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Volume Knobs have Poor Response on Fender Jazz

C

catyak

Sep 10, 2010
130
1
Denver, CO
#1
I have a stock MIM Fender Jazz, 2008. Both pickups provide a signal, but the response as I turn the volume knobs is flat+jumpy. From 1 o'clock to 11 o'clock, there's just a slight increase. Then the output jumps to very high and stays pretty flat for the rest of the rotation.

I'm new to this, but I'll assume that is not normal even though they both respond in the same way.

Is that something I could fix? What should I be looking at?

Or do I need to replace them? If I do, what should I be looking for?

EDIT - should be "pots" not "pups"
 
#2
It sounds like there is a problem with the controls. Either the controls are bad, or the leads were soldered on the wrong lugs, so you get a "reverse" taper.
 
#6
Jaco D said:
If they're linear taper pots, change them to log (audio) pots. Pots are cheap anyway so you can try them out for yourself which one (or mixed-and-matched combination) works for you. You know how to operate a soldering iron/gun, right?
Click to expand...

No, I haven't used a soldering iron. Is this a good project to learn on?

Also, can you explain the difference between "linear" and "log." I would guess that linear means a flat increase in the output while log means a logarithmic increase in output. Is that close?

I was expecting that something like 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 would be normal as I rotate the knob. That would be linear?

I'm actually getting something more like 1, 1, 1, 1, 1, 1, 1, 9, 9, 10. (Yeah, I'm making these numbers up since I'm reporting only on the sound I'm hearing through the amp, but they're close to what I'm perceiving.) It is almost like an on-off switch where it jumps.
 
#7
you are right about lin/log. a linear pot has a constant delta R per degree of rotation, a log pot has a log response, which is normally used for audio because the ear has a log response to changes in sound intensity. Usually, using a linear pot in an audio application (especially a volume pot) will end up acting as you describe, with all the action crammed up at one end.

It is a reasonable project for a beginner to change pots, but I'd recommend a small electronics iron (not the one your dad used for plumbing), rosin core solder (less corrosive than acid core), and a cheap DMM (digital multi-meter) for troubleshooting.

Take a digital picture before you start, so you can be sure to get all the wires back in the right places.
 
#8
Before taking your bass apart, I would have a look at several settings first. If you are usung an amp or pedal with some kind of distortion and or compression, please switch it all off and set everything to clean. If there is a drive or gain control, set it to a low level and use the main volume control to adjust the output level. Now try adjusting the volume controls of the bass. If they still suck, you should replace them. Otherwise you might have so much amplification that reducing the signal at the bass doesn't really reduce the cab volume, until you reach the beginning of the scale of the control. With an active Ibanez I had the same experience. I placed a resistor of about 20 kOhms in parallel with the output of the bass. The volume controls now are very responsive over their full scales.

Keep on playing subsonically!
 
#9
SGD Lutherie said:
Jazz basses use audio taper pots.
Click to expand...

It seems Am.Std. certanly does, it's not that clear about [Invalid or Expired Link Removed]. Pot description in their service diagrams is not exactly uniform, to put it politely.


Thunderbucker said:
a log pot has a log response, which is normally used for audio because the ear has a log response to changes in sound intensity
Click to expand...
except, volume pots in VVT are not exactly wired as standard volume controls, like in Precision. When you put on top of that high degree of interaction between volume controls, result is that there is no right or wrong pot tapper to use. There are two kinds of passive Jazz Bass players in this world: those who prefere linear volume pots, and those who prefere log pots. It's up to personal taste.
 
#10
catyak said:
I have a stock MIM Fender Jazz, 2008. Both pickups provide a signal, but the response as I turn the volume knobs is flat+jumpy. From 1 o'clock to 11 o'clock, there's just a slight increase. Then the output jumps to very high and stays pretty flat for the rest of the rotation.

I'm new to this, but I'll assume that is not normal even though they both respond in the same way.

Is that something I could fix? What should I be looking at?

Or do I need to replace them? If I do, what should I be looking for?

EDIT - should be "pots" not "pups"
Click to expand...

I have to ask "did this just start happening or has it been there all along?

I think it is a bad pot according to your description of "jumping around".

If all the solder connections look ok AND it looks wired per the drawings in the last post. Get a 250K Audio taper pot and replace it.
 
#11
you guys just knew i'd pipe in on this one!
recnsci said:
It seems Am.Std. certanly does, it's not that clear about [Invalid or Expired Link Removed].
Click to expand...
mexi fenders use 250k audio just like american stuff does. (that's all regular mexis and all regular americans, jazz, P, strats, all of it. the mexis actually use the same nice CTS pots as the USA stuff.)
recnsci said:
except, volume pots in VVT are not exactly wired as standard volume controls, like in Precision. When you put on top of that high degree of interaction between volume controls, result is that there is no right or wrong pot tapper to use. There are two kinds of passive Jazz Bass players in this world: those who prefere linear volume pots, and those who prefere log pots. It's up to personal taste.
Click to expand...
audios are traditional, but for bass (P or J), linear volumes just work better, in that they evenly go from loud to soft, rather than dropping off so fast from "10".

the only folks who prefer audio bass volumes that i can find are those who use lots of compression and distortion, and those who just think the original way was better no matter what.

what's worse is that jazz basses have the one tone necessarily wired "after" the two volumes; this causes the touchiness to be even more exaggerated. (search "gibson '50s wiring")

turn the tone down a bit on a stock J, then drop a volume pot a little; the volume will drop off even faster than before.

turn the volumes down a bit, then drop the tone; the tone will act like a second volume knob until it gets way lower, only then rolling off the highs.

linear volumes will even out this effect a little.
 
