When to use which pot taper?

[electrosonic]

What makes a pot taper sound right or natural? Constant db change per angle rotation? How would you figure out the ideal taper for a circuit?

Andrew.

[petey twofinger]

from what i gather , if the " action " is all at one end , a reverse log can smooth that out to a more even keel.

great question looking forward to seeing some folks who actually know the answer post up ...

[midwayfair]

When you're building your own box, the "right" pot is the one that results in the most usable range for you in that circuit. There's no other reasonable answer, because everything has exceptions.

The human ear hears volume changes in a way that requires a logarithmic taper for volume. But there are effects that don't have a ton of output from the volume knob and a big volume boost from the gain control, so a log taper means that your volume pot is hard to control when the gain pot is in the equation, so a linear pot becomes necessary.

Some fuzz pots that reduce the resistance to ground sound best as a reverse taper to prevent bunching. But what if you want a pot that has lots of shades of OD before it's full on fuzz? Then you need a linear or even audio taper.

Usually a linear pot is "right" for a tone, but there are some effects where the tone controls might be interactive with the volume or other tone controls, and you might need to use a different taper to increase the usable range where you're using it most often.

And these are just the easy situations!

[nocentelli]

First of all, you know how linear, log and anti-log pots work, right? So in layman's term (my terms!) linear pots have an even, direct relationship between rotation and resistance. So, turning it 10% sets the reistance between lug 1 and 2 to 10%, halfway up is half resistance, 75% rotation is 75% resistance. Log pots have a rotation-resistance relationship that is not directly proportional. From minimum to maximum, the rotation starts to slowly increase the resistance, the relationship changes, getting faster as the pot is turned. Antilog simply works like log in reverse, so the change in resistance is very quick at the start of the pot's rotation, but slows.

As for guidance on what to use when, it really depends on the circuit: Log is generally used for volume due to the reasons you postulate, but equally I've seen linear and even anti-log used here for various reasons. A rule of thumb is just to try out a linear pot: If the sweetspot on the pot is hard to dial in because the good-sounding settings are bunched up at one end, swap for the appropriate log/antilog pot: e.g. You've got a gain control, but a linear pot makes it hard to dial in a nice range of low gain sounds, you need antilog.

Alternatively, if there is not much variation beyond half-way to maximum gain, a log pot would "even out" the perceived gain range of the pot.

If you consider the Big Muff, these have apparently been built with both linear and log pots over the years: I prefer linear for tone, and log for both sustain and volume. A log tone pot skews the pot so 12 o clock is no-longer the standard mid-scoop with balanced high+lows: However, the log sustain pot isn't critical, it just makes dialling in low gain sounds a little more fiddly (and who uses a BMP with the sustain down low?), and a linear volume pot just means your pedal seems a lot louder than normal!

[Seljer]

Usually a linear pot is "right" for a tone, but there are some effects where the tone controls might be interactive with the volume or other tone controls, and you might need to use a different taper to increase the usable range where you're using it most often.

I recently changed to tone pot on my guitar to log taper. I can finally use the thing! it no longer goes from doing nothing at all to being comlete mud at 3/10 like it did with linear taper (though you lose the ability to do the faux-wah thing with the tone pot)

Of course, this doesn't apply to tone controls arrangments in general.

[Kesh]

I tend to think log works best for tone control of the type when it's in series with a cap to ground, in guitars and other circuits, but the only hard and fast rule seems to be log for a voltage divider volume controls, and I'm sure there are exceptions there too.

[Ice-9]

In general and making a short story of this, when the pot is adjusing something like a signal that the human ear perceives then a log pot is more fitting. When the pot is adusting an electronic adjustment like a LFO  then its more likely to be a linear pot. This is just very quick comaprison and there are other things to take into account and it's not this simple but my rule of thumb is  AUDIO=LOG, ELECTRONIC=LIN

[Mark Hammer]

If you need to know the "middle" of something, use linear.  So, for example, a blend pot that combines two signals in different proportions should be linear so that the "middle" implies equal portions signal A and B.

If one is ever adjusting the volume of anything, a log taper is preferred, since it corresponds to how the human hearing system works: logarithmically.

If one is controlling an LFO, for modulation purposes, a reverse-log is often preferred, since faster modulation rates require smaller resistances, and the last little bit of resistance in the pot tends to address a range of speeds that we can make very fine distinctions in.  You want to spread those out over a broader range of pot rotation, and reverse-log does that for you.

When setting gain in an op-amp, using the ground leg (between the inverting pin and ground) andcovering a broad range of possible gains, a reverse-log is preferred, because the gain is changed more in those circumstances by tiny adjustments in small resistance.  You'll want to "get through" the large changes in resistance quickly, and spread out the small changes in small resistance over a broader area.

No particular taper is "correct", and taper will not change whether the circuit "works" or not.  It may not offer the degree of "dialability" you seek, though.