HEY BRETT....PIGGYBACK BOSSTONE???

[brian wenz]

Hello Hello---
    Have been messing with the Bosstone circuit and tried  two piggybacked 2N3906's  for the Q2 position [with a 2N5088 for Q1] to see if it would be a little more "germ-like".   I've just started this today, so there's no revelations yet but it does seem to sound pretty good.
Anybody else??   {Brett??]
Brian.

[brett]

Hi Brian
Lately I've been looking for "rules of thumb" for piggybacking different transistors.  

I think that mid-to-high gain transistors like the 2N3906 (and PN200 and 2N5087) can all have 10k (maybe more) between the two emitters.  Where Ic is low (like Q1 of a fuzzface), that cuts hFE to about 1/4 of the non-piggy value.  Where Ic is higher (like Q2 of a fuzzface), it cuts hFE to about 1/2 of the non-piggy value.  So the ideal piggyback resistor is a function of the role the transistor has and how much gain you want.  Pete Moore sockets the resistor, which is probably a good idea.

have fun

[brett]

Hi.
I'd never looked at the Jordan Bosstone before.  Looks cool.

If given a nice tranny for Q2, this might be excellent without the diodes.  Are you planning on building it with or without the diodes?

Q2 is an ideal spot to do some piggybacking for low hFE.

Might have to build one of these.  Thanks.

[brian wenz]

Hello Brett--
    I'm using a Bosstone circuit that already has diodes.
So far, I've tried piggybacking two 2N3906's .....sounds pretty good..   I haven't used any res. between the two, though.  Any suggesrtions??
The stock Bosstone is a GREAT fuzz, so I'm real interested to get a bit more "germ-ness" out of it.  [You can use a regular germ for Q2 but it seems a bit noisey...]
Brian.

[Peter Snowberg]

Has anybody figured out ideal "target" Hfe measurements for a BossTone?

Take care,
-Peter

[brett]

Hi Brian, Pete

Brian, I'd suspect that you're well under 1 mA through that tranny, so 2 x 2N3906s are probably only giving you a hFE of about 15 to 20.  The original germaniums were probably variable devices, but I'd aim for at least 50.  To get to around 50, place a 4.7k, maybe even a 10k resistor between the emitters of the 2N3906 pair.  Higher value resistors reduce the "load" due to the extra junction.

The neat thing is that you can get get germanium gain with silicon quiet.

To get a bit more into the Ge sound, you might roll off some highs.  As RG has said, the old Ge transistors had difficulty covering the whole audio spectrum.  With hFE=100, and Ft = 1MHz, they might have only stretched to 10kHz.  So I sometimes place a small cap (say 100pF) across the base-collector junction of trannies that I want to sound more Ge-like.  That works well in an easy/fuzzface, so it might work here, too.

Let us know how it goes.