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 Post subject: TBX control
PostPosted: Tue Jun 17, 2008 8:21 am 
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Hi there.

I would like to change my tone potis on my strat. I wanna install 2 TBX potis instead. Would it make sense and would the basic sound of my strat (3 Lace Sensor Golds) change with the TBX potis in neutral position?

Thanks a lot.

Bluesmaster.K


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PostPosted: Tue Jun 17, 2008 8:32 am 
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As far as I am aware there is only one TBX pot on the normal setup.

Will someone please correct me if I am wrong??


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 Post subject: Re: TBX control
PostPosted: Tue Jun 17, 2008 8:42 am 
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bluesmaster.k wrote:
Hi there.

I would like to change my tone potis on my strat. I wanna install 2 TBX potis instead. Would it make sense and would the basic sound of my strat (3 Lace Sensor Golds) change with the TBX potis in neutral position?

Thanks a lot.

Bluesmaster.K


I don't have a lot of experience with either the TBX or the Lace Sensors.....but since I'm sort of becoming obsessed with topics like these, I did some research.

I found a topic on another forum that was discussing these specific products. (if you want the link PM me). Although Lace Sensors were not specifically discussed, ot offered a lot of discourse on the TBX pots, and if you know the general difference between standard passive pups and the Laces, you may be able to apply the information here....

This was the most useful information I found out of the topic discourse in regards to the TBX pots.

Question: Is it possible to change a TBX tone control to act as a mid boost? I would like to keep the half that acts as a regular tone control and only change the treble boost.

Thanks


Answer 1:

Not without fitting active circuitry.

BTW, the TBX is NOT a treble-boost. Passive electronics cannot boost anything. What it does is to give an artificially-strangled sound at the mid position (by connecting an 82k resistor in parallel with the pickup), so when this is removed from the circuit as you turn up to 10, the guitar SEEMS to get brighter and more lively.

In fact, the full-up sound is almost indistinguishable from a standard tone control using a 1Meg pot, and not quite as bright as a 'no-load' tone control at 10.


Answer 2:

On the stock TBX control, the 82k resistor is in the circuit as a shunt *all the time*, no matter where the knob is set. Yes, even when it's on "10". That's where the inherent problem lies.

A few of us belive that the control was developed to work well with low impedance pickups and active solid state electronics, such as found in Clapton & Buddy Guy Strats, where 82k in parrallel with say 15k has no deleterious effect on tone. But an 82k shunt resistor has no place in a guitar with standard high impedance passive circuitry. We don't know why it was just "thrown in" to a stock production guitar with passive electronics. It was poor judgement, or bad ears that allowed that to happen. Before it was featured, it should have been re-engineered. Makes me wonder why the paid "experts" couldn't figure this one out when it wasn't too difficult for me to do.

The TBX control is very useful if you modify it. You'd be surprised. The repair is easy. It involves removing the tone-sucking 82k resistor, adding a jumper between two of the pot lugs, and adding a 220k resistor. The new resistor is necessary to make the transition between the two potentiometers at mid-position a seamless transition, with no abrupt change in tone or apparent volume as the circuit is handed off from one pot to the other.

Rough sketches of the stock TBX control, and the modded control, can be found on Steve Ahola's "Blue Guitar" website. Take a look at those sketches, and after a while you can imagine what is happening as you turn the control knob.

could not find a direct link to the TBX wiring on Steve's site, but here's a way to get there:

For the stock TBX:
http://blueguitar.org/tbx.gif

And for the modified/ improved version I speak of:
http://blueguitar.org/tbx_doc.gif

Copy & save the diagrams for future reference.
Hope this helps.
-Doc


Answer 3 (same poster...."Doc" seemed to know what he was talking about when it came to this topic.)

