Anybody here with experience with the range of pot tapers in use?

[PhilC58]

I recently replaced the 300k pots that Gibson installed in 1993 in my LP STD with Bare Knuckle 550K pots at the same time migrating to 50’s wiring using SLOW taper pots.

I did this because I had the guitar electronics apart to replace a failed 498T bridge pickup. The replacement seemed way hotter and very difficult to tame tonally. Thinking that it was just that I’d had a guitar with an odd bridge pickup originally and that this was the way the pickup should have been I resorted to changing the pair with som unpotted lower output PAFs.

Whilst the PAFs are very very nice tonally with the open airiness that is very welcome from them, trying to balance them tonally when flipping between neck and bridge by adjusting the tone has not been so great. The bridge tone pot only really affects the tone between 0 and 2 on the pot. This is with an 0.022uF cap on that pot. I checked the new pot taper against the specification and it seems about right (within tolerances). The idea of SLOW taper was to provide the best control through the volume and tone changes. I am hoping to try a fast taper pot on the tone to see if that improves things, but wondered if others have had similar experiences when tweaking pots on their guitars?

Any experiences gratefully received.
Phil

 

[poor man's burst]

I don't know what "slow taper" means, but a tone pot affecting the sound from 2 to 0 is how I describe a linear pot action.

 

[DrewB]

I don't know what "slow taper" means, but a tone pot affecting the sound from 2 to 0 is how I describe a linear pot action.

When I was reading Phil's description of how the tone pot is acting, I was thinking "linear taper."

 

[PhilC58]

I don't know what "slow taper" means, but a tone pot affecting the sound from 2 to 0 is how I describe a linear pot action.

Pots are generally bought as Linear or Logrithmic. Logrithmic or otherwise audio pots can have a variety of ‘tapers’ or resistance curve plots varying from fast to slow taper and for volume pots used by some players for ‘swells’ they may want a fast taper to only need a short movement of the potentiometer to sweep in or out the volume. At least that is how I read things.

You might say from that that logically the tone pot should be linear but it seems that the pots being sold for guitars are generally Logrithmic. The slow taper pot that I have used is showing at position 5 on a 0 - 10 scale 40 percent of the potentiometers full resistance, so not linear but not that far off linear, however the tone change is anything but linear.

 

[poor man's burst]

A logarithmic pot at 5 should mesure 10-20%. If it mesures 40%, it is in the margin of error of being linear, which is coherant with its action being from 2 to 0.

 

[PhilC58]

A logarithmic pot at 5 should mesure 10-20%. If it mesures 40%, it is in the margin of error of being linear, which is coherant with its action being from 2 to 0.

This is where the pot ‘taper’ comes in. Medium Taper CTS curves suggest 20%, Slow 30% and Fast 10%.

I used slow taper thinking it would give easier control of the tone, but it doesn’t in my experience.

 

[PaulD]

Using a linear pot for tone controls will result in a very on/off type of control where almost everything happens between 0 and 2. The figures given would suggest that a "slow" taper at 30% would be closer to a linear pot than a standard log pot which would likely result in the sharp cut off that you describe (a true linear pot would be 50% and a true log pot 10%). A standard log pot (10%) would be a much better choice for a tone control.

All of this "hype" about pot tapers has come about from people measuring pots from vintage guitars to check the resistances and tapers. A 50+ year old pot will likely have significant wear to the pot track and the characteristics will vary somewhat from when it was new. Back in the day the choice was between log or linear pots and Gibson chose to use 500K log pots which works fine. In the Norlin era they changed to using 300K linear pots which personally I think doesn't work quite as well (certainly not for the tone controls anyway).

 

[PhilC58]

Using a linear pot for tone controls will result in a very on/off type of control where almost everything happens between 0 and 2. The figures given would suggest that a "slow" taper at 30% would be closer to a linear pot than a standard log pot which would likely result in the sharp cut off that you describe (a true linear pot would be 50% and a true log pot 10%). A standard log pot (10%) would be a much better choice for a tone control.

All of this "hype" about pot tapers has come about from people measuring pots from vintage guitars to check the resistances and tapers. A 50+ year old pot will likely have significant wear to the pot track and the characteristics will vary somewhat from when it was new. Back in the day the choice was between log or linear pots and Gibson chose to use 500K log pots which works fine. In the Norlin era they changed to using 300K linear pots which personally I think doesn't work quite as well (certainly not for the tone controls anyway).

I don't know about 'Hype' per se Paul. The trouble is that most tech articles seem to consider that the higher resistance pots i.e. 500k or 550k restain a better 'brightness' when compared against 300k or less pots. Now is that just the Vol pot or what?

Again the articles I have read, and I have read several, don't descriminate between Vol and Tone use of the pot.

I have a fast taper pot on its way so we'll see if that helps make the bridge pickup tone control easier to adjust over a wider sweep of the pots range.
Phil

 

[poor man's burst]

I don't know about 'Hype' per se Paul. The trouble is that most tech articles seem to consider that the higher resistance pots i.e. 500k or 550k restain a better 'brightness' when compared against 300k or less pots. Now is that just the Vol pot or what?

Again the articles I have read, and I have read several, don't descriminate between Vol and Tone use of the pot.

I have a fast taper pot on its way so we'll see if that helps make the bridge pickup tone control easier to adjust over a wider sweep of the pots range.
Phil

It is true that the higher the pot value, either the volume or the tone, the brighter the guitar sounds, when the pot is on 10. But it has nothing to do with the taper. The taper changes the way the pot acts when you turn it down.

 

[PaulD]

It's certainly the case that higher resistance pots will result in a brighter tone due to less high frequencies being bled off and that applies to both the volume and the tone pots, the effect will likely be greater in the case of the volume control and I doubt anyone would hear a noticeable difference with small changes (+/- 20% say) in the tone control value.

The problem with these things is that people hear what they expect to hear when the only real way to compare the differences would be to carry out a proper blind listening test where you can instantly switch between 3 different pots, say 2 that measure exactly 500K and 1 that measures say 550K, then ask people to pick out the one that sounds different. I'd put money on the fact that 75% of people would either not hear a difference or get it wrong and of the 25% that get it right most would be luck rather than judgement! This is what I'm referring to when I talk about hype.

Back in the 50's when Gibson were building the guitars that we all love and lust after they bought pots from CTS and Centrelab in the thousands, these were nominally 500K pots with a tolerance of +/- 20% so could have been anywhere between 400K and 600K. The pots went into a big bin and were picked at random when they went into a guitar. No one worried or cared what the actual values were and they certainty didn't worry about what the taper was, they were standard log pots.

 

[PhilC58]

The acid test was to install a Fast Taper Logrithmic pot for the bridge tone.

Where the Slow Taper post only really had any effect on the bridge pickup tone between 0 and 2, the Fast taper pot gave the same tonal swing as the slow taper pot but this time between 0 and about 4.5 on the pot so much easier to select a tone setting (not so hair triggered). This is much nearer what I was hoping for when I set about the task of switching to 50's wiring and upgrading the pots. Ideally the tome control range would be over more of the post sweep than it is even now but that could also be a factor of the capacitor used, in this case it is an 0.022uF cap which is what most seem to recommend for the bridge pickup.

Overall I am wishing I had bought fast taper pots all round and may well end up having to do that, which is a PITA as it's a faff taking the lot out each time which is necessary to because they are mounted on a metal plate before the p[ot shafts go out through the body wood and its essential to be careful that the pots threads are not fouling the body wood as they go through as it looks as if it would be easy to chip the nitro lacquer albeit behind the washer, nut and know that fits over it.

Hope this info is useful to others playing with their pots.

Phil.