Kit: MX649N (one each end); SugarCube7 (motor car)/SugarCube9 (dummy); SACC16 (each end); various Tantalums for stay-alive
Dapol's current HST range of models are great candidates for taking DCC sound..
Firstly, the motor coach, we use an MX649N direct 6pin plug-in sound decoder, and a SugarCube7 speaker, which just about fits
between the end of the chassis and the rear body clip. Be careful with the speaker wires though, that they don't catch on the
body when reattaching.
A small stay-alive can be squeezed in undeneath the end of the decoder, in front of the speaker - a SACC16 PCB cut-down to
minimum size, with a single flat/wide 330uF Tantalum capacitor is about all we can get in, but it is enought to help avoid
those little stutters in running.
With the MX649N plugged in, the body simply won't go back on flush, so we cut the plastic screw mounts underneath the PCB so
that the whole thing can sit a little lower.
A similar approach at the dummy end, with MX649N plugged straight in, with the screw mounts cut off. However, we can put in a
bigger speaker (SugarCube9 in this case) and more stay-alive (SACC16 with 5x 220uF Tantalums). This all goes in the gaping hole
where the motor would have been.
Here's a similar example, but with cab lights and drivers added too.