Why is it common to see recommendations for linear tone pots

[Yogi B]

I was reminded of this by sumgai's recent post in the Bass-cut and the G&L PTB system thread:

Aug 9, 2018 11:23:40 GMT -5 sumgai said:

Common practice is to have ... linear in the two tone (treble-cut) slots.

As I discovered a long time ago a linear tone control (especially a higher value), after following other 'advice' or talk of "common practice", a linear tone control has most of its effect in a narrow region at the lower end of its range -- that isn't for me. Or as JohnH notes in the Taper of Pots thread:

Feb 28, 2014 15:42:00 GMT -5 JohnH said:

This shows why we don't normally use linear pots as tone controls. All the action happens in the lower settings, and not much at all above 5.

I've had the question since I tried it out for myself, but so far I haven't found a good answer for it. However, it does seem to be a long standing idea -- here are two of the earliest mentions I could find:

October 2005 Seymour Duncan forums:

Generally speaking, you use log taper for volume, linear for tone.

July 2004 Guitar Noise Forums:

Tone control will tend to use a linear pot, while the volume should be log.

Though, I think my favourite advice is from (UK guitar parts supplier) Axesrus, because it is technically right:

The tone pot on most guitars is a fairly neglected control nowadays sadly. The tone of any given pickup at anything less than 9 seems somewhat muddy and woolly, so more often than not the tone pot is stuck on 10 and left there.

In our experience, most complaints with pots come purely from the control that the stock tone pot is offering to the player.

The reason seems to be that most tone pots (contrary to popular belief oddly) in any production guitar will in fact be a Logarithmic taper. This will make it behave exactly the same as the volume control (at least to our ears).

As we discovered earlier, a Log pot will have most of its control at the higher end of its sweep – which works absolutely fine for volume control – however, with a tone control, when you’re making a “selection” – it leaves a little to be desired, purely because each setting is not equal to the ear.

Some people are absolutely fine with this setup, and will use the tone pot to make minute tweaks in the higher numbers.

An alternative would be to use a linear taper pot rather than the standard Log version – this will give you much more accurate control over the tone of your pickups.

If you find that your tone pot cuts to much treble between 9 & 10 then, yes, a linear taper would help, but firstly I'm not sure that's a problem that anyone has, and secondly the jump from logarithmic to linear is a big one -- they would probably be better served with a larger value (still logarithmic) potentiometer with a tapering resistor in parallel.

---

So I suppose this is a three part question:

1. Where did this idea come from?
2. Does anyone themself prefer linear potentiometers for the standard tone control, or know of someone who does?
3. Even given the above, they would probably be in the minority, therefore why has this idea proliferated so?

[reTrEaD]

Aug 9, 2018 18:59:04 GMT -5 Yogi B said:

So I suppose this is a three part question:

1. Where did this idea come from?

I dunno but the more important question is:  Why can't we make it go away?

Aug 9, 2018 18:59:04 GMT -5 Yogi B said:

Does anyone themself prefer linear potentiometers for the standard tone control, or know of someone who does?

To be honest, I don't use the tone control on a guitar.  I leave mine wide open all the time.

Aug 9, 2018 18:59:04 GMT -5 Yogi B said:

Even given the above, they would probably be in the minority, therefore why has this idea proliferated so?

Bad information is like herpes?  idk.

[sumgai]

Aug 9, 2018 20:50:03 GMT -5 reTrEaD said:

Aug 9, 2018 18:59:04 GMT -5 Yogi B said:

So I suppose this is a three part question:

1. Where did this idea come from?

I dunno but the more important question is:  Why can't we make it go away?

The answer to the first is "Leo Lore", and the answer to the second is that we don't want it to go away... it's correct, although it's much more polite to include something like Yogi did - "for those who like it this way", or similar.  Heads off most arguments at the pass.

Once again, History rears its head.  Leo had a veritable factory building full of parts/components/gear/all kinds of stuff that he'd gotten from scads of Army/Navy surplus stores after the war. (The U.S. is not big on keeping things on the inventory sheet, they cost money to store, maintain, etc.)  The short version here goes, when he was developing the Telecaster (nee Broadcaster) and Esquire, he had a large bin full of 0.047 caps, and another even larger bin of 1M pots. (And probably not much else, insofar as designing for a guitar went.  Keep in mnd that these were all amplifier parts, as he'd already been in the amp business for a couple of years.)  Now recall two things:

A) Leo was not an engineer by any means.  All of his electrical experience came by way of service in the Army during the war.  This leads directly to: 

B) He designed everything by ear, fine-tuning things to the way he thought others would like it to sound.  Then he'd go out and ask those very same "others" to give him feedback on what they were hearing.  In short, he flew by the seat of his pants.

All of which says, a room full of 0.047mfd caps, and another room full of 1MΩ linear pots, and.... you can guess the rest, amiright?

Muddle forward through the decades, and for some inexplicable reason (/s), players/owners/modders just didn't like leaving things alone.  The next thing you knew, everybody and his dog had a "better" way of doing things.  Not that I'm against this, indeed it's exactly how I got my start in the game.  But to forget how things were done originally is almost criminal.  That's why people like me are still around, to set the record straight (once again).

tl;dr:

Linear works just fine, deal with it.  If one finds a better way, they should either use it and be happy, or else go into manufacturing and produce that better mousetrap.

Aug 9, 2018 20:50:03 GMT -5 reTrEaD said:

Aug 9, 2018 18:59:04 GMT -5 Yogi B said:

Even given the above, they would probably be in the minority, therefore why has this idea proliferated so?

Bad information is like herpes?  idk.

Define minority.   The idea proliferates because of my answer/response above.

