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Pots, audio or linear?

posted Oct 26, 2013 06:00:19 by MichaelWamback
If you are considering changing the volume and tone pots in your new Chibson, you'll quickly discover that there are two different types. These are normally referred to as "audio" and "linear" taper. So which to you need?

There is technically no correct answer to that question, as it often comes down to preference.

The difference in the two pots is in the taper, or how the resistance changes when you rotate the knob. At "0" or "10", there will be no difference in the two pots. It's what happens in between.

Linear taper pots reduce their resistance in a straight line. In other words, "2" is 20% of the pot's value, 3 is 30%, 6 is 60% and so forth.

Audio taper has a taper that drops off exponentially quicker from "10" to "9" and the slowly tapers out as you continue to decrease the settings. In essence, a curve rather than a straight line.

Either pot will work for volume or tone, but they have advantages and disadvantages depending on the taper.

If you use an audio taper pot for volume, the result is a volume that swells in intensity as you move toward "10". This is actually closer to how the human ear works, and many players find this an advantage if they use the volume control to create a volume swell. The disadvantage is almost all of your pot's range is between "7" and "10", with very shallow drop off after that. Some players find it more desirable to use a linear pot for volume, preferring to have a more subtle shift between "10" and "7", and better control over the volume levels all along the taper.

It's not unusual for most players to prefer audio taper pots for tone controls, but linear will work here as well.

Gibson uses linear taper pots for volume controls and audio taper for tone.

When purchasing a potentiometer, you also want to pay attention to the value. Common values are 250k, 300k, 500k and 1meg. Gibson installs 300k for volume and 500k for tone, but most players tend up upgrade the volume pots to 500k for humbucker pickups. It tends to open the pickup up a bit more. 250k pots are usually found on single coil pickups, such a Telecasters and Strats, but again there is no real rule. Many people experiment with different values of potentiometers.

Note: When choosing a full size potentiometer (about the size of a quarter), the most popular brand is CTS. If you install these on your Chibson, be aware that you will have to enlarge the holes in your guitar a bit as the shafts are a bit thicker than Asian metric pots. You will also have to purchase new knobs, as the spleens on USA standard pots are different than those on the shaft of the Asian pots.

If you don't wish to purchase new knobs, Bourns makes a very good quality potentiometer with the Asian size coarse spleen shaft. You will likely still have to enlarge the holes in the guitar if it came fitted with mini pots (about the size of a dime) but you will be able to install your existing knobs.
The two most important things to remember in life: "The only time it's acceptable to work with amateurs is if you are making porn." "If you want to work with clowns, join a circus."
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4 replies
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sjcrowe6 said Oct 26, 2013 17:57:12
Thanks Michael, great information! Maybe you can help me with the following questions:
Are pots normally marked to indicate their type and value?
Is it possible to test a pot's value without expensive testing gear?
Is it worth the extra cost to purchase pots that have been tested and are guaranteed to have values that fall within a certain range?
I was told that most Chibsons/Imports use short shaft pots while Gibsons use long shaft pots. Is it best/possible to convert to long shaft pots or stay with short shaft?
What are push/pull pots and how do they benefit playability?
Thanks for all you do,
Steve
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Chris Graham said Oct 26, 2013 20:16:47
I like a pot that cleans up as you roll the volume off and is pretty loose, meaning they move pretty easy. I love my EVH pots but I know those are a 1/4 and not the metric in size. and I need them to have the push pull so I can coil split. What would you recomend for my chinese prs ?
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TelepathicTrafic said Oct 26, 2013 21:59:45
Hey Steve. Thats A LOT of questions hehe.

Most pots are marked.
I doubt matched pots with make a difference to an average person such as myself, but I'm sure many would disagree.
Both of my Chibsons used the shorter shafts. The extra length is due to the cavity not being routed deeply. The Chibsons mostly have smallish maple caps, so are routed deeply and fit small pots. If you bought long shaft you might use them in a Supreme perhaps, but to make them shorter is a pain in the ass. You'll need extra spacers possibly, and its awkward to fiddle inside the cavity under the wiring harness to get the height just proper.
The push pulls allow to you to split the coils on a humbucker to get a single coil sound. The pickups must have the correct wiring 4 leads.
Whatever you do make sure you get the proper spline on new knobs if you replace the pots.
This is what I know, unless someone else knows different.

Cheers.
"I am for drink and the company of questionable women ... may your day hold equal favor!"
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MichaelWamback said Oct 26, 2013 22:46:49
To answer all your questions as best I can:

Markings for pots - since you are dealing with different manufacturers they mark their pots in different ways. They are not always (or hardly ever) marked as "linear" or "audio". Instead, they will have different part numbers that you have to cross reference with the manufacturer. Unless, of course, you test them with a multi meter - which brings me to the next question...

