'72 custom RI pot value query

pfogle · July 2nd, 2009, 06:35 AM

Hi, I've read several people recommending upping the value of the HB pots to 500k to cure a 'muddy' sound.

Question: if you have the pots dialled to 10 (which is where I normally have them) does the value of the pot make any difference at all? I would have expected that the pot is simply by-passed when on 10, so there should be no difference.

Can anyone confirm from experience that there is actually a difference?

I will say that I have noticed an improvement from lowering the HB a few millimeters. It's not big, but definitely has more chime now. So at least that's not a myth

Jim.Collins · July 2nd, 2009, 11:56 AM

Yes, the value of the volume pot will have an effect when you dime it. Assuming the volume pot is wired in a standard fashion, when the pot is full on, the total value of the volume pot is in parallel with the pickup. As you turn the volume pot down, a larger portion of the pot is in series with the pickup, and a smaller portion of the pot stays in parallel. Because of this, the value of the volume pot matters, even when it is full on. The larger the value of the volume pot (up to a point), the brighter the tone will be when the volume is full on. Also, the larger the value of the volume pot (up to a point), the more dramatic the treble rolloff will be as you turn the volume down.

gumbo · July 5th, 2009, 09:21 AM

What he said....

plus, without that, pot retailers would go out of business....

pfogle · July 5th, 2009, 06:04 PM

thanks, jim, I've been looking for that information for ages!

One more question... should the two HB pots be matched? What's the effect of the tone pot value?

thanks for you info...

Jim.Collins · July 7th, 2009, 12:34 PM

When you say "matched", are you asking whether the volume and tone pots should each by 500K? There is no rule that says they must be the same. In fact, you might want them to be different. A volume pot is wired in a manner different from a tone pot. The volume pot has a portion in series, and a portion in parallel, with the pickup. A tone pot is in series with the pickup. The only thing that changes, with a tone pot, is how much of that pot is in series. Thus, if you had a 500K tone pot, but always kept it turned down so that only 250K ohms were left, it would be the same as replacing the tone pot with a 250K pot, and leaving it dimed. I wouldn't do that, though, because it doesn't leave you with the option of increasing the brightness, should you need it. It might make a difference to replace the tone pot with a 1Meg pot, if you don't think it is bright enough at full volume and full tone. A 1Meg tone pot (with the same tone cap), full on, will be brighter than a 500K tone pot, full on. You can turn the 1Meg pot down to the point at which the tone control sounds just like a 500K tone pot, full on.

pfogle · July 10th, 2009, 07:35 PM

Jim, thanks, I really appreciate your reply. I don't have a circuit diagram, so I'm a bit in the dark.

As I'm a Brit, we don't have the expression 'dimed' - is that 0 or 10? and is 10 where the series resistance is 0 or 500k?

Also, when you turn the vol pot down and you get more of the pot in series, why does that not change the tone?

sorry for all the dumb questions!

thanks
Phil

July 2nd, 2009, 06:35 AM	#1 (permalink)
pfogle TDPRI Member Join Date: Apr 2009 Location: london, UK Posts: 67	'72 custom RI pot value query Hi, I've read several people recommending upping the value of the HB pots to 500k to cure a 'muddy' sound. Question: if you have the pots dialled to 10 (which is where I normally have them) does the value of the pot make any difference at all? I would have expected that the pot is simply by-passed when on 10, so there should be no difference. Can anyone confirm from experience that there is actually a difference? I will say that I have noticed an improvement from lowering the HB a few millimeters. It's not big, but definitely has more chime now. So at least that's not a myth

July 5th, 2009, 09:21 AM	#3 (permalink)
gumbo Tele-Meister Join Date: Sep 2006 Location: South Australia Age: 61 Posts: 204	What he said.... plus, without that, pot retailers would go out of business.... __________________ Heaven: A Bassman 410, a good pizza, and a nice lie down

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July 2nd, 2009, 11:56 AM	#2 (permalink)
Jim.Collins Tele-Holic Join Date: Feb 2005 Location: Pleasanton, CA Age: 55 Posts: 514	Yes, the value of the volume pot will have an effect when you dime it. Assuming the volume pot is wired in a standard fashion, when the pot is full on, the total value of the volume pot is in parallel with the pickup. As you turn the volume pot down, a larger portion of the pot is in series with the pickup, and a smaller portion of the pot stays in parallel. Because of this, the value of the volume pot matters, even when it is full on. The larger the value of the volume pot (up to a point), the brighter the tone will be when the volume is full on. Also, the larger the value of the volume pot (up to a point), the more dramatic the treble rolloff will be as you turn the volume down.

July 5th, 2009, 06:04 PM	#4 (permalink)
pfogle TDPRI Member Join Date: Apr 2009 Location: london, UK Posts: 67	thanks, jim, I've been looking for that information for ages! One more question... should the two HB pots be matched? What's the effect of the tone pot value? thanks for you info...

July 7th, 2009, 12:34 PM	#5 (permalink)
Jim.Collins Tele-Holic Join Date: Feb 2005 Location: Pleasanton, CA Age: 55 Posts: 514	When you say "matched", are you asking whether the volume and tone pots should each by 500K? There is no rule that says they must be the same. In fact, you might want them to be different. A volume pot is wired in a manner different from a tone pot. The volume pot has a portion in series, and a portion in parallel, with the pickup. A tone pot is in series with the pickup. The only thing that changes, with a tone pot, is how much of that pot is in series. Thus, if you had a 500K tone pot, but always kept it turned down so that only 250K ohms were left, it would be the same as replacing the tone pot with a 250K pot, and leaving it dimed. I wouldn't do that, though, because it doesn't leave you with the option of increasing the brightness, should you need it. It might make a difference to replace the tone pot with a 1Meg pot, if you don't think it is bright enough at full volume and full tone. A 1Meg tone pot (with the same tone cap), full on, will be brighter than a 500K tone pot, full on. You can turn the 1Meg pot down to the point at which the tone control sounds just like a 500K tone pot, full on.

July 10th, 2009, 07:35 PM	#6 (permalink)
pfogle TDPRI Member Join Date: Apr 2009 Location: london, UK Posts: 67	Jim, thanks, I really appreciate your reply. I don't have a circuit diagram, so I'm a bit in the dark. As I'm a Brit, we don't have the expression 'dimed' - is that 0 or 10? and is 10 where the series resistance is 0 or 500k? Also, when you turn the vol pot down and you get more of the pot in series, why does that not change the tone? sorry for all the dumb questions! thanks Phil

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