Volume Pot Question

[hanumanlangur]

From what I understand, a volume pot is working as a variable voltage divider. With normal wiring, when a volume control is turned down, resistance is added to the tone control circuit that it is connected to, which filters out more of the treble, leaving a duller tone.

My question is that if the volume control is working as a voltage divider, then why would 250k pots or 500k pots make a difference with the volume control cranked (if it's a divider....)? I've noticed that when I change tone pots to higher values, I get a brighter tone. But I haven't noticed this with volume pots in the same way. Yet it is conventional wisdom that changing both pots affects the treble. Can any wiring gurus shed some light on this?

 

[Artie]

Re: Volume Pot Question

A volume pot actually performs two functions. The voltage divider to control output voltage, and pup "load". A pickup is a very small AC generator and the load it sees is partially determined by the volume pot value. This can have subtle affects on the current draw and other minute variables of the pickup.

 

[hanumanlangur]

Re: Volume Pot Question

A volume pot actually performs two functions. The voltage divider to control output voltage, and pup "load". A pickup is a very small AC generator and the load it sees is partially determined by the volume pot value. This can have subtle affects on the current draw and other minute variables of the pickup.

Would it make more sense to just use 250k pots for volume controls then? When these pots are turned down, it seems to me that they will add less resistance to the tone control circuit, preserving more treble.

Also, do the effects include more output or less compression in the signal?

 

[uOpt]

Re: Volume Pot Question

The load part of the volume pot dampens the resonance peak of the pickup, that means the resonance peak stays at the same frequency but it's amplitude is reduced. That's even with the volume pot at "10".

As you have experienced, depending on what pickup you have there this effect might be hard to hear if you just do it in isolation.

When you turn down the volume pot things get complicated because the actual load, again affecting the amplitude of the resonance peak also interacts with the input impedance of your amp or whatever the first active component in your rig is.

A treble bleed mod just pushes all highs. While that raises the resonance peak towards where it was, a treble bleed mod also pushes other highs that were not dampened by the volume pot load. So with treble bleed mod it still doesn't sound the same.

The only way out of this is volume pots after active stages, aka active pickups.

 

[locrian06]

volume pot and active livewire dave mustaine picks

volume pot and active livewire dave mustaine picks

Hello there, you´ll see, i´ve recently replaced my Duncan designed picks of my Jackson guitar with a pair of the livewire dave mustaine picks. My guitar is a Randy Rhoads model with only one volume potenciometer, and no tone controls. Now, the problem is that they do not seem to achieve a good distortion, and some of the highs are losing, just as if like the volume control was at half with a passive pick up. The guy who installed them says it is their normal sound, because of their low impedance?, but the guy who sold them to me says they would sound better if i install a tone potenciometer. Also i´ve checked the diagrams that came with the pickups and i think they are correctly installed... Anyone has a idea of what may be going on? May a pre-amp help to distortion better?

 

[ErikH]

Re: Volume Pot Question

First off, pickups do not have distortion built in to them. That comes from your amp and/or distortion pedals. That said, you may want to look at your amp settings. You're going from passive pickups made overseas to made in America actives, two totally different animals.

Active pickups have a low impedence but that is not why they sound that way. They are low impedence because they are designed that way. It's actually a good thing because a low impedence output drives the signal along the cable better than passive pickups do, which have a higher output impedence than actives.

First thing I'd check, aside from your amp/pedal settings, is make sure you have a fresh 9-volt battery in the guitar. And don't forget to unplug the cable from the guitar after you are done playing or you'll drain the battery dead in no time. If the battery is fresh, then what amp are you using? Is it a high gain amp or something else? I doubt it's the pickups themselves.

 

[locrian06]

Re: Volume Pot Question

First off, pickups do not have distortion built in to them. That comes from your amp and/or distortion pedals. That said, you may want to look at your amp settings. You're going from passive pickups made overseas to made in America actives, two totally different animals.

Active pickups have a low impedence but that is not why they sound that way. They are low impedence because they are designed that way. It's actually a good thing because a low impedence output drives the signal along the cable better than passive pickups do, which have a higher output impedence than actives.

