Changing Pots - What Can I expect?

Fajah · #1 11-18-2009, 11:16 AM

I've been searching around and got a some basic info, but I think I need something a bit more specific. At the present time, my bass is passive with an HB in the bridge and a SD Basslines stacked jazz in the neck. My bass has been a work in progress and so it didn't start out this way and still has 250k pots and a .047 cap.

I want to brighten up the tone a bit while still maintaing the bottom end and thinking of replacing the pots to 500k. Not sure which cap I should go with so a recommendation would be helpful. Is going to 500k pots the right direction for what I'm looking for and what can I basically expect tone wise if I make the change?

Thanks in advance.

Fajah · #2 11-19-2009, 10:12 AM

Let me ask this another way:

The wiring diagram that comes with the SD stacked jazz neck pickup shows 250k pots and a .047 cap. This is assuming one is installing two of them. However, I have the stock Douglas HB installed in the bridge. Based on this, would you;

1) Keep the 250k in for the neck. Don't know what a 500k pot would sound like.

2) Install a 500k pot for the HB.

3) Tone pot - not sure.

4) Keep or change the cap.

mmbongo · #3 11-19-2009, 12:57 PM

Switching the pots to 500k will brighten it up a bit.

Fajah · #4 11-19-2009, 01:01 PM

Quote:

Originally Posted by mmbongo

Switching the pots to 500k will brighten it up a bit.

Which is what I'm looking for. Keep the same cap?

walterw · #5 11-19-2009, 01:12 PM

Sure, try it and see. You might find that cap value a little dark for hot humbuckers like you have. A 0.02 might be less muddy when turned down.

Fajah · #6 11-19-2009, 01:19 PM

Quote:

Originally Posted by walterw

Sure, try it and see. You might find that cap value a little dark for hot humbuckers like you have. A 0.02 might be less muddy when turned down.

Great, thanks. I'll try both cap values while I'm at it.

walterw · #7 11-19-2009, 10:43 PM

if you do try 500k volumes, be sure to get linear taper, as audio taper 500s will drop off way too fast from "10". (keep the tone pot audio taper regardless.)

Diogenes · #8 11-20-2009, 09:49 AM

Quote:

Originally Posted by walterw

... be sure to get linear taper, as audio taper 500s will drop off way too fast from "10". (keep the tone pot audio taper regardless.)

Are you sure about that? My experience has been that audio taper is correct for volume because volume/loudness/decible level does not follow a linear algorithm... but linear taper pots are used for tone.

Fajah · #9 11-20-2009, 10:26 AM

I've always used audio taper pots for both volume and tone controls. Three 500k pots are in the mail with a couple Sprague Orange Drop caps (.047 and .022). As soon as they arrive, the experiment will begin and this is what I plan to do:

1) Replace all the 250k pots with the 500k while leaving the existing ceramic .047 cap installed.

2) Replace the .047 with the .022 to hear the difference.

3) If I like the .022, I'll keep it. If not, I'll replace it with the Orange Drop .047.

Should be interesting and will report back when all is done.

brandtb · #10 11-20-2009, 12:33 PM

When you remove the existing cap, consider taping the caps you want to audition to a piece of paper or something and label the values. Then, use wires with alligator clips for a more immediate comparison of tones.

Good luck and please share your perceptions!

pasta4lnch · #11 11-20-2009, 12:35 PM

not to hijack - I'd like to learn about this stuff. is there a good on-line resource I can browse?

**ExaltBass** · #12 11-20-2009, 12:38 PM

Quote:

Originally Posted by brandtb

When you remove the existing cap, consider taping the caps you want to audition to a piece of paper or something and label the values. Then, use wires with alligator clips for a more immediate comparison of tones.

Good tip!

Piedro · #13 11-20-2009, 12:39 PM

really interesting... i'll suscribed...

if possible record some sample of your experiment! that'd be nice!

Fajah · #14 11-20-2009, 12:53 PM

Quote:

Originally Posted by brandtb

When you remove the existing cap, consider taping the caps you want to audition to a piece of paper or something and label the values. Then, use wires with alligator clips for a more immediate comparison of tones.

