Volume pot capacitors - help. Charvel Custom Shop

[nevusofota]

There are 2 capacitors on the volume pot along with a piece of wire connecting the third terminal and the body of the pot (see pic). What do these 3 things do and are they needed? I'm pretty sure that one of the capacitors helps keep the highs as the volume knob is decreased, but which one? Any help would be greatly appreciated.
TIA

 

[nevusofota]

After further research I found that the wire from the terminal to the body is the ground and the capacitor is the orange tab and the other is a resistor. I'm looking for a slow even taper of the volume pot hence the reason to change out the pot. The new pot (both are 500k audio taper) has more friction than the EVH pot, which I prefer. However, I still don't seem to have a good volume taper. I removed the capacitor and left the resistor and it seems like the taper is improved and I don't seem to be losing highs at lower volume. This seems to go against the rule though. Any problems with just using the resistor and leaving out the capacitor?

 

[Luca79]

Look like a treble bleed. Is a resistor and a capacitor.

 

[guitarnerdswe]

After further research I found that the wire from the terminal to the body is the ground and the capacitor is the orange tab and the other is a resistor. I'm looking for a slow even taper of the volume pot hence the reason to change out the pot. The new pot (both are 500k audio taper) has more friction than the EVH pot, which I prefer. However, I still don't seem to have a good volume taper. I removed the capacitor and left the resistor and it seems like the taper is improved and I don't seem to be losing highs at lower volume. This seems to go against the rule though. Any problems with just using the resistor and leaving out the capacitor?

I hate to break it to you, but there is no way that you're not losing highs with just the resistor in place. In a treble bleed mod, the cap is there retain highs, and the resistor is there to adjust the taper. With just the resistor, all you're doing is messing with the taper.

 

[guitarobert]

Use a linear taper pot instead. Audio taper pots have a logarithmic taper, which means the volume will be cut heavily as you make small adjustments from 100% downward. This is technically "correct" because volume knobs on all audio products adjust dBs (logarithmic). But in practice for guitar, I think a linear taper feels more natural, and will give the ability to better fine tune the volume.

I'd put the treble bleed resistor/capacitor in with the new linear pot. That retains the highs. It does cause the taper to skew slightly, but that won't be as much of a problem when using it on a linear taper pot. The benefit of retaining the highs is worth it.

 

[nevusofota]

Use a linear taper pot instead. Audio taper pots have a logarithmic taper, which means the volume will be cut heavily as you make small adjustments from 100% downward. This is technically "correct" because volume knobs on all audio products adjust dBs (logarithmic). But in practice for guitar, I think a linear taper feels more natural, and will give the ability to better fine tune the volume.

I'd put the treble bleed resistor/capacitor in with the new linear pot. That retains the highs. It does cause the taper to skew slightly, but that won't be as much of a problem when using it on a linear taper pot. The benefit of retaining the highs is worth it.

Thanks for the info! That's what I'm looking for, a pot that has a very gradual and slow change in volume. Any particular brand of pot that you recommend?

 

[guitarnerdswe]

Use a linear taper pot instead. Audio taper pots have a logarithmic taper, which means the volume will be cut heavily as you make small adjustments from 100% downward. This is technically "correct" because volume knobs on all audio products adjust dBs (logarithmic). But in practice for guitar, I think a linear taper feels more natural, and will give the ability to better fine tune the volume.

I'd put the treble bleed resistor/capacitor in with the new linear pot. That retains the highs. It does cause the taper to skew slightly, but that won't be as much of a problem when using it on a linear taper pot. The benefit of retaining the highs is worth it.

Thanks for the info! That's what I'm looking for, a pot that has a very gradual and slow change in volume. Any particular brand of pot that you recommend?

I have to just chime in here and add that the linear pot will give you an even more abrupt on/off effect. We humans don't perceive volume in a linear fashion, and that's why volume pots in 99% of cases are logarithmic. The whole point of the logarithmic taper is so that we humans will perceive it as smooth and gradual, and with a linear pot, you must definitely won't get that. You will basically hear it as on or off, with no in between.

If you don't mind the loss of highs from removing the cap, just run the pot with no treble bleed at all. Remove the resistor and go from there.

 

[nevusofota]

Use a linear taper pot instead. Audio taper pots have a logarithmic taper, which means the volume will be cut heavily as you make small adjustments from 100% downward. This is technically "correct" because volume knobs on all audio products adjust dBs (logarithmic). But in practice for guitar, I think a linear taper feels more natural, and will give the ability to better fine tune the volume.

