fetzer valve

23 · January 29, 2011, 01:33:27 PM

Has anyone built 3 or 4 fetzer valves in a row? How/what does it sound?
Im bulding a stage 3 booster which is basically a FV with an MPF012 and was wondering what 3 or 4 together would sound like.
kinda like the box of rock idea.

MikeH · January 29, 2011, 02:22:16 PM

Look at any of the other FET based projects at ROG; they all consist of several FET stages cascaded. Of course each stage isn't exactly a fetzer, but they are pretty similar. Any of them would probably sound better than 3 cascaded fetzers though.

petemoore · January 29, 2011, 02:32:16 PM

It's all worth fiddling with.
Jfets @9v...read the Fetzer, see testing jig for biasing and choosing Jfets to put in 'there'. Choose your operating bias [es?].
I saw a Jfet/Mosfet>Jfet/Mosfet design recently, it had a 'staired' power supply, the voltage supply started low at the first stage and went up on successive stages from there.
IIRC it has some buffer/gain stages lined up with fixed and controllable voicings sprinkled in.

Renegadrian · January 30, 2011, 07:04:39 AM

This schem is a double one...Never tried it tho'...

Vitrolin · January 30, 2011, 07:40:09 AM

might wanna filter out some low end whane cascading

panterafanatic · January 30, 2011, 09:59:58 AM

R6 isn't needed, and just cuts signal as is. The highpass filters of C2-VR2/R4 and C4-VR4 have a cut-off of ~72 hertz, excluding the output Z of the JFET stages.

Also, since JFETs are depletion mode devices like tubes, paralleling them should double the gain. Which should put you closer to the gain of 1 tube stage. Half the 1k3 resistor to keep the same DC bias. Twice the number of FETs, twice the current. You may want to match the FETs a bit, but that's up to you.

Renegadrian · January 30, 2011, 11:53:57 AM

I guess TONMANN won't be disappointed if I put his link here...
http://s647.photobucket.com/albums/uu198/tonmann/Double%20Fetzer/

Wild E · January 30, 2011, 12:24:18 PM

My Uncle Fetzer has two Fetzer Valve Revisited in it. When the effect is on Fetzer 1 is always connected. A switch adds Fetzer 2 between Fetzer 1 and the volume pot. At full volume the sound of both is undesirable, but back it down a little and there's some goo distortion to be found.

23 · February 01, 2011, 04:19:49 PM

interesting......... IM boosting a jcm 800 2204 already using an OCD, lovepedal burst eternity clone , or dragonflys VMF (real thick reminds me of some of QOTSA tones). Recently Ive jsut become interested in fets and am trying to decipher my "own" circuit. I would like to achieve more treble out of the amp..... so now interest is on the Omega?

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fetzer valve