Tubescreamer bass mod

[Al Heeley]

I saw on Aaron Nelsons pages, a simple mod to the tubescreamer clone circuit replacing the tiny 51pF cap with a 0.47uF to make the pedal suitable for bass guitar distortion.
Since the T/S 808 is my fave overdrive for guitar I thought I'd build another with this bass mod built in.
Anyone else done this mod? Does it work well for bass guitar?
Would you need to look at changing the tone control as well?

[Al Heeley]

I went ahead and built it.

Finished the build, pretty pleased with the results. We have a standard classic TS808 circuit from DIYStompbox galley:
http://www.aronnelson.com/gallery/main.php/v/MarkMs-Gallery/album15/album76/TS808_TubeScreamer_LAYOUT.gif.html
Then D1 has been put on a DPDT switch with a second 4148 diode siwtchable in series to give the FULL or SOFT clip option,
I've wired up an ON/OFF/ON mini toggle switch to where C4 was sitting and wired so it gives either 0.047uF cap, 0.47uF cap or both in series to radically change the tone range. the rest of the circuit is pretty much stock.
With lead guitar feeding into it, the pedal gives the expected lovely rich overdrive with the mid/high boost tone, that is with clipping on full and range on high.
Switching range to mid or Phat gives a great heavy bass boost to the signal, maybe too flabby for some high gain stuff but maybe superb for baritone metal riffs.
Switching caps to soft introduces the third diode and assymetric clipping, which softens down the distortion gain quite a bit while giving a more creamy smooth softer tone. Very nice.

With bass, you really need tone range on PHAT or you just get a bit too much mid honk. Seems to work best with clipping on soft and gain up at half to give a softer fuzz-type overdrive. If you want to get really nasty, put the clip on FULL, the range on MID and bring the vol back a bit - very sharp aggressive tone, cuts out any bass flab, sounds more like a nasty fuzz.

Seems this little mod gives a pedal that should be incredibly versatile for either bass or lead guitar. Will be trying it out live at next Friday's gig in Wooldale.
Very constructive way to spend a Saturday morning

[Gus]

Some people like the stock value with bass when used live.

[Al Heeley]

I found the stock pedal build had had no presence at all when used with bass guitar, removed all the punch from the signal and boosted the mids way too much (which is what the pedal is of course supposed to do), guess it depends on the bass pickups and the amp used.

[Al Heeley]

Moving on from this pedal I added a separate veroboard section with 6-way rotary switch to investigate different clipping options.

THis has the same switchable input caps but you can choose si diode pair, asymmetric Si diodes, Si/Ge mix, LED's, LED/Si mix or Si diode pair with 100pF smoothing cap.
It works really well for bass or lead, has a huge tone range from smooth and creamy overdrive to quite harsh fuzz distortion - just need a resistor with the led's as the output volume is significantly higher when LED clipping mode is selected.

[theV]

(I changed my mind, I'll reply later)

[theV]

I write it here because it's clear that you like to experiment (and you're able to put it in reality) 

I was looking at this excellent page,

http://www.geofex.com/Article_Folders/TStech/tsxtech.htm

second drawing from the top (Clipping Stage)

Why not replace the 0.047 capacitor with an appropriately chosen inductor?
This would reverse the "magic" of the Tube Screamer, increasing gain at lower frequencies, and lowering it to unity at higher ones.

This way only the lowest range, comprising the fundamental notes (and maybe their second harmonics) would get overdrive, fatness and sustain, while all the treble (e.g.: plucking/pick noise and metallic timbre) should pass untouched, clean and dynamic.

I'd like a sound like this most... an overdrive at the core of the envelope, not at the edge.

But surely it's been already thought of and discarded...