Saturday, 12 April 2014

NPN Fuzz Face with BMP Tone Stack

This was a request but thought I may as well share it here in case anyone else wants something similar.  It's just a Fuzz Face with Big Muff tone stack which some may find useful, and can easily be adapted for a germanium build if you prefer.  I included a graph of the tone pot rotation frequency response thanks to the excellent Duncan Amps Tone Stack Calculator which I would recommend everyone use when working with the included tone stacks to fine tune the build to your own taste/gear.

I've put the 8K2 resistor to the far left hand side so if someone wants to add a trimmer to bias Q2, they can omit the resistor and add it in this position.  The trimmer legs may need a little fettling to span 4 rows but it should be easy enough to do.




And a second version with added base/collector Miller effect filter caps which cuts some high frequencies and makes it sound smoother and more like a germanium version.  Similar to the DAM Meathead.



22 comments:

  1. A great enhancement to the classic tone

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  2. Second version added with BC filter caps like the Meathead. I may as well do it while I've got the template open :o)

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  3. Built the second one, sounds pretty decent to me, though I'm certainly no fuzz afficiando :) Chords get a bit farty at some settings, but there're lots of nice lead tones there.

    Do you know any particular transistors to try? I've gone through some of the usuals I guess - 3904, 5088, BC550, MPSA18 - probably preferred the latter two, but I'd be keen to experiment some more if there are more sounds to be found.

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    1. Excellent Simon, thanks for verifying. BC107, BC108 and BC109 are always popular with the Fuzz Face. Also try 2N2222, BC183L and I really like ME4003's in this circuit, which you won't find in many places, but there is a seller on eBay who sells packs of 100 for around £7 (I think it is) and they're highly recommended. You may not need 100 but at least you know you'll never run out, and you could always go halves with someone else and keep 50 each for not a lot of money. By far the best Meathead I ever built was using the ME4003.

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    2. Great, thanks for the info. I'll have to pick some of them up with my next order, I don't have any on hand. I had a look for the ME4003 - I think I found the seller on Ebay, £7.70 for 100, but then unfortunately another £15 for shipping to Australia! So I'll probably have to go for some of the BC ones for the moment.

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    3. Gloups, they also charge £12 to ship to France, which is about 4 times what it will really cost :(

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    4. Ouch, I hate it when sellers do that. Especially as the price of the transistors has shot up too, when I bought them I paid £2 per 100 and so I bought 400, then they seemed to become popular and he bumped the price right up. That postage is shocking though

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    5. Can anyone tell me the pinout for the ME4003? Can't find anything online. Many thanks!

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    6. It is CBE and the flat side is the emitter.

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  4. Doesn't it greatly affect the volume?

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    1. The Big Muff tone stack gives you losses of around 7db, so it will certainly be quieter than a stock Fuzz Face, but you should still be able to get well above unity. If it was ever a problem you could always add a recovery stage like the one used in the Big Muff, but I don't think it will be necessary.

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  5. 666 verified!
    well done my children! HAHAHA!!!

    satan

    !!!

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    1. Ha ha, yes Miro sent me an email saying the same thing. It made me want to put a bit of Maiden on :o)

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  6. I built this last night and noticed a huge volume difference between my other drive pedals. It's pretty much half the volume of the others. I'm going to check all of my connections but, does anyone have any ideas about why this happens? This is the third fuzz I've built that does that.

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  7. I'm wondering if changing a few resistor values will allow for more volume output. I tried subbing the 100k vol pot for a 500k. Didn't exactly allow for more volume.

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  8. Hey Eric. You can increase the output by swapping the 330ohm resistor for a higher value. Try anything from 470ohm to 1K that you've got. Higher resistance = more output but if you go too high you'll have noise issues

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  9. Thanks Travis! Definitely going to take a stab at that.

    Mark, this site has definitely helped me out so much with learning about effect building. You rock!

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  10. All I get is a glitchy fuzz tone that only happens when I first hit the strings (like when you set a noise suppressor to aggressively). Im not really confident on the offboard wiring. I tried the one in the offboard wiring section here and the offboard wiring #2 from tonepad. Since this is my 3rd attempt at it, I will have to accept defeat and ask for help ;)

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    1. Most likely it's a bias issue. I've had this problem when building DAM Meathead and Colorsound One Knob Fuzz. hFe values of the transistors play a big role.

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  11. Although it says NPN Si for transistors, would this function okay with NPN Ge? I have some AC127Ks - Hfes of 69 and 71

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