OK, I'm sure this one is super simple, but I'll be darned if I can find the answer.

 

Can a sound decoder which is capable of driving a motor, but being used for sound only (a separate power decoder being used) be used in a situation where the motor draws significantly more current than the decoder is rated to handle?  In other words, can I use a 1A HO sound decoder, such as a DSD-100LC, in a large scale loco drawing 2 or 3A and powered from a separate and more powerful decoder?  I understand that some HO decoders have a voltage limit, but assuming for the sake of argument that that is not an issue, can it be done and work reliably?  It seems to me that the small scale decoders are MUCH smaller and less expensive than their large scale counterparts, and do the same job.

Yes.
I have used Tsunami and Soundtraxx DSD's that way. The one sound decoder I use the most is the Digitrax SFX064, but I have also used all the other versions, including the Digitrax SoundBug. Put the right 8 ohm speaker on them and the sound every bit as good as most other sound decoders, and they have more functions. Besides, they are in the 40 to 50 dollar price range. Get a PR3 to program them and you can do all sorts of stuff. I have about 15 of them installed so far.

Here is a video of a 40 dollar sound bug and a DG583S motor decoder in my K27.

 

This is another showing the alternate whistle I added using the PR3. (the second scene where it is backing up)

 

 

 

And here is a SFX N scale sound decoder in a field railway loco with a customized sound scheme installed using the PR3 to load the decoder. It too, uses a G scale motor decoder but with a "N" scale Digitrax Decoder. All their decodes are rated to 22 volts.

 

 

 

 

And Yes, "Dixie" is coming from the SFX decoder, but it also does all the usual bells,chuff's and stuff like that.