Fetzer Valve Question

[ildar]

From ROG: It can be easily modified to reproduce the higher gain input by moving the 1M resistor to the input and changing the 68k to a 33k resistor.


Does this mean 1M to ground at input, then the 68k (33k), or does it mean the two values in series, or are they parallel?

[ildar]

Anyone?

[RLBJR65]

http://www.runoffgroove.com/fetzervalve.html
1M to ground at input, then change the 68K to 33K, Yep I think thats right.

[petemoore]

http://runoffgroove.com/fetzervalve.html

[ildar]

Thanks for your replies. I've looked at the layout and the mod suggestions, that's how I was confused in the first place. The suggestion for the higher gain mod is worded ambiguously. Again, for this modification, does the 1M resistor go from input to ground before the 33k, or are they in series or in parallel?

[squidsquad]

Yes...the 1 meg goes from input to ground.  As if (looking at the schem) you cut it & pasted it in front of the resistor....an inch to the left.

[mojotron]

I have liked to do something like this with that kind of circuit:

1) bypass (short) the 68k resistor

2) use a .5uF - 1uF cap on the output cap

3) put a 1k-2kA pot in series with the 22uF cap

The additional 1k-2kA pot then becomes a gain pot. IMO, this circuit retains a fendery sound when you roll back the guitar's volume and gets more of a overdriven champ sound when you reduce the resistance on the gain pot, but you really need that 1M resistor in there on the front end. I use something like this as an input stage on the Mojotronics Saucy Jack OD pedal.

[ildar]

Thanks people. Maybe it should have been obvious, but I find the text to be less than precise regarding that resistor.

[ildar]

Got around to building this, and one last question: I'll have to ground the gate pin of the FET, even though the 1M resistor has been relocated, yes?

[vanhansen]

Nope, the gate doesn't get grounded.  The source gets grounded.  Build it as you see it on the schematic, just sub in the 33k for the 68k and move the 1M to ground resistor to be before the 33K and you're done.