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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  Another RM Axis Fuzz Question, Transistor Gain? 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: Another RM Axis Fuzz Question, Transistor Gain?  (Read 1071 times)
Posts: 34

Another RM Axis Fuzz Question, Transistor Gain?
« on: July 13, 2006, 02:56:49 PM »

Can anybody recommend a gain rating for the NPN and PNP transistor pair in the Axis fuzz that will keep me from having to change the bias resistors.  The original uses a 2n3904 & 2n3906 pair but I've heard Roger Mayer is very picky about his parts (picking specific values, gains, etc).  I don't even know if this fuzz works in a way like the Fuzz Face or not.  Any ideas?
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Re: Another RM Axis Fuzz Question, Transistor Gain?
« Reply #1 on: July 13, 2006, 03:04:07 PM »

  those 3904/3906 are about the same [med gain] ~300hfe transistors that are recommended.
  Similar animal to the Fuzz Face as far as the Fuzzboost sound.

Convention creates following, following creates convention.
Posts: 3816

Re: Another RM Axis Fuzz Question, Transistor Gain?
« Reply #2 on: July 13, 2006, 06:30:26 PM »

My experience is that it is similar to the fuzzface, but more controllable and less woofy in the bass.
The only downside is that it is less expressive than the germanium number.  A Ge fuzzface gives mild then strongly asymetric clipping as the signal strength goes up, before moving to full-on fuzz.  So it is very sensitive to playing style, especially with single coil pickups.

If possible, grab some low hFE transistors out of an old hi-fi or radio.  Modern 2N3904s and 6s have hFE over 300, but the old ones seem to be around 200.  A 2N2222A might be a good modern alternative to the 2N3904.  Check out charity shops and rubbish dumps for 1970s hi-fis.

have fun

Brett Robinson
Let a hundred flowers bloom, let a hundred schools of thought contend. (Mao Zedong)
Posts: 517

Re: Another RM Axis Fuzz Question, Transistor Gain?
« Reply #3 on: July 13, 2006, 07:27:50 PM »

I tried the 2N2222A and it does something that may be more or less desirable.  It's not quite as nasty as the stock transistor and lets more of the shimmering highs come through on a Strat neck pickup.  Ultimately, I liked the nasty tone of the stock transistor and switched back.  It's almost like going between Jimi's cleaner tone during the verse of a song and then his solo tone (a bit dirty like the Axis outtro).

builds completed: boutique fuzz, rangemaster, BSIAB2, PT-80, Tonepad wah, Ross Comp, Axis Fuzz, MOSFET boost, Thunderchief, Big Muff (triangle), Mr. EQ, Dr. Boogey,  Neovibe, Dist+, EA Tremelo, ADA Flanger, RM Octavia
next build(s): Huh
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