Today, I offer some comments about connecting speakers to the new ESU 73900 LokSound Select NMRA DCC Sound Decoder 21MTC Connector decoder.  

By the way, these comments apply to ESU 54499 LokSound V4.0 NMRA DCC Sound Decoder 21MTC Connector and ESU 64499 LokSound V4.0 M4 Muli-Protocol 21MTC Connector as well.

You will notice the only wires on this decoder are two brown wires for the speaker connection.  Some DCC-Ready locomotive models use internal circuitry on their adapter board to connect to the speaker to the decoder.  This can be referred to as an integral speaker installation.  This is one of the advantages of the 21MTC connector.  Pins 9 and 10 on the integral 21MTC Connector are reserved for speaker connections.

The ESU 73900 LokSound Select NMRA DCC Sound Decoder 21MTC Connector has two ways to connect the speaker.  Pins 9 and 10 on the integral connector and the two brown wires.  The two brown wires are used for an isolated speaker installation only.  They are not required and can be removed when the model incorporates an integral speaker installation.

If, for example (and I won’t say exactly how I learned this), you plug the ESU 73900 LokSound Select NMRA DCC Sound Decoder 21MTC Connector into your ESU 51900 LokTester Decoder Test Set so that you can program it with your ESU 53452 LokProgrammer Set AND you connect the two brown wires to the speaker connection not thinking that the ESU 51900 LokTester Decoder Test Set features an integral speaker installation. 

When the process of loading the sound file is finished, you switch to Cab Driver to test the installation and you get nothing.  A mute sound decoder.  Bummer.  You stare at the whole mess for a few minutes and have another one of those “light bulb moments” when your focus lands on those two brown wires.  

You think out loud, “Oh yeah, I bet that ESU 51900 LokTester Decoder Test Set has an integral speaker installation...”