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Zimo MX644D (21-pin direct) Sound Decoder

Code: MX644

Zimo MX644 Sound Decoder Zimo MX644 Sound Decoder 30x15x4mm
1.2A continuous / 2.5A peak
25V direct stay-alive (16V via LifeLink/SACC16)
21pin direct plug-in
3W audio / 8 Functions
With native 25V stay-alive
supplied with example capacitor

NOTE: The MX644 has been superseded by the MS440

Zimo MX644 Sound DecoderZimo MX644 Sound DecoderZimo MX644 Sound DecoderZimo MX644 Sound Decoder

Variants / Sub-Products

MX644D'D' Version (All 8 full-power AUX outputs)

MX644C'C' Version (5th+6th AUX outputs are logic-level)


The MX644 sound decoder from Zimo is the industry leader of 21-pin MTC direct-plugin sound decoders, packed with all the features you have come to expect from Zimo, plus 8 AUX function outputs for lighting, smoke generators, auto-couplings etc., and 'smart stop' energy storage facilities built-in (just add an external capacitor to take advantage).

Supplied with the MX644 is normally a 470uF/25V electrolytic capacitor - worth connecting, but also worth considering an upgrade to 1000uF or more if you have space in your model, or even an amazing SuperCap (6800uF or 17000uF). Note that a SuperCap (or any 16V capacitor must be connected via our LifeLink PCB as the MX644 is designed for 25V capacitors directly).

Technical Specification

  • 3W audio power
  • 4ohm - 8ohm speakers supported
  • 6-channel output.
  • 1.2A continuous motor output / 2.5A peak for short periods
  • 8 AUX function outputs, max combined 0.8A
  • 2 logic level outputs e.g. servo control / SUSI
  • Energy storage support with Smart Stop
  • 32 MBit memory
  • Railcom
  • DCC, DC-Analog, MM, AC-Analog

Soldering stay-alive wires to an MX644

MX644D as shippedNeed length of blue wire, grey wire and capacitorTin (solder-coat) the corner pads on the decoderNote capacitor long leg is +VE, short leg is -VE (and also has stripe down side)Snip capacitor legs shortBend legsTin capacitor pins and wire endsSolder wires to capacitor and decoder (blue is +VE and is left-most looking from the rear)For models that do not have speaker connections, purple wires can be soldered directly to decoder socket pins (WARNING - invalidates Zimo warranty)

Related Products

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Electrolytic Capacitor

6800uF 15V
Zimo SC68 SuperCap

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