Bass Guitar Pot Question: 250K vs 500K

[RockYoWorld]

I bought a used Fender Precision Bass Special a couple months ago. I like how it plays and how it sounds. I'm finally figuring out some bass presets on my Axe FX III. However, the pots are a bit noisey (especially the tone knob). I'm thinking of replacing them. Can anyone give me advice on if I should get 250K or 500K pots? Since I have to take the pickguard off (and loosen strings, etc), I don't want to take it off until I'm ready to do the soldering. Otherwise, I'd just look at what values are in there now.

[RockYoWorld]

UPDATE:

I was tightening the pots and broke one of the pots, which have obviously been replaced by someone along the way, since it was split shaft instead of solid like the others. Took pickguard off and found that they're 250K pots. Have more ordered and will replace all pots for a fresh start.

[andrewsrea]

I'd recommend looking for some used Gibson 300k pots and fill the split shaft gap on them with tooth picks, to keep them from breaking / bending. They were made by CTS, audio taper, are just a little bit brighter than a 250k and when people started converting back to 05's specs on their humbucker guitars - can be had very reasonably.

If you want to go new I recommend Emmerson Pro made by CTS, in a 250K value. They are audio taper, very smooth and durable. I am a volume pot tweaker when I play and these have the right looseness to tightness ratio and last longer. I can go through a Bourns and an Alpha in 100 hours of playing. I've yet to break one of these.

500k will have too much top end for a bass and go darkfast when you roll off the volume. Better to go 250K and set your amp brighter, if you need more highs.

[Mossman]

250k pots and a .047 cap are the appropriate values (and what comes stock from Fender). Split shaft or solid shaft is a personal preference. I don't use solid-shaft pots, myself, because my knobs never fall off when I use split-shaft. Set screws on knobs always have a way of jiggling loose.

I used to use audio taper for everything, but lately, I've been getting fed up with the way they behave like an on/off switch as a volume pot, with very little change for most of its sweep. My Ibanez AS93 has linear taper volume pots (as far as I know, it's the first guitar I've owned that has), and I think I like the way that functions better. It's not as useful for volume swells, or riding the knife-edge between clean and break-up, but I play mostly clean, and I like the fact that 50% output is at the half-way mark, not the 1/3 mark, and that I can hear change (albeit subtle) throughout most of the sweep. I'm not saying I'm sold on linear taper pots, and I probably shouldn't even open up this can of worms, because everybody has a different opinion about it, and every time it's mentioned on a guitar forum, arguments seem to invariably ensue. But I am using a linear taper pot for the volume on the baritone that I'm building (just wired it last night), to see how I like it on that. I think I'll always use audio-taper for tone, though.

I don't think it's as much of an issue for bass, as you don't typically ride the volume control that much. I think audio-taper is fine for both on a bass.

[Mossman]

BTW, audio-taper pots are the reason why I think the 4-control, Gibson-style layout is useless. I never hear any real difference when trying to "blend" the pickups, because no real change happens until you turn the pot almost all the way down. The blend is a lot more noticeable and varied on the Ibanez with linear taper pots.

[andrewsrea]

BTW, audio-taper pots are the reason why I think the 4-control, Gibson-style layout is useless. I never hear any real difference when trying to "blend" the pickups, because no real change happens until you turn the pot almost all the way down. The blend is a lot more noticeable and varied on the Ibanez with linear taper pots.

How you describe audio taper is how I describe linear. It is strange how ear perception can be so different.

Are you a leftie by any chance?

[RockYoWorld]

I'd recommend looking for some used Gibson 300k pots and fill the split shaft gap on them with tooth picks, to keep them from breaking / bending. They were made by CTS, audio taper, are just a little bit brighter than a 250k and when people started converting back to 05's specs on their humbucker guitars - can be had very reasonably.

