAME RESULTS.

The Princeton always had an issue where the distortion got ratty sounding above about #6 on the volume knob. With an OD pedal it was even worse at the upper ranges of volume. With the new volume pot I've run it wide open and it's got that really nice BF distortion. The OD pedal makes it really sing. The volume knob is now more even from 2-10 instead of all volume coming on below #6.

The Super had an issue where it would sound really thin with the volume at below about #3, and at that level it was insanely loud. With the CTS I can now get the volume very low but still that big fat Super reverb tone.

No more Alpha pots for me...

Just wanted to share.

Having done many plots on pots the Alphas are usually 2 step (two lines no curve) The CTS are usually 3 ~ 4 and the PEC are 4~5.
You will also find the dead zone at each end varies greatly, but is usually 1 number or more
Not talking tolerance here which is usually 20% !!!
Most of the CTS are 10% audio taper and the Alphas usually 15% or 20%
The PEC are usually 10% and yes that makes a big difference. Any time I have tried a Alpha that is 10% audio combined with the cheating "curve" they don't sound right at all.

PS Nylon shaft CTS are no longer available.