http://www.soundtraxx.com/dsd/tsunami/playsound.php?s=emd645t
This is a sound sample for the 645 turbo engine from soundtraxx.
I don't have experience with the digitrax sound decoder, but I have an MRC steam sound decoder which I had to replace because it fried. Now, the new decoder will not allow me to program CVs. I would hesitate to recommend MRC to anyone. I would spend a little extra money and get a tsunammi TSU-750 with EMD 645 sound before either of the above. From what I have heard, the sound quality is far better.
Any opinion on better sound option, a Digitrax unit or MRC?