Influence of the resistor on the pot's taper
- Thread starter CarlosG
- Start date
freefrog
Well-known member
Let's share a 5Spice sim of a Fender style single coil plugged to a 1M amp input through a 370pF cable, with a normal tone control and various volume pots, set from 10/10 to 1/10.
The curve of your solution, with resistor between outer lugs, is pictured on the upper left side. On the upper right, for comparison, is simulated a 250k pot without resistor. Bottom left = 500k volume + resistor from center lug to ground. Bottom right side = the same thing with resistor from center lug to hot. This last option maintains the 500k resistance when the pot is full up but changes its taper...
Not enough time for a longer answer but there's also some food for thought in the page below (scroll down for explanations and screenshots):
http://www.geofex.com/article_folder...s/potscret.htm
FWIW. HTH.
The curve of your solution, with resistor between outer lugs, is pictured on the upper left side. On the upper right, for comparison, is simulated a 250k pot without resistor. Bottom left = 500k volume + resistor from center lug to ground. Bottom right side = the same thing with resistor from center lug to hot. This last option maintains the 500k resistance when the pot is full up but changes its taper...
Not enough time for a longer answer but there's also some food for thought in the page below (scroll down for explanations and screenshots):
http://www.geofex.com/article_folder...s/potscret.htm
FWIW. HTH.
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I think there is something that I'm not getting. You say 500k is too bright but then you say you need something between 1 meg and 500k. That would be even brighter!
beaubrummels
Well-known member
I would just buy the right pot. They are not that expensive, nor that difficult to install.
Teleplayer
Active member
No. The resistor does not affect the taper. However this is an issue with using 1M pots in general - They lose a lot of high end frequencies when the volume is rolled off. For myself I'd stay with a 500k volume control because of that.
If you are they type of player who rides the volume control a lot, you can consider adding a treble bleed if there is not enough brightness with the tone control on max.
If you are they type of player who rides the volume control a lot, you can consider adding a treble bleed if there is not enough brightness with the tone control on max.
I like 1M pots with my Distortion/59 set. Usually adding an 82-150pF capacitor (depending on the guitar) partially fixes the problem. Resistor and cap in parallel works the best, but changes curve to more linear, so it's not good for hot pickups because it won't clean on high gain.
Adding treble bleed don't change tone when pots are on max
Teleplayer
Active member
Adding treble bleed don't change tone when pots are on max
Good point. If max volume gives an overdrive tone, the extra brightness may not be needed anyway. It depends on the player and usage.
eclecticsynergy
Well-known member
Adding a resistor-and-cap-in parallel treble bleed seems to change the taper.
I haven't encountered this when adding a 470K jumper to make a 500K pot sound like a 250K..
Not that my personal experience with that has been extensive.
I haven't encountered this when adding a 470K jumper to make a 500K pot sound like a 250K..
Not that my personal experience with that has been extensive.
freefrog
Well-known member
My screenshots in post 3 were an attempt to suggest without long rambling that a parallel resistor doesn't change significantly the taper until the resonant frequency in 3/4 of cases but modifies the curve beyond this resonant peak.
Now, it's necessarily a variable phenomenon, firstly because the behaviour of a pot with passive PU's depends on the input impedance of the host amp (or pedal) and secondly because the "morphing" of the resonant peak according to how pots are set depends on the inner parasitic capacitance of the pickup (!).
No wonder if personal experiences vary, so...
Now, it's necessarily a variable phenomenon, firstly because the behaviour of a pot with passive PU's depends on the input impedance of the host amp (or pedal) and secondly because the "morphing" of the resonant peak according to how pots are set depends on the inner parasitic capacitance of the pickup (!).
No wonder if personal experiences vary, so...
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eclecticsynergy
Well-known member
My screenshots in post 3 were an attempt to suggest without long rambling that a parallel resistor doesn't change significantly the taper until the resonant frequency in 3/4 of cases but modifies the curve beyond this resonant peak.
Now, it's necessarily a variable phenomenon, firstly because the behaviour of a pot with passive PU's depends on the input impedance of the host amp (or pedal) and secondly because the "morphing" of the resonant peak according to how pots are set depends on the inner parasitic capacitance of the pickup (!).
No wonder if personal experiences vary, so...
Thanks, freefrog. Your posts are always well-grounded :wink: in electronics.
Very helpful for those of us with less understanding of it.
It hadn't occurred to me that the taper would not be consistent at different frequencies.
Adding a parallel cap & resistor treble bleed to a log pot results in a more linear taper, which many don't like.
I think this is primarily what the OP was worried about.
I'm curious - would adding such a treble bleed change the taper of a linear pot also?
Would it become something like reverse-log, or would it just stay linear?
freefrog
Well-known member
You're welcome.
With a treble bleed made of a resistor parallel to a cap and added to a linear pot, yes, the resistor should change the linear response in a reverse log curve... and with its hi-pass effect, depending on its value, the cap might complicate the whole thing enough to make wrong any attempt of clear explanation.
For the fun, I share below another (hastily botched) "series" of sims illustrating how the response of a volume pot can vary with various values and uses of simple components. I've selected arbitrary values for the treble bleed variations but "you'll get the picture".
