Pots driving you potty

Rabs

CTS pots...   Been using them the whole time ive been building but I do notice that they do not all seem the same..

Most recently ive been buying the 500k CTS 450 series pots that apparently have an extra 10% tolerance and thus are actually 550k insuring that you get the full 500k output at least..

I definitely did notice that these pots seem more stable and have a really nice taper as where ive had some  CTS pots where the taper is so bad that its barely functional as a volume level.

The thing is how do you know what you are being sent?  The so called 450 series doesn't have any special serial number or marking from what i can see so when I buy them how do I really know what im getting?  I know I can test it with a multi meter and see how fast the resistance goes up and down but is there any other way to tell the difference between the exact pot type you have by looking at them?

normula1

CTS have a pot code datasheet https://www.ctscorp.com/wp-content/uploads/450G.pdf

Rabs

normula1 said:

CTS have a pot code datasheet https://www.ctscorp.com/wp-content/uploads/450G.pdf

Thanks for that..  It was interesting to look at but those codes seem to be for ordering pots from them..   Im talking about how to identify the code on the pots..  It says CTS 500 (obvious) then 1721 which as far as I know indicates the date it was made not the serial or model number of the pot.

Danielsguitars

It's funny you saying this as I recently put cts pots in a guitar and found one pot read 450k the other 480k and i think it affects the highs in the pickups volume

I'm now going to swap 2 vol back out and see what it's like then, I'm also going to swap caps, just sounds like it's got a blanket over it

I know wd music offer the premium cts 9% tolerance so I'm going to try them, they guarantee at least 500k 

I like linear volumes log tones which is hard to find good consistent 500k or above ones to match log ones

It's not very good imo

ICBM

customkits said:

It's funny you saying this as I recently put cts pots in a guitar and found one pot read 450k the other 480k and i think it affects the highs in the pickups volume

You can very easily test this with a few resistors and a small switch. For example if you have a 450K pot and a 30K resistor, connect the resistor between the pot ground terminal and the casing, with the switch to bypass it - that will let you hear the difference between a 450K pot and a 480K pot.

You can also use much higher value resistors (in the 1M - 10M range) to reduce the effective value of a pot, by connecting them in parallel with the whole track and again using the switch to either connect or disconnect them.

Then you use the switch to change the resistance on the fly while playing, very carefully listening to the sound from right in front of the amp's speaker. You will be able to fairly easily find how much of a difference in pot value is needed before it becomes audible.

Danielsguitars

ICBM said:

customkits said:

It's funny you saying this as I recently put cts pots in a guitar and found one pot read 450k the other 480k and i think it affects the highs in the pickups volume

You can very easily test this with a few resistors and a small switch. For example if you have a 450K pot and a 30K resistor, connect the resistor between the pot ground terminal and the casing, with the switch to bypass it - that will let you hear the difference between a 450K pot and a 480K pot.

I normally directly solder the ground lug to the casing, if i unsoldered it and put a resistor in between will that increase the pot value, if so I didn't know that and that's really good to know

I don't fancy unsoldering the pots again I must say, putting resistors in is much easier

ICBM

You can’t do it other than for testing - it will stop the volume going to zero.

It will actually only seem to drop to about half with a tenth of the pot value in series.

Danielsguitars

ICBM said:

You can’t do it other than for testing - it will stop the volume going to zero.

It will actually only seem to drop to about half with a tenth of the pot value in series.

Thanks for clearing that up, i tried it again today and came to the conclusion that the taper is utter rubbish anyway so ive ordered the wd pots to replace the whole lot, I'll see if I like them

It would be nice just to get the same pots every time without the hassle of worrying if the taper is good etc

ICBM

In that case I will answer the question for you and save you the trouble .

The difference in resistance doesn’t start to get audible until about 25% below and 33% above the ‘spec’ value. While it’s due that higher-quality pots may have a nicer taper, smoother physical action etc, they don’t sound better because they’re ‘more accurate’ or because they have 10% higher resistance.

There is a good reason why the standard manufacturing tolerance on pots is 20%.

You might be able to hear the difference between the two very outer ends of the tolerance range, but 450K to 550K is most likely not audible.

Rabs

ICBM said:

 While it’s due that higher-quality pots may have a nicer taper, smoother physical action etc, they don’t sound better because they’re ‘more accurate’ or because they have 10% higher resistance.

.

This is what I want in my pots..  Consistent smooth action and taper. Youd think they would be able to make all of them the same in that regard?

