Tube Screamer without tone control

[rockhorst]

A while back I built a TS clone, with some standard mods. Now I've noticed that I absolutely never use the tone control in any other position than fully on, so I would like to ditch it to save some space. I always fancy less controls and components. Now referring to the diagram of the tone circuit on Geofex:

Geofex Technology of the Tube Screamer

Can I just bypass the entire tone section with a jumper wire, starting a the input of the 1K to the input of the level knob? Or should it go to the NP capacitor just after the opamp (or some place else)? Thanks in advance.

[ItZaLLgOOd]

I'm not sure if it would sound the same without the tone control as it does with the control maxed out.  If I did it, I would jump it to the cap and resistor before the volume pot.

[PRR]

[rockhorst]

Thanks for the input PRR! I already tried something close to this, quick and dirty: took out the pot and connected loose wires. I got sound, but it was very noisy and muffled. I'll try this tomorrow. Could you elaborate a bit on why you leave the rest in place? What would be 'wrong' with bypassing the entire section from the 1K on the lef to the input of the level pot?

[twabelljr]

To simulate tone full on what would be wrong with soldering a 25K resistor across where the tone pot wires from lugs 1 and 3 would be on the board, then jumper the 0.22 cap to whatever side of the resistor is the same as having the pot turned full on or up. This way the circuit would be the same but without the actual pot being there so it should sound the same. Of course this is if you are only trying to save some space on your enclosure that the pot takes up. If you are trying to save circuit board space then please disregard this suggestion. 

[B Tremblay]

There's always the Tube Reamer...

[PRR]

> took out the pot and connected loose wires.

So you replaced 25K with a dead short. That's gotta do something wrong.

> bypassing the entire section from the 1K on the lef to the input of the level pot?

That was my first thought, but you state: 'never use the tone control in any other position than fully on'. I read that as "wiper to the right, to A2 pin 6". What happens there? 1K against 220 forces gain of 5.5, real boost. 220 against 0.22uFd cuts everything below 3KHz. Response is unity from low to 600Hz, rises to 3KHz, a real tone-shaper.

> would be wrong with soldering a 25K resistor across where the tone pot wires

That's reasonable. If you follow how an opamp works, you will see the 25K is not necessary IF you don't use it as a more/less fader. (A2 is forcing its inputs to zero voltage. If there's nothing hung on the middle of the 25K, then zero current flows in it, and it "does not exist" as far as the rest of the circuit can tell.)

[rockhorst]

And it works Although it's just a tad too sharp now, guess the pot mellowed it a bit (or it was only close to full on). Would bypassing the whole tonestack take down the overall output and soften the tone a bit? Or am I then misinterpreting Pauls description?

[rockhorst]

Note to self: just install a trimpot...I always forget that those things exist