I think some of the MI Audio-Boxes are very interesting. The Crunch Box-secret is allready known, but how about the NEO FUZZ because of this quote:
The circuit concept is the same as that of the GI Fuzz, but instead of NPN high gain silicon transistors, the Neo Fuzz is built around a pair of hand selected early 70s NOS AC128 germanium transistors. There's also a third silicon transistor which is not involved in the fuzz tone generation. The tone is pure germanium. Each germanium transistor is tested for leakage current and gain, and only the best of these transistors is used in the Neo Fuzz. The other cool feature is the high intensity pink LED. Very cool!
[...]
Once again, the Neo Fuzz is not a clone of anything out there. It is new design which I worked on for about a year.
A silicon transistor that ist not involved in the fuzz tone generation? What is it used for? Driving the LED or what?!
And a NEW Fuzz-circuit
Infos for other MI Audio-Pedals are welcome, too ...
But would the load-pot make sense if there is a input buffer?
Yes
With the normal Fuzz Face you got a very different tone if played with active pickups.
If you buffer it's Fuzz face input you will always have that kind of different tone no matter if passive or active pick ups are used (and fix the problem with the Wah pedals as well)
Then you insert some variable resistance between the buffer and the fuzz face and you can alter that different tone and even get closer to the traditional Fuzz Face tone (this time with or without active pickups) this variable resistance loads the it's inputs...
Gus has worked a lot with this kind of thing with his 3trans circuit and some others like the Aron's Rocket I think, but with no variable "r"
you mean buffer -> load-pot -> "real fuzz"? That would make sense, but I don' think the guitar volume-pot would work anymore like it's demonstrated in the samples (back off = clean/little dirt - full = FUZZZZzzZZzzZZZzz).
When I say "not work" for the guitar vol pot i mean don't have that effect of cleaning the tone like turning the fuzz pot down a bit... of course
my engrish
i'm a noob of sorts, and not an experienced builder. a friend of mine recently asked me to build him a high gain germanium fuzz with a flexible tone control, and alluded wildly to the neo fuzz. since i couldn't find any schematics (and i found this thread a lot later), so based on this thread, i embarked on building a workalike.
what i essentially did was build a fuzz face using (AC128 and AC188, NKT275 impossible to find, tested for leakage and gain according to RG Keens excellent instructions) followed by a baxandall tone stack followed by an LPB-1 at low gain. this worked inconsistently - at first i thought it sounded very good, and liked the way it sounded... on a couple of settings. but the tone controls were quite ineffective.
then i searched some more and found this thread. i cut a few tracks on the PCB last night and rewired it so that the LPB would be the first stage, followed by an "nput bias" knob (a 200k pot wired as a variable resistor) which is followed by the fuzz face circuit, the single knob bax tone stack with a "mid" knob and the output volume. holy moley, it sounds great! not vintage, not modern, something in between and a lot of flexibility. using the "less" knob, it cleans up beautifully and the tone control goes from scoop to hump.
BUT: i have a couple of problems. it motorboats on extreme gain settings (i suspect that the gain of the LPB is set too high), the "mid" knob is only distinctly effective within the first quarter of it's travel (will switch to a linear pot)...
the biggest problem however is that the output volume, when set on max, is roughly the same or only very slightly louder than the input volume. on a low gain setting, it actually is a bit softer than the bypassed volume.
i can't figure out how the neo fuzz does it with just three transistors - i would assume there is some sort of a buffer on the output and not on the input to make up for the losses in the bax tone stack. hence, i assume that i have made a big mistake somewhere. could somebody point me in the right direction? the schematic is attached below, i hope it is readable...
Attachments
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In the interest of full disclosure, I am Animal Factory Amplification.
sorry for the second post, but i can't figure out where the "edit post" button is. i just noticed that i had left out two entire sentences before the last paragraph, these being:
"the neo fuzz has a lot of output on tap. i would like to ideally achieve unity output at the 12 o' clock position of the volume knob with my workalike. i can't figure out how the neo fuzz does it ... etc."
In the interest of full disclosure, I am Animal Factory Amplification.
Take the output in the fuzz face section from Q3's collector instead of the 1k/8k2 junction. If you do that you'll get quite a bit more volume. That also means you can eliminate R4 (1k). You might also reduce the size of the 8k2 so that the bias trim pot is more effective (maybe a 4k7 or so).
PurplePeopleEater wrote:Take the output in the fuzz face section from Q3's collector instead of the 1k/8k2 junction. If you do that you'll get quite a bit more volume. That also means you can eliminate R4 (1k). You might also reduce the size of the 8k2 so that the bias trim pot is more effective (maybe a 4k7 or so).
damn... i didn't think about that at all, despite having worked on a tube amp design with the EQ taken off the cathode follower for the express purpose of having as much volume as possible!
it would also reduce the output impedance, i suppose?
meh.... it doesnt work. no significant increase in volume, and a MAJOR side effect: with the fuzz pot turned all the way down, the output is shorted to ground... i totally missed that! als, mine is motorboating quite a bit with the gain on full - probably too much gain at the input buffer.
one thing i did was to short out the "shift" pot in the baxandall EQ and voila, there was a *slight* increase in volume. so i think i will have to look at my equalizer section a little more carefully. will try and proto a new version, perhaps with the woolly mammoth output section. something tells me that my EQ is dimensioned wrong and is attenuating unnecessarily. anybody have any other ideas on how i could make the bax work here?
i wish there were gut shots of this one somewhere...
In the interest of full disclosure, I am Animal Factory Amplification.
flood wrote:meh.... it doesnt work. no significant increase in volume, and a MAJOR side effect: with the fuzz pot turned all the way down, the output is shorted to ground...
How can this be? The fuzz control is part of the Emitter circuit, and your output is coming from the Collector...
I would put the buffer at the end of the circuit after the tone controls. That would give it a constant impedance, so the tone controls would sound the same regardless of what you plug it into.
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran
![[smilie=a_goodjob.gif]](./images/smilies/a_goodjob.gif "Good Job!"){kind=small}
yeah right that was in the post,
