Best Pot for Volume Swells with Humbucker/500K pots--Audio or Linear (Audio!)

[Platefire]

Since I am in the process of changing pots out in guitars lately---a part of my guitar technique is doing volume swells mostly for steel guitar type bends/swells in backing up a vocalist.

So Audio Taper is an un-even taper that suppose to sound more natural to the human ear and Linier
is a even taper throughout. I think I got that right? So I'm thinking that an Audio taper would be better for volume swells in that it covers more of a change in a shorter travel but not sure because I've never discussed or thought about it that much up till now! I use my pinkey on my volume to accomplish this. The fenders are easy reach and the Gibson LP clones is a bit of a reach but still use the same approch on them also.

So I'm thinking most gutiars comes with Audio taper. The Jay Turser I'm working on has a AlPHA B500K
which is Linier. There is my Aria 335 that need changing for the neck pup(haven't found out what existing pot is yet). Several other fenders I have that seemed to work great for swells. It's the gibson type copies that are sluggish on volume swells--so I'm wondering what I need to do to get my humbucker guitars with 500K pots more swell friendly. I would appreciate any discussion to help me with this. Platefire

[John]

In my very limited experience, maybe just changing to new better quality 500K pots would do the trick. Mine (Dimarzio) kick in around 1.5 - 2, and then increase pretty smoothly all the way to 10.. although... when I get home I'm going to double check myself and make sure my memory is right.

[simonallaway]

You could simply find the pot whose behaviour you like and measure it's 'curve'. Set it to 50% rotation and see if its resistance is 50%. If it is it'll be linear; otherwise logarithmic.

This definitely falls under "no right answer except what works for you" :)

I used to use a compressor to help with volume swells as it made them more predictable. One day I'll build a decent compressor. Forum member SLW has a PCB for a Ross clone I think.

[G._Hoffman]

There are actually several different "audio" tapers.  I can't remember what the details of them are (perhaps PRR will drop in and shed some light on the matter), but basically, they use different log calculations.  Which you will prefer is up to you, but the most commonly prefered taper is the one you will find on the CTS audio taper pots that are used in Gibson's, Fenders, and then copied by just about everyone else.  The other one that some people like is sold by Dimarzio, which is less linear than the normal CTS pots. 

A true linear taper pot will sound like all of the volume change is happening in the top 10% or so of the pot's travel.


Gabriel

[Platefire]

We'll letz not get corn-fuzed 

Now I thought it was the Audio that had all the volume change withing the first part of the travel
and Linier was even all the way through???? According to you I have that backwards. I thought I studied up on that last night and had it straight??!!! maybe not?    I need to get it straight once and for all and mark in on the wall or someting. Platefire

[John]

God, I'm glad I'm not the only one that happens to!!

[stingray_65]

We'll letz not get corn-fuzed 

Now I thought it was the Audio that had all the volume change withing the first part of the travel
and Linier was even all the way through???? According to you I have that backwards. I thought I studied up on that last night and had it straight??!!! maybe not?    I need to get it straight once and for all and mark in on the wall or someting. Platefire

Gabriel had said a linear pot will SOUND like all the change is in the last 10% [of rotation]

An audio pot will SOUND like a linear climb in volume, dialed to 5 it will sound half as loud as at 10.

It is how our ears perceive volume, to sense a doubling in volume, 10X the power is needed.

http://www.conradaskland.com/blog/2008/10/decibel-levels-and-perceived-volume-change/

Much like a 10W amp SOUNDS only twice as loud  as a 1W amp and half as loud as a 100W.

It is commonly accepted to use Audio taper for Volume controls and is why they were developed in the first place.

[Platefire]

This is a good general discription of how the pot works read in conjunction with looking at the attched picture. Helped me to understand operation a little better.

SummaryConstruction of a wire-wound circular potentiometer. The resistive element (1) of the shown device is trapezoidal, giving a non-linear relationship between resistance and turn angle. The wiper (3) rotates with the axis (4), providing the changeable resistance between the wiper contact (6) and the fixed contacts (5) and (9). The vertical position of the axis is fixed in the body (2) with the ring (7) (below) and the bolt (8) (above).

