Dirt Bag - boost/overdrive/distortion thing

[slacker]

All new* boost/overdrive/distortion circuit, all my own design, apart from the bits I stole off other people, complete with schematics and everything

* It's not really new it's just a development of my hard/soft clipping idea from this thread http://www.diystompboxes.com/smfforum/index.php?topic=72404.0. I played about with it a bit more and found cool little tone control that someone posted a link to a while ago, and stuck that on the end. (I'll find the link and give proper credit)

Basically stick the gain pot in the middle and crank up the volume and you get a booster. Turn the gain control anti clockwise (assuming you've wired it up right) and you get soft clipping like a TS only there's a bit more dirt if you want it. Turn it clockwise and it's like a Distortion Plus/OD250 but again possibly with a bit more filth on offer.
The tone control goes from mud to icepick 



Vero layout and soundclips to follow.

Enjoy

[jacobyjd]

I'mma steal this. 

I liked that idea when I first read about it--I can't wait to hear some clips on it!

[slacker]

Cheers.

Here's a link to the tone control http://roymal.tripod.com/ReverbTone.htm originally from this thread http://www.diystompboxes.com/smfforum/index.php?topic=82305.0 Thank's to Chris S for the link and Mr Mallory for sharing it with the world, even if he didn't actually invent it.

[Ben N]

Cool, Ian, I loved the idea back then, and I'm glad you got it sorted out. Anything special about the opamps? Maybe a 741 for U2?

[slacker]

Thanks Ben, Yeah I used a 741 for U2, forgot to put that on the schematic. I don't think U1 is critical, I'm using a TS272 because I had one lying around, but a TL072 should do the job.

[auden100]

oh man. For once I have all the materials and desire necessary to try out this circuit. Unfortunately, my little breadboard has been crammed full with an Omnidrive for the past two weeks. Really looking forward to giving this a try though.

[Brymus]

Ha, I recorded a band from Victorville Ca, several years ago called DirtBag.
They were a freakin kickin punk\thrash group did an amazing set here in the desert (sorry OT there)
That pedal looks cool,the name made me think of the band.
Post those clips soon.

[slacker]

Here's a few clips, apologies for the odd bum notes, didn't have much time.

Strat > Dirt Bag > Fender Concert  > mic to PC no effects or "post production"

dirtbag.mp3 - Clean, then max soft clipping (TS side) followed by max hard clipping (OD250 side)

dirtbagtone.mp3 - tone control starts about 4 o'clock then sweeps round to about 8 o'clock

dirtbaglowgain.mp3 - Couple of lower gain hard and soft clips with different tone settings

dirtbagboost.mp3 - quick boost example, unfortunately you can't really overdrive the Fender without blowing out the windows, so it just gets louder

Doubt the clips will earn me an endorsement or cause anyone to run through the streets naked, but I like it.

[dschwartz]

 

absolutely love it!!!!!!!! congratz
it has its own personality, i like that, and i like the textures it can get..

but i won´t run around naked for this! 

maybe if you add a 70dB clean-flat boost at the input (to get a tube like response), and add 45 more gain stages and 4 compressors in different places......i will.

[Brymus]

Yeah sounds really nice,that Fender amp sounds really great clean BTW
I am not understanding the TS vs OD250 sides ?
I was looking for diodes to ground and a blend pot between the two types of clipping,what am I not getting ?
Is it just op amp clipping from the 741 you are refering to ?

[slacker]

Thanks guys.

Bryan yeah it's a lovely amp. it's one of the early 1980s Paul Rivera models.

The hard/soft clipping works like this. If you turn the Gain pot so that on the schematic the wiper is at the top of the pot, then if you ignore the upper 10k resistor connected to the output of U1A, U2 is a non inverting stage like a TS. So you get soft clipping from the diodes in the feedback loop.
If you turn the Gain control so the wiper is at the bottom of the pot then the + input of U2 is connected to Vref, and U2 is an inverting stage. With an inverting opamp stage the - input is ground for audio signals so the diodes and the 1k resistor act the same as if they were connected to ground like in a OD250 and you get hard clipping.

[Brymus]

OK I get it now,thanks Ian.
That really IS pretty ingenious.

[roseblood11]

This sounds really interesting!
Slacker, do you have a vero layout for this circuit?

[slacker]

I'll get one posted in a day or two.