what fuzz could this be based on?

[Gus]

I just made a DC sim of a Silicon fuzz influenced by an old Ge fuzz circuit.
Output volume section is missing and caps can be adjusted in value. The bias control moves the Q2 collector over a wide range.
Not built yet.
Add lowpass filtering if needed
Q3 can be adjusted for the collector voltage you might want
Did a google search did not find a Si version like this has this been done? EDIT found this link http://www.diystompboxes.com/smfforum/index.php?topic=83647.msg695432#msg695432

[Kipper4]

Maestro FZ1 ?

[midwayfair]

Maestro FZ1 ?

Or TB MKI.

[Gus]

MK1
Anyone build the circuit mac posted in the link?

[Kipper4]

Nope not I Gus. maybe one day I'll get around to doing another fuzz.
Is it a good one?

[mac]

Gus,
I posted this Silicon TB MKI a few years ago,
http://www.diystompboxes.com/smfforum/index.php?topic=101610.0



The trimmer can be an external pot to adjust Q3 voltage at will.
I added series resistor between stages.

mac

[Gus]

mac

I missed that post.  Nice looking circuit
I did find another post of yours that I added to my first post.  I see you added another bias adjust at the third stage I am guessing because it is a grounded emitter.
You also have series resistors to the base of Q2 and Q3. 
I noticed in sims and builds it can be tricky to bias a grounded emitter. 
I used a emitter resistor to use fixed voltage divider values for the third stage.

Gus

[mac]

I see you added another bias adjust at the third stage I am guessing because it is a grounded emitter.

Yes, the grounded emitter makes bias more tricky.
But I added that trimmer (it should say *an external pot*) to adjust the collector at will from 7v to 9v with the specified hfe.
Q2 pot changes bias and fuzz. I thought it would be nice to change Q3 bias too.
Besides I tried to keep things as close to the original as possible.

You also have series resistors to the base of Q2 and Q3.

To avoid loading of the next stage. IMHO it sounds better this way.
And as I wrote in the post, I had high freq feedback through the roll off and interstage caps if those resistors are not present. Some resistance breaks the path from Q3C to Q2B.

Nice looking circuit

mac

[Kipper4]

My layouts done, my irons hot. I'm gonna do it Gus. I'll report back.

Edit;
Using 2n3904 for Q2,Q3 Smart move?
Dont have any 2N2222s

[mac]

my irons hot

mac

[Kipper4]

Im a little confused about my voltages at Q2
c 9v
b 0v
E 0v

is it even on?

surely i should be getting around 1v at the base of Q2.
I did a quick and dirty calc of the 330k (r8)  32k (r9+r10) voltage divider to derive the 1v.

Most of the other voltages on the other bjt are similar to gus's sim.
Remember im using 2n3904 for Q2 and Q3.

I'm using a 22uf polar cap at c2 (Schematic form gus first post)
anode to the source of Q1, cathode at the base of Q2.

I wonder if it would have been better using a 50k trimmer (R9 and R10) instead of a 100k like i did.



Geez this things loud. Quite well rounded for a fuzz too. Not too woolly on the low end.

[Gus]

Kipper4

When I simmed this with 2N2222s a fixed 22k and a 0 to 100k variable resistor showed a good range of voltages at Q2's collector. 
It reads like Q2 did not have a range of collector voltages like in the sim
Biasing a grounded emitter can be tricky.
What was the hfe of Q2?
The caps are from looking at MK1 schematic on the web.
I have not got around to building this.
Thanks for building this and the feedback.
what did you end up with around Q2?

[PRR]

> my voltages at Q2 c 9v b 0v

R8 open.

B-C shorted.

[Kipper4]

C B Don't you mean B E Paul ?
Spot on it was a solder bridge. I'm gonna sort it now.
I'll repost voltages soon. Cheers.

[Kipper4]

Q2
C 6.7v
B 0.65v
E 0v
thats better
I think i need to throw in a few power smoothing caps its very noisey on the test rig. Open to the elements.


Q2 Hfe 365 Gus

[Kipper4]

Did I say it's noisy?
Well not in a good way, setting the bias with my R10 ,100k trimmer on q2 is like the old days radio tuning. When radios still had bottles

[Gus]

Try a transistor that's beta/hfe is 200 or less for Q2

[Kipper4]

 Thanks Gus will do

[Kipper4]

I can bias Q2 with the 100k R10 that's not a problem. Despite note using the recommended 22k and trimmer. Thinking about it I might have been better using a single 50k trimmer to set the Q2 biasing.

I tried various bjts even a 2n2369 with hfe's 28.
Yes it's noisy but I'm getting over that. It's a fuzz after all.

There's a pronounced low octave sound.

I temporarily put a 100uf power smoothing cap in. It's no less noisy
And I have a 100R resistor on the +9v power rail. A habit I'm trying to use as a matter of course in fuzzes since a prior recommendation from a forumite.
For info I took out Q3s emitter bypass cap 47uf.
I'm thinking I might try a 2n5088 in Q1 instead of the 5089.
In an effort to make it less noisy I fitted a small ferrite bead to both in and out wires.
The pcb is still out of the box which migh contribute to the noise.
I'm sorry if I appear to be saying noise too often. I'm pretty certain it's coming from the power rails because of the change in freqauncy when biasing Q2.

Can I ask why no output cap?


Just messing around and learning.
Enjoying the ride too truth be known.
Thanks Gus,Mac and PPR.

[Gus]

in my first post "Output volume section is missing".  I left out the coupling cap and other stock parts. The screen shot is the buffer distortion fragment of the circuit.

I am wondering why a 500k volume and series 2.2meg resistor was used in the MK1?

When I get around to building this I am going to try a 1uf and 50K volume control.