Good luck and please share your perceptions!

Glad you brought it up. I was thinking of doing something like that as well.

Fajah · #15 11-20-2009, 12:54 PM

Quote:

Originally Posted by Piedro

really interesting... i'll suscribed...

if possible record some sample of your experiment! that'd be nice!

Absolutely!

walterw · #16 11-20-2009, 01:10 PM

Quote:

Originally Posted by Diogenes

Are you sure about that? My experience has been that audio taper is correct for volume because volume/loudness/decible level does not follow a linear algorithm... but linear taper pots are used for tone.

yep, try them and compare.

you'll find that linear volumes sweep evenly from 0 to 10, while audio volumes will drop off fast from 10. (especially higher values like 500k.)

you'll also find that linear tones do little until they're almost all the way down.

there's actually a fair number of threads about this around here; i've been making this argument for a little while, and the only pushback i ever get is from people who haven't tried it but want to quote stuff about the logarithmic nature of the ear. my response is that you don't plug basses into your ear, but into the front end of clean amplification systems (i.e., bass amps), and linear volumes just work more evenly.

so far, everyone who's tried it seems to prefer it.

Diogenes · #17 11-21-2009, 08:09 AM

Quote:

Originally Posted by walterw

yep, try them and compare.

you'll find that linear volumes sweep evenly from 0 to 10, while audio volumes will drop off fast from 10. (especially higher values like 500k.)

you'll also find that linear tones do little until they're almost all the way down.

there's actually a fair number of threads about this around here; i've been making this argument for a little while, and the only pushback i ever get is from people who haven't tried it but want to quote stuff about the logarithmic nature of the ear. my response is that you don't plug basses into your ear, but into the front end of clean amplification systems (i.e., bass amps), and linear volumes just work more evenly.

so far, everyone who's tried it seems to prefer it.

Well then you now have someone on your register who disagrees and prefers audio taper.

I have retried linear volume pots many times these last few decades to see if maybe my ears have changed (believe it or not, you're not the only or first one to argue the case of linear pots) but the results are always the same. That's why I questioned your findings. My experience has been different than yours so I'll continue with whatever works for me.

walterw · #18 11-21-2009, 09:01 AM

Quote:

Originally Posted by Diogenes

Well then you now have someone on your register who disagrees and prefers audio taper.

I have retried linear volume pots many times these last few decades to see if maybe my ears have changed (believe it or not, you're not the only or first one to argue the case of linear pots) but the results are always the same. That's why I questioned your findings. My experience has been different than yours so I'll continue with whatever works for me.

aha! What value pots, what kind of bass, and what didn't you like about them?

Diogenes · #19 11-21-2009, 10:47 AM

Quote:

Originally Posted by walterw

aha! What value pots, what kind of bass, and what didn't you like about them?

The brand names I can remember for the pots were Alpha and CTS... as for the ones I can't remember, whatever Mouser, Olsen Electronics and other local electronics stores were selling at the time. The values ran the gambit from 10k to 1M depending on what pickup configurations I was using, how I made them, what I was trying to accomplish and how I was wiring them. The basses were varied... mostly basses that I was building.

I think audio taper pots have smoother volume transitions... just as long as they're not wired "backwards" or a reverse audio pot is used when a "standard" audio pot is required.

walterw · #20 11-21-2009, 12:35 PM

Quote:

Originally Posted by Diogenes

The values ran the gambit from 10k to 1M depending on what pickup configurations I was using, how I made them, what I was trying to accomplish and how I was wiring them.

so you're saying you've never tried it, then.

I have noticed that with active basses things behave differently. a Marcus miller jazz for example (single coil pickups, 250k audio pots), will exibit the typical rapid dropoff in passive mode, but not nearly so much when the preamp is kicked in.

Also, when running a bunch of compression and/or distortion, audios will behave more evenly (which is why I always recommend them for guitar players doing anything other than pure jazz.)

but in the case of passive pickups, putting higher value pots in there to brighten things up will have the side effect of making the volume drop off too fast for most folks. linear volumes in this case will just work more evenly.