Can pot taper be adjusted?

[bluedot]

I just finished a custom build of an Ibanez Destroyer - dual humbuckers with 500 cts pro pots, 1 tone control with a 220 orange drop cap. Pushback and shielded old school wiring. I had great fun doing a french polish on it!

Sounds great, and is very quiet - but I just don't like the taper on these pots. My main players are my ibanez jems, and their taper is very smooth and even.  Is there anything I can do to make them work better across their full range?

Thanks!

[curtisa]

You haven't mentioned what it is about the taper that bothers you. Rolls back too fast? Does nothing from 10 to 3 and then drops rapidly from 3 to 0?

What taper pots did you install in the Destroyer - logarithmic or linear? Are log or lin pots used in the Jem?

There are certain tricks you can do to pots by strapping fixed-value resistors across 2 of the 3 terminals that chage the taper at the expense of changing the pot's base value, but we'll need a bit more background to offer a suggestion to try out.

[bluedot]

Sorry about my ambiguity. Trying to put words to this.

Nothing much from 0-7 - then too fast from 7-10. All the pots including the tone. I used 500k CTS Pro pots from stewmac, https://goo.gl/5p19oC 

I don't know if they are logarithmic or linear. The pots used in Jems are Ibanez, 500k. I've never heard these terms used with pots - and did some searches without any luck.

I have used Bournes 500k pots in my Jem builds and they were ok, but don't know if they are lin or log. 
https://goo.gl/P4WDLy

 

[curtisa]

22 hours ago, bluedot said:

I've never heard these terms used with pots - and did some searches without any luck.

Linear taper means that the rotation of the shaft of the pot is directly proportional to the resistance of the pot. Logarithmic taper indicates that the relationship between shaft and resistance varies in a logarithmic fashion.

http://www.resistorguide.com/potentiometer-taper/

If two pots of equal value, one with linear taper and one with logarithmic were wired up as volume controls, they'd behave differently. Logarithmic should give the perception of an even volume change as it winds from one extreme to the other. Linear taper will probably sound as if all the change is in the first quarter of a turn from zero.

In addition, some log pots are "more log" than others, so the perceived smoothness of the same type of pot can vary between manufacturers.

 

22 hours ago, bluedot said:

500k CTS Pro pots from stewmac

It's not clear what the taper is on those pots, but in the photo provided the rear of the case is stamped "250KA". The "A" usually indicates that the pot is logarithmic. Although it's just a photo and shouldn't be relied on for what you actually get...

 

23 hours ago, bluedot said:

I have used Bournes 500k pots in my Jem builds and they were ok, but don't know if they are lin or log.

Again, the photo and product description doesn't make it clear, but if they felt "more right" to your ears, then probably log.

 

23 hours ago, bluedot said:

Nothing much from 0-7 - then too fast from 7-10.

Sounds as if the taper is too logarithmic. Quick fix which might work at a pinch is to strap a 1 meg or greater fixed value resistor from the middle lug of the pot to the outer lug (ie, the opposite side of the gound connection). Other than that you could try a different brand of pot. If you had success with the Bourns then you can always swap for those.

[alderbody]

Pots with a carbon resistive path can be tweaked by scratching the carbon evenly (just increasing pot's value) or not (tweaking the taper) across the perimeter.

Two things that need to be mentioned:

1) it's kinda hard to achieve the desired taper, since you have to be very delicate with the x-acto knife.

2) This method will ONLY make the pot's value larger.

[JohnH]

A parallel treble bleed circuit will move the taper towards what youd like and also maintain more consistent tone. 150k in parallel with 1nF if you have a 500k pot, od use 120k with a 250k pot

Edited December 18, 2017 by JohnH