Released this year in 2021, the Zimo MS500 has been long awaited by N-scale sound fans: finally a sound decoder not bigger than any NEM651 standard decoder. Here is a quick overview.

MS500: The smallest, but also powerful

14 x 10 x 2,6mm, that’s basically the size of most standard NEM651 decoders on the market (albeit slightly higher). The Zimo MS500 fits in many engines that previously couldn’t fit a sound decoder (at all, or without extensive DIY). It’s standard length is its strength.

But that doesn’t make it less powerful. As a decoder from the recent “MS” series, it offers Zimo 16bits sound, 4 outputs + 2 unpowered outputs. Also of note, is Zimo’s new feature to connect capacitors up to 1000uF to a specific pad, without having to worry about a protection circuit (with a resistor and a diode). Additional capacity can of course be added using the aforementioned circuit, or even using Zimo’s new “STACO” module.

Zimo MS500 sound decoder Zimo MS500 sound decoder

Zimo’s usual quality, at a price

I’ve mentioned Zimo several times. So here’s my uncensored opinion: in terms of user friendliness, they are terrible; if you’re not an engineer wannabe, then programming their decoders can be a hassle. On the other hand, as I always mention, they make excellent, very powerful products. This decoder is a testament to this, they are the first manufacturer to be able to release such a small decoder.

Uploading a sound project from the Zimo MXULFA programmer and a USB stick isn’t that hard. In fact, in order to promote the new 16 bits sound of the MS series, Zimo has been releasing quite a few new and free sound projects on their website. That’s a very good point.

Zimo MS500 sound decoder Zimo MS500 sound decoder

Of course, your model train stockist may offer to upload the sound project for you, which makes it much easier.
The decoder is available with a NEM651 socket or wires.

Testing in in real life

My perfect candidate was a steam engine from Arnold that I reviewed in this article: Unboxing: Arnold BR 02 0201-0 (HN2428).
After slightly altering the tender metal casing, I was able to fit not only the MS500, but also 4 SMD capacitors as a buffer and the speaker in the tender.

Arnold engine

Speaker prepared for engine

Zimo MS500 with added capacitors

Zimo MS500 with added capacitors

Zimo MS500 in Arnold engine

Programming the Zimo decoder

Programming the decoder

Zimo MS500 in Arnold engine

Zimo MS500 in Arnold engine, with capacitors and speaker

The result is very satisfying. Have a look at the video on top for yourself!


All in all, the MS500 decoder will be the perfect solution for people looking to add sound to very small engines. In fact, it has already been used by many enthusiasts in very small N scale engines such as the famous Köf II.
Of course, you still need to find some space to fit a reasonably sized speaker. But that won’t be a challenge for the expert DIYers out there!