#12
LoveThatBass said:
I have to ask "did this just start happening or has it been there all along?
Click to expand...

It's been that way since I bought it. Since both volume knobs respond the same way, I didn't think much of it. It wasn't until I played another bass and its volume was much more responsive that I began to wonder to about mine.

I think it is a bad pot according to your description of "jumping around".
Click to expand...

It doesn't jump around. The volume stays very low until near the end of the rotation, then jumps to very loud. In between, the volume is constant. The sound is nice and warm, there aren't any crackles or spikes in the volume level.

The sharp rise near the end of the rotation sounds like a log pot. Based on the notes above, that is as it was coming from the factory.

I'll take it apart and check the connections and the wiring. If they look good, I'll go look for a linear pot and replace one to see if that gives the response that I'm looking for.

Next question, of course, is what to look for. Will any 250k linear pot work or should I look for a particular brand?
 
#13
catyak said:
I'll take it apart and check the connections and the wiring. If they look good, I'll go look for a linear pot and replace one to see if that gives the response that I'm looking for.

Next question, of course, is what to look for. Will any 250k linear pot work or should I look for a particular brand?
Click to expand...

SGD is right about the linear thing. The deal is that a log pot is designed to give equal changes in apparent volume for equal rotations (like the volume control of a radio). But there are two things that mess up this plan in a bass. First is that in a passive bass the volume control is loaded with other circuits. In a radio (where the pot was designed to work) there is next to no loading. This creates a big change in how the pot works. It makes a linear pot respond more like a log and a log pot respond...well not so good.

And the second thing is that unlike a radio where it might be loud or it might be soft, generally playing a bass means you'll be doing most of your adjustments at or near louder levels. Thus, what we like is to spread out the "loud" part of the pot to more rotation. This is EXACTLY what a linear pot does!

These are the reasons that SGD and many others have discovered that while a linear pot is supposed to be "wrong" for a bass volume control it nevertheless works best!
 
#14
bassbenj said:
SGD is right about the linear thing. The deal is that a log pot is designed to give equal changes in apparent volume for equal rotations (like the volume control of a radio). But there are two things that mess up this plan in a bass. First is that in a passive bass the volume control is loaded with other circuits. In a radio (where the pot was designed to work) there is next to no loading. This creates a big change in how the pot works. It makes a linear pot respond more like a log and a log pot respond...well not so good.

And the second thing is that unlike a radio where it might be loud or it might be soft, generally playing a bass means you'll be doing most of your adjustments at or near louder levels. Thus, what we like is to spread out the "loud" part of the pot to more rotation. This is EXACTLY what a linear pot does!

These are the reasons that SGD and many others have discovered that while a linear pot is supposed to be "wrong" for a bass volume control it nevertheless works best!
Click to expand...

Thank you. Very good explanation.
 
#15
Jay2U said:
Before taking your bass apart, I would have a look at several settings first. If you are usung an amp or pedal with some kind of distortion and or compression, please switch it all off and set everything to clean. If there is a drive or gain control, set it to a low level and use the main volume control to adjust the output level. Now try adjusting the volume controls of the bass. If they still suck, you should replace them. Otherwise you might have so much amplification that reducing the signal at the bass doesn't really reduce the cab volume, until you reach the beginning of the scale of the control. With an active Ibanez I had the same experience. I placed a resistor of about 20 kOhms in parallel with the output of the bass. The volume controls now are very responsive over their full scales.

Keep on playing subsonically!
Click to expand...

I have an Ibanez GSR200FM that I really like but the volume knobs have always bugged me. Now that I've decided to do something about it, it seems I have to learn a lot more than I originally planned, just like about everything in music these days. I thought this was an active bass, I mean it has a 9v battery, right? Well, according to the spec sheet at Ibanez it has a single coil STD J PASSIVE pickup and a dual coil humbucking STD P PASSIVE pickup! and the only thing Active is the Phat EQ gain knob! Still, both volume knobs have always gone 1-2-3-4-5-6-7-10 and I would like a steady change all the way up. The question is, is it the Pot or something else? In the manual it says there may be a volume drop off if the pickup(s) is too far from the strings. I'm quite a novice to the bass as far as electronics go, and I've never had anyone adjust it for me, (and not sure how many people in the store where I bought it I would trust to do that) but I'm not sure I should do it myself either. Unfortunately, Ibanez doesn't seem to have the wiring diagrams for anything after 2008 on their website, so I'm not sure how this thing is wired. Don't know if it's a linear or audio/log pot. Also, how do you place a resistor "in parallel" with the output? Is that inside the bass or outside? What to do, what to do...?
 
