crusty philtrum
Vintageologist
I built a guitar recently with two hybrid humbuckers (Custom/59 bridge, Jazz/59 neck, both with aged A5 magnets) and two volume cotrols/master tone control.
Because the instrument was a sonic unknown, I've been doing some experimenting. After a couple of magnet swaps i decided to turn my attention to the pot values. The ones i originally installed were CTS 500K audio-taper.
I was thinking about changing the pots to 300K linear (i have never liked the way audio-taper pots seem to cause all the volume action to happen between 7 and 10 on the dial, i prefer a smooth increase in volume spread evenly from '0' to '10'). However, after changing magnets on covered humbuckers a couple of times, changing pots and possibly doing that more than once was just too much for me at this time, so I decided to try a quicker way to get an idea of how different pots would behave and sound.
Basically i decided to clip various resistors across the 500K pots to change their value. This would be quick and easy using a couple of alligator-clip test leads. I calculated what pot values i could create using standard resistor values.
If you know about speakers, you will know that another resistance of the same value will reduce the load to one half ... i.e. putting a 500K resistor across the 500K pot will make it's value effectively 250K. I wanted to hear what a 300K pot would sound like, and then other values between 300K and 500K.
For my test purposes, the resistor would be clipped across the outside two lugs of the volume pot (I used the neck pickup mostly) and the 500K tone pot remained in circuit.
Here's the calculated pot values created with standard resistor values paralleled across the 500K volume pot ..... (the symbol ' // ' means 'parallel).
500K (pot value) // 820K (resistor) = effective pot value of 310 K
500K // 1 Meg = 333K
500K // 1.2 Meg = 352K
500K // 1.5 Meg = 375K
500K // 1.8 Meg = 391K
500K // 2.2 Meg = 407K
500K // 2.7 Meg = 421K
500K // 3.3 Meg = 434K
None of the resistors really changed the taper of the pot in any noticeable or useful way. Of course the tone and output changed ... the lower the value of the resistor (and thus the overall pot value), the less treble and volume. All of the resistors created useful sounds, it becomes a matter of personal taste and would no doubt vary between different instruments and pickups. But each resistor had an effect. I initially went from the straight 500K pot to the '310K' value created with the 820K resistor to hear the largest change, then i worked through the resistors in the order I have listed them. Of course this involved some critical listening, clipping the resistor in and out several times for each value.
I later tried clipping the resistors across the volume pot between the wiper and ground, the wiper and hot, the tone pot (essentially the output on a 2V/1T configuration) and any other way that seemed possible. To my ear, if there were any changes, they were the same as my original method of clipping them across the outer lugs of the volume pot.
There are more configurations I could try, but haven't yet. I haven't tried doing this with the other volume pot and/or tone pot treated in the same way at the same time. But the results of what i have done yielded some great results, particularly for instrument/pickup combinations that may have a little more brightness than needed. This would probably also work really well combined with 'no-load' tone pots, and is possibly something that can be factored-in when considering magnet swaps.
It could also be possible to use a miniature preset pot instead of the resistor to give an constantly variable 'fine-tune' facility that could be accessed with a small screwdriver through a small hole in the control plate cover.
Given that a handful of resistors would cost less than a dollar, and a couple of alligator test leads wouldn't cost much more, it's a very worthwhile experiment to fine-tune the high end of a guitar's sound. If and when you find a resistor that works in a way that suits you, simply trim it and solder it in place.
Because the instrument was a sonic unknown, I've been doing some experimenting. After a couple of magnet swaps i decided to turn my attention to the pot values. The ones i originally installed were CTS 500K audio-taper.
I was thinking about changing the pots to 300K linear (i have never liked the way audio-taper pots seem to cause all the volume action to happen between 7 and 10 on the dial, i prefer a smooth increase in volume spread evenly from '0' to '10'). However, after changing magnets on covered humbuckers a couple of times, changing pots and possibly doing that more than once was just too much for me at this time, so I decided to try a quicker way to get an idea of how different pots would behave and sound.
Basically i decided to clip various resistors across the 500K pots to change their value. This would be quick and easy using a couple of alligator-clip test leads. I calculated what pot values i could create using standard resistor values.
If you know about speakers, you will know that another resistance of the same value will reduce the load to one half ... i.e. putting a 500K resistor across the 500K pot will make it's value effectively 250K. I wanted to hear what a 300K pot would sound like, and then other values between 300K and 500K.
For my test purposes, the resistor would be clipped across the outside two lugs of the volume pot (I used the neck pickup mostly) and the 500K tone pot remained in circuit.
Here's the calculated pot values created with standard resistor values paralleled across the 500K volume pot ..... (the symbol ' // ' means 'parallel).
500K (pot value) // 820K (resistor) = effective pot value of 310 K
500K // 1 Meg = 333K
500K // 1.2 Meg = 352K
500K // 1.5 Meg = 375K
500K // 1.8 Meg = 391K
500K // 2.2 Meg = 407K
500K // 2.7 Meg = 421K
500K // 3.3 Meg = 434K
None of the resistors really changed the taper of the pot in any noticeable or useful way. Of course the tone and output changed ... the lower the value of the resistor (and thus the overall pot value), the less treble and volume. All of the resistors created useful sounds, it becomes a matter of personal taste and would no doubt vary between different instruments and pickups. But each resistor had an effect. I initially went from the straight 500K pot to the '310K' value created with the 820K resistor to hear the largest change, then i worked through the resistors in the order I have listed them. Of course this involved some critical listening, clipping the resistor in and out several times for each value.
I later tried clipping the resistors across the volume pot between the wiper and ground, the wiper and hot, the tone pot (essentially the output on a 2V/1T configuration) and any other way that seemed possible. To my ear, if there were any changes, they were the same as my original method of clipping them across the outer lugs of the volume pot.
There are more configurations I could try, but haven't yet. I haven't tried doing this with the other volume pot and/or tone pot treated in the same way at the same time. But the results of what i have done yielded some great results, particularly for instrument/pickup combinations that may have a little more brightness than needed. This would probably also work really well combined with 'no-load' tone pots, and is possibly something that can be factored-in when considering magnet swaps.
It could also be possible to use a miniature preset pot instead of the resistor to give an constantly variable 'fine-tune' facility that could be accessed with a small screwdriver through a small hole in the control plate cover.
Given that a handful of resistors would cost less than a dollar, and a couple of alligator test leads wouldn't cost much more, it's a very worthwhile experiment to fine-tune the high end of a guitar's sound. If and when you find a resistor that works in a way that suits you, simply trim it and solder it in place.
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