This is a scaled-down version of Nelson Pass' Zen power amplifier for my headphones. For this use, the Zen topology is perfect excellent sound quality, simplicity, linearity and no multi-stage feedback. It is a single stage class A MOSFET design with the right gain and a low output impedance. Here we don't have the limitations of the Zen amps at least in the single-stage implementations regarding speaker compatibility. A single stage topology with correct interfacing values misses very few things in the original music message.
The gain device in the original Zen amplifier is biased by fixed current source. For this amp, I employed an active current source described in Pass' patent no. 5,710,522 (see Zen Variations Part 2). The benefits of an active source include higher output current, lower distortion and 50% theoretical operating efficiency (compared to the 25% efficiency from a fixed source). This type of current source is featured in the Aleph power amplifiers from Pass Labs.
Build Accurate LC Meter and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging and reset function to make sure the readings are as accurate as possible ... [more]