#16
it's normal for an "active" bass to consist of passive pickups feeding a preamp (the preamp is what makes it active).

your issue is indeed the volume pot, and you'll want linear taper for that. a 500k linear volume (before the preamp) would do nicely.

don't worry about resistors in parallel, you shouldn't need any of that.
 
#17
walterw said:
it's normal for an "active" bass to consist of passive pickups feeding a preamp (the preamp is what makes it active).

your issue is indeed the volume pot, and you'll want linear taper for that. a 500k linear volume (before the preamp) would do nicely.

don't worry about resistors in parallel, you shouldn't need any of that.
Click to expand...

Thanks for the reply but how do I know what I have (especially since Ibanez doesn't seem to have the wiring diagrams or detailed specs)? The idea of linear makes more sense than log (or exponential?) pot, but I have heard comments that "linear is better than log" and vice versa. If I knew what I had, I'd try the other, natch. but also, how do I know if my volume is before the preamp and would that make a difference which type of pot I use? I'm sure once I get it right, I'll know, but right now it's confusing and a little frustrating since I'm not an electronics/hardware wiz.
 
#18
ericjschroeder said:
I have an Ibanez GSR200FM that I really like but the volume knobs have always bugged me. Now that I've decided to do something about it, it seems I have to learn a lot more than I originally planned, just like about everything in music these days. I thought this was an active bass, I mean it has a 9v battery, right? Well, according to the spec sheet at Ibanez it has a single coil STD J PASSIVE pickup and a dual coil humbucking STD P PASSIVE pickup! and the only thing Active is the Phat EQ gain knob! Still, both volume knobs have always gone 1-2-3-4-5-6-7-10 and I would like a steady change all the way up. The question is, is it the Pot or something else? In the manual it says there may be a volume drop off if the pickup(s) is too far from the strings. I'm quite a novice to the bass as far as electronics go, and I've never had anyone adjust it for me, (and not sure how many people in the store where I bought it I would trust to do that) but I'm not sure I should do it myself either. Unfortunately, Ibanez doesn't seem to have the wiring diagrams for anything after 2008 on their website, so I'm not sure how this thing is wired. Don't know if it's a linear or audio/log pot. Also, how do you place a resistor "in parallel" with the output? Is that inside the bass or outside? What to do, what to do...?
Click to expand...

Hi, I might be a little late, answering your question: I just returned from a holiday. The active component is a little amplifier. I did some measurements and found out that the amplification is just one with the knob turned down. This means that in that case the output has the same level as if there were no amplification. The signal is only a little stronger and less susceptible to noise picked up by the cable between the bass and the amp. A small variable resistor (multi-turn potmeter) of 50 kOhms accross the input of the active amplifier (in parallel with the outputs of the elements) makes the volume controls a lot more responsive. A potmeter gives you the the possibility to adjust the output to your liking. Just in case I have to connect to an amp with a less sensitive input, I put a swith in series to be able to go back to the original configuration. A diagram of the electronics is not really required. The pick-up elements are connected the potmeters and from there they are wired to the input of the active pre-amplifier.
 
#19
Jay2U said:
Hi, I might be a little late, answering your question: I just returned from a holiday. The active component is a little amplifier. I did some measurements and found out that the amplification is just one with the knob turned down. This means that in that case the output has the same level as if there were no amplification. The signal is only a little stronger and less susceptible to noise picked up by the cable between the bass and the amp. A small variable resistor (multi-turn potmeter) of 50 kOhms accross the input of the active amplifier (in parallel with the outputs of the elements) makes the volume controls a lot more responsive. A potmeter gives you the the possibility to adjust the output to your liking. Just in case I have to connect to an amp with a less sensitive input, I put a swith in series to be able to go back to the original configuration. A diagram of the electronics is not really required. The pick-up elements are connected the potmeters and from there they are wired to the input of the active pre-amplifier.
Click to expand...

I appreciate the reply, and I understand the words, but not the meaning. In other words, I don't really understand what you're describing since I have never done any electronics work before. Are you talking about adding another volume knob (drilling holes) or replacing the current ones, or adding this resistor (where/how do you put it in?) and/or adding a switch like you mentioned (more holes?)?
 
#20
ericjschroeder said:
I appreciate the reply, and I understand the words, but not the meaning. In other words, I don't really understand what you're describing since I have never done any electronics work before. Are you talking about adding another volume knob (drilling holes) or replacing the current ones, or adding this resistor (where/how do you put it in?) and/or adding a switch like you mentioned (more holes?)?
Click to expand...

Hmm, For me it's the other way round: I'm a technician who tries to play the bass. The switch would require an extra hole if you want to be able to reach it at any time. In the attached drawing the modification can be seen. This applies to my GSR200EX. I soldered the switch and the 50 kOhm volume potmeter to the input of the pre-amp with two yellow wires. The metal housing of the switch (dashed box) is connected to the black wires for screening purposes. I also connected the metal screening of the lid to those black wires. This makes the screening against unwanted signals notably more effective. The switch can be left out by connecting the yellow wire to the potmeter directly. If you don't feel confident modifying your instrument, I would advice to ask someone who understands the diagram. I hope it helps.
 

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