I'd love to know if there's a clever usage for low gain (60 hFE and below) germanium transistors. Any interesting circuits you guys can throw my way? I'd prefer pedal circuits (fuzz / boost / etc), but they don't even have to be music related, anything is interesting to me!
Thank you! :D
Q1 and Q2 in a MKIII / MKIV Tone Bender.
I'm just now making a clone of a Catalinbread Karma Suture which in turn is a modified clone of the Interfax Percolator. Excellent fuzz from demoes.
Also Q1+Q2 of Burns Buzzaround (built a DAM Buzzotron clone which is a modified version). I believe Fuzzrites and it's a-likes takes low gain germs well, but somebody can correct me if I'm wrong.
I know how you feel with the leftover low gain germs! That's all I have right now. I got half a mind to just start buying pre-sorted HFE from now.
Q2 in a germanium Mosrite fuzzrite. Really low even works well, I've had success with around 30 hfe.
Quote from: dennism on March 10, 2021, 08:01:27 AM
Q2 in a germanium Mosrite fuzzrite. Really low even works well, I've had success with around 30 hfe.
i got my mosrite working on the breadboard with only 17hfe.
the Bazz Fuss, use 2 low gain Ge's and configure them as a Darlington pair, although a Bazz Fuss is easier if you have NPN's or if you insist on using PNP's you can get away with a Si NPN power transistor in an npn sziklai configuration.
(https://sound-au.com/articles/dcp-f1.gif)
cheers
Anything 50+ should work fine in a Rangemaster circuit as long as the leakage is low. I've done four of them using trannies in the 50-60 range and they all biased just fine using a 5k trimpot on the emitter. As mentioned above, the GE Fuzzrite is likely a good contender for those real low gain units. I haven't built the GE version, but I was surprised on how the SI ditto came alive after swapping the 120-150 hfe trannies that I originally put in it for others in the 40-50 range. You might need to supplement it with a volume boost stage to get unity level across the sweep of the depth knob.
Low gain works alright in the hudson broadcast, as well as the harmonic percolator.
I haven't tried it, but many germanium transistors can be run "in reverse", i.e. emitter to V+, which usually results in very low hfe. You could then try that in a complementary pair like iainpunk suggested.
http://www.muzique.com/lab/reverse.htm
Make Darlingtons.
Quote from: turbofeedus on March 10, 2021, 02:58:01 PM
Low gain works alright in the hudson broadcast, as well as the harmonic percolator.
I haven't tried it, but many germanium transistors can be run "in reverse", i.e. emitter to V+, which usually results in very low hfe. You could then try that in a complementary pair like iainpunk suggested.
http://www.muzique.com/lab/reverse.htm
in lots of GE transistors, the gain doesn't reduce much when placed in reverse Beta. the OC171 i tried lost less than 5% of its gain. some ASY16, ASY17, ASY19 and ASY23 transistors lose about 30% of their HFE.
leakage doesn't seem to change.
Si transistors lose way more HFE in reverse Beta. the 2N2222A i tested lost 73% of its HFE!
cheers
Quote from: iainpunk on March 11, 2021, 09:36:40 AM
Quote from: turbofeedus on March 10, 2021, 02:58:01 PM
Low gain works alright in the hudson broadcast, as well as the harmonic percolator.
I haven't tried it, but many germanium transistors can be run "in reverse", i.e. emitter to V+, which usually results in very low hfe. You could then try that in a complementary pair like iainpunk suggested.
http://www.muzique.com/lab/reverse.htm
in lots of GE transistors, the gain doesn't reduce much when placed in reverse Beta. the OC171 i tried lost less than 5% of its gain. some ASY16, ASY17, ASY19 and ASY23 transistors lose about 30% of their HFE.
leakage doesn't seem to change.
Si transistors lose way more HFE in reverse Beta. the 2N2222A i tested lost 73% of its HFE!
cheers
Yes actually there were some Ge transistors that were specifically marketed to be reversible, to fit specific hfe needs. I think OC139 was one of these.
Jack goes into this in the article, but the specific manufacturing technique in early Ge transistors (alloy junction) is what allowed for usable reverse gain. Later Ge transistors and then silicon used new techniques (mesa and expatial layering) which basically eliminates reverse gain.