Ok I can't for the life of me figure out why the power supply is having the plus go to the ground.



It's from http://www.geofex.com/Article_Folder...ace/fftech.htm that site.

Also why is there a Polar Capacitor from the signal...and how does the signal get biased...or does it?

 

Nothing with that.
There are positive or negative as ground or dual and more supplies.
It's designer choice.

Polar capacitor and diode are different.
Capacitor still work with reverse polarity for small signal (milivolts or even volts).

 

Ok. Well why is it polar? Yet the other 0.01uF is not?

 

The original Fuzz-Face circuit used old fashioned germanium PNP transistors. Their circuits frequently had a positive ground.

Have you seen how distorted it is? It has clipping at the top and bottom and the bottom has much more clipping. So it has odd harmonic distortion from both top and bottom being clipped and has even harmonic distortion because they are not symmetrical.

A little 0.01uf capacitor is never polarized. A big 2.2uF capacitor is frequently a low cost polarized electrolytic type. The input capacitor will have its + terminal at 0v and its - terminal wikll have the negative base voltage of the first transistor on it.

Negative feedback biases the circuit a little.

Here is a simulation of the circuit slightly modified and with silicon NPN transistors:

Attached Images

Sim- Fuzz Face.PNG (22.9 KB, 24 views)

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Uncle $crooge

 

Some old cars had a positive earth but it caused problems with corrosion so the idea was abandoned.

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So it does essentially cut off most of the bottom half then.

 

It shouldn't, it's just an over driven amplifier, if it's clipping the bottom so much more like that, then it's biased wrongly. But bear in mind Audioguru has used different transistors, and the resistor values may still be those for the original germanium devices.

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They wanted the Fuzz Face circuit to clip the bottom much more than the top so it produced even harmonics in addition to the odd harmonics from having both top and bottom clipping. Then it had harmonics all over the place.

The circuit we are talking about and one of many mods to it including the version with silicon transistors came from this Fuzz Face article:
http://www.geofex.com/Article_Folder...ace/fftech.htm
The article analysed that it has assymmetrical clipping.
(It used AC128 germanium transistors. Remember them?)

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Uncle $crooge

 

Still got some!

Although they were mainly output transistors for small amplifiers (in push pull with the AC127, and later the better spec AC176), such as used in radios etc.

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I think the AC128 was cased in glass like a light bulb, then surrounded with thermal grease, then covered with the metal can.

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Uncle $crooge

 

Yes, it was like an OC81 wearing a metal can!. The OC81 was the higher power output version of the classic OC71.

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