I found tis circuit in na old documentation from 1958. The circuit uses germanium transistor availble that time and hard to obtain today. The circuit is indicated for phono applications using variable reluctance transducer.
This circuit appears in various parts of this site and this section, with diverse origins. This is from...
This circuit, called Kames Dandy, can mix signals from a wide range of frequencies and is...
In the figure we have the way to obtain an adjustable constant current source of 2 mA. The...