Post by ChristoMephisto on Feb 8, 2009 10:44:40 GMT -5
Recently replaced the volume pots in my dual humbucker (Hagstrom Swede '80) after I found out some previous owner had 250k linear volume pots with 470k Tone pots. The pots were kinda low measuring about 460k, so I took them apart to bring them up to 'specs'. Both pots were new, but when the bridge volume goes past 9.5, this boost/distortion kicks in, kinda cool i guess. I did the neck one right, as the mid point measures 100k instead of 70k, only after I did the bridge one and scraped the wrong side. Increasing the resistance at the end of the rotation instead. Can't see the 30-40k at the end could boost it soo much, then remembered I had this before. Also got a '97 Squier Tele that came with the stock pups and 500k pots, and it also had the same boost at 10. When I swapped out the pups for Keystones, there was no more boost, sorta glad to say.
Does a pot behave differently when its at full, or do pups have a resonance peak related to the amount of volume?
Most pots that guitar suppliers sell are either rated at ±10% or ±20% variance. Either way, 460KΩ is within specs. I doubt the difference would be audible.
I took them apart to bring them up to 'specs'.
I did the neck one right, as the mid point measures 100k instead of 70k, only after I did the bridge one and scraped the wrong side. Increasing the resistance at the end of the rotation instead.
It is not clear to me what you did to these pots. Scraping one end of the track doesn't change the resistance at the midpoint, unless you are redefining "midpoint" to mean the midpoint of the unscraped portion of the track.
You said you were replacing these because a previous owner had 250K linear pots installed. Are your replacements audio taper? And how are they wired?
but when the bridge volume goes past 9.5, this boost/distortion kicks in, kinda cool i guess.
Also got a '97 Squier Tele that came with the stock pups and 500k pots, and it also had the same boost at 10. When I swapped out the pups for Keystones, there was no more boost, sorta glad to say.
Just a guess, but you may be dealing with a microphonic pickup in both cases. Perhaps that's why the prior owner changed the volume pots in the first place.
I'm thinking you have inadvertantly created yourself a no-load volume pot.
There is generally a resonant peak at the cutoff of the LCR filter made up of the pickups, controls, cable and amp input. This does usually flatten out as the guitar's volume is turned down. It would be a bit sharper with a no-load pot.
It's really not a full-range boost, but I suppose the extra treble would make it sound louder in a psychoacoustic kind of way.
Post by ChristoMephisto on Feb 9, 2009 17:50:04 GMT -5
Thanks for the replies. When I said to bring it up to specs, I more or less really meant I wanted to bring them up to an nice even 500k by adding some resistance to the beginning of the taper. I changed the taper by lightly scraping some of the carbon off the tracks.
Don't think its a 'no-load' pot tho. I made one of those out a p/p pot, and if there was a no-load at the volume, wouldn't the volume cut out instead?
Well, an increase in maximum resistance would change the resonant peak at cutoff. The no-load thing changes this maximum resistance to infinite (or close enough). The difference between 460K and 500K should be nearly imperceptible, though.
If you cut the pot at the "high end", it will be truly no-load. That won't cause it to turn off when turned all the way up, no. If you cut the other end, you'll have the same thing when turned all the way up. In between, you'll have a reostat, a varying series resistance which will not have quite so drastic an effect on volume as the normal voltage divider. When turned all the way down, it would short out as normal and go silent.