[Platefire]

Another bit of info:

Linear taper potentiometerA linear taper potentiometer has a resistive element of constant cross-section, resulting in a device where the resistance between the contact (wiper) and one end terminal is proportional to the distance between them. Linear taper describes the electrical characteristic of the device, not the geometry of the resistive element. Linear taper potentiometers are used when an approximately proportional relation is desired between shaft rotation and the division ratio of the potentiometer; for example, controls used for adjusting the centering of (an analog) cathode-ray oscilloscope.

Logarithmic potentiometerA logarithmic taper potentiometer has a resistive element that either 'tapers' in from one end to the other, or is made from a material whose resistivity varies from one end to the other. This results in a device where output voltage is a logarithmic function of the mechanical angle of the potentiometer.

ALSO:

Log & Lin Controls
Two Types of Track
Two types of potentiometers with different tracks are available. These are Linear (Lin) or Logarithmic (Log) tracks.

With linear potentiometers, the resistance between one end of the track and the wiper varies at a constant rate as the slider is moved along the track. In logarithmic types, the change in resistance is much less at one end of the track to the other. A graph of the change in resistance for given equal movements of the slider follows an (approximate) logarithmic curve, this effect is often referred to as "taper".

 
Logarithmic potentiometers are used as volume controls in audio equipment because the response of the human ear to the loudness of sound is also logarithmic. Using a log pot therefore gives the effect that a setting of full volume on the control sounds twice as loud as a setting of half volume. A linear pot used as a volume control would give large apparent changes in loudness at low volume settings, with little apparent change over the rest of the control´s range.



Most (cheaper) "log" potentiometers are actually not logarithmic, but use two regions of different resistance (but constant resistivity) to approximate a logarithmic law. A logarithmic potentiometer can also be simulated (not very accurately) with a linear one and an external resistor. True logarithmic potentiometers are significantly more expensive.

Logarithmic taper potentiometers are often used in connection with audio amplifiers as human perception of audio volume is logarithmic.

[Platefire]

IN CORNCLUSION:::

LINEAR: Even Taper of audio change all the way through pot rotation

AUDIO/LOG: Varied Taper of audio change with the largest increase at the beginning of pot rotation and less change at the end.


Now the question still remains, which one is best for guitar volume swells?

[G._Hoffman]

IN CORNCLUSION:::

LINEAR: Even Taper of audio change all the way through pot rotation

AUDIO/LOG: Varied Taper of audio change with the largest increase at the beginning of pot rotation and less change at the end.


Now the question still remains, which one is best for guitar volume swells?

Incorrect. 

Linear taper gives an even change of resistance through the rotation of the pot. 

Audio taper gives varies the rate of change of resistance (well, in the case of audio, it's really impedance, but lets not complicate things), so you get the largest change of resistance at the beginning of the rotation. 

A couple terms should be addressed.  Volume has nothing to do with electronics.  There is no such thing as a volume control.  Volume, in this context, is a strictly acoustic property that has to do with changing pressure in a medium (usually air, though it could be in water).  The "volume" control on your guitar/amp/effects is, in fact, a voltage control.  Now, varying the voltage of your guitar's output will, when it is turned into sound, vary it's volume, but you can not directly control volume electronically. 

But humans don't hear sound in a linear fashion.  Our ears sort of "compress" sound.  Evolution wise, this means that we can hear quiet things without blowing out our ears when we hear things which are really loud, which is good.  So, as has been pointed out, in electronics we need 10X the power to get double the perceived volume.  Double the volume of 1 watt is 10 watts, and double the volume of ten watts is 100 watts.  Similarly, if you want double the volume of one trombone player (for instance), you'll need 10 trombone players.  Audio taper pots attempt (and mostly succeed) to adjust things so that when you have 50% rotation you will have a 50% reduction in volume. 

As to which is better, well, I reject the concept.  This is something where there is no better, only personal preference.  That being said, the VAST majority of people who notice the difference will prefer an audio taper pot, as it will give an even change in volume, which requires a logarithmic change in voltage and/or power.  Now, if you are doing quick volume swells, you might like a linear taper pot, as it would allow you to only turn the pot down part way to get a near zero volume, and then a quicker swell as you turn it up.  It would drive me bat-s#*t crazy; but as my father would say, it's not a long trip.


