Tubescreamer tone pot

[Al Heeley]

I've made both the standard TS808 and the SRV special tubescreamer from the pcb layouts on these pages. The tone pot seems to make most difference only on the last 10% of its travel. Between zero and 90% it's a bit too muffled and doesn't really change the tone much. To get a more balanced tone control range, would it work to swap the 20k pot with a 5k and put a 15k resistor in series with it, ir is it a bit more complicated than that?

[aziltz]

I've made both the standard TS808 and the SRV special tubescreamer from the pcb layouts on these pages. The tone pot seems to make most difference only on the last 10% of its travel. Between zero and 90% it's a bit too muffled and doesn't really change the tone much. To get a more balanced tone control range, would it work to swap the 20k pot with a 5k and put a 15k resistor in series with it, ir is it a bit more complicated than that?

check out small bear's W Taper 20K (or 25K I can't remember).  I put it in my Route 66 and it does so much more with the tone control now.

[Kitarist]

Just swap the 20k with the 25k i have it on my botique modded tubescreamer and it works great

[Mark Hammer]

You're describing an issue of taper.

I would suggest first reading the excellent article Jack Orman has posted about the TS-9 tone control, and some alternative arrangements.  http://www.muzique.com/lab/tstone.htm

When finished that, consider use of parallel resistors in conjunction to alter the taper and introduce more "dialability" in certain parts of the control's range.  That info can be found on Jack's site as well as on www.geofex.com.

[Al Heeley]

  thanks guys 

[skiraly017]

The pictures aren't linked anymore but the info is still good.

http://www.diystompboxes.com/smfforum/index.php?topic=37882.0

[BAARON]

Another popular mod is to just straight up replace the tone pot with a 2k or 5k linear pot, like in a Lovepedal Eternity.

[John Lyons]

Yep, 5k linear is the way to go. If you end up with the pot past 2pm then try the 2K linear.
If you want less high end travel try 10K...

john

[Al Heeley]

thanks, i'm going to swap them out and give it a go, now i need to get my dyna comp circuit working

[LucifersTrip]

Yep, 5k linear is the way to go. If you end up with the pot past 2pm then try the 2K linear.
If you want less high end travel try 10K...

john

i know it's old...but TS is always relevant to someone. a friend asked me to drop a 5K in his for a better sweep.

will that do anything else other than give a better sweep?

[teemuk]

It's an RC filter, of course it will.

[LucifersTrip]

should've been clearer...will it affect anything I don't want it to affect?

[Mark Hammer]

The fundamental challenge is that the TS tone control tries to accomplish a lot; perhaps too much.  The tone control in the TS is a "reciprocal" control.  So, the one pot adjusts two things at once, and the more it does of one, the less it does of the other.

The first thing it does is increase the gain of the tone stage by reducing the resistance of the ground leg of the tone stage.  As it does that, it not only increases the gain but also alters the low end corner frequency of that stage in exactly the same way as the analogous control does in the MXR Distortion+ (gain goesd and and bass gets cut).

The second thing it does - by virtue of how the control is connected - is gradually add a 2nd .22uf cap in parallel with the one just after the clipping stage.  The 1k/.22uf network after the clipping stage already provides a 6db/oct lowpass filter at 723hz.  Adding the 2nd .22uf cap moves that corner frequency even lower.

So, in complementary fashion, the one control either increases lowpass filtering as it decreases the gain of a potentially treble-boosting stage, OR it minimizes the lowpass filtering as it increases the gain of a potentially treble-boosting stage.  Jack Orman explains this nicely, and offers some alternatives: http://www.muzique.com/lab/tstone.htm

If a person likes what the tone control accomplishes, but wants better control, the simple thing to do is to unyoke those two complementary/reciprocal functions.  So, a person could have a 20k pot and .22uf cap to ground to adjust the lowpass filtering, and a second 20k (or 10k, or 5k) pot in series with a 220R resistor and .22uf cap to ground to adjust the gain of the treble boosting stage.  More complicated, yes, but much better control.

[LucifersTrip]

thanx for detailing what the tone control does...but I was just hoping that someone could give me a quick idea of what changing the value of the pot does other than affect the sweep.  I didn't do any extensive reading on this yet, since this was supposed to be a quick mod for a friend...

Though, I did already read the Jack Orman article. He shows two schematics at the beginning, one full cw and the other full ccw.  In both instances the pot is out of the picture, so the pot size has little or no bearing if it's full cw or ccw?

Jack continues to show various other arrangements of the components, but leaves the pot at 20K for all examples.

[Mark Hammer]

thanx for detailing what the tone control does...but I was just hoping that someone could give me a quick idea of what changing the value of the pot does other than affect the sweep.  

Lesser/lower pot values do a bit of one (treble rolloff) and a bit of the other (treble boost), instead of a lot of one and not very much of the other.

As to whether 5k is a "better sweep", that would depend on what tone one is aiming for.  Given that, I can see where  - with the appropriately chosen cap values, a person might find that it dials in their preferred tone more easily.

[zombiwoof]

The 25K "W" taper pot that Small Bear sells is the stock replacement, and stock part.  I'd give it a try first, if it doesn't work then go for the options.  It's a cheap pot, so what do you have to lose?
Al

[LucifersTrip]

thanx for detailing what the tone control does...but I was just hoping that someone could give me a quick idea of what changing the value of the pot does other than affect the sweep.  

Lesser/lower pot values do a bit of one (treble rolloff) and a bit of the other (treble boost), instead of a lot of one and not very much of the other.

this is just in the middle of the sweep?  if I've read correctly, the pot size is insignificant on the ends?

full treble


full bass


my friend was more worried that the different pot size would change more than amount of treble or bass

As to whether 5k is a "better sweep", that would depend on what tone one is aiming for.  

he just wants to unbunch the treble from the last ~ 10% . I was just going to go with a rev log, but realized I was out of em and my friend needs it too quickly to order. thus, my search for alternatives

[LucifersTrip]

The 25K "W" taper pot that Small Bear sells is the stock replacement, and stock part.  I'd give it a try first, if it doesn't work then go for the options.  It's a cheap pot, so what do you have to lose?
Al

I actually ordered that and was sent the wrong pot...now, it's too late for my friend to order another