Fetzer valve is cool!

[Lonehdrider]

Just wanted to say I was looking for a low gain pedal with more of a bluesy feel to it, tube like sounding. Thanks to the guys at Runoffgroove for putting the Fetzer valve out there, much appreciated. I wired one up yesterday and after tweaking the trimmer got just what I was looking for. After looking at the schematic, I recognized (as it mentioned) that it was a FET version of a tube circuit (I recognized it from the Ruby Tuby which I've been struggling with due to a enormous hum I've yet to deal with).
Parts count is real low, board size is rediculously small and its got good tone (for my needs), great beginner project in my opinion (if you have a meter to set the voltage as specified, although just tweaking it till it comes on will give you sound).
I'm thinking it could work pretty well in the ruby tuby circuitry with a little tweaking for a cool little tube like practice amp using adjustable gains for those wishing more grunt than the Fetzer valve has. For my needs its perfect as it is.
Sound is smooth and rounded, not fuzzface like and works great for a bluesy sound. Thanks guys!

Regards,

Lone

[Jim Jones]

I finally breadboarded one of these about an hour ago...  Lots of potential for experimentation!  

Jim

[petemoore]

That's a good one.. I like Jfet tone character!!!

[Fret Wire]

It's a nice sounding little booster. When you run it through a Fender amp, it makes a nice, "clean" booster that retains the Fender sound. I used the MPF102, sounded best at 5.1v (9.5 on battery). Has anyone tried the Hi-gain input values? I just tried the low-gain values. Maybe in the next day or two, I'll try the high-gain version. Maybe a toggle for both.

[Bill_F]

Has anybody tried this into a Professor Tweed?

[Hungeryhippie]

i tryed it running into a LM386 amp like the little gem.

[slajeune]

Hi Lone,

After looking at the schematic, I recognized (as it mentioned) that it was a FET version of a tube circuit (I recognized it from the Ruby Tuby which I've been struggling with due to a enormous hum I've yet to deal with).

Hum, hey... I can think of a few possible sources:

- Did you regulate and filter your vcc comming from your wallwart?
- I didn't get a lot of hum, but, at first, it squealed almost as loud as a siren.  Putting cap C6 and resistor R7 cleared parts of it.
- The tube that you are using.  It's a fact that some tubes are noisier than others.  I got very good results using 12AX7 from Electro Harmonix.
- The LM386 chip could be an issue.  When I tried the ruby tuby with an LM386-N1, everything was 9V, which is way below the 12V required for the heaters.  Moving to an LM386-N3 solved this odd issue.  This opamp is available at small bear electronics ( http://www.smallbearelec.com ).

The major hit was regulating and filtering the DC.  Other than that, it was very quiet, even though it was on a breadboard.

I'm thinking it could work pretty well in the ruby tuby circuitry with a little tweaking for a cool little tube like practice amp using adjustable gains for those wishing more grunt than the Fetzer valve has.

I think that you are very right here.  A fetzer valve instead of the opamp section might do a few things:

- Sound more 'tubish'
- Easier to build (less parts, no voltage divider r10/r11/c7, etc..).
- Easier to tweak sound wise

Definately something people should try.

Let me know the specifics of your problem with the ruby tuby, I will help as much as possible (I don't have the ruby tuby on my breadboard at the moment).

Cheers,
Steph.