If you want to go new I recommend Emmerson Pro made by CTS, in a 250K value. They are audio taper, very smooth and durable. I am a volume pot tweaker when I play and these have the right looseness to tightness ratio and last longer. I can go through a Bourns and an Alpha in 100 hours of playing. I've yet to break one of these.

500k will have too much top end for a bass and go darkfast when you roll off the volume. Better to go 250K and set your amp brighter, if you need more highs.

I got 2 CTS full sized pots for the 2 volumes and a Bourns mini pot for the tone, all 250K audio taper. I got the mini for the tone because the current one is a mini and the space looks really tight. I'll have to look into Emmerson Pro for the future, but I generally have really good experience with CTS pots.

[RockYoWorld]

250k pots and a .047 cap are the appropriate values (and what comes stock from Fender).

Is the .047 uF really the standard? That's what I use on guitars and I have a bunch of orange drops lying around. I saw people on another forum mention using .022 on their basses so I ordered some.

The higher the capacitor, the quicker it gets dark as you roll back the pot, right? If I ever use a tone knob, it's very slight roll-off. I may want to consider using .022 on a guitar to try it out.

[RockYoWorld]

BTW, audio-taper pots are the reason why I think the 4-control, Gibson-style layout is useless. I never hear any real difference when trying to "blend" the pickups, because no real change happens until you turn the pot almost all the way down. The blend is a lot more noticeable and varied on the Ibanez with linear taper pots.

How you describe audio taper is how I describe linear. It is strange how ear perception can be so different.

Are you a leftie by any chance?

I agree with you on volume. Volume is logarithmic so having an audio taper is supposed to give you more linear results as you rotate the knob. I could see using linear on tone knobs being better, though. However, as I said in another post, I don't use tone knobs that often so I'd rather keep my parts more standardized since I'm not as good at keeping things organized as I should be.

[andrewsrea]

The higher the capacitor, the quicker it gets dark as you roll back the pot, right?

Correct. The bigger the value, the darker and more immediate the tone pot gets as you roll it off.

0.047uF is what you'd find on a vintage Tele or Strat. 0.022uF on a Vintage Gibson w/ humbucker.

I prefer 0.022uF or 0.033uF for Strats and 0.022uF on the bridge of a humbucker guitar and 0.015uF on the neck, as a starting point (and usually what I stick with).

[Mossman]

BTW, audio-taper pots are the reason why I think the 4-control, Gibson-style layout is useless. I never hear any real difference when trying to "blend" the pickups, because no real change happens until you turn the pot almost all the way down. The blend is a lot more noticeable and varied on the Ibanez with linear taper pots.

How you describe audio taper is how I describe linear. It is strange how ear perception can be so different.

Are you a leftie by any chance?

Haha, no... I'm not a lefty using righty pots. But I think you may be confusing how audio and linear pots function depending on whether they're being used as a volume or tone control. I still have trouble keeping it straight in my head sometimes. I'm kind of a weirdo in that I can actually perceive the change in linear-taper pots where other people don't seem to be able to, but I believe the general consensus of audio-taper, when used as a volume control is that there is little perceivable change when rolling back the pot, until you hit about 4 or 3, then the volume drops precipitously. That's why they're good for volume swells. The change is more pronounced from 0 to 4, then it kinda (but not really) levels off. The Ibanez, with its linear-taper volume pots is not as immediate. You can do swells, but you have to turn the knob a lot further to hear a change. I don't do swells, and if I did, I think I'd prefer to use a volume pedal, so I don't mind exchanging that for broader, more precise volume control, and the ability to actually hear pickup blends. Because honestly, when I roll the bridge or neck pickup up or down with audio-taper pots, I hear no difference at all until one of the pickups is almost all the way down. Then, because of how the 4-knob wiring works, it starts to decrease the over-all volume until both of the pickups are off.

