Old fuzz project from PE

[Mark Hammer]

This may have been posted before (I figure somebody must have stumbled onto it in the intervening 47 years), but looks novel to me. 

Circuit/article by A J Bassett can be found here: https://archive.org/details/PracticalElectronics1967November  It's about 20 pages in.

[armdnrdy]

Cool article Mark.

Here's some data info for the MAT series transistors...might come in handy.

[UKToecutter]

Fortunately I'm not QUITE old enough to remember that first time around........

[LucifersTrip]

I have to admit, I tried to build that one a couple years ago, but I never got it to sound good enough to box. I remember trying to tweak
everything...  Here's the schematic I saved. Maybe I'll try again. I still have all the components in a ziploc bag.

[Mark Hammer]

Different than the schematic shown in the article I linked to.  Not drastically different (i.e., chips instead of trannies), but different enough to possibly make a difference in working vs not.

[midwayfair]

Q2 is pretty different, LT. The Base resistor in the one Mark linked to is only 10K. Also, your Q3 would have been much higher gain.

I can't tell if they're supposed to be germanium or silicon transistors in the original. That could make a big difference.

[armdnrdy]

More info on micro alloy transistors. (toward bottom of page)

http://www.wylie.org.uk/technology/semics/Semics/Semics.htm

[armdnrdy]

Schematic captured.

[LucifersTrip]

Different than the schematic shown in the article I linked to.  \

yes...Thanx. I should have seen the "1967" in the link. I was just in the middle of taking a screen shot, also,
and doing a little research.




http://www.radiomuseum.org/tubes/tube_mat101.html
http://www.radiomuseum.org/tubes/tube_mat120.html

[midwayfair]

What's with the single diodes in each stage here? Clip one half first, amplify and invert, clip the other half? Haven't seen that done before, but Q3 has enough gain that I'm not sure how asymmetrical the signal will be once it's done.

[Mark Hammer]

The 3-knob Tonebender Mk III also has a diode to ground from the base of Q3.

[midwayfair]

The 3-knob Tonebender Mk III also has a diode to ground from the base of Q3.

Right, for temperature stabilization. I guess that's what's going on here.

[Mark Hammer]

I wasn't aware of temperature stabilization being one of the goals, but given that they're GE, that makes sense.  But don't those diodes also provide some clipping?

[Govmnt_Lacky]

I was kinda surprised that this circuit calls for higher gain range transistors in Q1 and Q2 and lower gain range for Q3 

Or did I read that wrong from Larrys data above?

[armdnrdy]

That's what it looks like assuming all of the info is in order.

[midwayfair]

But don't those diodes also provide some clipping?

Yeah. It will sound different without them there. I use them with a lot of circuits (when it doesn't completely bugger things). That's why I was thinking that the circuit might take advantage of clipping half the wave before reamplifying.

Govmnt_Lacky: The lower gain transistor in Q3 is biased really low. It's using the first two transistors to slam it. Similar to what happens in the Mosrite/Orpheum, for instance.

I just noticed how huge C4 is ... there are some weird things going on in this circuit.

[jrod]

Here's goes the same circuit with a few slight changes that Renegadrian has had in his gallery for a while.

http://www.aronnelson.com/gallery/main.php/v/Renegadrian/old-book/04+-+improved+fuzz+booster.gif.html?g2_imageViewsIndex=1

[LucifersTrip]

That's cool...did you notice it was silicon

Also, there's a switch on D2. If you guys read the PE article, they write that if you remove one or both diodes, you can get some type of trem effect.