Tone Pots: Linear or Audio? Why?

[David Schwab]

My two cents worth on this discussion...

I have been replacing the audio volume pots on most of my guitars with linear pots for a specific reason: if you need to turn down your volume when it is set to 10 you have much more control with a linear pot. This is very important to me if I am constantly adjusting the on-board guitar volume control all night, from song to song and during the songs themselves. I was using my Tele B-Bender last weekend and I hadn't already replaced the audio taper volume control- it was a real b*tch keeping the volume at the levels I wanted.

So my rule of thumb is this: if you are mainly concerned with turning down the volume from 10, then a linear taper works better. If you are mainly concerned with turning the volume up from 0- like doing swells- then an audio taper is better. (As is the case for all thumb rules, there are plenty of exceptions!)

Of course someone might just use a volume pedal and leave their on-board volume pot(s) set to 10 but that ain't me...

Steve Ahola

+1

This is exactly what I have always been saying! Audio taper is to hear a smooth taper when doing fades. If you aren't turning the pot, it makes no difference.

If you look at the faders on a mixer, you can see the log scale printed on the board. Faders are made to do fades, so they need that taper.

If you want to know that you have reduced your output by half, when the pot is on 5, then you need a linear taper pot.

[Mark Hammer]

That's a VERY interesting perspective, and one I'm ashamed to say had never dawned on me before. Indeed, it maps onto the very reason one uses a log pot in the first place: upward and downward adjustments anywhere in the full range of amplitudes should be perceived as gradual, and log does that...across the entire range.

So, if one is building an amp, you bet your bottom dollar that a log volume pot is essential since the level will be adjusted in all sorts of ways, but mostly in the middle of the volume range and below, with noticeably less use in the top range. This is completely different than a guitar volume pot where the default is full volume, and adjustments are generally only in a downward direction.

As I am fond of saying, context is everything, and something that may be ideal for one context may be pointless or even antithetical to another.

Nice post, Steve. Great idea. Where's that thumbs up icon when I need it?

[Guitarist]

Hammer's dual range tone pots has worked great for me recently. I actually took a few apart and opened the half way point with a circular dremel disk so center opens the tone bleed altogether.

The top center of the resistance trace is scratched off:

Ω

I used a 250K audio so each tone circuit sweeps evenly across about 100K. This get you tone roll-off quick enough. While they were apart, I should've dinted the pots at the zero point so it's more set and forget.

I wonder where else these could be used.

[Mark Hammer]

That's clever what you did with the dremel. Essentially two no-load tone controls in one pot! I should try that since I find the lack of a centre detente a little too attention-demanding for my tastes.

As for calling it "Hammer's dual range tone pot", the original idea was actually in an article by Craig Anderton on tone controls in Guitar Player about 30 years ago. All I've done is trumpet its virtues and suggest some component values. But thanks for the nod anyway.

[phfobric]

Craig Anderton - Mandrake Memorial!! ooooo I'm o-o-o-old...if this thread isn't completely dead...I am reconfiguring an HSS to a HB and two stacked coils. It's got the master (1 vol, 1 tone) going out and it being a HB environment, conned myself into thinking I needed to get 500k's. Where's the debate (or thread) on this? And I'm taking out a .022 cap; what's the consensus here on to what put back with the different pots?

[pdf64]

As there's a regular high inductance humbucker in there, a 500k vol control, and either 500k or 250k no load tone pots, would ensure getting the most top end out of the humbucker, so minimising the tonal discrepancy between the pickup types.
As for the tone cap, it's a personal taste, and matching to the pickup's characteristics, kind of thing - agree that 0.022uF is a good value start with.

Regards using linear vol pots on guitars, I agree it would work better when playing fairly clean, but if much overdrive is being used, they make it very difficult to clean up the sound.
My LP had all linear pots as stock, which now I've changed to log types is much more usable.

[phfobric]

Thanks for the help and reassurance. We use to rip into nearly every guitar we owned as "kids", but it has been a while, since, and the thing has gone full-circle, now. Here I am again, but I haven't lost the sense of "adventure", nor the ability to get tight solder joints. Thanks again!

[billyz]

I just got a Les Paul with the linear taper pots in it. I hated them. The Tone pot seemed to do nothing until down to 2 or 3 and then wham , all the highs were gone. The Volume was actually better but not much. In General, I had to use extreme settings to the low end of the pot to get anything of use.

I found a set of old Centralab 500K audio pots . first , I measured them. Wow, they all measured over 600k . Put them in with some vintage CDE .02 caps.
The improvement was radical. Nice smooth predictable roll off of Volume and tone. I can roll the volume to 6 and the guitar really cleans up my amp. The volume control is very useful all the way down even at 3. Rolling the tone off is very smooth , at 6-7 just a bit of edge is removed, down to 3-4 it is mellow and very clear, all the way off = Woman tone. Ok, I confess I did rewire to vintage spec . I don't think that had much to do with it though, because I tried it before changing pots, and I did not really notice a difference.

