Update at runoffgroove.com: A Closer Look at the Fetzer Valve

[B Tremblay]

We've updated and expanded the Fetzer Valve article.  Check it out: http://runoffgroove.com/fetzervalve.html

[WGTP]

WOW 

[Arn C.]

Great Job!   

Thanks for all the hard work!!!

Peace!
Arn C.

[Geoff Hunter]

Really good read!

Thanks!!!!!

[RDV]

I've been wondering what you've been up to.

Hmm.

RDV

[Quackzed]

the fender input stage is a huge tone mojo building block. It's cool you guys are digging in to get it to the next level... Definately seems like this little circuit will be enjoyed. for such a small little circuit the fetzer valve definately delivers alot of that fender sparkle!

[Peter Snowberg]

 

Top notch, as always. 

[mutant_guitar]

wow...

i had to read through two time just to get a basic understanding of what was written...  now my brain kinda hurts a little.

[MartyMart]

Great guy's, wonderful explaination ... I learned some more about Jfets today
I'm running a "Hamptone preamp" through a kind of Fetzer circuit, sounds wonderful

Marty.

[markm]

Very informative fellas, NICE work.
I going to read it through a couple more times to understand it more.
Truly fascinating.
    MarkM

[Gilles C]

Very nice reading.

Btw, a 22nF input cap is mentionned in the article. I would not see the need for it with a guitar, but in case someone want to add one, what would be the best place to add it? I mean, right at the gate, before or after the 33K? I think I once read it was making a difference.

Your timing is good, because I began experimenting on the best value for Vd yesterday. I'll have another reason to work on it tonight...

Gilles

[gaussmarkov]

thank you!  there is lots to chew on in there.  what a great example to try to follow. 

[seanm]

Great article. Nice job!

[B Tremblay]

On behalf of the runoffgroove.com team, thank you for your enthusiastic support!

Also, PCB layouts have been added to the article, courtesy of Pablo de Luca (aka Gringo).

[petemoore]

  That's going to help.
  Seriously well written info rundown.
 

[stm]

The Fetzer Valve Revisited & Deluxe can be thought both as a building blocks and as circuits.  Consider the following hints:

1) The Fetzer Valve Deluxe powered from 18V can make a great booster.

2) Moreover, if a little bass slimming is desired, it is a matter of reducing the output 47n cap to 10n or even 6n8.  The latter value will produce a frequency response pretty close to the Marsha Valve. Now you may consider a 6n8 cap with a bypass switch that adds 47n, being capable of covering both responses.  Maybe this mod should be added to the Fetzer Valve Deluxe circuit.

3) Don't overlook using the Presence capacitor.

4) The Fetzer Valve Revisited used without the volume pot at the end can be placed whenever a moderate gain recovery stage is needed, for instance after the BMP tonestack.

5) One last point to consider: it is advisable to always include the 33k/220p elements at the input in order to prevent detecting AM radio stations.  When used in between gain stages, the 220pF cap may be increased to as much as 1nF in order to tame shrillness, if desired.

Cheers.