CTS Pot Taper

[Littlewyan]

I've just built an amp and used CTS Pots across the board, but I have to say, I'm not impressed with the audio taper at all. On the volume controls, between 0 and 1.5, nothing happens. Then above 1.5 the volume will ramp up quite quick, which makes it difficult to get a good volume for bedroom playing. Is this the norm for CTS pots? If it was nothing between 0 and 0.5, I'd understand, but this seems like a large area of taper to lose.

[wpaulvogel]

Measure the resistance and make sure you didn’t get linear. I’ve used CTS on several amps and they work great.

[Littlewyan]

They're definitely Log Audio, they just don't seem to come on until the volume control is at 1.5 from 0 (Control goes to 10). Have you found this on your amps?

[martin manning]

Based on a few Googles, the CTS audio pots seem to have that characteristic.

[pdf64]

What pots don’t? Seems standard / typical to me. Electrical rotation is generally 10 to 15% less than mechanical rotation, eg 240 / 270. And with the cheap pots we use in this application, it’s invariably an untoleranced characteristic.

[Littlewyan]

I found an old post where someone compared various pots and you're right, it seems CTS do have this characteristic. Alphas appear to be better in that they do come on sooner, so I may switch to those. I have used them before in other amps so will do some tests on those first.

I realise I can't expect new pots to come on as gradually as pots from yesteryear, but having nothing between 0 and 1.5 (would actually maybe say it's more like 1. is a real pain for getting a bedroom volume on the amp.

[Guy77]

I found an old post where someone compared various pots and you're right, it seems CTS do have this characteristic. Alphas appear to be better in that they do come on sooner, so I may switch to those. I have used them before in other amps so will do some tests on those first.

I realise I can't expect new pots to come on as gradually as pots from yesteryear, but having nothing between 0 and 1.5 (would actually maybe say it's more like 1. is a real pain for getting a bedroom volume on the amp.

I have experienced the same thing as you have with the CTS audio taper pots coming on a little later than the alpha pots. At first I thought it was a defective pot but then after going through about 10 cts pots from 4 different sources I realised it is just how the cts pots are built.
What I do now is just use alpha pot for my volume and master volume and cts/alpha for other controls.

Happy Holidays!
Guy

[pdf64]

Maybe the CTS track is intended to also accommodate the incorporation of a rotary switch actuating at full CCW.

[Littlewyan]

Possibly. Cost cutting maybe?

It sounds like my best option is to just replace the volume pots with alpha pots. I did look at PEC, but they are incredibly expensive and don't appear to be all that reliable going by some reports I've read.

Thanks for your responses guys.