L'Overdrive de la Révolution Trois - Light Overdriver

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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briggs
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Post by briggs »

Here is the blurb from my Blog:

Schematic:
Click HERE!
The next offering in the "L'Overdrive de la Révolution" Series is here! Trois!

It's a light overdrive/boost effect (There isn't a great amount a clean headroom here though) utilizing a Jfet stage running into some germanium clippers all cascaded into a common Mosfet gain stage. It's a very dynamic and resposive circuit, I wanted it to be controllable from your guitars volume and tone pots, goals which it definatly scores!

Inspiration for the front end JFET section was taken from the great runoffgroove "Omega" project which is a great versatile booster project which really is worth a build. I loved the way the Omega's "Range" control worked and wanted to see this put into use in an overdrive circuit, a few simple ideas later and here you have it: "L'Overdrive de la Révolution Trois".

There are loads of notes on the schematic image identifying possible mods and changes. A great one is the alternate clipping setup - which I am actually currently using in my build :-)

Give it a try on breadboard, it's a super easy build and a great sound to boot! You won't be dissapointed :-)
Last edited by briggs on 20 Feb 2008, 09:49, edited 1 time in total.
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Post by analogguru »

470n to gnd after the 39k input resistor ?

I think there will not be much treble.....

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Post by briggs »

The first stage produces enough treble to allow it to become just a little harsh, when you back back your tone knob it's just right. The clipping diodes add quite a bit of treble back into the signal... 8)
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Post by analogguru »

I was talking about the 470n from the gate of the first stage to gnd.

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Post by briggs »

Yeah, I actually upped that from an origianl value of 220pF as well as increasing the size of the input resistor from 33k to 39k. The combo I used seems to produce just enough treble roll off to please my setup (335 type guitar -> Twin reverb)...
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Post by analogguru »

I actually upped that from an origianl value of 220pF....
Yeah..... 220pF or 470pF would make sense... but 470n is 470.000pF.....

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Post by soulsonic »

analogguru wrote:
I actually upped that from an origianl value of 220pF....
Yeah..... 220pF or 470pF would make sense... but 470n is 470.000pF.....
Yes, I sense a possible typo in the scheme.
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Post by bool »

"drive" knob seems to be very noisy to me; and dc coupling not very healthy in such circuit. I'd move the 47n cap between the q1 drain and hot pin of this knob.
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Post by briggs »

Ah, I see AG, it is 470pF not 470n as I've put! Sorry, tired eyes and stupid brain ;) I'll post the updated and improved scheme when I wake up. I really should triple check for typos!

bool: Thanks for noting that. I have a feeling that I already have the drive pot set up like this and I've noted it down incorrectly.

Anyone else breadboarded? I like the character of this little circuit, it's nice and "soft" 8)
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Post by marcao_cfh »

It looks interesting. Any soundclips?
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Post by briggs »

Scheme updated :D Thanks for all the checks guys.

As you can see there are still a few "strange" things going on with the structure. I like it though - qwirky :wink:

In my current build I'm using a 500kA "drive" pot a "100kB" "body" pot and the alternate clipping arrangement - it works best for my stuff. The marshall amp I played through (I forget the model number! It was nothing special though, bog standard) prefered the original drive pot of 100kB, body pot of 500kA and original clipping setup. The differences are subtle - but they are there.

Unfortunately the few pieces of recording gear I owned were nicked a couple of weeks ago so I can't make sound samples :cry: If anyone wants to breadboard one up and take a few I would be very grateful!
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