Fuzz Face biasing: What does this mean?

Started by mrsuspend, October 23, 2014, 05:17:54 PM

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mrsuspend

I'm trying to properly bias my self-built Fuzz Face but this well known instruction confuses me:
http://www.physics.mcgill.ca/~grant/Stuff/fuzzface.txt
The author states "With a voltmeter, measure the voltage at the collector "c" on the first transistor. Make this be -0.5V under ground by adjusting the 33K resistor"
What is meant by "under ground"? Does it mean 8.5V if the current at ground is 9V?
I'm sure I must have misunderstood but I don't understand what he is trying to say.

Thanks for any pointers! Feel free to use  ::) if I'm being an idiot  :icon_biggrin:

/Magnus

GibsonGM

No shame here, Magnus.  I believe he's referring to a FF that uses a POSITIVE ground, like the originals...PNP germanium transistors instead of today's NPN silicon units.
So he probably meant bias it to read .5 "under" ground, meaning -.5V.

Neat, huh?

In modern NEGATIVE ground units, that would just mean to make it .5V.     
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mrsuspend

Thanks GibsonGM! My FF is positive ground (using a MAX1044) so I guess that would mean -.5V for me then.

Here she is ;D