PPA v1 Amplifier Board
The PPA is ppl's Portable Amplifier. ppl has been building and advocating Jung multiloop type buffered headphone amp designs for a long time.
You can think of the PPA as a major extension of the design concepts that lead to the META42 plus some that appeared in previous ppl amps and some new ones we've pioneered for the PPA. By using a larger board than we allowed for the META42, we have been able to exceed the META42's performance considerably.
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.
- One to four
Intersil HA3-5002 buffers per output channel.
- Room for over a thousand mics of
rail capacitance even with low-density
caps like Black Gates, Cerafines, and Silmics. 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 45mA on a minimal
feature set to about 150mA when maxed out.
- Enhanced JFET cascodes for
biasing the op-amps into
class A.
- Switchable bass
boost.
- Board-mounted ALPS "Blue Velvet" volume control (RK27 series)
- 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.
