Guitars that get dark when turned down.

[rockman627]

I have a Harley Benton tele, red dual f hole. It had a real good feel and I installed 2 TV Jones filtertrons in a P90 form. It sounded pretty good but got dark when I turned down. I've read why this happens but some of my guitars don't do this. Others have treble bleeds. Anyways I would like to get a couple of 1meg pots to brighten the sound. Are there brands of pots that don't darken?
What are the mechanics of this? I have a Les Paul with Jim Wagner pickups no problem. I have a PRS SE that I put a Dimarzio Dual Sound and a Tom Anderson Humbucker no problem. Others needed a treble bleed. Is it better pickups and pots?

[Helmholtz]

The source impedance at the wiper of the vol. pot together with the cable capacitance forms a low pass filter.
The effective source resistance increases when you turn down the volume, so you lose treble.

The higher the pot resistance, the stronger the effect.

[rockman627]

How are the Les Paul and PRS avoiding this? Is it scatterwinding the pickups as some claim?

[Helmholtz]

How are the Les Paul and PRS avoiding this? Is it scatterwinding the pickups as some claim?

They don't.
But as they produce less treble, the amp might be adjusted differently or the difference is less noticeable.
Using a 1M vol. pot definitely requires a treble bleed cap.
What's the recommended pot value with your TV Jones Filtertrons?

Also the treble loss reduces with a lower capacitance guitar cable.

[daz]

I just went thru this and for me i never have this issue with most guitars, but most for me are single coils. P90s, fender singles. I just use treble bleeds and it works perfectly. But with humbuckers i find it much harder and in fact, while i own single coil guitars 99% of the time, i've had a few humbucker guitars in the last decade all of which had this issue. The one i posted about a week or 2 ago here is a epiphone LP standard and i've been pulling my hair out tryng to get it to clean up. I finally tried something that seemed to do the trick tho i am still evaluating it. But so far it gets much cleaner. I have a 500k pot who's actual value is around 430k (was using a 520k but removed it a few days ago....long story) or thereabouts. I did this with no actual understanding of what it would technically do but i had a idea. I put a 220k resistor from the wiper to ground. I figured it would lower the overall pot value some which i did NOT wanna do because then i may as well use a 250k but didn't want to ruin the tone when the volume is on 10, but i tried it anyways. It seems to have made the guitar get probably 25-50% cleaner when i roll down to 4 or 5 on the dial. What shocked me is the overall pot value went UP, way up ! I don't understand it but it went fro 430k to almost 100k higher. If someone wants to explian that i' al ears ! Tested it by lifting the ground lug and turning the wiper all the way to 10 and reading the outer lugs. Anyways, give it a try, takes 10 seconds to tack a resistor fro the wipe to gound.

[Helmholtz]

What shocked me is the overall pot value went UP, way up ! I don't understand it but it went fro 430k to almost 100k higher.

That is not possible, so must be a measuring error.

A 430k pot with a 220K resistor between wiper and ground will measure 146k between the outer lugs when turned fully up (CW), thereby lowering full volume treble response.

[daz]

That is not possible, so must be a measuring error.

A 430k pot with a 220K resistor between wiper and ground will measure 146k between the outer lugs when turned fully up (CW), thereby lowering full volume treble response.

You're right more or less, tho it depends on the rotation. All the way up it;s actually 156k or thereabouts and the other way however it does measure more than the pot value. Strange....i'll have to see what i am doing wrong. funny thing tho, it actually seems to sound great on 10. Maybe i SHOULD just use a 250k or a lowish one like a 220 or whatever i can find thats low. Then again, maybe that wouldn't give me the same clean sound i'm getting on 3-5.

[Helmholtz]

When you turn down the pot with the 220k resistor, the input resistance gradually increases and approaches the original pot value without the 220k.

As mentioned above, a lower value pot gives less relative treble loss when turning down.
Question is, if the 100% setting still provides enough treble.

[tedmich]

Fletcher–Munson curves! Definitely try a bleed cap,!

This is a handy collection : https://drkevguitar.com/2016/11/24/t...d-mod-roundup/

as with anything, when there are a TON of solutions, probably none of them is very good

[daz]

I haven't owned a guitar in 30 years or more without putting a treble bleed in it. Doesn't do much in this one because as i said above, humbuckers just don't work with them the same as single coils

[Chuck H]

Helmholts already covered most of what I'm going to say but I'll add my piece anyway. (As always, corrections accepted Helmholtz )

First, a higher value pot will be brighter ONLY at ten (volume full up). With a higher value pot the treble loss with the volume below full is worse. So a higher value pot will not fix the problem and it will change the tone of the guitar with the volume at full.

