Pot education please

[Kurt Veltman]

Hi all. I'm looking to learn more about pots. I have watched just a couple videos on YouTube about the difference between 250 and 500 K pots but want to know much more. My questions are specifically directed towards pots used in basses. Is there a way to tell if a pot is a linear taper or audio taper using a multimeter? Is it recommended to use an audio or linear taper for either the volumes or the tone? I am building a bass for charity and want to do volume / volume / tone. Is there a generally recommended pot for each of these positions? For example, 250's for the volumes and a 500 for the tone, 500 for all three, etc? I have DiMarzio Ultra jazz pickups for this, and it will be passive. I'm sure there is much more info you all can give me about pots, and any information is welcomed and appreciated! Thank you!

[Brian Evans]

Pot values and taper are a personal choice. They all work fine, they just work slightly differently and the difference amounts to personal taste. Most people like an audio taper pot for volume, it gives a more even adjustment over the range of the control. A linear taper will seem to have more effect at one end, based on the fact that the ear hears volume in a non-linear way (hence why audio taper pots were invented, and have that name). Most people are happy with a linear taper pot for tone control. Most people like 500K pots for humbuckers and 250K pots for single coil, but both work just fine with any passive pickup. You just get a little difference in tone, and only you can tell the difference for you.

If you take a linear taper pot and set it at halfway, you can measure from the center tap to either of the outside taps and it will be quite close to the same resistance. If you take an audio taper pot and do the same test, you will get around 20% resistance at one tap and 80% resistance at the other tap. Wiring diagrams (and all of this information, for that matter) can easily be found on Google. Pots can't tell if they are in a guitar, a bass, or anything else for that matter, they could care less.

[Kurt Veltman]

Thanks for the response Brian.

Now I'm looking for opinions. Would a push/pull "slap switch" make this bass more appealing, or would it just be added fluff that won't make much of a difference.

Also, can I even incorporate a "slap switch" in a passive bass?

[Gordon Bellerose]

A Push/Pull switch for what function?
And if you are looking for an easy operating switch, go for a Push/Push.

[Brian Evans]

In my opinion, a bass is best served simple. I would not add bells and whistles, I would just do it the way it's been done for decades. The players I like the best just played a simple, straightforward instrument. But that's just me. I personally hate push/pull switches, push push switches, rotary switches and all sorts, because I can't tell what setting they are in without operating them. I far prefer toggle switches where I can visually or physically tell exactly what setting they are in.

Brian

[Gordon Bellerose]

I use Push/Push switches for coil splitting on my electric guitars. It does make sense for an electric guitar, giving it more options tonally.
Visually they work well, as when you push them they pop up. The next push causes them to stay back down. I get individual coil splitting on each pickup, with one volume, one tone, and a 3 way.
I guess you could use them for the same function on a bass pickup that has the same capabilities.
The pickup would have to have a 4 wire lead.


I'm currently building a bass, and I'm going with a conventionally wired instrument.
The controls I am using are: Volume, Blend, Tone.

[Kurt Veltman]

Thanks for the responses gentlemen.

Gordon, most of my basses I have wired as you are planning, vol/blend/tone. Someone recently suggested vol/vol/tone, citing that you may get better tone with that setup. Another bonus I'm just realizing is that you don't have to wonder which way to turn the blend pot to get more of this pickup or that pickup. Not a big deal, just something to consider.

[David King]

Pots are very imprecise elements. They are hard to manufacture reliably consistent. Also note that their behavior in a circuit is very much affected by the rest of the circuit which changes radically depending on the cable you use and the amplifier you plug into. Luckily we generally like to hear what we are used to hearing so it's easy to make most people happy by sticking with the tried and true. Not knowing who the ultimate owner/player is going to be takes you off the hook. You can't possibly guess what their preferred tone it so go for the brightest tone you can get as it's a lot easier to dull a bass down than it is to brighten it up after the fact.
I'll buy a bag or 20 pots and keep switching them out until I find the ones that do the job well enough. You can always pay more and buy pots that someone else has preselected for you.

[Gordon Bellerose]

The blend pot I have selected is made by Bourns.
It is a bit different in the fact that it operates on a different sound curve.
One of the issues in a typical blend pot, is that as you turn toward one pickup or the other, the volume drops off as you approach center.
When you get to the detent, you are at 50% on both pickups. This results in a significant volume drop.

The Bourns pot keeps the volume of the one you are turning away from at 100% until you get just past center, where it drops off quickly until it is at 0%.
So at the center detent, you have 100% of both pickups.
A much smoother volume transition I am thinking.

Has anyone else used these. Am I wrong in my assumption?

[David King]

Actually most if not all blend pots use this special MN taper with 0 Ohms in the center detent position. There's nothing special about the Bourns pots. What the pot manufacturers don't tell you is that a 250k blend pot has only 125k of resistance path per element so it's the equivalent of using two 125k volume pots or having a 67.5k path to ground bleeding your signal away at all times. You're much better off using 500k blend pots for that reason and it also explains why no one uses blend pots in guitars.

[Gordon Bellerose]

I am using a 500 k 0ot.

[Joshua Levin-Epstein]

I misunderstood the topic being discussed. I thought we were going to be wistful about the 60s and 70s...

As Brian says the conventional wisdom is 250k pots for single coil and 500k for humbucking (as well as audio for volume and linear for tone). Fine with me. The reason for the different values (not the tapers) is the greater resistance the pot, the more highs are allowed to pass when the pot is fully open. Leo's first guitars had 1 meg pots and Leo thought they were too shrill, ending up with the 250k pots we all know and love in his guitars. The Gibson pickups were wound to a greater DC resistance and needed help with getting the highs out, hence the traditional 500k pots.

The pick ups you are using are indeed humbucking. I might be tempted to use 1meg pots to let as much through as possible. But I'll bet I wouldn't hear the difference, which I'll attribute to loud music as a youth rather than my advancing years. In my retail years, when people complained that dimarzio pick ups were muddy, their rep suggested using 1meg pots. To my ears they were still muddy but that's just an opinion.

If you were hell bent on some switching in your bass, you could have series/parallel switching in each pick up. I might prefer the parallel wiring of each pick-up (more highs) but you didn't ask that. There's lots of things you can do to complicate things, but I agree with Brian: keep it simple. Stock jazz bass wiring is my preference, but you didn't ask that either.

[Daryl Kosinski]

Unless the pot itself is wirewound it will have no direct effect on frequency. It will effect the load on the pickup and that will have some effect on frequency. How the pot is connected in the circuit will also have an effect. If the impedance of the pickup measured at 400 HZ is less than 1/10 the resistance of the pot then it should act like a volume control and not effect the tone much. Over thinking this can drive a insane person sane. Try many pots and use the one you like best.

[Brian Evans]

Or try one, say "Damn, that's fine!" when you play it through a vintage Fender amp for the first time, and go on to other things... That's what I just did when I put new single coil pickups in my Godin Tele, which previously had humbuckers...