RM Axis Fuzz Notes !!

[petemoore]

I know a few of you built these recently, as I'm about to endeavor there...any cool tips before I start building?

[Fret Wire]

Pete, I can't remember, but it seems like there was something on the schematic for euro power supplies that should be left off. I think Doug H had a build report, but I couldn't find it.

http://bryant02.home.att.net/schematics/axisfuzzschem.gif

http://diystompboxes.com/sboxforum/viewtopic.php?t=18554&postdays=0&postorder=asc&start=0&sid=9d985eda68d674fe7ffe03c3e6d0ce7a

http://diystompboxes.com/sboxforum/viewtopic.php?t=20564&start=0

[dev]

You may want to use sockets for the following parts:
    Input cap (you know the drill larger more bass)
    22uf drive cap (smaller values=less octave overtones)
    1st transistor
    2nd transistor (you might want to sub a jfet like nte 458 here *note  
    j201  has a different pin out)
Also, try different values for the 680k resistor if the 1st tranny isn't biasing right.I strongly recomend using a pot or trim pot for the 47k by the drive pot.   And an input volume control may be a good idea too.
I'm using this pedal alot, it works well with my gear but I also cut the bass from my guitar with a high pass cap on my guitars "second volume control".
good luck with it
Dev

[brett]

Hi Pete
I've been trying this out and a few variations.  The 2k2 pot is hard (almost impossible) to find.  I use a 1k pot, which means I lose the "little bit of fuzz" end of the range.  For me, it's not an issue.  

One of the key changes is the 47k feedback resistor.  Some folk like to drop this to 33k or lower.  Lowering the resistor increases feedback and lowers gain.  I mainly use 2N3906 and 2N3904 transistors, which have low hFE, so excessive gain isn't an issue for me.  If you were to use 5087/5088s or PN200/PN100s, then a drop to maybe 22k might be warranted.

As someone else said, you can drop the 220 ohm/0.001uf (I think?) combination.  

Also, there's nothing special about the 180k/820k pair of bias resistors on Q1.  You can use a single 1M. (thanks for pointing this out, RG).  The bypass cap should then go from 9V to ground, like every other pedal.

Have fun, this is a cool circuit.

[petemoore]

Please...and thank you!!!
 I'll report on My progress ...

[brian wenz]

Hello Hello--
    When I first built this circuit I used Radio Shack 3904 and 3906 trannys  but later I used better quality  ones and the difference was noteable.  [I've got one with some older European trannys and one with Fairchilds and they both sound real good.  I also built one using a BS170 for Q2 that sounds great.]   This circuit was designed around the 2N3904 and 2N3906 trannys, so I wouldn't advise using any higher-gain ones.
[Although, the BS170 sounds real good in Q2!]
Also.... the 47K res that goes from Q1 emitter to Q2 collector can be lowered to 22K - 33K or-so.   When using the pedal in a loud band situation  the tone can be a bit muddy with humbuckers and by lowering the value of that res. you can  "un-muddy" things a little.
Brian.

[Doug H]

Here's one of the older axis threads:

http://diystompboxes.com/sboxforum/viewtopic.php?t=18554&postdays=0&postorder=asc&highlight=axis+fuzz&start=0

I used a 27k feedback resistor, fairchild 2n3906 1st stg and metal can motorola 2n2222 2nd stg. The motorola transistor with lower hfe smooths it out a little and sounds real nice.

IMO, the way to approach this fuzz is to dial in some amp dirt, turn the fuzz control up to about 90% (sweet spot with lower noise) and start with your guitar volume on 5. I rarely dime my guitar vol (humbuckers) with it except for emphasis, octave harmonic sustain, and freak-out swells.

Doug

[brian wenz]

Hello Hello--
   Yeah,  this thing works best when used with an already-dirty amp.  You can get a lot of different "fuzzies"  with various guitar-and-pedal settings.
 Using it with a clean amp, however.......................................  blecchhhh......
Brian.

[brett]

Clean amp.....that concept is new to me..
I suppose in theory you could do something with that sound
 :twisted:

[Doug H]

FWIW, I think it sounds pretty good with an amp I just built (tube), on it's clean setting. But it will sound much more "alive" and responsive if the amp is breaking up too.

Doug