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L'Overdrive de la Révolution Trois - Light Overdriver
Posted: 19 Feb 2008, 14:38
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
Posted: 19 Feb 2008, 15:13
by analogguru
470n to gnd after the 39k input resistor ?
I think there will not be much treble.....
analogguru
Posted: 19 Feb 2008, 15:47
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...
Posted: 19 Feb 2008, 16:00
by analogguru
I was talking about the 470n from the gate of the first stage to gnd.
analogguru
Posted: 19 Feb 2008, 16:41
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)...
Posted: 19 Feb 2008, 17:55
by analogguru
I actually upped that from an origianl value of 220pF....
Yeah..... 220pF or 470pF would make sense... but 470n is 470.000pF.....
analogguru
Posted: 19 Feb 2008, 19:05
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.
Posted: 19 Feb 2008, 22:38
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.
Posted: 20 Feb 2008, 00:53
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"
Posted: 20 Feb 2008, 03:25
by marcao_cfh
It looks interesting. Any soundclips?
Posted: 20 Feb 2008, 09:59
by briggs
Scheme updated
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
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
If anyone wants to breadboard one up and take a few I would be very grateful!
