Yes !!! It's another TubeScreamer question

[Blues_Boy_4096]

Hi guys!

I have a friend who asked me to mod his Tube Screamer in a few ways.

He Wants:

    1 - More Gain
    2 - Bass Boost
    3 - Mid Cut
    4 - Treble Cut

I'm comfortable with 1 and 2, but I'm a bit puzzled about 3 and 4. I've been reading The Technology of the Tube Screamer but I'm still a bit lost...
Could you point me out the right direction to start looking?

Thanks

[Steben]

4 can be achieved by raising the feedback cap of 51pf to 100pf or 220pf.
3 is tricky, since the TS typical mid hump is achieved by bass and treble cut. If you raise the bass, the mid less pronounced already.

[Blues_Boy_4096]

4 can be achieved by raising the feedback cap of 51pf to 100pf or 220pf.

Yeah, after the third passage at the Geofex article, my bet was on that one too...

About the mid cut, I guess the interdependence of the tone stack makes it harder to target those frequencies in particular...

Thanks for your response

[kurtlives]

I think you could decrease the value of the cap (0.047mF) that is connected to the 4k7 resistor in the clipping stage to reduce the mids.

[sean k]

I think getting more bass into the circuit would help and simply raising the input cap a fair amount might help. That and cutting tops straight away as well with a cap to ground, I don't know, maybe .001. Then you've got the 1k resistor with it's end at the 10k that sets bias and that is almost the same as the output from the opamp where the 1k is followed by a .22 cap to ground so why not put a .22 to ground after the 1k on the 510k bias and base junction so you've got a low pass even before it hits the first transistor.

More bass in, a top cut and a low pass filter even before you hit the buffer. Then you've still got the feedback loop with the diodes and the roll-off as well as the tone controls to tweak it all.

[wampcat1]

Let's look at a schematic so we have something to reference to:
http://www.generalguitargadgets.com/pdf/ggg_its8_sc.pdf

C2 is already a 1uf, increasing it isn't going to make much of a difference.

Here's the thing - the gain stage is boosting at around 723 hz, then cutting highs above 723 hz. There's your mid hump. Add on top of it a tone control that emphasizes high mids and highs and you have alot of mids.

Give it more bottom, make c3 larger. make the low pass filter less - decrease c5 to allow more highs through, then change c9 to a .1uf or so. personally, I remove it from where it ties back in  before the 2nd opamp, and swap r17 with this tone pot, though I decrease the tone pot to a 10k or so, then I use a small cap in place of c9 so it isn't boosting as much high mids.

I'd make c1 and c10 larger too - try a 1uf and see what you think.

Hope that helps!
bw

[R.G.]

It's not widely realized (outside of Boss and Ibanez' designers at least) that the tone control circuit in the TS is set up like a single-band graphic EQ. It's easy to make it into a more-bands EQ if you like.

But you will have to worry about what this does in combination with the other frequency changes in the pedal.

In answer to the original questioner: you need to go read "The Technology of the Tube Screamer" at GEO.

[wampcat1]

It's not widely realized (outside of Boss and Ibanez' designers at least) that the tone control circuit in the TS is set up like a single-band graphic EQ. It's easy to make it into a more-bands EQ if you like.

But you will have to worry about what this does in combination with the other frequency changes in the pedal.

In answer to the original questioner: you need to go read "The Technology of the Tube Screamer" at GEO.

I think jack has a link on his site somewhere, muzique.com -
bw

[R.G.]

I'm sure he does, but here is the link to all of the "Technology of..." articles at GEO

http://geofex.com/fxtech.htm

For those of you who know how to find  GEOFEX, the links in the upper left hand corner are very useful.

[wampcat1]

I'm sure he does, but here is the link to all of the "Technology of..." articles at GEO

http://geofex.com/fxtech.htm

For those of you who know how to find  GEOFEX, the links in the upper left hand corner are very useful.

oh yes - http://www.geofex.com/Article_Folders/TStech/tsxfram.htm

bw