PIMETA v1 Headphone Amplifier
NOTICE: This version of the PIMETA board is no longer
available. We are working on an improved
design, PIMETA v2, which should be out sometime this summer. See
its FAQ for up-to-date news.
What was the PIMETA v1?
The PIMETA v1 was 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.
Features of the PIMETA v1 design:
Small board size: 3.0" × 2.4" (76mm ×
61mm)
The board should work with most FET-input op-amps in DIP-8
and SOIC-8 packages.
Burr-Brown BUF634 buffers on
the outputs.
PPA-like 3-channel setup so
return currents from the headphones don’t disturb the signal
ground.
Reverse power supply voltage protection
With low-voltage op-amps, minimum supply voltage is 5 V
on a minimal feature set.
The op-amps can be biased into class A.
The buffers’ bandwidth can be scaled to balance current
draw with sound quality.
The board will accept either the small and cheap Panasonic
EVJ or ALPS RK097/RK098 potentiometers or the nice, big and
expensive ALPS RK27 series potentiometer (a.k.a. “Blue
Velvet”).
All resistors are on 0.100" × 0.300" spacing so you can
put a DIP socket in their place and socket the resistors for easy
experimentation. Similarly, many other holes are placed on 0.100"
centers to allow the use of socket strips.
It strikes a careful balance between spaciousness for things
like large, premium capacitors, while still keeping the board small
enough to fit in small, portable cases like the Serpac H-65.
The board’s layout is optimized for minimum trace
length and no vias.
Where To Next?
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