Fitting DCC Sound to a Bachmann Class 45

This article describes the process of fitting DCC sound to a Bachmann class 45 locomotive.

The locomotive described in this article started life as a Replica model with the ex-Mainline pancake motor. This was found to be inadequate, so a replacement chassis was purchased from Bachmann. The replacement chassis is the type fitted to the class 45 when Bachmann reintroduced the model as their first can motor/cardan shaft drive diesel loco. It is an excellent runner.

Sound Decoder

My sound decoder of choice is the excellent ESU Loksound:

These decoders are a single package, combining traction control with 4 functions and sound. They are back-EMF decoders and provide excellent control. Because the decoders integrate traction and sound, the sound is properly synchronised with the motor operation.
The ESU decoders come supplied with a speaker and a baffle box into which the speaker fits. Wherever possible, I try to fit the larger ESU 40x20mm speaker as this gives better sound reproduction.

Loco Preparation

The chassis block of this loco predates DCC Sound and therefore has no provision or space for a speaker. Therefore, the chassis block must be cut to create space. The first picture below shows the chassis block on the unmodified end. The other pictures show the modified end:

It is very fortunate that Bachmann have had the forsight to recess the bogie mounting screw deeply in the chassis block. This is really helpful because it means that when the chassis block is cut to accomodate the speaker as shown here, the bogie mounting is not affected in any way (see pictures below).
This chassis block is actually quite easy to cut if a hack-saw is used.
The reason for the significant amount of space created is because a 40x20mm speaker will be fitted.

It is important to either cover or dismantle and remove mechanical parts while the chassis block is being cut so that metal chaf does not enter the drive system. Some models are less easy to dismantle to remove the motor, such as this one, therefore, tissue paper was stuffed into every hole possible and later removed and dusted.


This locomotive predates DCC decoder sockets and therefore requires hard-wiring of the decoder. Because this loco has directional lighting in the form of a high-intensity beam light, the wiring is a little more complicated than normal. During the process of decoder installation, the light bulbs at each end were replaced with LED's with resistors in series.
There is a copper-strip 'bus' fitted to the model which runs the length of the chassis block. This needs to be shortened to accomodate the new space created for the speaker.
The following pictures show the completed wiring:

The first picture shows the completed wiring with the supplied speaker temporarily located in place. Note the bogie mounting screw is slightly recessed, but is otherwise unmodified. The second two pictures show the same, but with the 20x40mm replacement speaker fitted in place.
The baffle box of the speaker has had to be cut down in height in order to fit within the curvature of the roof of the body shell.
It is very important to ensure that all wiring is enclosed and properly insulated so that no stray connections can come into contact and cause shorts and therfore, damage, to the decoder. As can be seen, electrical insulating tape has been used to prevent this.

Bodywork Modifications

Sound is not very effective unless it is allowed to 'escape' the loco, otherwise it is 'caught' inside the model, reverberates and can create strange noises in the bodywork which are not heard on the prototype. To this end, I normally drill out exhaust outlets and replace fan grills with proper meshes. Generally it is a good idea to place speakers under these meshes or in the fuel tanks facing downwards.

Results - The Model in Action

Class 45 - stopping

Class 45 - at speed

Graham Plowman

ESU Loksound Decoder, sound and speakers supplied by:
South West Digital Logo

Locomotive manufactured by:

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