Friday, May 15, 2020
German Tooth Fuzz
If you've got a bunch of NPN germanium transistors kicking around, this Fuzz Friday's for you. Here's Zzoyd's adaption of the Basic Audio Spooky Tooth for use with germanium transistors. The first 2 stages each use 2 germaniums in a Darlington pair, with the 3rd stage using either a 2N7000 MOSFET or an NPN silicon transistor (pinout is CBE on Q5 if using a BJT in place of the MOSFET). Trimmers are for biasing the Darlington pairs, so adjust till it sound right to you.
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Very cool post! I expect nothing less if Zzoyd had anything to do with it.
ReplyDeleteWhat type of diode is D1 please?
ReplyDeleteI used a socket. Right now I've got a 1N5817 in it. Sounds good. Mark it verified.
Deletehttps://freeimage.host/i/JEaDl9
DeleteHopefully Zzoyd will chime in re the diode. Thanks for verifying! Looks great
DeleteDavid, you are the best!
DeleteI took 4148
ReplyDeletehttps://youtu.be/0RXQV46LE7Y
ReplyDeleteDemo, how lt sounds
Would a loop recorder pedal be possible to build? I searched the internet and found nothing, why? :(
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteI built this and it sounds killer with verrrry low hfe/leakage germs (it wasn't too picky once I dialed in the trimmers). What is the purpose of the switch? I can't tell much difference except when Texture is very low.
ReplyDeleteSo the Spooky Tooth is based on the Fuzzrite topology, which is two cascaded gain stages with a pot (labeled "texture" here) that allows you to blend the signal from the first gain stage with the signal that's been through both. Since the two gain stages are out of phase with one another, you get cancelation of certain frequencies which causes really cool sounds at some settings but can also sound thin and hollow. In this version of the circuit, the signal from the first gain stage has to go though D1 to get to the texture pot, so you only get the part of the waveform that is above the forward bias voltage of the diode (so you get a little less than half the signal). Any noise or trash signals that are below the threshold at which the diode conducts will also be gated out. The switch shorts the signal path across the diode so you get the full waveform from the first gain stage. That explains why it doesn't make much difference unless the texture is set so that most of what you hear is from the first gain stage.
DeleteBoth germanium gain stages are set up as darlington pairs, in which both the gain and leakage of the first transistor is multiplied by the gain of the second transistor. That explains why the best results are when using low hFE, low leakage transistors.
Yes, you are right, diode working only from 7 to 12 o'clock Texture.You know why
DeleteAll great info and makes perfect sense. As for the phasing, with the switch off you get a dead spot in the center of the texture pot. Clever idea to circumvent that:)
ReplyDeletewhat do you mean about |dead spot in the center of the texture pot|? I have sound everywhere, no dead zones.
DeleteHi, and thank you so much for really great work.
ReplyDeletePlease add to FuzzFriday rubric this one:
http://tagboardeffects.blogspot.com/2017/07/krank-krankshaft-overdrive.html?m=1
I think, is so different, that KDM, right?
Million thanks,
just another tube screamer! Make green Rhino & be happy!
Deletesir wht is the voltage of 100 uf capacitor??
ReplyDelete16v or more.
DeleteHi, what hfe the germanium transistors should have, please. Thank You
ReplyDelete