I used the cap. The decoder puts out a DC voltage also so the cap prevents the DC from getting to the speaker, though I have run it both ways. That is why it is a bipolar cap.
The newer SoundTraxx do not need the cap for the speaker. They use a different cap for sound stay alive in the present SoundTraxx decoders.
I have used the older decoders for LED's. I just put in a 1k resistor. Usually standard for LED's for most people. Maybe your loco had a resistor already before you added your own resistor.
By the way, SoundTraxx has stopped producing the present Tsunami line. If you want any, get to your LHS.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
It is the older decoder. I am using the bulbs that came in the engine since the instructions with the decoder does not recommend LED's. I did try them but they burn at a low level when on. Depending on the direction of the engine, the corresponding LED burns at a higher level. Did you use the capacitor on the speaker that they include with the decoder?
I have to assume you have the older DSD decoder in yellow shrink. I have some and work just fine with an eight ohm speaker and baffle.
I use a 1k resistor for LED's which allows 9 ma current and look fine.
What does your loco use, LED or light bulb?
i am installing a older Soundtraxx sound decoder in a Proto engine. Having trouble getting the sound to work. I am using a newer sugar cube speaker and have tried it with and without the capacitor that came with the decoder. I also had trouble with the 680 ohm resistor that came with the decoder causing the lights to be very dim. I changed this to a 180 ohm resistor that helps with this. Any words of wisdom?