We found this amplifier in a publication of 1990, but it can be mounted today with some exchanged components. In the original they were used transistors that can no longer be found with ease. The current source should be in the 500 mA order. The source must have excellent filtering, to prevent any noise. The output consists of headphones 8-600 Ω impedance. The input impedance is high and has also high sensitivity. It can operate with signals of a few millivolts. This circuit does not include the volume control that can be a 10k pot at the entrance.
