Jack Orman - Fet Muff

patafix · Post by **patafix** » 18 Jan 2008, 17:42

Seems that the fet muff schematic is lost or deleted...

Does anyone have it ?

I understood it was a big muff without the diodes... 4 cascaded fet stages...

Am I wrong ?

patafix · Post by **patafix** » 20 Jan 2008, 10:03

Still no Fet Muff here...

For the moment seems it can only be found one AMZ CD....

minor7th · Post by **minor7th** » 20 Jan 2008, 11:01

patafix wrote:Still no Fet Muff here...

For the moment seems it can only be found one AMZ CD....

At the moment, the Fet Muff will only be found on the AMZ.

Doug did the Fet Muff Plus, which was a modded version of that.

If you want all the fet muff details and layout, just spring for the AMZ CD. Support Jack Orman who has given a lot to the hobby, industry AND boutique builders (depending on who you are, no names mentioned). I've got one, and there's a heap of interesting stuff on it. There was some stuff that Jack asked me not to release to 'discussion.' Hey, I'll respect that for the very reasons outlined.

CD details here.

And no, I will not provide you with details of the Fet Muff!

I am not preaching about the rights and wrongs of it all.

It's my personal opinion based on Jack's contribution. If someone else will give it to you- go for it.

minor7th

patafix · Post by **patafix** » 21 Jan 2008, 12:13

Thanks for your opinion.

I'm just a little french DIYer, working on stripboard !!!! This mentioned, I will, in no way, try to make profits with my builds... except maybe from the music I might play through them.

I also agree with the fact that some DIYers, such as J. Orman, gave a lot.

Maybe I'll try to design my own 4-fet-stages distortion... It might be a lot more interesting than copying one's designs....

Post by **modman** » 21 Jan 2008, 14:22

With all due respect to Jack,

When I ordered my AMZ cd, I found an old backup of the website and nothing that wasn't online yet, it seemed. Don't know for sure, it's such a mess, really. I'd better bought some Indyguitarist ebooks!

I searched for the Fet Muff schematic on there for a half an hour. Only found the clip. Anybody can proof me wrong?

minor7th wrote:
patafix wrote:Still no Fet Muff here...

For the moment seems it can only be found one AMZ CD....
At the moment, the Fet Muff will only be found on the AMZ.

Doug did the Fet Muff Plus, which was a modded version of that.

If you want all the fet muff details and layout, just spring for the AMZ CD. Support Jack Orman who has given a lot to the hobby, industry AND boutique builders (depending on who you are, no names mentioned). I've got one, and there's a heap of interesting stuff on it. There was some stuff that Jack asked me not to release to 'discussion.' Hey, I'll respect that for the very reasons outlined.

CD details here.

And no, I will not provide you with details of the Fet Muff! I am not preaching about the rights and wrongs of it all. It's my personal opinion based on Jack's contribution. If someone else will give it to you- go for it.

minor7th

MoreCowbell · Post by **MoreCowbell** » 21 Jan 2008, 16:14

minor7th wrote:
Doug did the Fet Muff Plus, which was a modded version of that.

Wasn't it Frank Clarke who did the Fet Muff Plus , not Doug ?

p.eat · Post by **p.eat** » 21 Jan 2008, 16:53

Here you go. I can't remember where I found it, but it must have been available sometime as I don't have the CD.

Stuggi · Post by **Stuggi** » 21 Jan 2008, 22:35

Would that circuit work with IRF540's?

minor7th · Post by **minor7th** » 22 Jan 2008, 01:07

MoreCowbell wrote:
minor7th wrote:
Doug did the Fet Muff Plus, which was a modded version of that.

Wasn't it Frank Clarke who did the Fet Muff Plus , not Doug ?

It was. Just seeing if anyone was actually reading it! Amazing what happens when you stir things up a bit- the responses start flowing...

And if you pop over to super-freq you can see one built about 6 months ago!

Ciao ...

MoreCowbell · Post by **MoreCowbell** » 22 Jan 2008, 01:38

minor7th wrote:
MoreCowbell wrote:
minor7th wrote:
Doug did the Fet Muff Plus, which was a modded version of that.

Wasn't it Frank Clarke who did the Fet Muff Plus , not Doug ?
It was. Just seeing if anyone was actually reading it! Amazing what happens when you stir things up a bit- the responses start flowing...

And if you pop over to super-freq you can see one built about 6 months ago!

Ciao ...

I occasionally pay attention !

Nice looking build, BTW...

patafix · Post by **patafix** » 22 Jan 2008, 08:37

I might be missing some theory, but I still have a question :

Why is there only one diode in the feedback path on the FETs instead of two in the original big muff ?

The switch selects between diode clipping and FET overload distortion, right ?

p.eat wrote:Here you go. I can't remember where I found it, but it must have been available sometime as I don't have the CD.

estragon · Post by **estragon** » 22 Jan 2008, 11:37

patafix wrote:I might be missing some theory, but I still have a question :

Why is there only one diode in the feedback path on the FETs instead of two in the original big muff ?

This diode thing bugs me also. Since the capacitor is charged in one direction by the diode, it has no discharge path, except for the reverse leakge current allowed by the diode. IME, the only way for this to work is using high-leakage diodes, i.e. Germanium. When this is engaged, I would expect the bias point to shift when the capacitors charge, and then return slowly to its "normal" operating point as the note dies away.

Is there anyone who has actually built this circuit that can give a clue on how the diode mod sounds?

soulsonic · Post by **soulsonic** » 22 Jan 2008, 20:49

I haven't built one, but I think putting a large-value resistor across the switch contacts may help with the potential problem, so that the cap still has a path, but it's essentially "turned off" as far as it's impact in the circuit.

Post by **modman** » 27 Jan 2008, 11:13

Ok, sorry, yes I found it on the cd now. Want to set that straight, but it still dosn't seem indexed anywhere.

R.G. · Post by **R.G.** » 23 Mar 2008, 12:51

I still have the PCB layout for that somewhere. I automated the switches with JFETs, just for grins.

jg · Post by jg » 24 Mar 2008, 21:15

estragon wrote:
patafix wrote:I might be missing some theory, but I still have a question :

Why is there only one diode in the feedback path on the FETs instead of two in the original big muff ?
This diode thing bugs me also. Since the capacitor is charged in one direction by the diode, it has no discharge path, except for the reverse leakge current allowed by the diode. IME, the only way for this to work is using high-leakage diodes, i.e. Germanium. When this is engaged, I would expect the bias point to shift when the capacitors charge, and then return slowly to its "normal" operating point as the note dies away.

Is there anyone who has actually built this circuit that can give a clue on how the diode mod sounds?

? wut ?
When the diode conducts, it provides negative feedback such that the gain drops to 1. The 1Meg (470K on the 2nd stage) will bleed off any DC from the gate. Drive the gate of the FET high enough and it behaves just like a forward biased diode. I don't understand why you think the capacitor is getting charged by the diode? Looks to me like the diode clips the signal when the gate goes negative and the FET clips it when it goes high enough positive (the FET is basically full on)