Submitted for your viewing pleasure (I hope) ... new fuzz circuit

[Aurin]

I would like, if I may, to submit to you a "new" fuzz circuit.... Most of the resistance values have been borrowed from R.G.'s fuzz face technology article.... However, that said, I filled
out power and tried to implement a new idea -- Maxing the first transistor out at 1/2 of the total voltage (With it being input biased to half of -that-) .

My thinking behind that is that the first transistor should achieve saturation quicker and provide a different type of distortion/clipping ....

I ran the circuit through LTSpice (Awesome program) and got "expected" results so it -should- work. I have NOT built it yet and probably won't get a chance to for a while....

At any rate, here's version 1.0.1. of the Wuzz Fuzz:



Added a 100k resistor in series with the .1uF input cap, should now be high impedance input ;-)

[petemoore]

  I'm pleased 
  Looks [what would be a High Gian] FF 'contained' in an interesting bias arrangement...Cool !!!
  I may have to try that out !!!
  I've got a Parapedal and a Reverb Circuit on the front burners right now.
  I'ts probably possible to mess with the bias even more using a pot [trimpot?] 'as the middle' of a resistor string, to move one of the base up/down...

[Aurin]

Now that I'll drink too. *cheers!* =)

I'm looking forward to building the circuit myself.... just a matter of time and, of course, money.

[puretube]

sorry: probby only worx in spice, or with function-generator: input-impedance = <<500 Ohm...
?

[Aurin]

True enough ... "fixed" right now =) heh.

The trimpot is a nice idea -- would allow more "tweaking" for individual taste... which is of course what it's all about =D .

[puretube]

still don`t see much signal left @ the base...
(100k//500R//B-E, what`s left is being shunted to ground by 1µF...)

[Aurin]

Perhaps I'm not understanding you correctly.....  But... Q1 has a 2.25 volt Bias (from my power network...) to the base ...  Is your concern about loss of signal from the feedback loop (100k resistor connecting Q1's base from Q2's emitter) ?

[johngreene]

I think you intended to have a series resistor on the bias supply for the base of each transistor. The way it's shown connected you have large value caps to ground connected to both. You might get 10Hz through it. Also your input jack shows the negative of the battery connected to the tip instead of the ring.

--john

[Aurin]

Hmm.... I didn't think that mattered from a DC source? If it does then yeah, of course we could up the caps appropriately (Or the resistors -- As either goes up, rolloff freq should go down =)).  No offense John but I'd like a 2nd opinion on that bit just to clarify.

[johngreene]

Don't worry, you can't offend me. 

I seriously doubt that you can get 2.25 volt bias on a transistor with a grounded emitter though.... at least not with a working transistor.  Might be time to look for a new simulation program....

--john

[Steben]

I see people don't read my impedance topic from yesterday.

Input impedance is determined by the transistors. In the case of a silicon fuzz face you have a couple of kohms. Putting a 100k resistor in series with the input only weakens it even more. This is NOT an Opamp, where you toy with resistors to get your wanted impedance. Only way to raise the input impedance is putting a MOSfet in place at Q1 or even a darlington.

I think you should het rid of the second voltage divider (1k,1k,10uf). It only brings trouble. I guess it even breaks the compression effect of the negative feedback loop.

[puretube]

... The way it's shown connected you have large value caps to ground connected to both. You might get 10Hz through it.

if the 10Hz make it thru the 0.1µ beforehand... 

[Aurin]

I think overall the idea is functional but the circuit itself might have some design problems.... I think one major thing I could do would be take the non-inverted output of q1 and invert the output of Q2, that way the feedback doesn't cause a direct path to ground.... at any rate, Wuzz Fuzz WILL live... it's just a matter of time =P

[Steben]

remove the 1k, 1k and 0.1uf biasing and remove the power shortcut link to base of Q2. This makes a stock fuzz face with half power at Q1's collector resistor, your original main idea, no? Which is, IMHO, not bad an idea at all, my friend. Try step by step mods and test them.
I really would remove the 100k input resistor or serieously lower it, this not a FET or Tube input stage; I mean, you will hear when testing...

BTW: the ring sleeve of the DC jack should go to ground also 

[Aurin]

Steben,

Basically, yes, but what about input biasing for Q1? (which is what the 2 1ks + 1uf cap are for - to drop to 2.25 V bias) ....

I think I will have to re-think a few things... And yeah, forgot to paste in a ground symbol for the DC jack, thank you for catching that.

[Steben]

Q1's base is biased (if proper) on a very complicated way by Q2's emitter. Somewhat around 0.5-1Volts with silicon. This brings the input in the non-linear region of Q1's base-emitter, giving the FF its typical second-order harmonics, soft clipping, etc... A fuzz face will sound completely different if not done so.
It's your choice.

[Aurin]

I think I see what you mean.... And yeah, that would make the second voltage drop to 2.25 V un-necessary, then .... I still like the idea of 1/2 powered Q1 though....