legacy schematic tone mod

[n0nspaz]

wondering what will happen if i swap out a 500k pot for the 1Meg bass control pot in my Legacy.
schematic: http://www.glguitars.com/schematics/Leg ... iagram.pdf

changing C1 to ~.0044uF should correct the RC frequency calculation, but i am concerned about 1. changing the load on the pickups and 2. changing the source impedance on the 250k pot. wondering if this will change the sound much.

any ideas besides 'try it out' appreciated, thanks

[n0nspaz]

SORRY, meant to post this in DIY (this is my first post on the boards here)
please move this to DIY, thanks.

[Craig]

SORRY, meant to post this in DIY (this is my first post on the boards here)
please move this to DIY, thanks.

I moved your post here from The Project Page sub-forum where you posted it. Please read the READ THIS FIRST - About The Project Page sub-forum post in the Announcements of that sub-forum. Also, please read this post too: Welcome! Read This First.

[NickHorne]

I'm not sure why you are wanting to do this; replacing the 1M bass pot with a 500K will just reduce the amount of bass cut available on the control, but will not do anything else.
When the bass control is fully up, it behaves just like a piece of wire. It conducts straight through from the pickup selector to the 250K volume pot, without changing any pickup loading or frequency-dependant effect of any kind.
It's the relationship between the bass control capacitor and the volume pot which determines the frequency response of the bass control; the bass pot value just determines how much cut you can get when it's rolled right back. The bass pot has no ground connection. The circuit is just the signal going to the volume pot via a capacitor; this will roll off lows as the resistance of the pot becomes significant at low frequencies where the capacitor conducts the least. The Bass pot bypasses the capacitor to an adjustable extent, completely shorting it when fully up so no lows are then lost at all.
If you want to experiment with the frequency response of the bass control, just try some different caps there, and don't be confused into changing its pot value. This still won't affect pickup loading at all.

[n0nspaz]

thanks nick, it is good to hear that you think a lower bass pot value won't affect the tone or the loading. the reason i want to do this is to stack the PTB pots using a concentric dual pot thus freeing up the middle pot for a dedicated mid pickup volume. this will allow more tone blending which is useful in the studio. i will compensate the lower value pot with a higher value cap.

can anyone recommend a source for dual concentric 500k pot, hopefully with the right taper? i understand it is a reverse log taper on the bass (HPF) but i am not sure about the treble (LPF) pot.

thanks
mark

[n0nspaz]

i have found one here http://www.mojotone.com/guitar-parts/gu ... 3-50PldV8F and have inquired with them as to what the tapers are. will report back.

i suspect this could be a useful mod for a lot of people. freeing up a pot is no joke...opens up a lot of options. depends on the player of course.

[NickHorne]

I obviously wasn't quite clear.
A different value cap will not compensate for the change in pot value for the Bass control.

What the change in pot value will do is to reduce the amount of bass cut you get when the control is turned down. It won't change the frequency response.
But changing the cap value will alter the frequency response when the control is turned down, and you may not like it; a larger cap will pass more bass, making the control even less effective.
If anything, a lower-value cap would be more logical, except that the bass-cut would then take effect from a higher frequency, i.e. taking mids out too and probably getting thin.

It might be better to just live with a reduced range of bass control, and leave the cap the same.

The LPF pot track probably wants to be 250K, and regular forward log ("audio") taper.
I have successfully taken CTS dual-concentric pots apart and replaced one of the tracks with one from another CTS pot. Obviously, the track nearest the bushing is easier (you can just leave the back half alone), and this one is controlled by the outer of the two shafts. CTS do make "left-handed" 500k log pots, and you could try the track from one of these in your dual.

Googling "potentiometer CTS dual concentric" or similar should find you a supplier.

But unless your Bass pot track is 1Meg, you will have a reduced range of control, no way around it.

[GeorgeB]

Using a dual concentric for the (original) volume would be the easiest solution, wouldn't it?

[n0nspaz]

nick, thank you for the clarification that the bass pot value determines the throw of the bass control and not so much the frequency.
big help.

george, that is a good idea. my personal preference would be jazz bass style concentric tone pots. we'll

good news, just got the call that my Legacy came in. very fast, i ordered it on Apr19. thats only 34 days in production, amazing. let's see how it is. talk soon