[84] Tube Screamer mix control

Date: April 3rd, 2008 | Comments : [3] | Categories: DIY.

TS-9 clipping section

This is a quick and easy mod for the Tube Screamer or its many clones. It involves adding a new control to adjust the “mix”.

The schematic section shown above is typical of the TS-type distortion pedals. It is a non-inverting amplifier with a pair of clipping diodes in the feedback loop. When the diodes conduct, they will become low impedance and this suddenly reduces the gain of the amplifier… but it doesn’t actually clip the signal, it only reduces it to Av=1 because when the feedback loop of a non-inverting amplifier is closed (as in a buffer), the gain can go no lower than unity.

Modified TS-9 clipping section

We can take this idea a bit further by inserting a 5k to 10k pot in series with the clipping diodes as shown here. This will increase the minimum gain which has the effect of adding in more of the input signal to the clipped output, and thereby softening the sound of the distortion. When the pot is at its minimum resistance, the sound will be identical to the original pedal but as it is adjusted so the resistance increases, the distortion sound will have more clean signal mixed in.

You can use a higher value pot but as its value is increased, the amount of clipping is reduced. This is an easy way to extend the sound of a classic distortion circuit. It even works on the ubiquitous Boss SD-1. Try it out!

More info on warp controls can be found in the AMZ Lab Notebook.


3 Responses to “Tube Screamer mix control”

[413] Rick Says: 12:30 pm, April 20th, 2008

Could a switch be wired in its place, to provide three different settings, perhaps say one pole as bypass, one at 5k and one at 10k to have three clean mix choices?

[2861] Doc Plus Says: 1:15 pm, April 23rd, 2012

Thanks a lot for that !
I tried 10, 25 and 100KB. I keep the last one. So dynamic !

[2862] Doc Plus Says: 1:53 pm, April 23rd, 2012

The best sound on my SD-1 is with the pot level at 12h, but the volume is too loud compared to the bypass. If I deacrease the level (10K), it looses some highs. How can I avoid that ? A cap between lug 3 and 2 ? What value should I try ?


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