Treble retention circuit...

[crazymanandy]

I have a question about these treble retention circuits. I noticed that some people use only a capacitor whereas others use both a capacitor and resistor. What is the deal?

CMA

[dd842]

crazymanandy said:

I have a question about these treble retention circuits. I noticed that some people use only a capacitor whereas others use both a capacitor and resistor. What is the deal?

CMA

Hi Andy,

I am not sure, but this sounds like the same idea as TBX.

I think the deal is that you have a flat center detent position, and then you end up with either a high pass filter or a low pass filter, depending on which direction you go - so either treble or bass can be cut.

Dan

[sumgai]

Dan,

I don't think CMA is talking about the variable tone control systems, I got the impression he was speaking of the so-called 'treble bleed' capacitor place across the hot and wiper lugs of the volume control.

Andy?


sumgai

[crazymanandy]

Sumgai is right. Sorry about the confusion there Dan. I suppose calling it a circuit makes it seem a little more complicated than it actually is, lol.

CMA

[dd842]

crazymanandy said:

Sumgai is right. Sorry about the confusion there Dan. I suppose calling it a circuit makes it seem a little more complicated than it actually is, lol.

CMA

No sweat, Andy - I could have read a little less into it, myself.

Dan

[JohnH]

I find that a pair of 220k resistor in parallel with a 1nF cap. across the centre and outer hot lugs of a 500k volume pot is the best for preserving consistent tone as you reduce volume. The resistor seems to keep the response in balance, rather than having relatively too much treble at low volumes. I did some tests on pSpice, and also made some sound clips which confirmed it for me. With the sounds, I made a series at steadily reduced volume, then 'normalised' them on the computer all back to equal volume. They were reasonably consistent in tone, until down to very low volume, so I think that is the best you can do, without active powered circuitry.

John

[crazymanandy]

Do you use 500k pots on your single coil guitars John?

CMA

[ChrisK]

I always use 500 K audio taper tone pots. When turned down to only aboot "8" (on a Strat knob), they're already down to 250 K. the rest of the way down then tracks a 250K pot.

It kind of makes your tone control go to "12".


TBX my foot, use a 1 Meg Ohm audio taper tone pot and yer almost all the way there anyway.

[dd842]

chrisk said:

TBX my foot, use a 1 Meg Ohm audio taper tone pot and yer almost all the way there anyway.

I never* realized that - good information, Chris

Dan

* edit: sorry ... "never" is a little misleading, as my electrical ejumacation has spanned all of about nine months

[JohnH]

crazymanandy said:

Do you use 500k pots on your single coil guitars John?

CMA

Yes I do. I always want to have the series options for pup combos, and 500k pots are appropriate for that to reduce load (compared to 250k), for the same reason that they are best for Hb pups. I also like a 'no load ' tone pot, where the track is cut at position 10. So at max treble, you get infinite resistance (ie no load!) and max treble. These are easy to make yourself from a standard pot.

John

[crazymanandy]

chrisk said:

I always use 500 K audio taper tone pots. When turned down to only aboot "8" (on a Strat knob), they're already down to 250 K. the rest of the way down then tracks a 250K pot.

It kind of makes your tone control go to "12".

I never knew that, thanks for lettin' me on the secret! ;D

I noticed you said 500k tone pots, do you use 500k on the volume pots as well?

johnh said:

crazymanandy said:

Do you use 500k pots on your single coil guitars John?

CMA

Yes I do. I always want to have the series options for pup combos, and 500k pots are appropriate for that to reduce load (compared to 250k), for the same reason that they are best for Hb pups. I also like a 'no load ' tone pot, where the track is cut at position 10. So at max treble, you get infinite resistance (ie no load!) and max treble. These are easy to make yourself from a standard pot.

John

Interesting. How is that technique done? So does the usage of a 500k pot effect capacitor choice? (Not the cap for the treble retention thing, but the tone pot cap)

Thanks guys,
CMA

[setain]

projectguitar.com/tut/pots.htm

[JohnH]

Thats a good reference. I do the scratching with the tip of a small screwdriver, which being less sharp than a knife is less likely to gouge the track. I also connect a multimeter across the outer lugs measuring resistance, while I scratch. Then i can see the resistance gradually increasing with each stroke, until it goes off the scale. I have not tried with nail polish, but all the ones Ive tried have worked fine afterwards.

I did this last week to a tone pot on my new old LP. It was 250k, which gave a nice gradation but could not get to max treble. The no load mod gave it an extra lift at 10.

John

[korus]

projectguitar.com/tut/potm.htm (from : "Let's Talk About Treble Bleed Mods And The 3 Types I'm Showing") is the good reference/starting point for treble bleed mod.
What it does not tell are the differences. My findings are :

1. just a cap ~ 150pf - 1000pf (eg Ibanez uses/used 330pf, PRS 180pf),
pro: the simplest solution
con : alters resonant pick of the pickup

2. cap and res in parallel ( cap ~ 3300pf - 1200pf, res ~ 100k - 220k)
pro : retain bass also eg. when below 3 or 4
con : res alters the taper of the vol pot bringing audio taper closer to linear taper

3. cap and res in series ( cap ~ 1000pf, res ~ 48k - 220k)
pro : does not alter the pot of the taper and closest to turning down the vol on the amp (which is The Idea of this mod isn't it?)
con : below 3 or 4 sounds tends to sound too thin/looses bass more then lowering volume on amp

The issue is that there is no optimal solution for every guitar/ player, hence here goes the Tone Quest.

My suggestion : connect >= 1m 2wire cable to the vol pot (where treble bleed will be) then try all the options/combos and diff values for them on the table.

If you settle for opt 2 or 3 connect a pot instead of res (as a variable res) test it that way - altering the value on the pot while playing, than when you settle for the value on the pot measure it and then replace the pot with the res with the closest value to measured.

The whole idea is to play, both clean and overdriven while changing components and values and to have (almost) instant A/B test.

If feasible you should record all the testing with no or minimal effects, pronouncing what is connected before or after playing (eg: "serial 680p 220k vol 8" like samples of pickup sounds on SD site), then put guitar away break the recording to short clips/samples and just listen without playing at the same time. IMHO it will help hear the differences one usualy does not perceive while playing.

Good luck.

[GuitarTechCraig]

I have a simple method for adjusting a treble retention circuit for any value potentiometer and any type of pickup. I use a 250k trim pot in series with a .001 uf capacitor. Simply set the trim pot to 0k resistance, play the guitar with volume on 10, turn down the volume a bit and adjust the trim pot to your personal taste. Takes all the guess work out of what values of resistor (if any) to use for a specific guitar.

[sumgai]

GTC,

Good suggestion!

Now, since half the members here are not noted for their acumen vis-a-vis the electronic trade, why don't you spend a moment giving them a short lesson one what a trim pot looks like, how its size compares to other components, and where a body might be able to buy one/several of them. Please include links, and for extra credit, how about a picture or two.


sumgai

[GuitarTechCraig]

A trim pot is much smaller than a regular pot but works the same way. There are many shapes available, but I'll post a pic of a common shape.

I buy my trim pots and capacitors online from Mouser. They have a huge selection.
www.mouser.com/index.cfm?handler=home

[sumgai]

Craig,

Well done, sir. A +1 for your efforts in bringing a new toy to the table for everyone to drool over.


sumgai