Gabriel

[John]

But humans don't hear sound in a linear fashion.  Our ears sort of "compress" sound.  Evolution wise, this means that we can hear quiet things without blowing out our ears when we hear things which are really loud, which is good.

Great explanation.

[John]

Follow up: I really paid attention to exactly what happens with the volume (apologies to Gabe  ) . From zero, it kicks in at 2.5 and then smoothly and evenly increases to around 8. Then from 8 to 10, the increase is more gradual. These are the 500k Dimarzio pots. FWIW, YMMV. Hope it helps!

[G._Hoffman]

Follow up: I really paid attention to exactly what happens with the volume (apologies to Gabe  ) . From zero, it kicks in at 2.5 and then smoothly and evenly increases to around 8. Then from 8 to 10, the increase is more gradual. These are the 500k Dimarzio pots. FWIW, YMMV. Hope it helps!

Yeah, well, carbon tracks are never all THAT precise.  Most pots are 20% tolerance parts - you can't expect all that much precision.  I was mostly talking about the theoretical version of these pots, after all.


Gabriel

[HotBluePlates]

And on to your original question.

The "real" logarithmic (audio) pots have a 10% taper, because that follows the logarithmic curve most exactly. The percentage number is what percentage of the total resistance you have after rolling from the bottom to halfway. 10% increase in resistance sounds like half of full volume. However, it might feel like it needs a big rotation to swell the entire range you might want to achieve.

There are also audio taper pots with as much as a 30% taper. The volume change seems to happen faster at the lower end of the pot. You might like that for a smaller needed twist of the volume knob to get the swelling action. In a guitar amp, these might be problematic, because all the clean range seems to happen between 1-4 (depending on the amp design).

I might remember wrong, but it seems Danny Gatton liked to use a linear taper pot for his tone control, because he did wah wah swells with it. With a linear taper, the resistance change is even from bottom to top, but that makes it sound like all the action happens between 0-2 or 3. That's bad for a volume control, but works great for wah wah swells with a very small movement of your little finger.

[G._Hoffman]

And on to your original question.

The "real" logarithmic (audio) pots have a 10% taper, because that follows the logarithmic curve most exactly. The percentage number is what percentage of the total resistance you have after rolling from the bottom to halfway. 10% increase in resistance sounds like half of full volume. However, it might feel like it needs a big rotation to swell the entire range you might want to achieve.

There are also audio taper pots with as much as a 30% taper. The volume change seems to happen faster at the lower end of the pot. You might like that for a smaller needed twist of the volume knob to get the swelling action. In a guitar amp, these might be problematic, because all the clean range seems to happen between 1-4 (depending on the amp design).

I might remember wrong, but it seems Danny Gatton liked to use a linear taper pot for his tone control, because he did wah wah swells with it. With a linear taper, the resistance change is even from bottom to top, but that makes it sound like all the action happens between 0-2 or 3. That's bad for a volume control, but works great for wah wah swells with a very small movement of your little finger.

Linear pots are fairly common for tone controls, and they work just fine for tone controls.  Again, I'm not too fond of them, but there are a fair number of people who like them.  Again, most people probably don't notice at all, but among people who do....


Gabriel

[HotBluePlates]

If linear is typical for tone pots, maybe Gatton used an anti-log pot. That's where there is a 90% increase in resistance at 50% rotation.

[G._Hoffman]

If linear is typical for tone pots, maybe Gatton used an anti-log pot. That's where there is a 90% increase in resistance at 50% rotation.

Most Gibson pots have been 500KA, though in the seventies they did (for a while) use 300K linear pots, at least for the tone pots. 


Gabriel

[Platefire]

I put two A500K ALPHA pots in the Jay Turser PRS Copy today. They work real well for volume swells. Platefire

[Platefire]

The Austin/PRS Copy Guitar I've got presently for sell on E-bay has a B500K Linear Volume and it just don't work good for volume swells. It does work to some degree but you have to work harder and get more pot travel to get the effect.

On the Jay Turser I just put in two new ALPHA A500K volume pot works great for volume swells. This pot gets the swell effect with a lot less travel and pretty much achives all I need for my swells. This pretty much answers the original question I ask. It was pretty much already pre-determined in you guys mind already, but I just needed to settle it in my mind because swells is so intertwined in my playing style I needed to know for sure. Thanks, Platefire