What is a fetzer valve?

Noplasticrobots · March 12, 2006, 01:51:12 AM

The name says it all...what exactly is a fetzer valve? From what I gather it's a generic name for any miscellany that you don't know the proper name for; like the scene in Fletch. Am I right or did I just make a complete ass of myself?

lethargytartare · March 12, 2006, 02:52:19 AM

Not complete...

It's a booster. At least that's what it was when I built one.... and I think (it's been a while) it's intended to be a fender-feel booster.

http://runoffgroove.com/fetzervalve.html

try it -- it's pretty cool!

ltt

Quote from: Noplasticrobots on March 12, 2006, 01:51:12 AM
The name says it all...what exactly is a fetzer valve? From what I gather it's a generic name for any miscellany that you don't know the proper name for; like the scene in Fletch. Am I right or did I just make a complete ass of myself?

B Tremblay · March 12, 2006, 07:56:41 AM

Quote from: Noplasticrobots on March 12, 2006, 01:51:12 AM
From what I gather it's a generic name for any miscellany that you don't know the proper name for;

Yes, that's the colloquial definition. I thought it was a good name for a circuit based on that, but what really clinched it was the phonetics: "FETs or valve?"

Noplasticrobots · March 13, 2006, 02:12:23 AM

HA!!!!! Holy shit that's clever! I didn't even get the "FETs or valve?" joke. Brilliant. that's why you get paid the big bucks.

mojotron · March 13, 2006, 03:06:41 PM

I use the Fetzer circuit to replace the input stage on other circuits to give them a fenery sound - so I see it as more of a building block for an integrated design rather than a stand alone circuit. One of the things I was thinking of doing is to use a Fetzer like circuit to feed a fender-like phase splitter stage with some degenerative feedback (to develop more of an AT7 - clean headroom sound) - softening the highs a bit - and feed this to either something like a power amp (lm386) or perhaps a mosfet to more of a complete fendery sound.

I suppose with a bridged set of lm386s you could get sort of a fendery SS practice amp pretty easily. Also, if you add back-to-back Fetzers and add 50 ohms of degenerative feedback on the source of the 2nd stage - and add a simple bass/treble circuit in between stages, then feed this into an lm386 you would pretty much have like a SS "champ" sound.

Anyway, what you can do with the circuit as a building block is pretty cool - playing with different FETs is important to the process.

Noplasticrobots · March 14, 2006, 11:51:06 AM

I just built the circuit as a stand alone pedal. I figure I can plug it into any breadboarded effect to combine them to get a generic sound and then re-breadboard the entie circuit if I like it.

phaeton · March 14, 2006, 12:05:12 PM

Anyone got any data (real or speculatory) on the power consumption of the fetzer valve? I'm willing to bet that a 9V battery would power this circuit nearly forever. As Mr. Tremblay says, it'd make a great onboard booster for a 'weak' guitar, such as a Strat.

Ge_Whiz · March 14, 2006, 12:54:49 PM

Certainly less than 1mA. Add an indicator LED, certainly more than 11mA. Moral? Ears are cheap, eyes are expensive.

Noplasticrobots · March 14, 2006, 01:20:06 PM

I tried using at as input to a bazz fuss but I could not get it to work. I figured the two were simple enough circuits for me to combine, so I took the output from the fetzer valve and ran it into the input of the bazz fuss but got nothing! What'd I do wrong?

Threefish · March 15, 2006, 02:06:54 AM

QuoteI just built the circuit as a stand alone pedal.

You say you built the fetzer as a stand-alone...but did you get it working?

QuoteI tried using at as input to a bazz fuss but I could not get it to work

Do both of them work individually on their own?? Try them each by themselves. Sounds to me like one of them isn't working, so it seems to you like they both aren't.

Noplasticrobots · March 15, 2006, 12:45:16 PM

Yeah, I got the Fetzer Valve working, but I don't know what was wrong initially. I had taken it off the breadboard for a few days then when I retried it it worked.