Testing pots - To test a pots value, you need a multi meter. They are not expensive, I think I paid somewhere in the range of $30 for mine, and there are some that are less than that. You can pick them up at electrical stores, Home Depot, most hardware stores, Radio Shack and of course Ebay or Amazon. Even most department stores if they have a tools section. To test the value of a potentiometer, you set the dial to the OHMS setting. You can also tell if the pot is an audio or linear taper by attaching the meter and then rolling off the pot. If it is linear, the readings will drop in an even line. If it is audio, you will get a more dramatic drop initially with a tapering off as you move toward "0". It's good to have a multi meter to test pots if you have a sound issue with the guitar - only way to know for sure if the pot is bad.

As for range - having pots that are well matched is definitely a plus, but I'm not sure it would be considered essential. Good quality pots like Bourns or CTS are usually within a fairly tight tolerance. Cheaper pots may have a greater +/- range. But if you can use a set of pots that are well matched, so much the better - but don't loose too much sleep over it. So long as your 500k pot measures somewhere around 500k or a bit above on your meter, you should be fine.

As for shaft length. The rule is that you can always use long shaft pots no matter what. In fact, some people prefer it. The advantage to long shaft is that you can use a 2nd nut on the inside of the guitar cavity to set the precise depth you want. Of course, you can do that with washers as well. But some people like the precision of setting the pot depth. If your guitar uses short shaft pots, then why not keep it that way? Chances are, no one is going to take the control cover off your guitar to see what kind of pots you used.

Push/Pull pots allow for multiple ways of wiring the guitar when using pickups that are made with 4 wires. If you use 2 wire pickups like Wilkinson or original PAF's, then they won't do you much good. The Push/Pull pot acts as a switch. You wire jumper wires in various configurations on the switch for things like coil splitting (shutting off one coil), out of phase wiring (reversing the polarity of one of the pickups), acting as a straight through to bypass the volume and tone controls to run your pickup straight through your amp and so forth. There are a number of ways to configure them. There is also a version called a "Push/Push" that switches functions every time you push in on it. It allows you to create more different types of tones with your guitar. If you are soldering up 4 wire pickups and don't use a push/pull switch, then 2 of the wires from the pickup get soldered together and taped off.

EVH Pots - Bourns do make pots that are "low friction" - I used them on my Tele. The ones I used were audio taper, which might work best for you since you are likely looking for a volume swell. I can tell you that when they say low friction, they mean zero friction. I could almost change the settings by blowing on them. Absolutely no resistance what-so-ever. Their normal pots are a bit stiffer than CTS for sure, but I don't find them to be too stiff. They also make push/pull pots. I did a little research and got conflicting info as to whether the push/pull were low friction or not. I suspect the best thing to so would be to contact Bourns customer service and ask them - and ask for a part number if they do make low friction push/pull pots. Or you could contact some of the sellers on Ebay that offer Bourns pots and ask them, as many of them are pretty knowledgeable.

The only real choices for keeping Metric coarse spleen knobs are Bourns or Alpha brand. With pots, it's much like cameras. You have Nikon and Cannon at one level, and everyone else trying to catch them. In the case of pots, you have Bourns and CTS, then the rest. Unfortunately, CTS doesn't make a DP/DT push/pull pot, other than as a special order (meaning you have to order minimum of 2,500 of them.) The only source I can find for them sells as Mojotone on Ebay. I've actually bought some Switchcraft switches from him and gotten good service. Not sure about the friction in those, but if it is CTS pots, then they should be fairly low friction compared to Bourns regular. And they do have the 24 fine spleen USA shaft. You might contact him with questions, as they are very professional. But if you like your EVH pots in US spec, then no need to worry about CTS.

Alpha does make push/pull pots as well. Not sure about the resistance. Bourns would likely be the better quality of the two, although I've heard that Alpha have gotten better. Only real choice for metric knobs. And I would still contact Bourns to ask if the push/pull are low friction - as you will be happy with how easily those turn.

If all you are doing is coil splitting, then you could possibly use the push/pull for your tone pots, and then regular low friction pots for you volume controls. I think I've seen that done, but don't quote me. You may want to do a bit of research. But as I recall, the push/pull function essentially operates the double pole/double throw arrangement on the bottom of the switch. You would then run your wires from there back to your volume pot, rather than the push/pull pot itself. And then your capacitor back to the lugs on the push/pull potentiometer to act as tone. But like I said, a bit outside of my area of expertise, since I usually use a more standard wiring on my guitars. Although I have been wrestling with the idea of installing push/pull pots in my SG.
The two most important things to remember in life: "The only time it's acceptable to work with amateurs is if you are making porn." "If you want to work with clowns, join a circus."
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