by Don Fiehmann

See also Decoder Installation Handout (PDF - 1.02 MB)

Product Pages
TDS Speakers are available here.

This is a preliminary comparison of DCC sound decoders by Don Fiehmann. It will be updated with many performance features as the units become more available and more testing is completed.


It is interesting how technology works it way into main stream use. In the mid 1890's superheated steam was the latest in high tech for locomotives. But it was not until about 1906 that this high tech invention was put into big production in steam engines. Why the delay. The superheated steam was so hot and dry that existing lubrication would failed. It took about 10 years to develop a high temperature lubrication to make superheated steam workable.

DCC came out in the mid 1990's and around 2005 technology made sound a very practicable and affordable part of DCC. SoundTraxx got the ball rolling and then QSI stepped in supplying sound to BLI for their locomotives. In 2005 a number of sound players got into the act. MRC came out with a new line sound decoders for steam and diesel called “Brilliance”. Digitrax announced they were going to produce DCC sound decoders called “SoundFX” at the 2005 NMRA convention. Digitrax sound decoders were going to be in Kato locomotives. ESU of Germany has been making sound decoders since 1999 and is now marketing them in the USA. The ESU line of decoders is called “LokSound”.

The big advancement in sound decoders is downloadable sound files. Both Digitrax and LokSound have this ability. What this means for the dealer is they only stock one DCC decoder and then download the locomotive sound file that the customer ordered. If the modeler has a programmer they can change or modify the sounds in the decoder to match their requirements. A decoder that was programed for diesel sounds could be reprograming for a steam engine.

Many of these sound files are created by recording locomotives that are in museums. Newer models are recorded from operational locomotives. An Internet note from Athearn said they were going to Colorado to record the sounds of an SD45 so their new model would be as authentic as possible.

Another area of downloadable sound files is modified or new sound files created by modelers. Now a modeler can make up a sound file to match some low production locomotive that would not be feasible for the sound decoder to make. This is a new area of model railroading.

SoundTraxx's line of decoders is called Tsunami. The sounds have been recorded with 16 bit sound samples.

TCS's WOW sound decoder, the newest entry among sound decoders, is the only manufacturer that has sound samples recorded at 24 bits, a 16 bit DAC, and a 16 bit DSP micro controller. TCS sample rate is 44,100 which puts TCS at CD quality, which is higher quality than any other sound decoder on the market.


The sound that comes out of the tiny speakers in our locomotives are subject to a many variables. It starts with how the sound was originally recorded. The location of the microphone can make a big difference. Sound recorded with 24 bit will sound better than 8 bit recording.

Once recorded the sounds are cut up into pieces to make very small sound segments. These are used to make the sound files that are programed into the decoders. These short segments can be less that a second to a few seconds long. Sustained sounds like a diesel idling may only be a short recording that is looped and played back continuously unit the engine speed is increased. Whistle sounds may need many parts. The startup sound, sustained sound and then the sound when you let your finger off the key.

Downloadable sounds can vary in quality and sound level. I’ve downloaded different sound files and found some to be louder. With some files you may find that one item may not sound right to you. I’ve found that the bell in a few did not sound like a US locomotive bell. Easy to try another sound file.

The installation and speaker also plays a part in the way the locomotive sounds. Last is how we remember hearing a locomotive and are own ability to hear the sounds.

Sound Decoder Features

SoundTraxx Tsunami
QSI Titan
Digitrax Sound FX
ESU LokSound 
Decoder Scales
N, HO, & O
HO, O & G
N & HO
N, HO, O, & G
Speaker Impedance (Ohm)
Included Speaker Size
28 mm, no enclosure


Available Decoders
Tony's Price From