I'd put the treble bleed resistor/capacitor in with the new linear pot. That retains the highs. It does cause the taper to skew slightly, but that won't be as much of a problem when using it on a linear taper pot. The benefit of retaining the highs is worth it.

Thanks for the info! That's what I'm looking for, a pot that has a very gradual and slow change in volume. Any particular brand of pot that you recommend?

I have to just chime in here and add that the linear pot will give you an even more abrupt on/off effect. We humans don't perceive volume in a linear fashion, and that's why volume pots in 99% of cases are logarithmic. The whole point of the logarithmic taper is so that we humans will perceive it as smooth and gradual, and with a linear pot, you must definitely won't get that. You will basically hear it as on or off, with no in between.

If you don't mind the loss of highs from removing the cap, just run the pot with no treble bleed at all. Remove the resistor and go from there.

So yes, I just read more info and it seems you definitely want an audio taper pot for smooth volume change. It seems that linear pots are used more for tone controls.

So in general, does the following seem acurrate:
- 150k resistor is used for a better taper
- The orange capacitor is added to maintain the highs at low volume

 

[guitarnerdswe]

Pretty close. The resistor is added to change the taper to have a more even "bleed through" of the highs, otherwise it might get too bright as you turn the pot way down. The downside to this is that the first part of the pots travel gets a bit more abrupt. Some companies like Suhr have 2 resistors and a cap to work around this (cap and 1 resistor in parallell, and then a resistor in series to both of those).

 

[nevusofota]

Pretty close. The resistor is added to change the taper to have a more even "bleed through" of the highs, otherwise it might get too bright as you turn the pot way down. The downside to this is that the first part of the pots travel gets a bit more abrupt. Some companies like Suhr have 2 resistors and a cap to work around this (cap and 1 resistor in parallell, and then a resistor in series to both of those).

Ok, so I've realized that I actually do not want a treble bleed as I use the volume knob as sort of a tone knob also. If I want less bite to my tone, aka less treble, I have always turned the volume knob back some. I am used to this as I rarely touch the tone knob and most of my guitars only have a volume knob. The main thing I want is a smooth even change as I turn the knob. I'm not concerned about losing high frequencies. So this must be why I preferred only the resistor and no orange capacitor at all. Is my thinking in line?

 

[guitarnerdswe]

Pretty close. The resistor is added to change the taper to have a more even "bleed through" of the highs, otherwise it might get too bright as you turn the pot way down. The downside to this is that the first part of the pots travel gets a bit more abrupt. Some companies like Suhr have 2 resistors and a cap to work around this (cap and 1 resistor in parallell, and then a resistor in series to both of those).

Ok, so I've realized that I actually do not want a treble bleed as I use the volume knob as sort of a tone knob also. If I want less bite to my tone, aka less treble, I have always turned the volume knob back some. I am used to this as I rarely touch the tone knob and most of my guitars only have a volume knob. The main thing I want is a smooth even change as I turn the knob. I'm not concerned about losing high frequencies. So this must be why I preferred only the resistor and no orange capacitor at all. Is my thinking in line?

Yep, you're probably correct. Try it without the resistor, I suspect the taper will be smoother than with it.

 

[moltenmetalburn]

Lose the treble bleed, use a linear taper

 

[guitarobert]

Use a linear taper pot instead. Audio taper pots have a logarithmic taper, which means the volume will be cut heavily as you make small adjustments from 100% downward. This is technically "correct" because volume knobs on all audio products adjust dBs (logarithmic). But in practice for guitar, I think a linear taper feels more natural, and will give the ability to better fine tune the volume.

I'd put the treble bleed resistor/capacitor in with the new linear pot. That retains the highs. It does cause the taper to skew slightly, but that won't be as much of a problem when using it on a linear taper pot. The benefit of retaining the highs is worth it.

Thanks for the info! That's what I'm looking for, a pot that has a very gradual and slow change in volume. Any particular brand of pot that you recommend?

I have to just chime in here and add that the linear pot will give you an even more abrupt on/off effect. We humans don't perceive volume in a linear fashion, and that's why volume pots in 99% of cases are logarithmic. The whole point of the logarithmic taper is so that we humans will perceive it as smooth and gradual, and with a linear pot, you must definitely won't get that. You will basically hear it as on or off, with no in between.

I respectfully differ on this point. If you want a more gradual taper starting from 100% volume downward, then a linear taper will be more gradual. Humans do perceive volume in a logarithmic fashion, but the concept of logarithmic volume perception doesn't directly correlate to the concept of a linear vs. logarithmic taper volume curve.