[David Schwab]

I just put a set of 500K audio taper volume controls into a bass, wired Jazz Bass style that I have been using. I didn't mean to use audio taper, but I forgot when I ordered them.

It's really awful trying to mix the pickup. You pull one down from 10 to 8, and you've lost all the output from that pickup in comparison to the other one.

My other bass with two volume controls has linear taper pots, and they do what you expect them to do. It's easy to mix the two signals.

Maybe audio taper pots work better in a Les Paul because the controls are wired to shunt both pickups when you turn them down. But they don't work well in Jazz bass type circuits.

Now don't forget, Gibson is using 300K pots in their guitars, so a 600K pot (which is way out of spec) would sound a lot brighter and with more range as you turn the control.

That has nothing to do with being audio or linear taper. They don't sound different.

[billyz]

I was under the impression that most Jazz basses used 250K A pots.

I measured the Gibson and the original pots were 500K + , all linear. I agree the extra 100+ ohms should make the highs more evident.

BTW, I own several Jazz Basses 65, 67, 72. They are all stock and I have no issues with the volume / pickups balance. They work very predictably. Perhaps active circuits benefit from linear taper pots. Or it is just a personal preference.

As my dearly departed mother would say " To each their own".

[ReginaldBisquet]

Reading through this thread, I was curious to see what people say about P90s.

My latest project guitar is an SG currently supplied with humbuckers. Removing them to install a set of humbucker-sized P90s and was curious if I should switch out the stock 500k controls controls for 250k audio pots (volume) and 250k pots (linear) for tone with a .022uf capacitor across each tone control.

I use the volume and tone controls a lot on my PRS Soapbar - which is equipped with one volume and tone control (both 500k audio) and a .022 across the tone.

What do you guys think?

[J M Fahey]

I still could not understand why anybody would use anything but a linear pot for tone. The logarithmic compression that your ear hears in, is only for volume, not tone/frequency differentiation

Fact is, you are not "tuning" anything, the standard tone control only attenuates highs more or less, so it is really "the volume of the highs" , benefiting from a Log response.
Using a linear pot will cause practically nothing for about 80% of the rotation angle available, and a sudden treble cut in the very last part.
If that's fine with you ... good ... but in that case you might just use a tone switch.
Better than any Cafe type discussion, you can play continuously any chord you like on your guitar, volume on 10 on a clean channel, and have somebody move the tone knob from 0 to 10 and back, hearing the effect.
With a Log pot, you will hear a reasonably smooth tone change , at least over a great part of the scale; with a Lin one, nothing ... nothing .... nothing .... sudden treble loss in the last 20% or less.

[David Schwab]

I use linear tone pots, and they don't act like a switch. I get a very good range from barely on to almost all the way up.

Log volume controls are made for fading, so you hear a smooth sweep. That's not how you use them for guitar. Turning a log volume control half way down does not reduce your output by half.

If you wire up a two pickups like a Jazz bass, you will see that you cannot blend them using two log volume pots! All the useable range is in the last 10% of the rotation, which is unsuitable for blending two pickups.

So the fact is when you turn a linear tone pot half way off, you have ruced the high end by that same amount.

[LtKojak]

I use linear tone pots, and they don't act like a switch. I get a very good range from barely on to almost all the way up.

Log volume controls are made for fading, so you hear a smooth sweep. That's not how you use them for guitar. Turning a log volume control half way down does not reduce your output by half.

If you wire up a two pickups like a Jazz bass, you will see that you cannot blend them using two log volume pots! All the useable range is in the last 10% of the rotation, which is unsuitable for blending two pickups.

So the fact is when you turn a linear tone pot half way off, you have ruced the high end by that same amount.

I've always thought A=audio taper, B=logaritmic taper.

What do you mean when you say Linear taper? A or B?

I'm all ears!

[pdf64]

European and USA manufactures have used A and B designations in opposite ways to describe log / lin pot tapers, ie EU A=lin, B=log, (C=reverse log) ; USA A=log, B=lin.
Not sure about Japan.
Another complication with this is the steepness of the taper.
Normally, log/audio taper has the rotational halfway point at 10% of the electrical rotation, ie at halfway, 1V in would give 0.1V out.
However, other tapers are available, see the weber pot page, ie 30%, so that at halfway, 1V in would give 0.3V out.
BF fenders generally used 30% log pots for the volume and treble controls, 10% for the bass. That arrangement seems to give a very smooth control range. If 10% pots are used for the vol and treb pots, the control range seems to be skewed into the 7-10 region.
I think that 30% pots on guitars would please most people, the exception being guitarists that use a lot of gain.