I have talked about the Sabaj PHA1 headphone amplifier before. Let’s open it this time and see what makes it tick.
I am using a Sabaj PHA1 headphone amplifier with my Sennheiser HD555. The sound quality is OK, but the amplifier gain is too high for the relatively sensitive and low impedance HD555. To be able to use the full volume range, I decided to build a stepped attenuator to reduce the audio signal received by the amplifier.