Tone Pots: Linear or Audio? Why?

[SlidePicker]

I've seen recommendations for both linear and audio taper guitar tone pots. Which works best? Why?

[Mark Hammer]

The general rule of thumb is that audio taper is used for volume and anything approximating the volume-like function, where linear is used whenever knowing the "middle" of something is important. As you might expect, linear pots are used for things like blend/mix/balance controls, as well as for EQ controls where identifying exactly where you are either boosting or cutting is important.

Beyond that, my experience is that it would depend on your needs. Some folks want all the control at one end of the range, some want it at the other, where others want equivalent "dialability" over the entire range of control for that pot. For instance, say an LFO for a flanger goes from .1hz (one sweep every 10 seconds) to 5hz (5 sweeps per second). One player may want to be able to dial in subtle differences between .1 and .5hz, where another may be far more interested in the range between .7 and 3hz. What makes for more "dialability" for the one player may be exasperatingly restrictive for the other. And THAT is the essence of pot taper; you go with the taper that allows you to easily replicate settings you are interested in. In some instances, that might be linear, in others audio/log, and in others it may be reverse audio/log.

My own inclinations lately have been to use a bidirectional tone pot, where I treat a single 1meg linear pot as two parallel tone controls, each with a different kind of rolloff. In one direction it cuts at one frequency, in the other it cuts at a different frequency, and in the middle it doesn't cut at all. Because I have essentially taken the rotation of each virtual control and cut the amout of rotation needed in half, it really doesn't matter what the taper is because with such a reduced range of rotation, you don't have the sense of portions of the rotation as being "useless" - i.e., you notice an effect no matter which way you turn or how much.

For folks who like a traditional sort of tone control, though, you can wire up either a lin or log pot and it'll work just fine. If you want to be able to dial in small differences in mutedness, you may want to go with log or reverse log. If you feel more at ease knowing that you really need to roll back the tone control before you start losing treble, then linear is likely better.

[SlidePicker]

Thanks, Mark!

How about in the typical situation with a pot and tone capacitor in series, shunting the output of a pickup?

[Mark Hammer]

Well again, I have to ask you: What do you normally use your tone control for and how often? I also have to ask if this is a LP-type dual vol/tone scenario, a Tele-type single vol/tone scenario, or a Strat-type vol/tone/tone scenario.

Some info about your normal needs will shed appropriate light on what strategy to deploy.

[SlidePicker]

Personally, I mostly use the LP type arrangement. A volume and a tone pot for each pickup.

[Mark Hammer]

Okay, then the suggestion would be log. Why? Because those guitars/pickups tend not to have a whole heap of treble. As such, dialing in nuances of crispness is not really the primary function of the tone controls. My sense is that players of those types of guitars want a kind of "safe zone" whereby a tone pot set anywhere between maybe 7 and 10 won't really sound different. As if it was a zone you could haphazardly jump to to get away from muteness quickly, without having to worry about exactly where you set it, as long as it wasn't near 1-3. My apologies if I assume to much here.

In any event, a 500k log pot will make most of the action happen in the 1-3 zone. A linear might as well, but a log pot definitely.

Take a look at the "Secret Life of Pots" article over at www.geofex.com to learn more about custom-tapering pots. Since the classic tone control is essentially a variable resistor, this opens up lots of possibilities for using parallel fixed resistors in tandem with a 500k or even 1meg tone pot to achieve a taper that suits your own preferences.

If it were my guitar, I'd use a tone cap of .01-.015uf for the bridge PU, and something a little higher (.022-.033uf) for the neck PU. Alternatively take a look at the nifty tone control used in the old Peavey T-60 guitar (http://www.peaveyt60.com/images/T-60%20wiring.jpg). It provided for a pan from single coil tap to humbucker to muted humbucker. A *very* clever circuit and guitar (http://www.peaveyt60.com/). Using a classic tone control for the bridge PU and the Peavey one for the neck PU would permit a huge spectrum of tonal possibilities without having to do ANY routing of the body whatsoever.

[SlidePicker]

Thanks, Mark!

[aaronp]

And coming from my simpleton's POV, an audio pot will have a more even correlation between turning control and the ammount of increase or decrease of the desired tone: a smoother sweep, whereas a linear pot will kind of seem like it's doing nothing until you have turned it about half way. Then all of the tone sweep will be condensed into the second half of the turn. Personally, I don't like linear pots for that reason. I much prefer the even increase/decrease of audio taper pots.

[David Schwab]

I prefer linear pots for everything. I know how the ear works, but I like the fact that turned halfway up is half the volume or tone. The taper mostly comes into play as you are turning... if sounds smoother. But since I leave my volume and tone all the way up most of the time it doesn't matter.

Likewise when I am adjusting volume or tone, I'm doing so with my ear, and I know when to stop turning.

Generally though, audio (log) taper is used for volume, and linear taper is used for tone.

While I'm on the subject... Stew-Mac sells a log taper dual ganged blend pot. Sounds like a good idea, except it should be one pot log, and the other anti log, but it isn't. They both go the same way, and make mixing pickups the ay you expect impossible! It's really a log taper stereo volume pot.

[zorro]

What David said, is what I always felt was right.

"Generally though, audio (log) taper is used for volume, and linear taper is used for tone."

The ear hears volume in a logarithmic fashion, so you would use a log pot for volume.
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. The frequency response of your is not flat, but it isn't logarithmic. Your ear is most sensative from 1kHz to 4kHz. below 1kHz it starts to drop. It's a slope, but I still would consider this drop as linear

[SlidePicker]

Generally though, audio (log) taper is used for volume, and linear taper is used for tone.

That's what I had thought proper, and I've built amps that way.

[MarshallPlexi]

Great comments guys. Thanks for the information!

[David Schwab]

What David said, is what I always felt was right.

"Generally though, audio (log) taper is used for volume, and linear taper is used for tone."

The ear hears volume in a logarithmic fashion, so you would use a log pot for volume.
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. The frequency response of your is not flat, but it isn't logarithmic. Your ear is most sensative from 1kHz to 4kHz. below 1kHz it starts to drop. It's a slope, but I still would consider this drop as linear

Yeah, you wouldn't use a log pot for a tone controls on an amp or console, so I have no idea why someone would want to use them for passive tone controls, unless they don't use their tone pot much.

I also don't care for the tapers of some audio taper pots. Since they are not true log taper, but are a mix of two linear tapers, you get a sudden jump on the last 10% of the rotation. In cases like that, I'd rather have a linear taper pot for volume. Better quality audio taper pots work fine though.

Unless you plan on doing fades, it doesn't matter, since you are setting the volume pot where you want it, and not listening to it as you sweep it.

[SlidePicker]

I appreciate your input. I've used the linear pots for treble-bleed tone pots on amps and guitars and found them to work just fine. I had an "expert" harshly berate me on a guitar board for my ignorance about that, but I know what my ears tell me works. I know it can't be regarded strictly as an isolated circuit element without effect from the inductance and capacitance of the surrounding circuit parts like pickups and cables, but the response of an RC filter with variable resistance ought to be linear.

[jack briggs]

For guitars audio log taper for both volume and tone. Tried linear - didn't care for the tapers.



Cheers,