Hfe Readings and results?

Started by CodeMonk, May 06, 2008, 11:59:07 PM

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CodeMonk

Ok, I know I should have searched, but its been a really long and stressful say (plus the 2 Valiums I took).
I have built a Jordan Bosstone. Great sounds. I especially love the way it pushes my Flanger!.

Anyway, today I got around to actual measuring the Hfe readings on the 2N2222's.
What is the optimum reading for these, as well as what would various other readings contribute to the sound.
I have several that read anywhere from 246 up to 301, and one that reads 146. It also has a 3906(or 3904?, ins Dragonfly's) can't get a reading on that yet, but thats probably because I cut the leads to short. What about this one.

Thanks.
And sorry again of this has been asked  :P

brett

Hi
For this circuit, it is Q1 that "controls" the tone.  I would use a transistor in the range of 150 to 200, as found in many circuits of this vintage.  High hFEs (e.g. 400) will give a different, high gain sound (gain = 2 x hFE in this circuit).  I've used BD139s with hFEs of 150 and liked the results very much.
cheers
Brett Robinson
Let a hundred flowers bloom, let a hundred schools of thought contend. (Mao Zedong)

CodeMonk

Well, after I wrote my message, I tried several of the 2222's out.
In what way do they control the tone BTW?
I seem to like the one that read at 285 best.
What about Q2, what does that control?

I also changed the voltage input resistor (R1) from 18k to 100k. Gave a grittier sound I think. Kinda like it.
At first by mistake I put a 1m resistor in there (bad eyes). Totally killed the sustain.