It's a PPA-Inspired META42 successor. It's about the same size as the META42 board, but the topology is closer to that of the PPA.
The PPA headphone amplifier was designed by Team PPA in late 2002 as a community service project. Over the past few years, PPL created a series of pocket headphone amplifiers using opamps and open loop buffers which were the inspiration for Apheared's #42 and the META42.
The PPA is ppl's Portable Amplifier. ppl has been building and advocating Jung multiloop type buffered headphone amp designs.
Uses type 5687 Dual Triodes.
This is a four channel amplifier ideally suited for use with quadraphonic equipment such as a Sound Blaster Live card.
During the past few years a number of excellent designs have been published for domestic audio amplifiers. However, some of these designs are now rendered obsolescent by changes in the availability of components, and others intended to provide levels of power output which are in excess of the requirements of a normal living room. Also, most designs have tended to be rather complex.
Uses LM3876 Hi-Fi amplifier IC from National Semiconductor.
When your monster (or not so monster) power amplifier is switched on, the initial current drawn from the mains is many times that even at full power. There are two main reasons for this, as follows ...