# Disappointed with the Digitrax SDXH166D HO, sound decoder.



## Dennis461 (Jan 5, 2018)

I put a 8 bit SDH166D in a Mantua, 4-6-2 and it works fine.
I put a 16 bit SDXH166D in a Mantua 2-8-2, and I don't like it.
With sound on, the loco stops and starts randomly. It also stops when I sound the whistle.
I've been reading the internet, and now think this was a poor choice.
I turned off BEMF with no noticeable difference in opertion
If I "mute" the sound, the loco runs OK.

I wonder if adding the keep alive (power extender) would help, or is it sending bad money after good?


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## CTValleyRR (Jul 26, 2014)

I'm not an expert on this stuff, but it sounds to me like the sound features on the decoder are drawing too much power, or possibly the motor draws too much, starving the sound features. I'll let the experts suggest solutions, though.


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## Dennis461 (Jan 5, 2018)

Digitrax said to return it !?


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## CTValleyRR (Jul 26, 2014)

Then return it. Defective happens, even to the best of products.


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## Dennis461 (Jan 5, 2018)

Decoder returned. It still does same thing. Going to replace it with the 8 bit sound decoder.


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## Dennis461 (Jan 5, 2018)

So, both 8 bit and 16 bit mess up in the steam loco. I put an 8 bit in a Bachmann F7B and the diesel sound is great, loud, and motor never stalls.


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## Dennis461 (Jan 5, 2018)

Replaced the decoder with a XL Systems model 1911


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## graywolf06 (Aug 14, 2019)

Since this topic is about Digitrax decoders I thought I could get some expert answers. I plan to use a SDHX136 decoder in a Bachmann 44 ton GE diesel. The problem is very limited space and I was wondering if I could eliminate the capacitor that is part of the decoder package. I also plan to remove the speaker it comes with and substitute a Sugar cube speaker.


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## Lemonhawk (Sep 24, 2013)

If is the capacitor in series with the speaker, no it blocks dc from the speaker. Wise choice going to a sugar cube - much better output, it won't sound so muffled.


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## graywolf06 (Aug 14, 2019)

Thanks for the reply. So it seems I can just cut it off and tape the ends of the wires?


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## Lemonhawk (Sep 24, 2013)

It looks to me like the capacitor is the DC block for the speaker and should not be removed. You can cut the speaker cables and connect the sugar cube to them. Its likely that if you were to traces the cap one lead will go to one of the speaker wires via the PC board. The Capacitor is on long wires so you find a place to put it.


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## graywolf06 (Aug 14, 2019)

Thanks I am getting the impression that I will have to deal with it. I may stick up thru the roof and call it some kind of sensor or antenna. Haha


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## Lemonhawk (Sep 24, 2013)

Sand Dome! You might look at other decoders that use an amp circuit that does not require the large cap. by the way, I have a Digitrax sound decoder in my NKP Berk and the speaker that came with it was worse than terrible. Sugar cubes did not exist so I use an Apple phone speaker, made a world of difference. Yankee Dabbler has nice $12 sugar cube like speakers that I use in my F2, also great speakers very flat size wise.


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## graywolf06 (Aug 14, 2019)

Ordered everything from Streamline Backshop since he had a 8x12mm speaker available which gives me a little more room. Got the LEDS from him also. He is loading a sound program in it for me after going thru the offerings at Digitrax. I choose Diesel loco T769 which hopefully should be a hoot. Listen to it!!


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## MichaelE (Mar 7, 2018)

That cap might also be a 'keep alive' cap if it is of good size.


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## graywolf06 (Aug 14, 2019)

It's only 100 micro farads so probably only keeps the sound on for a second or so. I could remove it to see what happens and always reattach it if needed. All my switches are powered so hopefully the engine will make it across.


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## MichaelE (Mar 7, 2018)

If it is a keep alive cap, it's not so much for the sound as it is the motor. The sound on my locomotives with keep alive caps will cut out for a fraction of a second while the locomotive runs smoothly on by on a less than spotless area of track.

After a wipe with a gun cleaning patch the sound is fine.


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