"matt weber" wrote in message
...

Mostly history and technology. The first transistors were germanium
point junction transistors. Germanium transistors has lower charge
carrier mobility than Silicon, and higher voltage losses across the
junction than Silicon. To get significant power, and gain, these
devices needed much higher voltages.

Point contact transistors were never used in consumer transistor radios.
The earliest radios used germanium junction transistors.

The typical voltage drop across a germanium junction is about a quarter
volt. A silicon junction drops from a half to three quarter volts.

9 Volts also allowed
manufacturers to save some money. The speaker could be connected
directly to the output stage (no transformer), something that is hard
to do with 3 volts and a class B output stage.

The early transistor radios used transformer output stages. Push-pull
output stages were the rule, driven by an phase split interstage
transformer.


9 volts is the norm for
these devices into the 1970's. So almost anything you see from the
1950's and 1960's uses 9 volts.

Can't disagree with that.

Frank Dresser