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Hi there, welcome to my blog - La Revolution Deux. It's an odd name - but I like it! Here you will find all the info on my various DIY Guitar effects builds, amplifiers and guitars. Everything from a humble Ibanez tubescreamer to the holiest KLON Overdrive.

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Thursday, 5 July 2012

Fairfield Circuitry - Barbershop Overdrive


Guillaume Fairfield of Fairfield Circuitry makes some cool pedals, and his circuit designs are refreshingly interesting. The Barbershop Overdrive is one of the most interesting, a nice transparent overdrive/boost pedal (I would say it's an overdrive/boost pedal as the gain in this thing isn't super high) with a cool "Sag" control that controls the voltage the pedal's circuitry is running at and alters the compression and colouration of the overdrive. You can use the Barbershop to stack with your other dirt pedals in so many different combinations - it adds a great touch sensitivity and sparkle to almost any circuit!

Here's the description from the Fairfield Circuitry website;

"Have you ever sat in a barber's chair wishing your tone was as slick as your freshly shaved upper lip? With the Barbershop Overdrive on your pedalboard, you could keep your moustache and sound good doing it.

The Barbershop is an original design, not a clone.

Raw, gritty, warm, smooth, open and transparent are all terms that have been used to describe this overdrive. It sounds great with any setup, but truly shines when used to dirty up a tube amp."



Here's the customary ProGuitarShop demo video of the Barbershop Overdrive in action;


Not only are Guillaume's designs interesting they are also well thought out and manufactured to a great standard. Here's a gutshot for the Barbershop Overdrive (check out the cool logo on the PCB!);


So, without further rambling (and with thanks to WhiteKeyHole and Guillaume) here's a schematic of the Fairfield Barbershop Overdrive;


So what have we got? It's two cascaded Jfet gain stages followed by a simple NPN transistor emitter follower. The mosfet device is there for polarity protection. The 10kB pot is the "Sag" control that affects the overall supply voltage to the circuit and the clipping in the cascaded jfet/emitter follower stages. Guillaume has suggested that he sets the bias of the two jfets at around 2/3 of the supply voltage (when measured at the jfet's drain). I'd replace the drain resistors with 25k trim pots which will allow you to dial in the 6.66v bias point a little easier than using trial and error with set resistors.

If you want to build one of these up you're going to need a vero layout, there's one available here; http://tagboardeffects.blogspot.co.uk/2012/06/fairfield-circuitry-barbershop.html, at IVIark's brilliant tagboardeffects blog.

Here's another vero layout for you;


Check out the forum topic on freestompboxes.org, Guillaume offers some really great info and tips to guys wanting to build the circuit up; http://freestompboxes.org/viewtopic.php?f=7&t=4435

3 comments:

  1. love the details on this. nice one!

    ReplyDelete
  2. The components are different in the two vero layouts you provide. The tagboard layout only has 10 resistors and 3 transistors while the second vero and the schematic have 12 resistors and 4 transitors. I am assuming the tagboard vero is therefore incorrect.

    ReplyDelete
  3. Any possibility of getting an updated schematic or vero layout for the Millennium Edition?

    ReplyDelete

Comments are welcome on Revolution Deux. However, please do not spam links to unrelated sites - these comments will be removed! Thanks - Briggs.