How to identify NAC72 boards

[Richard.Dane]

The FAQ here should help;

Naim NA3xx and NA5xx Pre-amplifier daughter boards

Earlier Naim pre-amplifiers used interchangeable daughter boards. While the very earliest NAC12s did not use daughter boards, most were updated, and the early versions of the NAC12 and NAC22 used NA1xx and NA2xx boards that used knife edge connectors but were superseded by pin mounted NA3xx boards. The NA3xx boards that can be found and used in later NAC12s are; NA325 - Switching Relay, switch-on output delay x 1 NA321 - Main gain, output drive x 2 NA324 - Input Buffers x 2 NA322 - MM …