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Tone control not working properly
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10123&t=43173		 Page 1 of 1
Author:  Irving [ Wed Apr 09, 2014 11:12 am ]
Post subject:  Tone control not working properly
I wired up my most recent guitar with a .022uF cap on a new Alpha B pot. When adjusted, the tone control does almost nothing until the last 1/8th turn. It clips and snaps a bit and the tone rather suddenly turns all the way down. Anyone know what might cause this?

This is how I have it wired. I have wired many guitars like this and never had a problem.

Image
Author:  David Collins [ Wed Apr 09, 2014 3:18 pm ]
Post subject:  Re: Tone control not working properly
Your problem is the "B" - that means linear in modern pot codes, and this is how linear pots work when you use them for a passive tone control. You need to switch that one out for an audio pot. The "clips and snaps a bit" part is odd, maybe a dirty or mechanically defective pot, but the problem of no notable change until the bottom is just a function of the taper.
Author:  StevenWheeler [ Wed Apr 09, 2014 6:15 pm ]
Post subject:  Re: Tone control not working properly
Follow this link to Davids recently completed videos on this very subject. http://luthiersforum.com/forum/viewtopic.php?f=10123&t=43053 Lots of good info there. Thanks Dave!
Author:  dzsmith [ Wed Apr 09, 2014 7:19 pm ]
Post subject:  Re: Tone control not working properly
The wiring is different than most tone circuits I've seen.
Author:  Irving [ Wed Apr 09, 2014 11:51 pm ]
Post subject:  Re: Tone control not working properly
David Collins wrote:
Your problem is the "B" - that means linear in modern pot codes, and this is how linear pots work when you use them for a passive tone control. You need to switch that one out for an audio pot. The "clips and snaps a bit" part is odd, maybe a dirty or mechanically defective pot, but the problem of no notable change until the bottom is just a function of the taper.



Interesting, I thought that may have been it. I had always used A pots in the past. Until recently I was buying some pots from a site (forget where, maybe guitar fetish) and they listed the A pots as volume pots and the B pots as tone pots. I figured huh might as well get a B pot for the tone then. Is this a desired effect of a tone control? (Aside from the clipping I described.) I have never seen a tone control perform in this manner where it doesn't do much until the very end of the turn.
Author:  David Collins [ Thu Apr 10, 2014 9:22 am ]
Post subject:  Re: Tone control not working properly
Yeah, I have no idea how this tidbit originated and spread, but several suppliers like AllParts and others list linear for use in tone controls. Must have been printed in a book or mistakenly spoken by an expert at some point, and repeated as fact and spread from there. Same goes for volumes having to be audio due to the human ear's logarithmic response to sound pressure levels (which is pure BS because an audio pot doesn't deliver anywhere near a logarithmic change in actual loudness as you turn it down when used in this setting).

Volume pots can be audio or linear (well over half the guitars being made today use linear), but tone pots are nearly universal audio. There are some very rare players who prefer linear here, because they want to do quick pinky tone swells while playing, and want the entire range packed in between 0 and 3 so they don't have to turn as far, with very little change happening between 3 and 10. For the vast majority of players though, audio is it for tone and linear just seems like an on/off switch with no real effect until the bottom.

You should really write the supplier back that you bought this from, and tell them it doesn't work for tone as advertised, and ask them to send you a proper replacement audio pot. I know it's only a few dollar part, but maybe if enough folks did this they might actually try using one for tone themselves, realize and correct the error, and stop misinforming other unsuspecting buyers.
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