DonnLaurent

As per my experience it works is that the same transformer that steps up the voltage to drive the headphones also provides high voltage to the bias circuit. Also the bias circuit drains off a little bit of current from the signal voltage to fill up the bias capacitors. And the diodes as being one-way doors for the electrons. Every time the music voltage peaks higher than the voltage that is already on the bias capacitors, some current flows into those capacitors, gradually topping them up. https://www.7pcb.com