Sziklai pair as Q2 in a Fuzz Face type circuit

[m7b52000]

If I can find a suitable pair of low gain resistors is there any sense in using them as an NPN/PNP Sziklai pair for Q2 in an otherwise orthodox NPN silicon fuzz face circuit?

[antonis]

low gain resistors

Is there such a bird..?? 

You can't implement a Sziklai pair in a dual npn BJTs FF circuit simply because there isn't such a topology in the particular circuit..
FF Q1 & Q2 aren't wired as Darlington configuration..
(2 discrete Collector resistors..)

edit:

Sziklai pair for Q2

My bad..

[m7b52000]

The Sziklai pair effectively become 1  transistor with a single E, B and C. So, can it be used as Q2 in a fuzz face?

[R.G.]

Yes, it can.
However, the question of why you would want to is valid. A Sziklai pair is a 100% feedback amplifier. You get a lot of current gain out of the transistors. It's not quite hfe1 times hfe2 because the first transistor is working at 1/hfe2 currents and the gain of a bipolar goes down at low currents, but the product is still big. But the 100% feedback means the two transistors are using the gain to cover up any quirks and nonlinearities of the transistors. There is a chance it hides something you like about the sound.

Compound transistor hookups work pretty good in silicon, but not so good in germanium, as any leakage of the first transistor it amplified by the gain of the second transistor, so leakage becomes serious in germanium compounds.

I'd be interested in what you turn up. let us know.

[m7b52000]

What about a very low hfe silicon NPN (no leak) as the first in the pair then a low gain germanium PNP as the second in the pair. My understanding was that the pair acted as a new NPN transistor without amplification of leakage. I have used this successfully in a simple 1 transistor fuzz (bass/bazz??) but not in a FF type circuit. I'll see what happens if I can find a pair that produce a total hfe of less than 150...

[smallbearelec]

If I can find a suitable pair of low gain resistors is there any sense in using them as an NPN/PNP Sziklai pair for Q2 in an otherwise orthodox NPN silicon fuzz face circuit?

Yes. I did a couple of articles (with help from R. G.)
http://diy.smallbearelec.com/HowTos/BreadboardRMs/BreadboardRMs.htm
http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

that should help you. More than anything else, the key to success is finding a few NPN germanium devices that are both low-gain and low-leakage. Fortunately, in my experience, the two qualities are common and often go together. My store remains closed for awhile yet, but you should be able to find suitable "remainder" parts elsewhere.

[iainpunk]

most Silicon transistors work when the C and E are reversed, but their gain is reduced. with most NPN transistors, the gain is divided by 3 and most PNP's its divided by 5. this does not work with most germaniums.

using a reversed NPN power transistor and low gain germanium transistor could get you in to a workable ballpark. but its all open to experimentation

good luck experimenting
Iain

[soggybag]

Here's a related question, can you combine PNP and NPN transistors in a Sziklai/darlignton pairs?

[m7b52000]

If I can find a suitable pair of low gain resistors is there any sense in using them as an NPN/PNP Sziklai pair for Q2 in an otherwise orthodox NPN silicon fuzz face circuit?

Yes. I did a couple of articles (with help from R. G.)
http://diy.smallbearelec.com/HowTos/BreadboardRMs/BreadboardRMs.htm
http://diy.smallbearelec.com/HowTos/BreadboardGeDarlingtonFFs/BreadboardGeDarlingtonFFs.htm

that should help you. More than anything else, the key to success is finding a few NPN germanium devices that are both low-gain and low-leakage.

Thanks. Why do I need necessarily a low gain NPN Ge? Why not Si NPN for Q1 then for Q2, Si NPN + PNP Ge?

[smallbearelec]

Thanks. Why do I need necessarily a low gain NPN Ge? Why not Si NPN for Q1 then for Q2, Si NPN + PNP Ge?

Also possible. I should have said that the arrangement you pick depends on what's available.

[m7b52000]

Here's a related question, can you combine PNP and NPN transistors in a Sziklai/darlignton pairs?

yes. In a Sziklai pair, NPN into PNP = NPN. Not sure about Darlington which are slightly different.

[antonis]

Pair gets its type name (n-p-n or p-n-p) from the first in orded BJT..
Also, both BJTs of the same type (n or p) form Darlington pair.
Of different types form Sziklai pair..

so:
npn -> npn = NPN Darlington
pnp -> pnp = PNP Darlington
npn -> pnp = NPN Sziklai
pnp -> npn = PNP Sziklai

[iainpunk]

Here's a related question, can you combine PNP and NPN transistors in a Sziklai/darlignton pairs?

yes, a sziklai pair has both NPN and PNP, per definition
sziklai pairs seem to have a little more linearity in them compared to darlingtons...

cheers,
Iain

[m7b52000]

the key point is that otherwise not particularly useful low gain germanium PNP transistors can be tucked away, as the 2nd transistor, inside Sziklai pairs and their PNP awkwardness ceases to be a problem 

[bushidov]

I've done a couple Sziklai Pair combos in pedals. I started with SmallBear's Sziklai Pair Range Master and Fuzz Face and went from there. Actually, I found a sweet combo of both a Sziklai RangeMaster going into a Sziklair Fuzz Face that sounded awesome for Baritone tuned guitars, doing Doom/Sludge Metal style music. I had a Germanium NPN 2N229 and Germanium PNP 2G301 pair for my Sziklai RangeMaster (thanks again, SmallBear for the hookup on the Germanium stuffs!) and a Germanium NPN 2N211 for the first NPN in the Fuzz Face, with a Sziklai Pair for the second "NPN" in the Fuzz Face made up of a Silicon 2N334A (Again, thanks SmallBear), and a 2N43A PNP from DIYGuitarPedals.com.au.

Below was my schematic:


I printed off some PCBs of it and it works pretty good. I call it my "Plagued Distortion". "Plagued"... "Sick"... "Szik"... puns....

[soggybag]

I have a big bag of Ge PNP transistors and another smaller bag of Ge NPNs. This info makes them that much more useful.