Humbuckers- highs lost from the volume pot. Should I hack this 355' some more?

ggunn said:
Can you site a reference for this assertion?
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Not one I can link to. Many times many books though. Not so much EE texts; after all, the kind of variability we are talking about here is not a consideration in any but a few instances. They just happen to be audio situations. None the less, it is an often and regularly observed issue in guitar amps, and to a lesser degree in guitars. Seeing as how you've admitted that there is some high end bleed on a volume pot (which is good as it is a well established phenomenon), to what would you ascribe it?


Light

"Cowards can never be moral."
M.K. Gandhi
 
Ok, still digesting. The link to Helmuth Lemme's article was very helpful (but it's only partly sunk in.
The spot about using a stepped tone control sounds like it could be a fun addition to explore, but first. :)
dgatwood said:
Uh... AFAIK, guitars all either use either an audio or linear taper pot. Both of those are dead shorts when turned all the way up.

Once you have appreciable voltage drop on the line, everything changes, though. Since you effectively have capacitance to ground by virtue of having a shielded cable, the result is that the resistance between the pickups and the output coupled with this capacitance turns into an RC low-pass filter.
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I still can't tell if the capacitor bypass effects the tone when to volume is wide open or not. And am I to understand that as you turn the volume down it just compensates for the load change caused by the pot, but it still must lower the total volume right?
Light, what is the nature of the downside to the tone you don't care for?

Wayne
 
mixsit said:
Ok, still digesting. The link to Helmuth Lemme's article was very helpful (but it's only partly sunk in.
The spot about using a stepped tone control sounds like it could be a fun addition to explore, but first. :)

I still can't tell if the capacitor bypass effects the tone when to volume is wide open or not. And am I to understand that as you turn the volume down it just compensates for the load change caused by the pot, but it still must lower the total volume right?
Light, what is the nature of the downside to the tone you don't care for?

Wayne
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Yes, it effects the tone when the guitar is at full volume. It makes it a bit brighter, which I find unappealing. And yes, it still brings the volume down.




Light

"Cowards can never be moral."
M.K. Gandhi
 
Light said:
Yes, it effects the tone when the guitar is at full volume. It makes it a bit brighter, which I find unappealing. And yes, it still brings the volume down.




Light

"Cowards can never be moral."
M.K. Gandhi
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Thanks again for responding. Hmm. Brighter I don't need.
To bad it's a little tough to try this stuff out. At some points I start considering just getting one of the cheap copy guitars, have the tech cut a door into it and let them go at it. :rolleyes:
 
Light said:
Not one I can link to. Many times many books though. Not so much EE texts; after all, the kind of variability we are talking about here is not a consideration in any but a few instances. They just happen to be audio situations. None the less, it is an often and regularly observed issue in guitar amps, and to a lesser degree in guitars. Seeing as how you've admitted that there is some high end bleed on a volume pot (which is good as it is a well established phenomenon), to what would you ascribe it?
Click to expand...

Actually, that is not exactly what I admitted. I admitted that I didn't know if there is or not. ;^)

Please understand throughout all this that I am looking for what's really going on, and I am not sniping at you. To that end, and no offense intended, I'll just say that the terms "well established" and "widely accepted" are tossed around by many who use them to add apparent weight to what is really only their opinion. When I asked for a reference, though, it was not as a challenge, but rather a quest for what is the real deal, and from a source other than someone I ran into out on the internet. I've read a lot of your posted info, and you indeed appear to be knowledgable, but I am sure that you know as well as I that one cannot always depend on appearances.

As to what could cause this alleged bleed of high frequencies, the first thing I would consider would be parasitic capacitance in parallel with the resistance of the pot. The next time I have one of my guitars opened up, I am going to sever the connection to ground of the volume pot and see if I hear any diff.

BTW, I am well aware of the approximations to reality that are encountered in course work; I am degreed in EE and I have been a practicing engineer for over 20 years. My specialty, however, is not in analog circuits.
 
ggunn said:
BTW, I am well aware of the approximations to reality that are encountered in course work; I am degreed in EE and I have been a practicing engineer for over 20 years. My specialty, however, is not in analog circuits.
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Well, practice makes perfect.

Practice asking for clarification without sounding like a douche.
 
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