Yet another Fuzz

[col]

http://s159.photobucket.com/albums/t159/col07768/?action=view&current=highoutputfuzz.jpg

This is a modified version of the 'High output fuzz' in the book Hi-Fi, PA, Guitar and Discotheque amplifier design Handbook by B B Babani (from 1971). It should be Ok to post as it has several differences to the original, but if anone wants me to remove it I will.
I added the trim pots as when built with the original values it didn't work and this was due to mis-biasing of the transistors.The values of the trim pots were settled on after trying a 4k7 pot in the place and seeing where the values lay. The germanium transistor needs biasing first followed by the last one. I did all biasing by ear.
I chose the OC172 as I had a bag of them that I hadn't used. Any other PNP Ge should work but it might need a different value trim pot. Attaching the shield to ground definately helps with hiss in this instance. I added the diodes and depth pot to give it a bit of a harder edge to the fuzz. You can dial in as much or as little as you like with the 4k7 pot.
So how does it sound? It has a very good fuzz sound but it's slightly lacking in sustain compared to what I usually like. There is aslo a vary good if bright Ge fuzz sound available direct from the collector of the Ge transistor. It might be possible to put a pot or a switch between this and the output and vary the sound.

[petemoore]

  I've seen this before, when it looks like the middle transistor here is 'upside down.
  A pnp in a neg gnd circuit.
  Can't really be baised unless forced so by the previous transistor? or doens't have a 'linear range as such...I''m just trying to understand it, and guess it is being 'mis-used' intentionally.
  I've had FF's which sounded really smooth and fuzzy [misnomer...eh] but only reallly 'lacked' output, they were 'fixed' by flipping the transistor around..we used to miswire circuits and get great tones, fix them and wonder if it didn't sound better 'broken'.
  That's the long way around explaining...what's going on herew/Q2?

[col]

The book says the circuit was designed specifically by RCA to use their transistors and offers some alternatives but does state that they may not work correctly. I wonder how much difference the variation in the RCA products made. I just chose the nearest I had available to them. The Jordan Bosstone uses a pnp in a neg ground circuit in a similar way and I have seen others that do this. I don't know what I was expecting, possibly something tonebenderish. I might try a few different Ge transistors and see if the gains affect the sound in any way.

[col]

I just found the original circuit scanned in here:

http://www.triodeel.com/fuzz2.jpg

Someone might have better luck than me with the original values

[Dragonfly]

Its the rca fuzz that Jack posted as the "sixties fuzz". IIRC, jmusser built one and did some mods and debugging.

http://www.muzique.com/schem/sixties.gif

http://www.diystompboxes.com/smfforum/index.php?topic=14790.0

http://www.diystompboxes.com/smfforum/index.php?topic=38343.0

http://www.diystompboxes.com/smfforum/index.php?topic=38450.0

maybe this will help....