ICBM

You would. CTS used to, but their quality has gone down the pan in recent years - even their ‘premium’ ones aren’t as good as the ‘standard’ ones used to be in my experience.

Why a company can’t simply continue making a good product in the way they’ve always made it, without trying to constantly find ways to cut corners, I don’t know.

Rabs

ICBM said:

You would. CTS used to, but their quality has gone down the pan in recent years - even their ‘premium’ ones aren’t as good as the ‘standard’ ones used to be in my experience.

Why a company can’t simply continue making a good product in the way they’ve always made it, without trying to constantly find ways to cut corners, I don’t know.

Well this is one of the reasons I posted this thread. To see what other peoples experience is and know that its not just me 

Those 450 series one at the moment seem the most consistent ive seen in a while..

The thing is, is that how is a person meant to know what pots they have been sent?  Ive seen serial numbers on CTS pots before that indicate the model..  But the ones I just got only have CTS 500k and the date code..  The only way I will really know is once the guitar is done and playable.. 

Maybe the actual answer is to stop using CTS pots and find a more consistent maker? 

ICBM

Rabs said:

Maybe the actual answer is to stop using CTS pots and find a more consistent maker? 

In theory, yes. It’s finding one that’s actually better which is the problem... Bourns are good, but I’m not convinced they’re as good as the old CTS. Alpha definitely aren’t.

I’m just hoping Switchcraft jacks and CRL switches won’t go the same way.

Danny1969

Rabs said:

ICBM said:

 While it’s due that higher-quality pots may have a nicer taper, smoother physical action etc, they don’t sound better because they’re ‘more accurate’ or because they have 10% higher resistance.

.

This is what I want in my pots..  Consistent smooth action and taper. Youd think they would be able to make all of them the same in that regard?

To make a pot with an audio taper you either need to make  the curve of resistive material get progressively thinner at one end to create more resistance .... but then maintaining good contact with the wiper if more difficult  or you need to vary the thickness of the resistive material  ... but's that's actually not easily repeatable during  manufacturer ...... not for a £2 pot anyway. There are pots that are very good in that respect but they tend to cost around £12 each

In my work with mic pre amps, mixers etc I often add a resistor between the wiper and end lug to achieve a better taper for the application (a basic log pot is not a true audio taper) , that might be an option for you 

Rabs

Danny1969 said:

In my work with mic pre amps, mixers etc I often add a resistor between the wiper and end lug to achieve a better taper for the application (a basic log pot is not a true audio taper) , that might be an option for you 

Cheers man..  I may well decide to look in to that...

The ones that I got  from the 450 series are £6.95 each  https://www.ebay.co.uk/itm/CTS-Guitar-Pot-500k-Split-Shaft-Pot-Premium-450-Series-with-9-Tolerance/252917156436?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649  and as I say, so far they seem pretty good (on my third set),

And these long shaft ones also seem a bit more consistent in action and taper.

https://www.ebay.co.uk/itm/CTS-True-Vintage-Taper-500K-Split-Shaft-Audio-Potentiometer-Pot-long-shaft-/281241538241?var=&hash=item417b4d4ec1

You would think though with todays technology like laser cutting and measuring that they would be able to sort that out? Maybe theres a big gap in the market there?

streethawk

Rabs said:

Danny1969 said:

In my work with mic pre amps, mixers etc I often add a resistor between the wiper and end lug to achieve a better taper for the application (a basic log pot is not a true audio taper) , that might be an option for you 

Cheers man..  I may well decide to look in to that...

The ones that I got  from the 450 series are £6.95 each  https://www.ebay.co.uk/itm/CTS-Guitar-Pot-500k-Split-Shaft-Pot-Premium-450-Series-with-9-Tolerance/252917156436?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649  and as I say, so far they seem pretty good (on my third set),

And these long shaft ones also seem a bit more consistent in action and taper.

https://www.ebay.co.uk/itm/CTS-True-Vintage-Taper-500K-Split-Shaft-Audio-Potentiometer-Pot-long-shaft-/281241538241?var=&hash=item417b4d4ec1

You would think though with todays technology like laser cutting and measuring that they would be able to sort that out? Maybe theres a big gap in the market there?

I stock those too - quid cheaper than ebay.

To answer your original question: these particular versions have 'cp' stamped on the pot. If you zoom in on the second pic you'll just about see it.

http://www.amberguitar.com/wiring-for-gibson/189-cts-tvt-500k-potentiometer-long-shaft.html

The brass shafts are usually a good sign of uprated CTS pots.