# HO Sound Modules



## rreiffer (Jan 14, 2009)

Has anyone used any HO sound modules successfully in large scale? Pros/Cons if you did?


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## Dave Meashey (Jan 2, 2008)

I took the innards from an AHM HO steam sound gondola and put them in the tender to my LGB 2018D Mogul. I put two sets of contact bars on a tender axle, which gives about four exhaust beats per drive wheel revolution. The system works as expected off its 9V battery, however, it is heard better indoors. Outside the locomotive seems to be wispering. (I'm told that woodburners were more quiet anyway, but doubt that they were as soft-spoken as my locomotive.) This modification is about 15 years old. Perhaps today's small scale sound modules may have more OOmph. I know the ones on Tom Harris' Lakeside Lines HO railroad do, but again those trains are indoors. 

Yours, 
David Meashey


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## toddalin (Jan 4, 2008)

I bought three for diesels at $15 each. After listening to one, I wouldn't even consider installing them.


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## RimfireJim (Mar 25, 2009)

By "modules", what do you mean? DCC sound decoders? Or something else? 

For $15 each, I wouldn't expect much. A good quality sound decoder goes for substantially more than that. 

I don't have any actual experience with this, but one parameter that needs to be considered is the audio output power requirements. The bigger speakers used in large scale will require more power to drive them for the volumes expected in a large scale outdoor environment, as compared to the 3/4" or 1" speakers used in an HO loco on an indoor layout. A Soundtraxx TSU1000 (for small scales) has 1W output, whereas a QSI Quantum Magnum has 5W. Big diff there. Depends on how much you need for your tastes. I don't like the volume cranked up in either situation, as it makes the loco sound a lot louder (closer) than it should for the scale distance between it and me.


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## rreiffer (Jan 14, 2009)

I have been looking at the issue of output power and there are quite a few IC based audio amplifiers for about $2 each that have between 5 and 10W output. Put one of these in conjuntion with a good HO sound module and you might be able to come up with decent sound for less than $60 per engine. This of course is all speculation on my behalf. Taking sound volume out of the picture how have the HO based sound decoders/modules been as far as quality of the sound, etc? Thanks


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## George Schreyer (Jan 16, 2009)

Some HO sound decoders put out marginally enough for large scale. Some Digitrax units and LokSound v3.5 units do marginally well enough. The LokSound Select does better, it is loud enough. A Tsunami is also marginally loud enough. 

The Digitrax SFX0416 is NOT loud enough while the other models are ok. 

an "afterburner" in the form of an audio amp is pretty cheap. look to the futurekit.com FK602 for about $6 + shipping. You can roll your own out of basic parts for a little less.


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## Dan Pierce (Jan 2, 2008)

Watch out for voltage limits!!!! 

Zimo HO decoders do have a higher voltage rating than most and work well on small G engines such as the LGB rail truck. rating for the MX620 is 12 to 22 volts, MX640 is up to 24 volts. 

Newext MX642 is 30 volt and 3 watts of audio power 3 ohm minimum speaker. Can handle 1.2 amp of motor and over 2 amps total average power output per the spec. 

MRC G scale has a 21 volt limit, and the smaller scales are less. 

So, check the specs before using any decoder on G scale. some are much better than others but usually cost much more.


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## rreiffer (Jan 14, 2009)

Dan, 
Actually for any system that requires a lower voltage I put in a small Zener diode system that drops the DC voltage to the correct level. 
If you go to the following web site there is a good basic tutorial on zener diodes: 
http://www.electronics-tutorials.ws/diode/diode_7.html


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## George Schreyer (Jan 16, 2009)

If a decoder is truly compliant with the DCC standard (as defined by the NMRA) it must be able to deal with 27 volts. Many don't. 20 volts or more is unreasonable for the smaller scales but in large scale it is common and often necessary. 

I have used the MRC AD322 at 22 volts and one died, but I suspect that it wasn't due to over voltage. That decoder has other issues, especially as related to the reversing relay. Greg has toasted several of them, his track voltage is higher than mine, but no great loss. They were junk to begin with. 

The LokSound v3.5 decoder has issues at high voltage. It will handle high voltage (22 volts) at low motor current and will handle full (1.1 amp) motor current at lower voltages (16 volts or so), but it thermally overloads and shuts down when the track voltage and motor current are both high. This appears to be related to the load caused by the sound itself, the internal regulator cannot handle the current of the sound system at high voltage when there is additional heating from motor loads. It will run hot even when the motor is not running at high voltage but deals with it well at 16 volts. 

Digitrax decoders (sound and motor) seem to put up with 22 volts without problems but the audio power of the sound decoders is low so they don't draw much track current anyway. 

The one Tsunami that I have is on the edge, even in a very small loco (USAT Speeder). 

Older Zimo decoders (MX65) seem to have no difficulty at all, but these are larger than the typical HO stuff.


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## Dan Pierce (Jan 2, 2008)

A zener by itself is not a good idea to me. One must watch the bypass current and the zener ratings. 
I am very familiar with these devices and I would rather use a diode bridge and diodes to drop voltages as I can get 4 amp bridges and diodes to do the job and in large scale, there is plenty of room for these.


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## Axel Tillmann (Jan 10, 2008)

As Dan pointed out ZIMO MX642 uses the same AMP as the MX695. Function and capabilities are similar between the two. So Stainz and other one motor LGB engines do fine with this little integrated decoder (sound and DCC). As far as using an different sound unit from HO suppliers I am not certain that they give you 3 Watts output and then adding anopther audio unit is not the right strategy. Also keep in mind the cheaper the thingies the less capbilities/quality. That is a law of products.


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## DTI356 (Jan 3, 2008)

Rich, 

I have used Soundtraxx DSX sound only HO decoders in my 2 USA Trains Diesels and am quite happy with the sound. My engines are onboard battery powered with Airwire900 R/C DCC compatible control. I purchased the DSX decoders for my then 'O' scale trains. The Airwire allows you to piggyback another DCC decoder into theirs. 

Brian


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## rreiffer (Jan 14, 2009)

Thanks everyone for the great updates.


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## George Schreyer (Jan 16, 2009)

Note that the DSX is an older design that does not include very much on board storage capacitance. With a steady power source, such as a battery, it does fine. However when presented with a track powered situation and dirty track, the DSX simply chokes. 

Newer sound decoders have storage capacitors either integrated on board or wired externally which give them substantial resistance to upset due to intermittent power input.


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