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So what does a SoundTraxx Decoder do? It brings you locomotive alive with Digital locomotive sounds from inside your model locomotive. It’s not a speaker on or under your layout but actually in your locomotive. The chuffing or engine exhaust is synchronized with your throttle and you control the bell, whistle and other sounds!

Here I will review the various types for SoundTraxx decoders. If you’ve just read the Digitrax information and followed the link over you saw that I made the implication that there are two main categories of the SoundTraxx decoders:

• Sound Only Decoders – DSX Series
• Sound, Motor and Light decoders – All other Series

This is true and important. If you chose a sound only decoder, a DSX series, you will have the most sound functions and features. Foreground sounds, back ground sounds, bell, whistle, coupler clank, everything possible. Literally all the "bells and whistles" as related to sound. However you will have no motor and light functions, so you will also need a Motor and Light decoder, i.e., a Digitrax decoder. You can run the two decoders in consist, or more likely you will essentially "piggy back" them and run them at the same address. This is the most costly combination in both money and space, but it also provides ALL the advanced functions for both Digitrax and SoundTraxx and should not be overlooked. If you’ve got the room, it’s a very nice way to go.

A couple things to understand, SoundTraxx decoders do not have Speed Stabilization (Back EMF) or Transponding. If you really have to have these functions than the above combination for DSX and Digitrax decoders may be the best option.

But lets categorize this a little more:

• DSD-100LC Decoders – Their are two, steam and diesel. These are generic for any engine with many sounds, including motor and FX light control. They have a wire in harness, but do match the Digitrax flat 9 pin plug and can be plugged into engines that come with that pug in connector.
• Plug n Play – The are direct board replacement Sound, Motor and Light decoders that are designed to fit many manufacture types or even specific engines. They are easy install and usually take no more room in an engine than the constant lighting board that they will replace. Many include speakers and speaker baffle kits. This had many sound functions but not all that are offered with the DSD-150 or DSX decoders. Like wise they have several light functions, typically enough for the engine they are designed for but not as many as an advanced Digitrax decoder. 
• DSD-150 Steam & DSD-150 Diesel Series– These are specific engine sounds along with motor and light functions. They have a wire in harnesses, but do match the Digitrax flat 9 pin plug and can be plugged into engines that come with that pug in connector. These have all the same sound capability as the DSX with full background and foreground sounds, but also have the same motor and light limitations as all other SoundTraxx decoders, i.e., no speed stabilization or transponding.  NOTE:  These are no longer available

• DSX Steam & DSX Diesel Series – This is a sound only decoder. It has no motor control or light outputs. Thus it needs a Digitrax decoder to handle the motor and light control. They have a wire in harnesses, but do match the Digitrax flat 9 pin plug and can be plugged into engines that come with that pug in connector.  Sound Samples
• DSD-090 Micro Steam & DSD-090 Micro Diesel Series– These are smaller Sound and Motor/Light decoders. They are some what generic Steam and prime mover catagorized Diesel sounds similar to the Plug n Play but much smaller  They are a little more limited on the current. Your engine must have a stall current of less than 0.9amps.

Remember, along with the decoder you will need to have a speaker and preferable a speaker baffle too. Many of the SoundTraxx "Plug and Play" decoders include the speaker and baffle kit, but the other decoders do not and you will need to purchase them separately.

The general rule of thumb is, the bigger the speaker the better. I find the rounds put out more sound than the ovals, but sometimes the oval will fit larger speaker than a round for the same engine width. Multiple speakers will probably not give you much in return except for possible spreading out the sound. Multiple speakers should only be considered for the DSD-150 and DSX series decoders ad the impedance difference can damage the other decoders over time.

The baffle act like you speaker cabinet in your home stereo. If forces the sir movement (sound) forward out of the speaker and thus limits "waist" sound from leaking out the back where it does you no good. I HIGHLY recommend always using some sort of baffle, whether you purchase a kit, use what comes with the Plug n Play’s or build your own. You will get far more return for your money than adding another speaker. I can measure it but it seems to in most cases almost double the actual sound output. This makes sense if you able to prevent 50% of the sound going out the back of the speaker into the engine itself.

It’s mostly about the sound! - First determine the series you want based on the price, functions, and installation technique that suits you.  You can refer to the SoundTraxx Comparison chart for help here.  If you settle on the DSD-150 series or a DSX decoder, then go to the SoundTraxx Sample Sound Page and select the proper decoder by engine prime mover (EMD 1^st Generation, EMD 2^nd Generations, GE, etc). Once you’ve got that down listen to the whistle and bell sample and pick the one you like best.

Here is some other links to the SoundTraxx Manufacture site.  

More about SoundTraxx Decoders!

Manuals, Technical Bulletins and Application Notes

SoundTraxx Decoder Chart!

Check out the Sound examples!

Options and Accessories