Trim pot for 1 tone guitar to balance pickups

[bowyn]

Hi, Folks,

I've got a guitar with 1 Volume and 1 Tone. It's got a little bit of potential value as a collectible, so I don't want to make any irreversible mods to the looks of it.

The issue is, I have a Humbucker in the bridge and a P-90 in the neck. Now, normally I like a P-90 with 500k pots, but this one is a Surf-90 from GFS and it's PAINFUL with 500k pots.

The way it's wired, the pickups go straight to the three-way toggle switch and then to the VOL and TONE pots.

I was thinking of a way to modify the wiring from the Neck pickup before it gets to the 3-way switch and tame it some.

The idea I keep coming back to is to add a teeny-little Trim pot to the wire going from the neck pickup to the 3-way switch and let some of the signal go to ground.

In effect (if I am at all close to right) it will be going through the trim tone pot, through the switch, and through the master tone pot.

In order to keep it from being too drastic, I figured a 500k trim pot would do (I've been told that the pot itself, even turned all the way up, adds resistance so that going through 2 500k pots is similar to going through 1 250k pot.. I might be way off there).

I've drawn a crude diagram of what I'm thinking. I didn't bother with drawing the pot lugs or anything like that, because the wiring path from neck pickup to 3-way switch, and whether it will work like I'm thinking it will, is all I'm looking at changing. I'm pretty sure I can get the lugs right myself.

Hopefully, if this is legit, I can dial in the tone I like for the Neck pickup on the little trim pot, and have it just sitting (due to it's small size) in with the wiring, out of site and out of mind.

Any advice?

Crude Diagram:





Thanks!@!!!

[roadtonever]

It's a perfectly valid way of matching un-matched pickups IMO. The trimpot at "10" it will be like if you had 250k pots on the neck pickup. Correction: It will require a 250k trimpot for that effect. The 500k trimpot will be more like if you had 334k pots

But if you feel like it, try this little experiment: Plug in to your amp using a short patch cable. At best the reduced external capacitance might shift the tone from a harsh range to a potentially flattering range. If you like what you hear but want to keep your regular setup there are ways to achieve that. If not the trimpot should do the trick.

[reTrEaD]

bowyn-
Hello and Welcome to G-Nutz2!
I think you're on the right track. Increasing the loading on a pickup will tame down the highs. Use and audio taper trimpot if you can find one. And use the counter-clockwise terminal and wiper. As you turn the pot counter clockwise, the resistance will decrease. Putting the trimpot in parallel with the neck pickup will affect the Neck pickup and also the "Both pickups" selection. When used alone, the Bridge pickup will be unaffected.

[newey]

bowyn-

Rt's already welcomed you, so I'll just second the motion.

Rather than just playing with patch cables, you can do testing of the trimpot external to the guitar, which would give you an idea of whether a 250K pot is the ticket.

You would do this with the guitar set to the neck position, with the master V and T at "10". Sacrifice an old cable and wire the trimpot into that.

[bowyn]

Thanks for the feedback, guys.

I tried a really short cable (6", it was kind of comical trying to play like that) and it's still pretty wild. Sounds like a really bright and slappy bridge pickup.

I've searched and searched, but I don't think I'm going to be able to find a log trim pot. I figure as long as I pay attention to what I'm doing with setting the trim pot, I can get away with a linear, especially since I hope to be able to set it and leave it alone. Will be a little more of a pain setting it initially, but then the moment I opened a guitar up while warming a soldering iron, I made the decision to endure these occasional pains in the butt.

Unfortunately, finding one of these trim pots in the right value, even linear, is going to involve mail ordering, so it'll be a week or so before I can try it out. I'll be gleefully (I hope) updating this post at that time.

I'm a sucker for oddities, and this is like discovering a new trick.. and I've already got mod fever just thinking about it... must practice restraint.

Next project... Lucite guitar with UV LEDS under the pickguard... rotary switch off/on/blinking/random pattern/dimmed/extra-bright/etc...

