The Dapol N Gauge Britannia... installation guide for DCC sound...
When removing the tender body, and uncoupling the drive-shaft from the loco, you'll need to also unscrew the 2 wiring screws underneath the rear of
the loco. Next, remove the 6-Pin DCC circuit board and carefully file down the mounting points where the socket was attached - the aim being to make
as much room as possible.
The pictures below show the completed installation using a CT SL76 wired decoder, 100uF/16V tantalum capacitor (the yellow box), and a CT SugarCube speaker
(with slightly reduced height enclosure). The 3-wheeled tender is not quite long enough to stick the capacitor behind the speaker at the back (like we did with
the Dapol A4), so we've shifted the speaker marginally off-centre and fixed the capacitor on the side instead, using thin double-sided tape.
It all goes in very neatly, with minimal wiring and everything taped down using electrical tape or thin double-sided tape.
The finished article, sounding loud, crisp, and running smoothly: