Germanium transistor confusion

[agua_moose]

Hi all! I'm new here and I've got myself really confused over the germanium transistors that came with my fuzz factory clone kit.

From what I understand Q1 and Q2 are meant to be PNP germaniums, and the kit came with an AC176 and an AC128.

The AC176 was labelled with a "1" so I assumed it would go in the Q1 position and similarly AC128 was labelled with a "2" so into Q2 it went. Of course I was stupid and didn't socket them so when it eventually came time to test it out and it didn't sound right I started investigating.

I took both transistors out and added sockets to the board, and then swapped the transistors around and things sounded a little better (AC176 in Q2/AC128 in Q1).

But ultimately it didn't sound as expected so I started looking into things a little further and noticed that the AC176 is NPN and the AC128 is PNP.

Am I right in thinking that these 2 transistors can't be used together in this circuit?

I think I'm confusing myself further as when googling AC176/AC128 I'm seeing results for matched AC176/AC128 pairs which is making me think that they can be used together?

Sorry for the long post guys, any help would be much appreciated.

[iainpunk]

they can't work together in a stock fuzz face (the fuzz factory is just a fuzz face clone with added pots.)
they are an COMPLEMENTARY PAIR, which means they are an NPN and PNP pair that work together well in a class B (push pull) configuration or other situations where you'd want a pair like that.
i'd send a message to the source you got the kit from and ask for a replacement transistor and offer to send back the one you won't use.

that, or you order a pair of Ge's that is the same type (either NPN or PNP) and use the transistors for a Harmonic Percolator/Jerkulator

cheers, Iain

[agua_moose]

Thanks for clarifying Iain, I was tearing my hair out with this yesterday reflowing joints, checking resistor values, making a makeshift audio probe etc, I just assumed the AC176 was an equivalent replacement for an AC128, lesson learnt!

I've ordered a couple of pairs of PNP Ge's from eBay so hopefully that will get me up and running. I'll definitely keep the old one's for future projects.

Thanks again!

[duck_arse]

hello agua_moose, and as Iain often says, welcome to the forum.

you are allowed to tell us who the kit supplier is. also, why only two transistors when the your circuit diagram shows three?

[agua_moose]

Hi duck_arse, thanks for the welcome!

The kit is from FuzzDog, the kit itself is great, no issues re quality or anything like that.

Q3 in the schem is a generic 2n3904 which was included with the kit also, but I narrowed my issue down to being one of the germaniums after using an audio probe and hearing that Q3 seemed to be functioning correctly. That's when I started looking into the specs of AC128/AC176s.

[iainpunk]

hello agua_moose, and as Iain often says, welcome to the forum.

you are allowed to tell us who the kit supplier is. also, why only two transistors when the your circuit diagram shows three?

ow, i didn't even notice that he's new.
- welcome to the forum

you could also throw in a Si transistor in its place to get it to work if you have one or more in stock, especially in Q2 position where it has less of an effect on the overall tone. and change it out with a Ge when you get it.
changing around different transistors is a large part of the fun when it comes to fuzz pedals.
keep in mind that the pin-out can be different.
a transistor i like in this kind of circuit is a BD140, because its a power transistor, it has lower gain, more in the range of a Ge, but the pinout is way different

cheers, Iain

[duck_arse]

hmmm, well, see - this is why I dislike fuzzdog diagrams. no information as to parts values on them, means much, and any is too much, cross referencing. and causes confusions like mentioned in the thread title.

[agua_moose]

- welcome to the forum

Thanks!

you could also throw in a Si transistor in its place to get it to work if you have one or more in stock, especially in Q2 position where it has less of an effect on the overall tone. and change it out with a Ge when you get it.
changing around different transistors is a large part of the fun when it comes to fuzz pedals.
keep in mind that the pin-out can be different.
a transistor i like in this kind of circuit is a BD140, because its a power transistor, it has lower gain, more in the range of a Ge, but the pinout is way different

cheers, Iain

That's super interesting, I didn't know you could use these types of transistors. I've had a rummage around and I haven't got anything like that unfortunately, but it shouldn't be too long before my other PNP Ge's arrive.

I've been researching what I can make using the AC176 and came across the Multi-Face http://home-wrecker.com/multiface.html, I'm thinking of experimenting with a 2N3904 and the AC176, we'll see how that goes!

[agua_moose]

hmmm, well, see - this is why I dislike fuzzdog diagrams. no information as to parts values on them, means much, and any is too much, cross referencing. and causes confusions like mentioned in the thread title.

I must admit I did have multiple windows open, one with the schem, one for the BOM and another with the PCB layout after I had already soldered the components and needed to re-check my work 

[iainpunk]

the AC176 sounds terrific in a range master, although the bias should be changed a bit to make it sound good.
replace the 68k with a 100k trim-pot. you can substitute the 1N34A for a 1N4148 without any change in sound.
the trimmer would be turned until it sounds best, you can also make it gate and sputter if you like that sort of sound.


cheers, Iain

[agua_moose]

Excellent, I think I'll breadboard both the range master and multi-face at the weekend

Thanks for the suggestions!