The modded TBX will give you the same adjustable tone control range as the stock (regular 250k, not the DeltaTone no-load pot) control, but within about half the rotation. So at "1", both controls are full treble cut, deepness based on the chosen capacitor value. At "5" (at the mid-detent) on the modded TBX, tone is the about the same as a stock 250k wide open on "10". But with the modded TBX, you have the ability to increase the "air" or high end response progressively as you rotate from "6" up through "10". Since the series impedance on "10" is 1250k (1 megohm plus 250k), the response is very similar to that when being "unloaded", either with no tone control connected or with a Delta pot on its detent at "10". With the modded TBX, you don't get an abrupt change going from the slightly treble loading at "9" to the wide-open at "10" on the Delta. You can get a gradual, continuous adjustment up to that (effectively) unloaded point.

So they are the advantages as I see them. It may not be for you. Occasionally I really like to hear the sound of an unloaded middle or neck single coil pickup. You can't get that on a stock Stratocaster. Also, it's sometimes desirable to have the bridge pickup's brightness dimmed a little. With this modified TBX control attached to the bridge pickup, maybe using a .01uf cap, a nice slide tone or Clapton tone is possible, while reverting to a bright unrestricted tone (close to stock) with the control on "10".

So this modified TBX can make for a very versatile guitar. And since the rotational action is stiff, the control stays where you've set it.

For those who are looking at the diagrams on the website referenced above, the captions may not be clear. The final design, the one that works the best, is the one in the lower RH corner labeled "As wired by Doc 2/22/01". The diagrams in the top half of the page were earlier developments in trying to optimize the control to obtain a smooth transition across the center detent. You can see how the two resistance elements are seriesed, and how the 250k section becomes open or discontinuous after mid position where the 1meg takes over. The extra 250k fixed resistor replaces the now disconnected 250k pot element into the series string. We liked the expanded version with the added parallel 250k resistor. It seemed more user friendly.

If you look at the stock TBX control internal schematic (not the simple physical hookup diagram from Fender) you will see that the 250k pot's resistance trace stops at midpoint of rotation. Beyond that the 250k element goes open-circuited. There is a temporary "wide open" at that point, until the 1megohm pot's trace picks up and starts adding total resistance to the series string. My 220k resistor substitutes for the now departed 250k resistance trace, so that the series string becomes seamless and the increasing rotation toward "10" adds 220k to whatever portion of the 1meg trace is picked off by the wiper. At "10" you have 1220k total resistance in series with the .02uf cap to ground. Almost "no-load".


Hope this helps...

EDIT: Also found this review of Lace Sensors in Harmony Central:
http://reviews.harmony-central.com/revi ... ensor/10/1

Thing about the laces......a lot of folks are actually recommending...1 meg pots STANDARD on the tone controls! (shakes head)

And, last but not least:

Fender makes Vintage Noiseless (you'll need to use 500k pots with these
although 250k pots you can get away with). do NOT install one of these
for the bridge pup - your ears will thank you and so will your dog.
However these make great neck and middle pickups.

Fender Vintage Noiseless HOT - this is a really nice set.
Neck, Middle and Bridge set is excellent. (each pup is labeled
and has a slightly different wind for neck, middle and bridge).


All things to consider. This is definitley an interesting question posed in regards to tonality, and doing mods......


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 Post subject:
PostPosted: Tue Jul 01, 2008 2:53 pm 
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Bluesmaster,
You really only need one TBX. Also, definately do the blueguitar mod to change the .082K series resistor to .120K series/parallel. The TBX works sooooo much better after the mod. You could wire the TBX as a second tone control as on the AmStd or as a master tone. A while back I modified my 96 Strat Plus Deluxe to 2 Gold & 1 Silver FLS with 1 master TBX and 1 master Rothstein Guitars RG500D mid control. I also added a volume treble bleed cap/resistor to stop the treble from being suck out when volume is reduced. Now I have the best of most tone situations. I think the RG500D was around $20. The cap and 2 resisters were a buck or so at RS. Here's a link to my modified wiring diagram.

http://www.geocities.com/just_r_c/Silve ... Wiring.jpg

Here's a link to Andy's site for the mid control if you like:

http://www.guitar-mod.com/rg_passive.html

Regards,
RC


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