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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.

You may also find a few effects builds that I am looking to move on - usually in exchange for other effects/gear/cash. You can always check my ebay account to see what I've got up for grabs.

Have fun, enjoy the blog - Fred Briggs :-)

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Saturday, 25 February 2012

Fred Briggs - 'Face - Fenderish Booster/Overdrive


Here's the Face MKI schematic:


I really like this one, it's a booster/overdrive with a nice Fendery feel and voice to it. As you can see there are some values which you can alter on the schematic that allow you to tailor the tone to your exact needs. Firstly the supply voltage - the lower the voltage the less overall gain and clipping you'll get, more voltage = more gain and clipping. The jfet choice also makes a difference to the tone of the circuit; 2N5457s give more gain but are more compressed sounding (better for the Fender "tweed" emulation) than the MPF102s (better for the larger Fender "twin" type emulation) which have more headroom but less gain. You can use almost any jfet type in this circuit 2N5458, J201 (I didn't like these, they were too compressed and gainy - almost fuzzy!), you just need to find your type! If you want to learn a little about jfet's and their properties check out this article over at runoffgroove: http://www.runoffgroove.com/fetzervalve.html. Finally the 3n3 tone cap can be altered to your preference, a higher value will lower the high end gain, a lower value will allow more high end drive.

In my final build I'll be using MPF102 jfets running at 18V with a 4n7 tone cap to keep the high end under control. This setup provides a nice "cranked twin" tone and is really dynamic and reactive to your playing, a decent low end is retained while it still fizzes out at higher gains.



Here's the schematic for the version I built up (note the altered tone control which, I find, works better with the MPF102 jfets):



I took inspiration  from a range of sources for this little circuit; firstly this patent from 1943: http://www.muzique.com/amz/SRPP.pdf

And this microphone preamp (1997):


And one of Tim Escobedo's excellent circuit snippets - the Syrupp Booster (2002):

All comments are welcome, for the freestompboxes.org topic check here: http://www.freestompboxes.org/viewtopic.php?f=13&t=16321

3 comments:

  1. Hey, Fred -

    been coming back to rev'deux more and more - fantastic site with no end of fun circuits to wonder over and consider for builds. Clearly you keep pretty busy man. I have been gearing up to build a LovePedal Timmy (AEL) circuit with full-on Brigg's mod'd COT50 and some options like stock switching (COT50 controlled via AEL on/bypass, i.e. subordinate) to discrete COT50 and AEL, via a 3PDT toggle. I mention that cuz I see this and want to build it too of course. Considering the wealth of material that you do provide, one hesitates to ask for more -- so instead I'll ask if you might _already_ have a vero or pph layout for this Brigg's Face Fender Tone box. If not - well, like I said - you do more than enough already - and perhaps I can figure out how to lay it out myself. I find I'm ok at mod'ing existing layouts to incorporate mods, i.e. your mods to the Love-Timmy, etc.. and even some of my own -- but I've not taken the leap to do one from scratch (i.e. schematic); it's like I get this "forest for the trees" thing going on and can't get past it (yet).

    Thanks for a most awesome and inspiring website man.

    aprilia1k/Stephen

    ReplyDelete
  2. Great one, Fred - just build MKII and I'm really liking it, especially using dual MPF's. One 2N5457 and a MPF102 also sounds pretty good for those tweed-ish tones. Cheers!

    ReplyDelete
  3. Hi,

    I tried building this (with the stripboard layout from http://tagboardeffects.blogspot.com/2013/01/briggs-face.html ) and there's no sound. I checked the gaps between strips with a voltmeter, and knifed 'em for good measure. Here's my transistor readings:

    trim pot fully CCW
    Q1
    D 9.14
    S 8.28
    G 8.29

    Q2
    D 9.15
    S 9.14
    G 9.14

    trim fully CW
    D 8.31
    S 7.46
    G 7.48

    D 9.13
    S 9.13
    G 9.13

    Three differences in parts, due to what i have on hand: the transistors are 2N5458, the trim pot is 10K, and the 47pf cap is 100pf. Would any be enough to make it not work?

    I could understand if the trim pot is too wide of a range to find the sweet spot, but what seems weird is that the voltages hardly change, even with the pot completely on or off.

    Unfortunately I don't understand enough about how this works to figure out where my mistake might be. I appreciate any ideas or advice! Thank you,

    john

    ReplyDelete

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