4/12/2020

Modding a 18$ Tube Screamer clone



The Tube Screamer (TS) is an excellent overdrive platform for modding. Some versions of it like that one are still in production. There's a cult around the TS and when you look at modern overdrive and distortion schematics, you will see that a lot of them are mostly glorified TS mods. If you want to get started modding pedals, instead of destroying a 250$ pedal this 18$ CAD clone is very close to the original. In my case, I changed the range of the drive and tone, added more bass and replaced the useless switch to toggle clipping diodes instead, which completely change the drive structure.


First I verified all values against the excellent Electrosmash analysis of the Tube Screamer. And I didn't find any significant difference (aside from the clone to be true bypass).



Of course the components are not of the highest quality, but it sounds right, especially when pushing a tube amp or as a colored boost in front of another pedal. So we can really treat this clone as a Tube Screamer and make it closer to what you want. I always feel that TS cuts too much bass, is not dirty enough and doesn't completely clean off. I'm not alone, so it was easy to find how to modify it.

More clean, more drive, more bass

I like the mods from TDPRI and from Brian Wampler on Premier Guitar. I wanted the drive to go down to totally clean and up to more distortion. I like the mid bump of the Tube Screamer so I didn't change the shape of the filter, but I added more bass. I also like to play with clipping diodes as it has a big impact on the overdrive color. Here's a summary of the changes I applied to the clone:

  • Cleaner at min gain: R6=1.2K
  • More bass (around 338Hz) and more gain: C3=.33uf, R5=1.2K
  • Better bass (reusing C3): C1=0.047uF
  • Clipping loop filter (for the change of clipping diodes): C4=100pF

Here are a few specificities of that clone. When I changed de capacitor C3, I could reuse it for C1. The components I had were bigger than those on the circuit board, but it was still an easy fit.

One thing I noticed is that the labels on the switch between TS808 (100, 10k) and TS9 (407, 100k) are inverted. It doesn't matter to me because these components in the buffer stage do not have any audible difference, probably just a change of output impedance. So what I did is that I reused the switch for changing clipping diodes.

Convert TS model switch to clipping diode selector

So I repurposed the toggle to switch diodes in the clipping stage, which makes a huge difference in the distortion type. It was a bit hacky but I wanted to find a way to reuse as many components as possible. I left one original silicon diode and the toggle switches between the original silicon diode and a LED.




Result

Here is the end result.