As I recall, germanium was abandoned in transistors with the advent of silicon because SI transistors provided more gain and were more consistent.
Yeah
especially the consistency.
I for sure remember Roger Mayer mentioning the RF issue in an interview somewhere, and confirmed on
his own site for the "Axis":
"Electronically the Axis uses a discrete circuit configuration that is completely unlike the simple and crude Fuzz Face configuration. Both PNP and NPN
silicon low noise transistors are used in an unique configuration that is
temperature stable, free from radio interference and producing more output level and sustain than the Classic Fuzz"
He still offers germanium, though, in the Page 1 Classic:
"OUR GERMANIUM FUZZ FROM THE 60'S
In 1964 I designed my first fuzz guitar effects pedal that was used by Jimmy Page and Big Jim Sullivan and featured on many early hit records.
I am pleased to announce that after over 40 years this early ground breaking fuzz will be available again. It uses
carefully selected germanium transistors and has the same distortion section as the original 1964 version."
I found another interview where he mentions the inconsistency and especially the heat instability of early germaniums (in Arbiter Fuzz Faces he started modding):
https://www.premierguitar.com/articles/Roger_Mayer_Talks_Fuzz
"Especially with germanium, it was not quite as tightly controlled as silicon. It’s nothing to have a transistor selected for low noise, and then have the gain vary anywhere from 100 [hFE] up to 800 [hFE]....
Well, Jimi would buy half a dozen of these pedals, find one that sounded great, and then we’d mark it, right? One day it would work and another day it wouldn’t work so well in a different environment. Jimi would say, "What’s going on?" and I’d say, "Well, it’s got to be temperature, Jimi. That’s the only thing that’s changing." So that’s what got me to look inside the box. We got a good sounding one at a certain temperature, but as the temperature changed you could see the biasing completely shift. I started analyzing them a bit more carefully to find the combinations that work well."
Hmmm...he also says this in that interview:
"Then they (Arbiter) went on to the
silicon ones, which had a bit more gain and high end,
but they were terribly prone to pick up radio and start oscillating and were bloody unstable."
I think that is the RF comment I was remembering, but it
is about silicons,
in the Arbiter circuit, to be fair.
In order to pick up a radio signal you just need a rectifier (detector) and something to act as an antenna which is why a crystal radio works.
It can actually be more difficult to
not pick up radio signals. That's why I perform in a faraday cage suit:
I love me GE fuzz. Look at those germanium beauties:
Probably due to my early years handling mil spec components, I have Motorola TO-18 cans indelibly etched in my memory: