SoundTraxx DSX Decoder

The "Keep Alive" Capacitor

One of the main advantages of the DSX decoder series from SoundTraxx is the ability to add a “keep alive” capacitor, which keeps the sound going and reduces “resetting” due to minor track power drop outs.

Litchfield Station sells the capacitors for this use. If space permits, Bruce recommends the 2200 uF capacitor. However, the 470 uF will help (but only about 1/4 as much, due to the lower storage capability). CLICK HERE to browse the store.

SoundTraxx provides a Technical Note on the subject. They have removed it from their site. Here is a link to a copy Mr. DCC saved - not guaranteed to be the latest: CLICK HERE


However, they say that a picture is worth 1000 words. So, I’ve posted photos here of my install of a 2200 uF capacitor on a DSX. For this photo, the capacitor had already been soldered in place and the iron was cold - no smoke or hot tip to deal with when trying to take pictures!


Here is an overview of the installation. Where room permits, Bruce likes to attach the capacitor directly to the DSX as shown. If room is tight, he attaches color coded wires to the pads and to the capacitor, with shrink tubing for insulation on the joints. Frequently the track power leads from the DSX provide enough excess length for the purpose. If not, he follows the DCC color code - blue for positive and green/black for negative.

The metal piece just above the capacitor under SoundTraxx’ white shrink tubing is there for heat management and MUST NOT BE DISTURBED! Getting between that heat sink and the board to solder the wires requires a certain amount of soldering skill and a VERY SMALL iron, as shown in this photo.

Under Layout Sound

The DSX decoder can be attached to ANY 8 ohm speaker or speaker system. Since the DSX puts out 1 watt, Bruce recommends you limit the speaker to one rated in the 1 to 10 watt range. He used a small (about 4 x 4-1/2 x 7-1/2 inch) Radio Shack "Minimus 7" speaker system from the late '80s or early '90s under his layout. He used a 470 uF 16 volt bipolar capacitor for coupling. The input leads for the DSX connect to the track bus. Give the DSX the same address as your loco and you are running!

If you want to connect an external amplifier to the DSX and run larger speakers, check out SoundTraxx' technical notes; CLICK HERE to download the PDF file.

Litchfield Station now stocks the transfomers necessary to make this connection - CLICK HERE!

Copyright © Bruce F. Petrarca 2007 - 2018; All Rights Reserved