A lower value volume pot will have less treble with the volume at ten but will have less treble loss when the volume is reduced.

daz,
Your circuit with the resistor between wiper and ground on the volume pot is not a good one. What you have done is reduce treble with the volume full up and that is all. Since the series resistance between input and wiper has no parallel resistor you are still introducing the same series resistance. Your perception that the treble loss problem is reduced is not correct. What you have done is reduce your guitars treble at ten. So now when you turn down the difference in treble between full and reduced volume is less. You have not made it so that you have less treble loss when turned down. You have made it so you have less treble with the volume full up. That is all.

Ok. Now here it is in laymans terms. When a guitar volume is up full there is no resistance between the pickup (an inductance) and the cable from the guitar to the amp (a capacitance). The cable capacitance is a low pass filter, BUT, the direct connection between the pickup and cable (inductance and capacitance) with the volume full up forms a resonant circuit with a peak in the upper mid to treble range. The exact frequency depends on your pickup and cable. This resonant peak sounds bright. As a guitars volume control is turned down a resistance is introduced between the pickup (inductance) and the cable (capacitance). This resistance between the inductance and capacitance defeats the resonant peak so the cable capacitance only acts as a low pass filter. And the low pass filter effect is increased with more series resistance as the volume is reduced. All guitars with passive pickups do this. Some pickups in combination with the cable capacitance demonstrate less of a resonant peak and so don't seem to lose as much treble when the volume is reduced.

rockman627,
Your Telecaster only has a single volume control where the Gretsch guitars include a master volume control. The Gretsch guitars use 500k pots but since there are two in series the net load with both volumes full up would be 250k. And that would be the "correct" pot value to use for Filtertrons with a single volume control. If you are using a higher value volume pot and you like the tone then you should stay with that. But as mentioned, the treble loss relative to your full volume tone will be less with the 250k pot than with a 500k. And, again, using a 1M pot will only make your guitar brighter at ten and the treble loss problem worse. If you don't play with a huge amount of gain you could try the Fender type treble bleed circuit. This circuit does change the taper of the volume pot making it more linear and less log. But if you don't need really low volume pot settings you should still have decent control. The Fender circuit is shown below:

[rockman627]

Thanks, guys. Harley Benton informed me this guitar uses 500k pots. I think I'll get 1 meg pots, hopefully with an even taper, and treble bleed them. I have a bunch of small resistors and caps I bought for treble bleeds. With luck, I have the proper values. Should both volume and tone be 1 meg?

[daz]

perception[/I] that the treble loss problem is reduced is not correct. What you have done is reduce your guitars treble at ten. So now when you turn down the difference in treble between full and reduced volume is less. You have not made it so that you have less treble loss when turned down. You have made it so you have less treble with the volume full up. That is all.

Yes, but thats not what i was trying to accomplish. Treble loss is no longer an issue, the problem thats always existed before and after i dealt with treble loss is that the guitar doesn't clean up much, and it DID help that a lot. But after a time i came to realize i didn't like the tone as much with the volume all the way up. So i removed that mod. Now i'm on the hunt for pickups but i'm not sure whether i will because i know this will be a tough one and i will likely lose a lot of $ trying set after set. Been there done that, not sure i wanna do it again. But im researching them never the less.

[daz]

Thanks, guys. Harley Benton informed me this guitar uses 500k pots. I think I'll get 1 meg pots, hopefully with an even taper, and treble bleed them. I have a bunch of small resistors and caps I bought for treble bleeds. With luck, I have the proper values. Should both volume and tone be 1 meg?

But you haven't tried a treble bleed, right? Just try it. Takes a $0.50part and 2 minutes to tack it in between the two in and out lugs on the volume pot. Most guitars will benefit enough for the majority of players, mine is just a somewhat rare scenario. They work perfect on almost every guitar i have ever owned. Try a 250pf cap and if thats not enough try a 500pf. If it loses too much lows when you turn down there are resistor solutions u can use but give it a try then post any questions u have about fine tuning it here.

[Chuck H]

Thanks, guys. Harley Benton informed me this guitar uses 500k pots. I think I'll get 1 meg pots, hopefully with an even taper, and treble bleed them. I have a bunch of small resistors and caps I bought for treble bleeds. With luck, I have the proper values. Should both volume and tone be 1 meg?

Do you need the guitar to be brighter on ten? That's what will happen with 1M pots. This effect will be greatest with 1M on both controls. With a Tele and Filtertrons it seems unlikely the guitar needs more treble when full up. But every guitar is different and your tone is your own. So whatever you like is right.

If you don't want the guitar to be brighter on ten then I can't understand why you persist with the 1M pots??? If there's anything about the information in the thread that you aren't understanding I can try to explain it better.?.

And even if Harley Benton did make the guitar with 500k pots he didn't put Filtertrons in it as far as I know. If you want a typical Filtertron sound then a 250k pot should be used.

Using a 1M pot with a treble bleed is a losing battle IMHE. The greater series resistance exacerbates the circuits inconsistent behavior across the pots range. Tending to be too bright when turned down low.