A single channel of the Current Dr. amplifier has been prototyped according to the following schematic.
There are a few placeholder components present (R2–R4) and some were added after debugging the prototype (C1–C4).
The initial set-up consists of two operations:
- setting the quiescent current through the reference current sink Q2–Q3 to about 2.5 mA by adjusting R1 and measuring the voltage drop across R5–R6
- setting the output DC offset to a fraction of a mV by adjusting R10 and measuring voltage at the output with a load connected (a resistor of a few hundreds ohm is a suitable load)
The assembled prototype looks like this.
I haven't been able to measure the frequency response, THD, or the output impedance of the prototype yet. Listening to a single channel output suggests it has some potential, hence a proper characterization and development of a standalone stereo amplifier is to be done.