Stupid Germanium Tranny Question

[blearyeyes]

I have a hankering to build some more fuzz pedals.
I  have some AC127s but they all have high HFE over 100.
What should an old school AC127 average Hfe be?
I have a box of russian 404s that might be better.

Any advice?

[jessenator]

Calling jwin615
I scored some from him not long ago, and now he's got an Peak Atlas and been measuring the crap out of every bjt he can get his hands on

I swear the gain and leakage was written on my esd baggie , but can't find it. I used one in Q3 of the dizzy elk peccary/joe sent me. A negative ground Buzzaround by way of the PedalPCB 'Gnat'.

In the morning I'll look at my build notes what the gain was. Pretty sure it's in the nominal range.

[jessenator]

Alright, I just needed to look harder... it was written right on the top of the (voluminous) rectangle of a casing.
gain = 138
leakage = 0.23 mV

I love this sound in that Dizzy Elk, btw. Reach out to Joe and see if he has any PCBs left.

[jwin615]

AC127s over 100 hFE are definitely in the group of "good" assuming they're leakage isn't crazy. Spec was 50+ iirc.
Depending on the circuit, some need moderate leakage in certain positions(TB) but most circuits need low leakage (FF).
If you plan on subbing a Ge into Si circuits, which is fine, you want low to no leakage and you'll possibly need to bias them manually so maybe breadboard it.
I'm not going to write up an article because so many have already been done way better than I could.

See "anatomy of the fuzz face" series
Good old write up from smallbear
http://diy.smallbearelec.com/HowTos/FuzzFaceFAQ/FFFAQ.htm
And endless threads at diysb, many missing graphics...

Also' I'd say take anything recommending a particular hFE as a basic guideline. staying +/- 20-25% can work just fine but mind the ratios. So, if you see Q1 hFE as 80 and Q2 hFE as 120 recommended for a fuzz, don't be afraid to try a pair at 100/145 or 65/95.  hFE(DC/current amplification) isn't even a firm spec for our use, instead we should be concerned with hfe, which is small signal amplification. But it's waaay easier to measure hFE. And in modern devices, they're pretty linear to one another.
It seems, from my personal observations, that this isn't always the case for older devices, both Ge and Si trannies produced with older difussion or even early planar production techniques.  All that being said, mind your leakage, check your bias and believe your ears.