Now for tone control, it's a different story. If you use a linear pot, then it's like an on/off switch, and most of that change occurs at the lower numbers, but an audio-taper used as a tone control gives a smoother transition. But because for so many years, the default thinking was: volume = audio taper/tone = linear taper (or to simply use audio taper for all controls), I think we all just accepted it as the de facto standard. I, myself stopped caring about it and started using all audio-taper pots for all my mods and builds, but when I got the AS93 and heard how the controls work, I bought a mess of 250 and 500k linear-taper pots, and plan to replace the volume pots on all my guitars (eventually ).

[Mossman]

250k pots and a .047 cap are the appropriate values (and what comes stock from Fender).

Is the .047 uF really the standard? That's what I use on guitars and I have a bunch of orange drops lying around. I saw people on another forum mention using .022 on their basses so I ordered some.

The higher the capacitor, the quicker it gets dark as you roll back the pot, right? If I ever use a tone knob, it's very slight roll-off. I may want to consider using .022 on a guitar to try it out.

Yeah, that's the way they've always come from Fender. You can use a .022 cap, but you'll lose that signature P-Bass tone and growl. P-Basses are strong in the lows and mids (especially the mids!). I think a .022 cap would make it too bright, and thin.

[RockYoWorld]

Well the good news is that the pots and output jack came today and I rewired everything. Had the joy of having to re-run the ground wire to the bridge because I accidentally yanked the old one out. I also forgot how much of a pain it is stuffing wires into the cavity of a pickguard guitar like this.

Now that I'm done though, I'm definitely glad I bought this bass and switched out the pots. With the Axe FX III preset I made (through some help on YouTube from Leon Todd), I actually enjoy playing bass now. I never got that with my 5 string Schecter Omen, which doesn't have the same tone at all. This bass is the right tool for the sound I'm going for!

[Mossman]

Well the good news is that the pots and output jack came today and I rewired everything. Had the joy of having to re-run the ground wire to the bridge because I accidentally yanked the old one out. I also forgot how much of a pain it is stuffing wires into the cavity of a pickguard guitar like this.

Now that I'm done though, I'm definitely glad I bought this bass and switched out the pots. With the Axe FX III preset I made (through some help on YouTube from Leon Todd), I actually enjoy playing bass now. I never got that with my 5 string Schecter Omen, which doesn't have the same tone at all. This bass is the right tool for the sound I'm going for!

The Precision Bass isn't the most recorded bass guitar in history for nothing.

I favor the Jazz Bass, myself, but you gotta have a P!

[andrewsrea]

Haha, no... I'm not a lefty using righty pots. But I think you may be confusing how audio and linear pots function depending on whether they're being used as a volume or tone control. I still have trouble keeping it straight in my head sometimes. I'm kind of a weirdo in that I can actually perceive the change in linear-taper pots where other people don't seem to be able to, but I believe the general consensus of audio-taper, when used as a volume control is that there is little perceivable change when rolling back the pot, until you hit about 4 or 3, then the volume drops precipitously. That's why they're good for volume swells. The change is more pronounced from 0 to 4, then it kinda (but not really) levels off. The Ibanez, with its linear-taper volume pots is not as immediate. You can do swells, but you have to turn the knob a lot further to hear a change. I don't do swells, and if I did, I think I'd prefer to use a volume pedal, so I don't mind exchanging that for broader, more precise volume control, and the ability to actually hear pickup blends. Because honestly, when I roll the bridge or neck pickup up or down with audio-taper pots, I hear no difference at all until one of the pickups is almost all the way down. Then, because of how the 4-knob wiring works, it starts to decrease the over-all volume until both of the pickups are off.

Now for tone control, it's a different story. If you use a linear pot, then it's like an on/off switch, and most of that change occurs at the lower numbers, but an audio-taper used as a tone control gives a smoother transition. But because for so many years, the default thinking was: volume = audio taper/tone = linear taper (or to simply use audio taper for all controls), I think we all just accepted it as the de facto standard. I, myself stopped caring about it and started using all audio-taper pots for all my mods and builds, but when I got the AS93 and heard how the controls work, I bought a mess of 250 and 500k linear-taper pots, and plan to replace the volume pots on all my guitars (eventually ).