But I did like that alliteration with herpes. 

sumgai

[reTrEaD]

Aug 13, 2018 23:16:46 GMT -5 sumgai said:

tl;dr:

Linear works just fine, deal with it.  If one finds a better way, they should either use it and be happy, or else go into manufacturing and produce that better mousetrap.

Linear doesn't work well at all for a treble-cut control but there's no need to deal with it, almost nobody uses it ... not even Fender.  There are probably a few guitars with them (they were installed during a rewire because someone incorrectly told them that was what they should use).  But quite a few of those have been replaced after the person who installed them didn't like the fact that they did very little until the knob was rotated near the counter-clockwise extreme.

There are a lot of linear pots in guitars ... as volume controls in 2-volume configurations.  But that's a completely different issue.

[pedanticus]

Dang that's funny!

Begs the question why we don't have a Russian 'Leo' by now, given the penchant for paying top dollar for dusty Cold War caps?

I was taught that the "prefered" selection of taper, was based on human audio processing. We process volume change in a logarithmic manner. However, tone is percieved in liner fashion...hence the "correct choice" line. But this is art. So if you like your eggs green, make em that way. But if you got a problem, maybe this could help.

[reTrEaD]

Sept 5, 2021 5:55:22 GMT -5 pedanticus said:

We process volume change in a logarithmic manner.

This is true.

Sept 5, 2021 5:55:22 GMT -5 pedanticus said:

However, tone is percieved in liner fashion

This is false.

[newey]

Sept 5, 2021 16:29:17 GMT -5 reTrEaD said:

pedanticus said:  However, tone is percieved in liner fashion

This is false.

I'm finding it less and less linear as I get older, too. You disproportionally lose the higher frequencies as you get older, I find myself turning the treble up . . .

[Yogi B]

Sept 5, 2021 16:29:17 GMT -5 reTrEaD said:

Sept 5, 2021 5:55:22 GMT -5 pedanticus said:

We process volume change in a logarithmic manner.

This is true.

Sept 5, 2021 5:55:22 GMT -5 pedanticus said:

However, tone is percieved in liner fashion

This is false.

Although I agree with your sentiment here, I don't know that I'd outright agree with those very definite statements.

In general I'd say that humans 'perceive' most things linearly — a linear scale is easier to comprehend, regardless of the underlying physics of any particular phenomenon. It's more a of a question of how does the stimulus need to vary to fit with our understanding of what appears linear to us.

---

It's also interesting that wherever I see the justification for linear pots that humans perceive tone linearly, it's never qualified specifically what "tone" means — perhaps because if any more thought had been put into that statement then the person writing it would realise it couldn't be true. To my mind "tone" difference they're trying to describe can be thought of in two ways, either

• The amplitude of treble frequencies, relative to the amplitude of other frequencies;
• The frequency at which this amplitude difference occurs.

The first case is contradictory to the previous claim that a logarithmic taper is what is needed for a perceived smooth volume (amplitude) change. The second case should be obviously false to anyone who has ever looked at a fret board (or knows that, though measurements of pitch using semitones & octaves sound linear to a human ear, in fact an octave represents a doubling of frequency).

[pedanticus]

Yeah, the tone thing is very hard to pin down.

I did some research to follow up that unqualified statement, and I can find multiple references to the log scale in Human hearing in general, none on tone.

Unless you want to discuss intonation in human language..? Not me.

There are sound clips around, of log vs linear output. I wonder if someone has thought of building a "test rig" so one could check how their pot choice will sound in THEIR ears: young, old, hammered, reconditioned...

[Jack TriPpEr]

This is a demo video from YouTube where a guy demonstrates how both a linear pot and an audio pot perform when used as tone controls.

I thought this video would be a nice contrasting data-point to all the other replies above since this demo is auditory-based and all prior replies are theoretical-based.

At the end of the day, the "correct" choice should be decided by what your ears tell you, not your beliefs or theories.

[pedanticus]

Well, that's just the ticket.

Thanks.

I can't HEAR any logic in the argument for Linear Tone pots.

I found John S Cooper, did another one where he graphed out different pots.

Linear vs Audio taper is all good in theory, but different manufacturers muddy the waters with how they build their pots.

So the question becomes: Linear vs whos take on the Log scale!

This video takes a breif look to distill some science from those muddy waters:

Yes, the ears have it.

[Deleted]

I think he has his own web page and is ok person just to talk things over if you want

ive talked to him via messages and that isnt as easy as you think

[cooltone]

The scientific logic of linear Vs log pots is not really practical here because it comes down to the 'feel' of the pot while playing.


There's more to it than the logarithmic human hearing.


For example, some guitar amps have high compression and a linear vol lot might be preferred.


Similarly, tone roll-off is determined by the collapse of the resonance peak as the resistance is increased. It's complicated to work out and just as easy wire-in different pots and see what you prefer.

Personally, I like linear-volume and log-tone. I was quite surprised just how good a linear-volume worked with my valve amp.

I find the biggest problem with guitar wiring is that I never put back the cover plate😎

[sumgai]

Jan 6, 2022 5:19:21 GMT -5 cooltone said:

I find the biggest problem with guitar wiring is that I never put back the cover plate

Try using magnets in place of screws. It's hard to explain away when you're flailing away on stage, and your stash falls out of the cavity and onto the floor....

[ozboomer]

I'll make a quick jump through this frying pan... by referencing:-

Why is the relationship between frequency and pitch exponential?

...thereby complicating the issue further, as it (may) also be a function of the equally tempered scale...

...and perhaps the variation of tone perception with volume, as suggested by:-

The non-linearities of the Human Ear

...although, I find this second reference a bit hard to hear.

What does JohnH's Guitar Freak calculator show?