To clarify, if the Fetzer Valve is my first stage of a circuit, I would take the output from Drain and run it to the Base of the NPN, right?

PenPen · March 15, 2006, 02:23:29 PM

Quote from: Noplasticrobots on March 15, 2006, 12:45:16 PM
To clarify, if the Fetzer Valve is my first stage of a circuit, I would take the output from Drain and run it to the Base of the NPN, right?

You did put a coupling cap between them, right? Thats the only thing I could think of causing a problem. If you don't, then the DC from the drain would be biasing the BF on, in addition to the bias voltage from the BF messing with the drain bias on the FET.

Noplasticrobots · March 15, 2006, 02:57:53 PM

No, I didn't put a coupling cap. Would an example coupling cap be the 10 uf cap between trannies on the Buzz Box?
http://home-wrecker.com/buzzbox.png

How do I calculate the capacitance needed for a coupling cap?

PenPen · March 15, 2006, 03:08:53 PM

Yes, that is an example of a coupling cap. The cap blocks DC from effecting the bias of each gain stage.

Value isn't incredibly important, you can put any value that you like, but remember that you want it to be reasonably high, say 0.1uF or higher, otherwise it will cut out the lows in the signal. A nice big 10uF would allow all frequencies. Experiment with this value if the result is a bit muddy.

Let us know how it goes.

Noplasticrobots · March 15, 2006, 04:05:46 PM

Just go it on the bredboard and it's working! Of course the sound leaves something to be desired. I'll be doing some experimenting for sure!

It seems like no matter what tranny I plug in (2N5088, MPSA13, 2N3904, 2N5816, etc...) I get a sort of gated farty sound. Nothing extreme, but it's not something that compliments the Fetzer Valve. I'm really pleased with the Fetzer Valve alone though, so either:

A: I'm lame
B: I'm trying to fix something that's not broken
C: I have no real clue as to what I'm doing, or
D: All of the above

(If you guessed, D you're correct!)

Nonetheless, I will keep experimenting! thanks for the help.

PenPen · March 15, 2006, 05:19:33 PM

With all due respect to the BF ( I love that circuit and the sound it makes ), I wouldn't think it would make a good compliment to the FV. BF is fuzzy, buzzy, and farty all by itself, all you're really doing is driving it with a nice clean Fendery sound. Which is going to sound buzzy and farty.

Now that has me thinking. I wonder how it would sound if you paralleled the two, ran them into a buffer, with a blend pot between them? That may sound good.

JimRayden · March 15, 2006, 06:07:10 PM

Quote from: PenPen on March 15, 2006, 05:19:33 PM
Now that has me thinking. I wonder how it would sound if you paralleled the two, ran them into a buffer, with a blend pot between them? That may sound good.

Am I hearing a Gretsch Contro-Fuzz?

Check out home-wrecker.com, there should be clips of that kind of box. Quite ugly in my very personal opinion.

-----------
Jimbo

mojotron · March 15, 2006, 10:06:56 PM

Quote from: Noplasticrobots on March 15, 2006, 04:05:46 PM
Just go it on the bredboard and it's working! Of course the sound leaves something to be desired. I'll be doing some experimenting for sure!

It seems like no matter what tranny I plug in (2N5088, MPSA13, 2N3904, 2N5816, etc...) I get a sort of gated farty sound. Nothing extreme, but it's not something that compliments the Fetzer Valve. I'm really pleased with the Fetzer Valve alone though, so either:

A: I'm lame
B: I'm trying to fix something that's not broken
C: I have no real clue as to what I'm doing, or
D: All of the above

(If you guessed, D you're correct!)

Nonetheless, I will keep experimenting! thanks for the help.

This is a self biased gate circuit - requires a n-channel jfet (J201...) - you are using BJTs that require the base to be biased... Try a J201 or another n-channel jfet...

News:

What is a fetzer valve?