TS clean up ability with guitar volume knob?

[sebarb]

Hi everyone, I'm looking for a mod to clean up with guitar volume knob my Tube screamer unbuffered. I'm looking arround and didn't find way or link? Any id?

[GibsonGM]

Put the buffer in!  Just one idea...

[Mark Hammer]

I am guessing that what you want is for the pedal to still provide some boost (over bypass), but have that boost be cleaner-sounding, or get dirtier on demand.

If you have to turn your guitar volume way down to get to "clean", you won't have the volume boost anymore, and may as well just hit bypass.  So the goal, I assume, is for "clean" to be available, with some boost, when the guitar volume is only turned down to maybe 7.

I think the best solution for that problem is to raise the clipping threshold of your TS.  Doing so will let you stay below the clipping threshold, whilst still having some boost, without having to turn the guitar down too far. 

Presently, your TS will use a pair of silicon diodes for clipping.  The clipping threshold can be raised in a number of ways.  You can switch diode type (or use transistors as diodes, which many overdrive pedals do).  Or you can switch number of diodes.  Or you can switch both.

So, adding a second silicon-diode pair, in series, will effectively raise the threshold by 2x.  Adding a germanium or Schottky pair in series with what is already there may raise it by roughly 1.5x.  Replacing the existing diodes with a pair of red LEDs will raise it by about 3x.  And so on.  You don't want to raise it TOO high, because it might put the sort of overdrive tone you want out of reach, even with the guitar volume up full.

Whatever arrangement you use, it is useful to measure the forward voltage of the diodes you use.  They can vary a fair bit, even within type and batch.  My 1N914 and 4148 diodes can measure anywhere between around 500mv and 660mv, and germaniums can range between just under 200mv to just over 350mv.  Do the measuring, and accompanying math, and you 'll end up with a nice compromise that can get you the familiar TS tone when you want/need it.

As a parting comment, I will also suggest maybe considering an asymmetrical arrangement, such as is found in the SD-1, OD-1, and a bunch of other pedals that use diodes in the feedback loop.  having one half the waveform clip, while the other half doesn't, when you turn down, may be what you're looking for.  All the same measure-and-select considerations apply.

[teemuk]

IMO, "cleaning up with guitar volume" -thing is always sort of a compromise between both clean/dirt and the volume difference of them.

Almost any rig that has no ridiculous amount of gain can do that but you'll always more or less struggle with the issue that clean volume is lower than dirt volume. To compensate you usually have to rest satisfief with the fact that your cleans aren't exactly cleans and that your dirt doesn't really have that much gain and distortion. In addition, it's ususally struggle with picking dynamics where you have to strum the chords hard on cleans and tap tem gentlier when going dirt mode. For many these are acceptable compromises and may even be their preference.

IMO, the only switching where cleans are -really- cleans and the amount of dirt is not too restrained (some music genres really just need that) - and, which doesn't rob your dynamic area of picking, requires some kind of a channel switching scheme, in which elements like volume, gain and frequency response are preferably controlable.

[bool]

If I understood you correctly, then solder a 100K resistor across the input jack (guitar in).

This will load down the input so when you roll down your guit volume, it will cleanup faster than it would otherwise.

Caveat - this will only work when the fx is the first in your chain. Otherwise it won't work as advertised. Having a treble bleed cap installed in your guit will help as well ...

[karbomusic]

IMO, "cleaning up with guitar volume" -thing is always sort of a compromise between both clean/dirt and the volume difference of them.

There is only one exception that I know of and that is a nicely tweaked fuzz face circuit. That's one of my attractions to it...

Guitar volume (loose approximations):

9.5-10: Classic wooly ripped speaker sounding fuzz.
7-9: Rock n Roll marshally edgy distortion, no wool.
4-7: Edgy bright breakup.
1-4: Almost chimy clean and bright with almost as much volume as 9.

YMMV but that's the way I tweaks 'em.  

[sebarb]

Thank's guys, I get better clean up with higher clipping voltage, so i find my compromise with 1800mv in one side and 1200mv in other side with diode serie mix Si and Ge.
It's not fuzz face ability but it's a lot better!
Best regard

[antonis]

I think the best solution for that problem is to raise the clipping threshold of your TS.  Doing so will let you stay below the clipping threshold, whilst still having some boost, without having to turn the guitar down too far. 
Presently, your TS will use a pair of silicon diodes for clipping.  The clipping threshold can be raised in a number of ways.  You can switch diode type (or use transistors as diodes, which many overdrive pedals do).  Or you can switch number of diodes.  Or you can switch both.

Mark, I think there is another way to obtain this (like in some models of old VOX amps) ...
You can rise the clipping threshold "adding" some DC voltage to one side of the diode pair (preferably to that going to ground) with a voltage divider, a resistor  between diodes and ground and a blocking cap to the other side but I can't tell for sure that it wont "interfere" to the feedback loop of TS...

As long as I've tested on "hard clipping" circuits (like Rat & MXR Dist+) it worked just fine..
(even better if you make an adjustable voltage divider..)

P.S.
I'm sure that you are aware of this way    but it should be an interesting modification for circuits like TS..

[sebarb]

Hum! I will try that soon on my next TS like project with my feedback.
Thank

[Ben N]

IIRC it's been said (I think by RG, I'm pretty sure also by Paul Cochrane) that non-inverting opamps with feedback loop clipping can't do this, for structural reasons--because of the way they layer clean and clipped, or some such thing. I know Paul was at one time looking at doing a Timmy variant possibly with an inverting clipping stage as a strategy to get better cleanup. That said, it's hard to imagine anything better at this than a low gain FF, or similar.