Germanium Darlington question

[appliancide]

I have a handful of old germaniums with fairly low hFE. Would there be any harm in making darlingtons with them to achieve my desired gain? They will be in a fuzz pedal, so some noise is ok. I'll probably breadboard a few different combinations to see what happens.

By the way, I think this is my first post on here, so "hi" and thanks for all the great information and inspiring projects! I have probably gone through the entire picture thread twice! Amazing builders on here that's for sure!

My first build is a Rodent based on the GGG schematic (another awesome site). I'm still debugging it. Lot's of dumb mistakes so far! I don't think I'll try another stripboard layout that compact again for a while!

Cheers,
Paul

[Pedal love]

Germanium Darlington, ok I did that to a circuit I built revising the fuzz face. It sounded ok.

[jrod]

Hey,
There are several threads about ge darlingtons including some projects. You might want to use the search function and see what you can find. I know I found some info once search something like "low gain transistors". But, I do remember one post about how the leakage is amplified tremendously! So, that may something to consider. What do your transistors measure? They may be good for a one of the cool boosters found here and one of the forum members RnFR has a couple of really cool circuits that use lower gain ge's. Search for Dirty Boots and Toe Cutter. He used Russian ge's, but yours may work great.

[appliancide]

That Toe Cutter looks sweet. I will definitely check that out at some point.

I actually found a couple of decent GE germaniums to use for the pedal I was breadboarding today.

The low ones I have measure anywhere from 1 on up on my dmm. Some of them are really old metal can packages, which I read in the Toe Cutter thread (I think) can be difficult to get an accurate gain reading from.

[R.G.]

The problem with germanium darlingtons is the leakage.

Germanium leaks. The leakage of the first transistor of a darlington is multiplied by the gain of the following device. In many cases, this is more than a single transistor's gain, and will give even bigger leakage than a single device with the same gain; worse, it's temperature sensitive and drifts a lot.

If you have the germaniums already and are looking for a use for them, great. Try it but cautiously, knowing that you may need to tweak the circuit or replace transistors because of leakage and drift. Sometimes it will work fine, so use it but be ready just in case.

[noelgrassy]

Jack Orman has some delightful buffer ideas to accomodate the weak and leaky Ge xistors. They've got a real low parts count to boot.
I know they aren't fuzzes but after you gather up all your pedals you'll need to address the buffering issue. That's presuming your not on Pete Cornish's waiting list.

[appliancide]

I have been checking out Jack's site the past couple of days. Yet another goldmine! I want to put together another Rat(ish) pedal based on his tone clipper ideas. 

[mac]

I used Ge darlingtons in Bazz Fuss, The Rocket, Big MUff, etc, but as RG noted leakage is a problem.
I used Toshiba 2sa53 around (50, 20uAmp) in most of them, except BMP which has single 2sb176.

If you are going to use Ge darlingtons for your own projects you can design a bias network to be hfe & leakage independent.
A good example is the darlington pair in the 3-knob Tonebender.

mac