PPA v2 Amplifier Board
NOTICE: The PPA v2 amp board is no longer available. You may want to look at my PIMETA v2 instead. It is based on a similar circuit. The main difference in sound comes from the difference between the discrete buffers in the PPA v2 vs. the monolithic ones in the PIMETA v2.
PPAv2 was similar to PPAv1, except with a custom discrete output stage, plus a few other enhancements.
Specs:
- 6.3 in. × 3.925 in. board size (Eurocard size, 160mm
× 100mm)
- Isolated power rails reduce rail-modulated
crosstalk.
- Differential-drive topology gives the simplicities of virtual
ground without the crosstalk problems that normally go with that.
- The signal channels use the Jung multiloop topology for
low distortion.
- Compatible with most FET-input op-amps.
- Discrete diamond buffer output stage, with adjustable bias, to
let you trade portability for sound quality.
- Room for thousands of microfarads of
rail capacitance, even with low-density
audiophile caps. At the same time, differential drive means the
qualities of the rail capacitor bank don’t affect the sound of
the amp as much as in other topologies.
- Reverse power supply voltage protection.
- Quiescent power draw ranges from about 40mA on a minimal
feature set to about 120mA when maxed out.
- Enhanced JFET cascodes for
biasing the op-amps into
class A.
- Optional bass
boost.
- Board-mounted ALPS RK27 (a.k.a. "Blue Velvet") potentiometers
for volume control and bass boost adjustment.
- Resistors on 0.100" × 0.300" spacing allow the board
to be set up for easy
experimentation.
- A companion NiMH battery board
allows for portable amplifiers.
- Optional power LED turn-off circuit for indicating that the batteries need to be recharged.