Again I find ear perception and internet consensus, curious. And I do believe for you it behaves the way you describe, which is contrary to published Bell Labs audio standards (Yes, Bell and Edison were as much the fathers of electric music as Leo was!).

The average human hearing is supposed to be logarithmic: being most sensitive to 6dB changes in sound pressure levels, which equates to doubling (or halfling when decreasing volume) in power.

An average A-taper pot (audio) at about 80% travel (say '8' on a volume knob) is equal to 50% travel on a B-taper pot (linear) in reference to ground (zero signal energy). At 1/2 way, an A-taper is at 20% signal, where a B-taper is logically, 50%. At '2' on the volume knob (about 10% travel) the A-taper is at 1% and linear is 10%.

So if you had linear hearing, you'd still theoretically hear more at '2' on a linear pot and would hear the sudden drop off after '1' . A-taper pots get to halfling-power quicker, so if you have logarithmic hearing, you would be hearing reductions in power quicker with an audio pot than a linear.

Algorithmic hearing should be more noticeable with a clean guitar signal vs. a distorted tone. For my set ups (a-taper volume pots w/ treble bleeds), I play distorted most of the time with my amp at 80dB to 102dB when on '10' of the guitar. Hence, I will only experience a little loss of highs + fatness and get some added clarity, but little loss of volume on '7', as compared to '10'. I get volume drop and jangly cleaner tones between '4' & '6' and low volume clean tones at '1.5' to '3'. To me, it all seems smooth. But due to my rig being loud and overdriven, I don't sense loudness drop until '4' or '5'.

For my hearing, linear pots can do an excellent job of 'swells' at '2' to '5' on the volume knob. For tone, linear pots sound have a wah effect at the same spots. I rarely do those so its generally audio pots all around.

All that said, what works for me isn't gospel. Like I have said many times on AGF - try things out and trust your ears. Then, use what sounds good to you!

[mickey]

Rob, you have reminded me that I have always been amazed by the number of things Bell Labs invented purely and simply because they were the first people ever to need a {fill in the blank}.
I'm sure you are familiar with PLL's (Phase Locked Loops) & have likely used PLL chips in various things, well Bell Labs invented them because they needed frequency stability in early
carrier systems. The first ones took THREE, 16 foot tall bays of tube type equipment!!! I've actually seen those in operation because they were being done away with about the time
I first hired in with AT&T. Oh, and Bell Labs also invented the dB (deciBel) because they were the first people ever to need precision measurement of audio levels.
I wonder if the Labs even still exist?

[ID10t]

Rob, you have reminded me that I have always been amazed by the number of things Bell Labs invented purely and simply because they were the first people ever to need a {fill in the blank}.
I'm sure you are familiar with PLL's (Phase Locked Loops) & have likely used PLL chips in various things, well Bell Labs invented them because they needed frequency stability in early
carrier systems. The first ones took THREE, 16 foot tall bays of tube type equipment!!! I've actually seen those in operation because they were being done away with about the time
I first hired in with AT&T. Oh, and Bell Labs also invented the dB (deciBel) because they were the first people ever to need precision measurement of audio levels.
I wonder if the Labs even still exist?

The google says they are now an arm of Nokia and known as "Nokia Bell Labs."
I had the pleasure of using many Bell innovations before, during, and after military service.

[mickey]

I wonder if the Labs even still exist?

The google says they are now an arm of Nokia and known as "Nokia Bell Labs."
I had the pleasure of using many Bell innovations before, during, and after military service.

Thanks, I never thought of that! DOH!
I knew that back in 1984 when the Government split AT&T up eight ways that the Labs went with Western Electric
which became Lucent which ended up getting bought out by some french telcom (Alcatel?), after that I lost track.

[andrewsrea]

I wonder if the Labs even still exist?

Nokia owns them. I think the original lab in NJ still operates.

Yes, it is crazy how much they developed out of necessity.