Fuzz Face mod...not working right?

[phillip]

This afternoon I built another Silicon Fuzz Face with a 47pF in parallel with the 33K resistor on the collector of Q1 (as shown in the Tantalus project at ROG).  I also added a 100pF capacitor across the collector-base of Q2 to smooth it out some.

There's a very definite "fizzling" sound as the note decays, and adjusting the bias on Q2 doesn't help.  The voltages on the collectors are:

Q1 = 1.2V
Q2 = 4.5V

Any ideas if the 47pF capacitor could be causing this annoying problem?

EDIT:  I also just noticed that the "fizzing" sound also accompanies the notes as I'm playing.  The transistors are 2N2222, gains of 115 and 126.

TIA!
Phillip

[brett]

Voltages are good, cap values are similar to those I've used in similar positions....Genuine mystery.

Too much capacitance between base and collector can cause some "overshoot", but I've only seen that on Q1 and with >100pF.  On Q2 it usually works very well.  

How easy is it to swap the trannies?  2N2222s are noisey, strange things.

sorry I couldn't help more

[phillip]

The transistors are both socketed.  I've tried 2N4401, 2N2222, 2N2222A, BC108B and BC109C.  So far the 2N2222s have been the quietest of the bunch...the higher the gain got, the worse the fizzing sound got.

I also chaged the 100K feedback resistor to 47K, but I don't think that would cause any problems.

Phillip

[Ghandi]

Hey Phillip,
Yesterday I build a fuzz face and I have exactly the same problem as you had!
"fizzling as the note decays!"
The fizz is worse when I play a cord than when I play single notes!?
Very strange!
It's also a germanium face with leakage and gain selected transistors, I also changed them to another selected pair set the collector voltage on Q2 back to V/2 but the fizzling remains!

Have you solved the problem?
Or has anybody else an idea?

Thanks!

[petemoore]

Hey Phillip,
Yesterday I build a fuzz face and I have exactly the same problem as you had!
"fizzling as the note decays!"
The fizz is worse when I play a cord than when I play single notes!?
Very strange!
It's also a germanium face with leakage and gain selected transistors, I also changed them to another selected pair set the collector voltage on Q2 back to V/2 but the fizzling remains!

Have you solved the problem?
Or has anybody else an idea?
 What kind of caps are you useing for the 'unusual' placements ? I noticed small value rolloff cap types can sound different, I used a brown cap at Q2 C/B and noticed the high end, though rolled off a bit, and oscillation squelched, had a little fizz in it. Does it Fizz with the cap out?
Thanks!

[nightingale]

i know the sound.
i call it intermodulation? i first heard it when i built my 18 watter clone. then I noticed the exact same sound coming from a couple of low gain si FF's that i built using the 2n2369 trannys. [hfe 75-80].

here is a good link that describes how it happens in tube amps from the 18 watt site: http://18watt.com/modules.php?name=Downloads&d_op=getit&lid=125

as a matter of fact, i still have a little bit that exists in my 18 watter. i am going to try some different voltage zeners.

i would describe the sound as a real nasty fizzy phasory type of buzz.


hope this helps man,

[Fret Wire]

It's also a germanium face with leakage and gain selected transistors, I also changed them to another selected pair set the collector voltage on Q2 back to V/2 but the fizzling remains!

Post all the voltages for Q1 & Q2. What schematic are you using? Are the trannys PNP or NPN? Is it grounded pos or neg?

[RedHouse]

phillip
Any ideas if the 47pF capacitor could be causing this annoying problem?

Does it do it without the caps im the circuit?

I use both those in my FF's and have no fizziness issues.

[Jason Stout]

How does the layout differ from your past builds?

[Peter Snowberg]

Could there be a leaky cap?

[petemoore]

FF's..I had a funny one...worked on it a bit [couple hours] built another in 20 or so minutes!!!
 Wouuld be cool to see if you can figure these ones out for reference though...
 Here's my take
 Something wierd like a funky component, I think you know how to solder so well skip 'cold solder'...you tried different Q's,...hmmm  Caps...did you try a different Emitter bypass cap?
 Assuming
 Battery voltage is 'up'
 Wrapper wiring probly isn't it
 Only so many parts on these things...

[phillip]

I never got that mod to sound right...that crackly sound never went away.  I think that the circuit just didn't like the placement of that capacitor or something.

Here's what I think is the ultimate answer to the Silicon Fuzz Face circuit, the Axis Face Revision 3:



Give it a shot...I think you'll like it.  If the circuit doesn't have enough high-end response, try replacing the 0.047uF capacitor that parallels the 1K2 resistor with a 0.033uF...that will increase the highs being passed.

If the circuit is too "nasal" sounding, you can increase the value of the input capacitor so that the bass response is gradually increased.

Phillip

[Ghandi]

OK!
I changed every component in the face any the fizz is still there!
(In fact the fizz sounds more like a broken speaker.)

But I have come to the conclusion that it must be normal for the fuzz face cos my goal was to build a fuzz with overdrive characteristics at low drive settings!

With a full germanium face I think this is impossible, am I right?  
I mean at max fuzz there was no problem at all with the little beast!

Nevermind, thank you all for sharing my fuzziness!

[Ghandi]

Does someone of you know some "tricks" to make a fuzz face more useable for lower drive settings?
I mean its so touch sensitive but not really "clean" at low drive!?