Thoughts on higher hfe germ fuzz faces.

Locrian99

Locrian99

Well-known member
Obviously I can socket/breadboard which I’m going to do anyways. Just curious on what others have experienced with q2 hfe being 150-170. How much have you raised q1?

Normally i do 70-85 q1, 120-135 q2.

Have you ran into bias issues?
Im assuming its a bit more compressed?

Just curious on experiences here.
 
For DIY fuzz face, I think breadboard is essential. I have made Si Fuzzes with hFE like this, and I think the thing to watch for is the circuit going into oscillation feedback at high Fuzz setting. My humble opinion (ask me physical chemistry, if you want not-humble opinions) is that the cure is to put a series resistor inline with the Fuzz controls capacitor to ground so there is always some resistance to ground.

Be willing to play with any of the resistors (beyond the standard "bias" resistor for Q2, and maybe tweak the input and output capacitors to adjust the bass.
 
gtfields13 said:
For DIY fuzz face, I think breadboard is essential. I have made Si Fuzzes with hFE like this, and I think the thing to watch for is the circuit going into oscillation feedback at high Fuzz setting. My humble opinion (ask me physical chemistry, if you want not-humble opinions) is that the cure is to put a series resistor inline with the Fuzz controls capacitor to ground so there is always some resistance to ground.

Be willing to play with any of the resistors (beyond the standard "bias" resistor for Q2, and maybe tweak the input and output capacitors to adjust the bass.
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I use a trim pot with a bias pot. I will throw one on a breadboard, I’m just curious what people have experienced with them.
 
I really like the Si Fuzz Faces with higher gain but the Ge Fuzz Faces I've really enjoyed going the opposite direction with low gain hFE in the 50-70 range for both.
 
Locrian99 said:
I use a trim pot with a bias pot. I will throw one on a breadboard, I’m just curious what people have experienced with them.
Click to expand...
If you aren't already, try biasing with a trim pot on either the collector of Q1 or the emitter of Q2 (with the fuzz pot wired as a variable resistor in series with the emitter bypass capacitor). It won't change the tone or output volume nearly as much as using a trim pot on the collector of Q2.

To your main question, I have built higher hFE fuzz faces before and they sound great. From a tonal perspective, the difference between Q2 hFE being 140 vs 170 isn't all that dramatic. It's a different story when Q2 hFE is above 250ish or below 70. Low hFE tends to be darker/warmer and clean up better, higher hFE tends to be brighter and less inclined to clean up when you roll down the volume knob on your guitar. From a biasing perspective, I'd worry less about measured hFE and more about leakage.
 
PedalBuilder said:
If you aren't already, try biasing with a trim pot on either the collector of Q1 or the emitter of Q2 (with the fuzz pot wired as a variable resistor in series with the emitter bypass capacitor). It won't change the tone or output volume nearly as much as using a trim pot on the collector of Q2.

To your main question, I have built higher hFE fuzz faces before and they sound great. From a tonal perspective, the difference between Q2 hFE being 140 vs 170 isn't all that dramatic. It's a different story when Q2 hFE is above 250ish or below 70. Low hFE tends to be darker/warmer and clean up better, higher hFE tends to be brighter and less inclined to clean up when you roll down the volume knob on your guitar. From a biasing perspective, I'd worry less about measured hFE and more about leakage.
Click to expand...

Spot on! Higher HFE on Q2 also makes the germanium FF clean up more gradually and don’t get that glassy cleans (and I personally prefer the more gradual cleanup)
 
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