Fairfield Circuitry - Four Eyes Fuzz

D-Day · Post by **D-Day** » 02 Jan 2011, 23:21

That thing sounds cool!

RnFR · Post by **RnFR** » 03 Jan 2011, 00:55

mu amp I/P stage, followed by a voltage controlled state variable filter w/ resonance control into 3 parallel jfet fuzz circuits. at least according to YouTube. Mr. Fairfield has been nothing but generous in the past, no reason to doubt him. maybe just ask? he was very cool about the barbershop.

but, I'd have to agree about that 4 layer board, way better than goop! you'd have to really get your hands on the board and do some continuity checking.

~arph · Post by **~arph** » 03 Jan 2011, 14:07

Now that solder side picture made me grin. I have nothing but respect for that kind of smart thinking.

RnFR · Post by **RnFR** » 03 Jan 2011, 15:47

~arph wrote:Now that solder side picture made me grin. I have nothing but respect for that kind of smart thinking.

same here!

and the thing that's even better, is that he was one of the few builders to pretty much help with anything we asked.

culturejam · Post by **culturejam** » 03 Jan 2011, 16:44

Finally, a builder who has learned something from likes of us pirate-thieves.

Well, other than just stealing the circuits from the other builders who stole from someone else.

Steven_M · Post by **Steven_M** » 03 Jan 2011, 17:35

HAHA! Good work Mr. Fairfield. Very clever (Sounds good too!).

So the consensus is that this is a four layer board with the top and bottome layers being empty and the middle two being where the action is at?

Hides-His-Eyes · Post by **Hides-His-Eyes** » 03 Jan 2011, 17:54

Steven_M wrote:HAHA! Good work Mr. Fairfield. Very clever (Sounds good too!).

So the consensus is that this is a four layer board with the top and bottome layers being empty and the middle two being where the action is at?

The top/bottom layers may be power and ground pours.

fairfield · Post by **fairfield** » 03 Jan 2011, 19:23

Hey all, sorry I didn't catch this earlier. Could've told you it was 4-layers before taking it apart. Though I must admit, I did enjoy it a bit...

The description I gave on youtube and the website pretty much sums it up. The vactrols are used in the state variable filter, for voltage control. The fuzz circuits are simple, textbook JFET common source amplifiers. Much like the Barbershop the sound is in the biasing. Also, the mu-amp contributes quite a bit of pre-fuzz before going through the filter.

The top and bottom are indeed power and ground planes. Tracing the circuit is possible but would be quite a challenge, I don't recommend it. Needless to say it would void the warranty.

That said, JFETs are the shit...

lolbou · Post by **lolbou** » 03 Jan 2011, 19:35

fairfield wrote:Though I must admit, I did enjoy it a bit...

fairfield wrote:he description I gave on youtube and the website pretty much sums it up. The vactrols are used in the state variable filter, for voltage control. The fuzz circuits are simple, textbook JFET common source amplifiers. Much like the Barbershop the sound is in the biasing. Also, the mu-amp contributes quite a bit of pre-fuzz before going through the filter.

Thanks for the explanation so far...

fairfield wrote:Tracing the circuit is possible but would be quite a challenge, I don't recommend it. Needless to say it would void the warranty.

With a continuity tester? It's non-destructive, ain't it?

fairfield wrote:That said, JFETs are the shit...

You mean...? (straightly translated in french, it says that your JFETs are crap

)...

MicMicMan · Post by **MicMicMan** » 03 Jan 2011, 20:12

jfets are the shit means "les jfets ça déglingue"

super post guillaume, merci

culturejam · Post by **culturejam** » 03 Jan 2011, 21:01

fairfield wrote:Could've told you it was 4-layers before taking it apart. Though I must admit, I did enjoy it a bit...

Well played, sir. Well played.

lolbou wrote:You mean...? (straightly translated in french, it says that your JFETs are crap )...

JFETS are the shit. Not, JFETs are shit. Big difference in English. But I'm sure you knew that, you cheeky monkey.

Sum it up as "JFETs are très awesome."

lolbou · Post by **lolbou** » 03 Jan 2011, 21:06

Tabernacle! So now "shit" is "awesome"

... We'll have to update the dictionnary that JiM has set up in the Frenh subforum!

@lama00: what are these JFETs then, special ones?

culturejam · Post by **culturejam** » 03 Jan 2011, 23:10

lolbou wrote:Tabernacle! So now "shit" is "awesome" ... We'll have to update the dictionnary that JiM has set up in the Frenh subforum!

No, "shit" is not "awesome". But "the shit" is "awesome".

As in: "I just got a new guitar, and it's the shit!" (awesome)
Compare to: "I just bought a new guitar...it's shit and doesn't play well at all." (not awesome)

Why? I have no idea.

squrl · Post by **squrl** » 05 Jan 2011, 00:17

guillaume - i'm curious as to if the decision to make the board 4-layer was necessary for space/layout/etc. or if it was to "protect" the circuit to a degree? obviously you could have done the power/ground routing in the internal layers.

culturejam · Post by **culturejam** » 05 Jan 2011, 05:33

squrl wrote:guillaume - i'm curious as to if the decision to make the board 4-layer was necessary for space/layout/etc. or if it was to "protect" the circuit to a degree? obviously you could have done the power/ground routing in the internal layers.

Or he could've done a "ground pour" on one side and a "9v pour" on the other side. Get it all done with two layers that way. At least I think it should work. I've done it in the past on simpler circuits than this one.

I think it might be a combo of "how cool would be to do 4 layers" and "it's going to be hilarious to watch people to dry to figure it out".

Or most important: "It will stop Jetter from stealing the design and calling it Gain Stage: Spectacles".

squrl · Post by **squrl** » 05 Jan 2011, 12:02

culturejam wrote:
squrl wrote:guillaume - i'm curious as to if the decision to make the board 4-layer was necessary for space/layout/etc. or if it was to "protect" the circuit to a degree? obviously you could have done the power/ground routing in the internal layers.
Or he could've done a "ground pour" on one side and a "9v pour" on the other side. Get it all done with two layers that way. At least I think it should work. I've done it in the past on simpler circuits than this one.

I think it might be a combo of "how cool would be to do 4 layers" and "it's going to be hilarious to watch people to dry to figure it out".

yeah looks like he did a ground/power pour but i ws just saying that he could've done those as internal layers and the signal routing as top/bottom... that is certainly the combo of emotions i would be expecting too!

Thaxt · Post by **Thaxt** » 05 Jan 2011, 17:11

Looks pretty complex - hence likely capable of a great variety of sounds. 2 Op amps, plus those 2 Vactecs would seem to say it might involve some envelope triggered FX of sorts.

I'll check out the website - thanks for posting this -

fairfield · Post by **fairfield** » 09 Jan 2011, 14:28

Thaxt wrote:2 Op amps, plus those 2 Vactecs would seem to say it might involve some envelope triggered FX of sorts.

No enveloppe triggered funny business going on here. Like I said, the opamps form the state variable filter, and the Vactrols are for voltage control of the center/cutoff frequency.

culturejam wrote:I think it might be a combo of "how cool would be to do 4 layers" and "it's going to be hilarious to watch people to dry to figure it out".

That combo is pretty accurate. The ease of routing was probably the most satisfying though.

lolbou wrote:what are these JFETs then, special ones?

Nothing special at all, good ol' J201s.

Hides-His-Eyes · Post by **Hides-His-Eyes** » 09 Jan 2011, 20:45

What enclosure is that?

fairfield · Post by **fairfield** » 09 Jan 2011, 23:07

Hammond 1590BB