One simple way to look at it is to compare resistance at 50% volume, or 5 on the volume knob out of a max of 10. The resistance will be 50% of the max for a linear taper. For an audio/logarithmic taper it will be around 10% of max. So the logarithmic taper's volume will fall much more rapidly as you turn the volume down starting from 10. A linear taper's volume will fall less rapidly. See this plot. At volume level 7 on the guitar knob, the linear taper is around 70% (-3dB) and the logarithmic taper is around 45% (-7dB). At volume 5 the linear taper is around 50% (-6dB) whereas the logarithmic taper falls much further to 10% (-20dB). The effect here is that you'll get a more gradual reduction in volume using the linear taper than the logarithmic taper.

So yes, humans perceive volume in a logarithmic fashion, but the levels correlating to volume knob position will vary more gradually when using a linear taper. And if you like the effect of treble reducing as volume reduces, then just remove the treble bleed circuit. So I vote for a linear taper pot with no treble bleed in this case.

 

[Nilo]

Use a linear taper pot instead. Audio taper pots have a logarithmic taper, which means the volume will be cut heavily as you make small adjustments from 100% downward. This is technically "correct" because volume knobs on all audio products adjust dBs (logarithmic). But in practice for guitar, I think a linear taper feels more natural, and will give the ability to better fine tune the volume.

I'd put the treble bleed resistor/capacitor in with the new linear pot. That retains the highs. It does cause the taper to skew slightly, but that won't be as much of a problem when using it on a linear taper pot. The benefit of retaining the highs is worth it.

Thanks for the info! That's what I'm looking for, a pot that has a very gradual and slow change in volume. Any particular brand of pot that you recommend?

I have to just chime in here and add that the linear pot will give you an even more abrupt on/off effect. We humans don't perceive volume in a linear fashion, and that's why volume pots in 99% of cases are logarithmic. The whole point of the logarithmic taper is so that we humans will perceive it as smooth and gradual, and with a linear pot, you must definitely won't get that. You will basically hear it as on or off, with no in between.

I respectfully differ on this point. If you want a more gradual taper starting from 100% volume downward, then a linear taper will be more gradual. Humans do perceive volume in a logarithmic fashion, but the concept of logarithmic volume perception doesn't directly correlate to the concept of a linear vs. logarithmic taper volume curve.

One simple way to look at it is to compare resistance at 50% volume, or 5 on the volume knob out of a max of 10. The resistance will be 50% of the max for a linear taper. For an audio/logarithmic taper it will be around 10% of max. So the logarithmic taper's volume will fall much more rapidly as you turn the volume down starting from 10. A linear taper's volume will fall less rapidly. See this plot. At volume level 7 on the guitar knob, the linear taper is around 70% (-3dB) and the logarithmic taper is around 45% (-7dB). At volume 5 the linear taper is around 50% (-6dB) whereas the logarithmic taper falls much further to 10% (-20dB). The effect here is that you'll get a more gradual reduction in volume using the linear taper than the logarithmic taper.

So yes, humans perceive volume in a logarithmic fashion, but the levels correlating to volume knob position will vary more gradually when using a linear taper. And if you like the effect of treble reducing as volume reduces, then just remove the treble bleed circuit. So I vote for a linear taper pot with no treble bleed in this case.

Absolutely wrong. You have to take into consideration that a volume knob does not work as a variable resistor but as a voltage divider.
A logarithmic pot will be perceived as smoother than a linear one.
If you don't trust me, do the math yourself.

 

[nevusofota]

I tried a CTS 500k audio taper and it did nothing. Has the exact issue as the stock EVH pot. I ordered a 500k linear pot. Hopefully that gives it a smoother taper.

 

[Nilo]

The thing about most modern "audio" tapers is that they are not really log tapers. Most of them are just 2-3 different linear tapers pieced together.

Also, you need to think about how the volume knob in your guitar is working. If you have an overdriven amp and you are rolling down the volume to achieve different levels of gain, then you're not really affecting the amplitude of SPL. What you are really doing is controlling the amount of signal to reach the input stage of your amp. So, the logarithmic perception of volume can no longer be relied on.

My point is that you need to choose the taper depending on how you use it. If it's being used as a volume knob (amp clean) use a logarithmic taper. If your amp is dirty, find a taper that works for that. And remember, not all audio tapers are the same.

 

[Nilo]

Oh, and a resistor in parallell with the cap messes with the sweep and changes the taper. A better solution is to put the resistor in series with the cap. Then you can calculate the break of frequency and use the resistor to limit the effect the treble bleed will have. Then you can keep the taper of the pot you like, choose at what frequency you want the hi pass to start and with the resistor decide what amplitude you want these frequencies at.