This circuit is better than the previous one in that the control is isolated by a transformer. The transformer has 110 or 220 V primary and 6.3 to 12 V secondary with 200 to 500 mA current.
This circuit uses a variable transformer available at the time. This turns of the windings were...
Indicated to be used at the sensor input of a PC, this circuit was found in an English...
We found this amplifier for hearing aids or hearing aid using only transistors in a documentation from the...