Wednesday, 27 February 2013

Madferret Germageddon

Madferret's amazing and complete overhaul of those circuits that use low gain Ge transistors in darlington configuration to achieve fuzzy germanium bliss. This baby consumes 6 of your low gain/low loeak germaniums and adds not-completely-unlike big muff tone stack plus a recovery stage to keep the signal loud. Not to mention three different pots to tune it to your liking - including Choke control, Pregain and first stage Iintensity controls. It has six knobs, so you might want to use a big box for it. Or if you're feeling adventurous, you can always try it out with 9mm pots and fit it in a 1590B :)
This one uses negative power supply, so wire it for battery only or use appropriate charge pump.

From Madferret: Credit where credit's due by the way, this was based off the Germocide layout by Dragonfly, with ideas taken from all over the internet from places like DIYstompboxes, AMZ etc but especially from Mark's blog as I seriously wouldn't have a clue about making pedals if it weren't for all the information from this site and all the input from everyone that uses it. Go team!

Possible mods:
-To get more gain from the recovery stage, decrease the value of 3K3 resistor coming from Q7 emitter, or increase the value of 15K at the Q7 collector. Or do both.
-If there's too much fizz, try upping the 100p cap to 220p or 470p
-Lowest settings of Pregain and Intensity can be tweaked by swapping the 18K resistors for something like 4K7 or 10K.

Madferret's demo:


24 comments:

  1. Int.2 and sw2 are connected to nothing (trace cut col. 2 row 7), I think there is a mistake there ?

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    1. They are connected to each other, however, and doing it this way does avoid daisy chaining in the off board wiring and so makes it all a bit tidier. ( see Voodoo 1 ). Let's here it from the horses mouth, though!

      Anyway, way to go Madferret, think I'm gonna have to start accruing some germs. Added to my " to do" list, but probably not for a littlewhile

      Mark :-)

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    2. Yep, totally right, Int 2 goes to sw2. The switch sits between the boost section and the 'fuzz' section by having a switch for the caps it'll let you cut the bass by selection the 10nf cap, I put this in as I found it could get a little mushy at some of the higher gains, if you felt you wouldn't need it you could just omit whichever cap you wanted and connect Int2 straight to the other. Iused a dpdt switch (on/on) with the caps of each side but this way is much more tidy.

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    3. Horse agrees. That's "dummy connection" which i sometime use to avoid pot daisy chaining notes on the bottom. That translates to: Omit the connection on board - int. 2 to sw 2.
      +m

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  2. Thanks for this Miro, much appreciated, "not-completely-unlike big muff tone stack" very diplomatic way of saying features a tone stack stolen from the Big Muff ;)

    Anyone wanting a bit more post-fuzz gain can decrease the 3k3 resistor or increase the 15k, or both, just be warned that it'll get a little 'hissy' if you go too high. If you find it is a little too hissy then increasing the 100pf cap should cut some of the treble off that section.

    Credit where credit's due by the way, this was based off the Germocide layout by Dragonfly, with ideas taken from all over the internet from places like DIYstompboxes, AMZ etc but especially from Mark's blog as I seriously wouldn't have a clue about making pedals if it weren't for all the information from this site and all the input from everyone that uses it. Go team!

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    1. But there are other circuits out there that utilize low gain germs in darlington configuration - like Briggs' Pharmacy Fuzz. And BMP tone stack is featured as a base in "Tone Stack Calculator" :)

      I'll add some notes about possible mods and - yes. Give more credit :)
      +m

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    2. Cool, video on the way once I finish editing and uploading.

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    3. Ok, the video's uploading, sorry about the delay I did one yesterday but it just turned into me waffling on about gain stages for 20 minutes, pretty cringeworthy stuff so I recorded a shorter demo of just some of the key tones. The sound quality isn't great by the way because I used my camera but you'll get the idea.

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    4. So i can tag it? Post the link to demo, once it's up - i'll add it to the post.
      +m

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    5. Ah sorry dude, I used the horrible franken-pedal that I used for the design. I'll definitely be building it though as because of all the links and 3 daughterboards it porbably sounds more noisey than it should, also your's looks frickin cool!

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    6. Here's the demo for anyone that's interested: Germageddon Sound Test Demo, go easy on it as it's built using the test board that I used for the design rather than Miro's layout, Miro's should be much quieter in terms of noise because it won't have as many cables, crazy daughterboards and extra sockets etc to test different values, plus I didn't include the noise cancelling measures that I suggested above. Any feedback would be appreciated as I'm keen to learn from this and hopefully be able to design a pedal from scratch in the future.

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    7. Added the demo to the post.

      Sadly i have too many boards going on at the moment, so i can't build this just yet...
      +m

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    8. No problems, I'll get this verified at the weekend if it's not been done. I'm just working on the next one :D

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  3. Suggestion/ request: please don't call vid, " Madferret's 6 knobber". A google search could lead us to some dark places! Like a clip I once saw on my friends phone :-(

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  4. That's completely awesome. Love your knob arrangement - it kind of encourages you to go mad with psychedelic art-noise and feedback I think!
    You say it is a 6 knobber - but what's the pot without a knob in the middle?

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    1. The middle knob is actually the tone pot, the extra knob is a bias pot which I placed externally rather than as a trimmer just to help with development, you can get some different sounds with it but overall it sounds best biased to around 4.5v at the collector of Q6. All those knobs made it kind of fun to arrange them for it, they work pretty well together so it's fun to play with them :D

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  5. Building this looks like a real challenge! One question from a medium experienced diy-er with limited knowledge in electronics: In the schematics there's a small square with three blue dots inside and the text 22K. What does that mean?

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    1. That's 22K trimmer potentiometer.
      +m

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    2. Is that the centered knob James Parsons asked about?

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  6. Is The diode backwards in this circuit?

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    1. Nope. But in case you would be using NPN transistors, you'd want to reverse it. The original was and is a circuit that requires positive ground.
      +m

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