First thing I'd check, aside from your amp/pedal settings, is make sure you have a fresh 9-volt battery in the guitar. And don't forget to unplug the cable from the guitar after you are done playing or you'll drain the battery dead in no time. If the battery is fresh, then what amp are you using? Is it a high gain amp or something else? I doubt it's the pickups themselves.

I bought the battery few minutes before they installed the pickups. Now, about the amp, i´ve tried with a Yamaha f-20 and a marshall of 30 watts, and with the digitech rp 80 and a roland vg 88. Except of the roland, i think the others are small equipment, so i can not ask for much, but i have the doubt because some of the users said to me the pickups should distortion fine on any amp, whatever the size. Now, with the roland, some amp simulations seem to saturate fine but others that sound nice with the pickups do not. And with the rp 80, none of the distortion presets seem to work fine, except i put on a compressor.

 

[ErikH]

Re: Volume Pot Question

Have you compared it with another guitar with active pickups? Or just another guitar?

Again, the pickups don't distort, they put out a clean signal. They can cause distortion by overdriving the input of the amp.

There could be a cold solder joint in there that's stopping them from putting out their full output. The Mustain's are supposed to be similar tonally to the JB and Jazz set he used for years.

 

[locrian06]

Re: Volume Pot Question

Have you compared it with another guitar with active pickups? Or just another guitar?

Again, the pickups don't distort, they put out a clean signal. They can cause distortion by overdriving the input of the amp.

There could be a cold solder joint in there that's stopping them from putting out their full output. The Mustain's are supposed to be similar tonally to the JB and Jazz set he used for years.

ok ok, yeah i know they do not distort. I´m gonna check the joints with another thing. Could it be the volume potenciometer could be damaged? Only one more thing, so you say they have lower impedence level, i got it, but, can it cause that the guitar has less gain than one with passive sistem? in that case i think what i´m hearing is normal. thanks again dude.

 

[ErikH]

Re: Volume Pot Question

ok ok, yeah i know they do not distort. I´m gonna check the joints with another thing. Could it be the volume potenciometer could be damaged?

Possibly. If too much heat was applied during installation. What value pot is in there?

Only one more thing, so you say they have lower impedence level, i got it, but, can it cause that the guitar has less gain than one with passive sistem? in that case i think what i´m hearing is normal. thanks again dude.

Nope, not at all. If anything, it should have more.

 

[mustaine-who?]

Re: Volume Pot Question

If you could get some **** close up pics of the wiring and all, it would def help us with your problem. I ran the Mustaines in a guitar, and they are def hot with plenty of highs. Your's are wired wrong no matter what your "tech" says.

FWIW...I had an original set of Livewires installed years ago by a well known tech...and the dude didn't even change the pots...I was running them with 500k V/T!!

 

[hanumanlangur]

Re: Volume Pot Question

The load part of the volume pot dampens the resonance peak of the pickup, that means the resonance peak stays at the same frequency but it's amplitude is reduced. That's even with the volume pot at "10".

As you have experienced, depending on what pickup you have there this effect might be hard to hear if you just do it in isolation.
[...]

So does this mean that a pickup "sees" a 500k pot as more of a load, and reduces the amplitude of the resonant peak more than a 250k pot? Or am I getting this backwards? The conventional wisdom is usually that increasing the value of a volume pot will take out less treble (reducing amplitude of resonant peak), but is this correct?

 

[uOpt]

Re: Volume Pot Question

You got it backwards.

As I said, with most pickups it's hard to hear if you change only the volume pot and nothing else.

 

[locrian06]

Re: Volume Pot Question

If you could get some **** close up pics of the wiring and all, it would def help us with your problem. I ran the Mustaines in a guitar, and they are def hot with plenty of highs. Your's are wired wrong no matter what your "tech" says.

FWIW...I had an original set of Livewires installed years ago by a well known tech...and the dude didn't even change the pots...I was running them with 500k V/T!!

me again, i´ve got my guitar checked by another tech. the potenciometer was a bit damaged, but we installed another one of 100 k as required the manual and the overdrive didn´t improved. I guess that´s the sound of the pickups (hard to describe it from here). However we tried installing the pot the guitar had before changing to the Livewires (of 1000k) and the gain improved. I only have 2 questions, do you know why the manual asks to install pots of 100k? and another, is a volume pot and a tone pot the same, when they are not installed? or they just work different when they are installed?