[bowyn]

Aug 22, 2012 6:08:20 GMT -5 newey said:

Sacrifice an old cable and wire the trimpot into that.

That's a great idea. I've got one with a bad connection in the jack I could fix and then cut it in the middle, add a few alligator clips, voila, official testing cable.

There's no gear like ghetto gear.

[reTrEaD]

I like the idea of making an external cord with a pot for testing purposes. It makes for easy measurement of resistance without disconnecting anything inside the guitar. Just unplug both ends of the cable and measure. However there are a few caveats. For instance, make certain the guitar volume is a full clockwise. Else the results will be somewhat different from what happens when a resistor or trimpot is installed directly in parallel with the neck pickup.

You might want to temporarily wire the guitar to have the output from the pickup selector go directly to the output jack. Then use the external shunt to determine the "sweet spot" for loading on the bridge pickup as well as on the neck. At the moment, we're assuming that's 250k for the bridge HB (500k tone in parallel with 500k volume). But that might not be the case. If the sweet spot is 170k or less, you could use a 250k volume pot. I prefer to use 250k for volume whenever possible. It keeps the output impedance lower when the volume is rolled back. This allows less hum and noise to enter the system and reduces the treble loss associated with cable capacitance.

Once you have determined the "sweet spot" for each pickup as well as the both-pickups combination, we can work backward to determine the best way to approximate this with pot values and parallel resistance.

Also worth considering: putting the tone control in parallel with the neck pickup rather than the output of the pickup selector. This would allow you to dial down the treble when the Neck (and Neck + Bridge) is selected. But at the flip of the pickup selector, the Bridge is available without treble-cut. You might find this to be very handy. Or you might find the absence of a tone control for Bridge-only to be undesirable. It's all a matter of personal taste.

[bowyn]

Muahahahahaaa!

[seratone]

Replying to an 8 year old post - Hey Bowyn, did you ever install that trim pot? - I have a A Jazzmaster with a neck pickup that's got far more output than the neck - and these are brand new Lindy Fralin Noisless!


The trim pot solution looks like the best for me. 


In order for my neck p/u to equal the volume of the Bridge/Middle I have to lower the volume to 7. Wondering what sort of trim pot that would be - they seem the be available on Amazon.

P

[newey]

Seratone-

Hello and Welcome to G-Nutz2!

Bowyn hasn't signed in since a couple of months after he posted this, so he is unlikely to respond now to your inquiry. His diagrams have also disappeared into the ether as well. We can certainly help with any questions you have, and it may turn out that one of the other members may have treid this themselves and could give you feedback.

Or, perhaps you can email Bowyn, click on his profile to get his email address (unless he had it hidden way back when, as an admin I see all . . .). If the email addy is still valid, he might get back to you with more info.

[ashcatlt]

If you want to reduce volume rather than tone, it’s going to need the trim pot in series with the pickup rather than parallel. You’ll be creating a voltage divider with the trim pot as the top resistor and the other pots as the bottom. I think this is better than wiring the trim pot itself as a divider.

[sumgai]

What, did everyone decide to get on the First Law of GNutz2* bandwagon and simply "forget" to suggest that pickup height might be the solution?

And lest I be viewed as an impolite Admin..... hey bowyn: to The NutzHouse!







* The First Law of GNutz2: "Leave no lug unsoldered."^©

(copyright 2010, The Beta Particle Bombarder)

[newey]

Well, Bowyn came and went 8 years ago, it's Seratone we're now welcoming . . .

But, yeah, try the height adjustment first, 2 minute fix if it works.

[sumgai]

Nov 5, 2020 5:44:21 GMT -5 newey said:

Well, Bowyn came and went 8 years ago, it's Seratone we're now welcoming . . .

ARRRGH! Yer right of course, I simply forgot who was posting whilst scribbling my message, scrolled down to the see the OP name, and inserted it without checking any further. Gaaaaahhh, what a stupid blunder.....


seratone, my apologies, and a double helping of to The NutzHouse!!







sumgai