N Gauge isn't always the easiest scale to add DCC Sound directly to your locomotives, even with the latest micro decoders from CT and Zimo.
Having someone fit sound to your locos for you can be pricey, and to do it yourself comes with risks, not to mention those locos where
sound really isn't possible due to lack of space. Using a micro cube speaker (as opposed to a standard sugar-cube) is an option, but volume and quality of sound is reduced
A popular solution is to add a sound-only decoder into a coach or truck close behind the locomotive.
Dapol's light-bar ready coaches provide the ideal platform to achieve this, as they already have quality pickups.
Our example 'photo diary' uses a Dapol Collett brake coach as the donor, but the principle are very similar for most of Dapol's
light-bar ready coaches.
In terms of equipment used, we install a white Dapol light-bar, connecting to a CT GE75 sound-only (isn't actually sound only - it has
sound plus 2 function outputs for lighting, but no motor output) decoder for DCC control. Sound
is through an almost full-size CT sugar-cube, so plenty of volume, and we add a small capacitor to prevent light flickering and sound
break-up, which is more of a risk in a light-weight coach like this compared to an engine.
To begin with, disassemble the Collett coach. The Collett is probably the fiddliest of all Dapol light-bar ready coaches, as it has
wire pipe details at each corner which must be prized carefully out
It may seem brutal, but we chop off the wires and connector (actually use a soldering iron to disconnect the wires) from the light-bar as we will be hard-wiring the decoder's light outputs
to the light-bar directly. The more space we can save, the better the installation.
While we're at it, we'll add passengers too, which means we need to remove the seating mould altogether or else the glue for the figures
will cause mist to appear on the glazing later. It is also more convenient to remove the seating completely as we can do a neater job of
the cutting required to make space for the decoder, capacitor and speaker.
In this case we decided that the equipment would be situated at the end where the existing light-bar socket is located, so we unsolder
the socket's wires from the pickups under the seating mould and crack out the socket, which is usually held in place by a tiny amount
of glue. Don't worry about making a bit of a mess here, as we will be chopping and flattening this section of the mould anyway!
Next, let's prepare the sugar-cube speaker... before gluing the enclosure to the speaker, we reduce the height by about 1mm and round off the
top edges. This isn't strictly necessary, but a little reduction in height will ease the squeeze, and the rounding of the edges provides
somewhere for wires to run without being pinched, so it is worth doing, as it is such a quick and easy job. Volume is not affected by
reducing the height of the enclosure by this small amount - these sugar-cubes are astoundingly loud anyway!
Run a tiny amount of super-glue around the edge of the enclosure and carefully/squarely stick the speaker to it. Note also a couple of
capacitors pictured here. The bigger capacitor will provide better flicker-free light and crackle-free sound, but space used is a
compromise. Choose the size depending upon the amount of seating space you are prepared to give up - this is why YouChoos' normally
uses brake coaches, or kitchen coaches for this purpose! Tantalum capacitors offer higher capacitance for the same space, which you
could consider as an option, but they are 10 times the price!
We don't want the decoder, speaker, capacitor or wires to be visible from outside, so paint 2 or 3 layers of white acrylic paint
onto the inside of the glazing to mask the affected area. Measure the components to size, and cut away the seating moulds to fit what
File down and neaten the mould, taking care to leave any fixing holes, which are present in some of the Dapol light-bar ready coaches (not
all of them though). Chop off your passenger's legs (ouch!) and glue them in however you like, ensuring that their heads don't protrude
above the top of the mould! Liquid super-glue is as good as anything else for this purpose. You MUST let the glue thoroughly dry before
putting it back together though, or you will get nasty glue 'mist' on the glazing which is impossible to remove.
Once the glue is dry (a couple of hours at least), you can reassemble the seating and glazing into the coach, threading the decoder's
pickup wires (black and red) through the seating mould, and soldering them directly to the coach's pickup strips.
Test everything for space (as you probably should have done as you went through the previous steps too!), insulate anything that might
touch such as the bottom of the speaker or its connecting tags, the decoder, and the terminals of the capacitor. Remember that the decoder
will tend to get fairly hot, so don't cover it totally in electrical tape, as it will need to breath - instead, insulate the other components.
Once you have the decoder, speaker and capacitor installed neatly, trim and connect the function output wires to the light-bar. Blue from
the decoder is common +VE and goes to one side of the light-bar, and White from the decoder is -VE and goes to the other side. Test that F0
on your DCC controller switches the lights on ok with the coach on the track. If not, switch the Blue and White wires around on the light-bar.
Note that you DO NOT need any extra resistor in this circuit as the light-bar has all this built in already.
If you feel that the white light is too bright, you can either use a yellow version of Dapol's light-bar, which actually is quite poor in
terms of brightness (you can barely see it), or dab some mucky weathering oil over each LED on the strip, such as Model Mate's Mud Brown -
you can control the amount of oil you apply quite easily to attain the effect you want, and it will come off easily with a damp brush if
you decide it doesn't work for you.
Here is the finished item, all reassembled...
Below is another example, this time using a Dapol LNER Teak brake coach...