Linear Taper or Audio Taper Pots??

[37012player]

All,

Can you help me out here please. Should I be buying Linear Taper or Audio Taper pots for my guitar, as I want to change the tone pots from 250k to 500k? Could someone explain the difference between the two types please?

Also should I be looking for CTS solid shafts or is the Alpha brand the go?

Cheers,

Si...

[beatlefreak]

Audio taper (also known as logarithmic taper) pots have most of the resistance change towards one end of the pot's travel. With standard pots, the resistance changes evenly (at the same rate) throughout the pot's travel. In other words. on a standard 500k pot, if you turn it halfway up and measure the resistance from one end of the pot to the center wiper tab, the resistance will be 250k. On an audio taper pot, the resistance will be either greater or less than 250k (depending upon which end you measure from).

I would go with quality CTS solid shaft pots. As for audio vs. standard, I haven't measured one, and don't have a guitar with me right now - Anyone?

[johnallg]

To add to what Kris posted, our ears are logarithmicly. So with audio taper, even though the resistance changes quickly and then to not much of a change as you rotate from silence, your ear hears it as an even volume change rate. With a linear taper pot since the resistance changes at the same rate, your ear will hear a fast volume change initially over about 1/4 of the rotation, than not much of a change at all for the rest of the 3/4 turn of the pot as you go from full volume to turning it down. I.E. you will loose most of the volume from full volume in the first 1/4 turn.

Hope that is clear.

[doctorwho]

IIRC, and I'm not the expert here, most guitar/bass control pots are audio taper ... there are exceptions, e.g. I saw a pot for some model F****r that was linear taper.

[johnallg]

To add to what Kris posted, our ears are logarithmicly.

Logarithmic....

[37012player]

Kris, John and Gary,

Thanks guys, most informative. I love this forum and the knowledge generosity of it's members

I'm glad I asked this question, and even learnt something new about how I hear! Great stuff indeed.

Cheers,

Si...................

[stevebasshead]

I hear what's said about using audio taper for volume pots due to the way our ears work...but what about for tone pots, should they not be linear?

[beatlefreak]

Doubtful. As a visual representation of different audio frequenes is plotted out on a logarithmic graph, it would follow that our ears perceive frequency changes logarithmically also. After all, the frequency breaks on an audio equalizer use logarithmic spacing.

[johnallg]

Yup, Kris is right.

[beatlefreak]

Even if I do misspell 'frequencies'!

[jps]

Frequenes. Isn't that a mountain near France?

[stevebasshead]

Cheers guys. I was thrown a bit because one of the websites I visited looking for the CTS pots mentioned in the posts above recommended audio taper for volume and linear for tone. But it does make sense to use audio taper when I think about it because the action of rolling the tone off is actually reducing the volume of the higher frequencies.

[johnallg]

Using a standard taper for the tone would cause all the treble to disappear in about 10% of a turn of the pot, with the rest of the rotation causing a barely noticeable darkening, as you would already be at about maximum cut according to your ears.

[wints]

Clear now everyone?

[BlueAngel]

I hear what's said about using audio taper for volume pots due to the way our ears work...but what about for tone pots, should they not be linear?

No, tone pots should be logarithmic/audio taper - that gives a smooth change in roll-off as you turn the knob. If you use a linear, you get very little change from full up down to about a quarter or so, then a sudden cutoff as it reaches the bottom.

Volume controls can be either log or linear depending on what type of effect you're trying to achieve - with a log, most of the volume change occurs in the top part of the travel, so if you use the control to clean up an overdriven amp you probably want one, since you will lose a lot of signal level from full up down to halfway. If you play clean and want small 'volume' rather than 'gain' adjustments you may want a linear since it allows finer control in the top part of the range. They're also better for 'violin' effects with the volume control since it goes from silent to loud much more quickly without having to turn the knob as far. Neither is 'right', it's just a matter of preference. Some companies have used both types at different times or log tone/linear volume combinations.

Just to really confuse things, there are different types of logarithmic taper! A true 'Log' has 1/10th of the resistance ratio at 1/2 of the physical movement, but other ratios are available, and the conventional 'audio taper' isn't quite as steep as this (although I can't remember right now what it is!). Even worse, some cheap "log" pots are actually made using two sections of linear track to give a crude approximation of a log taper, because linear is much easier and cheaper to make. Many mini-pots of the type that most push-pulls are based on are like this - unfortunately the one in current 4003s seems to be so... I haven't measured it, but it certainly sounds that way, with no change at all until the knob is about 2/3 of the way down and then a sharp roll-off.