Printed Circuit Boards
Both versions, BJT and Mosfet, are included on the same EHHA board. Heatsink and mounting locations are provided for each type of device. The pads and traces for the O/P devices not used do not interfere with the operation of the chosen devices.
EHHA Single Channel Amplifier Board
The board has a top-side ground plane covering the main amplifier section. It also has two large +V and -V power planes on the bottom side to ensure lowest possible resistance in the power rails. The decoupling caps are placed bewteen various parts of the circuit to get as good separation as possible.
Input, Output, and Heater connections are made through simple screw type connectors. Connectors are not required, however. Leads can be soldered directly to the pads where the connectors normally go.
Mounting positions for the different O/P devices are marked Q8B, Q9B for the BJT devices and Q8M, Q9M for the Mosfet output devices. Two sets of heatsink locations are aligned with these mounting positions.
The servo Opamp capacitors, C4 and C5, have two pitch arrangements on the board permitting some choice in selection of these capacitors. They are labeled C4A, C4B, C5A, C5B.
You can see a computer generated 3D image at this link:
Not all components are rendered in this image, but both O/P devices are visible along with most of the rest of the components.