Having several Digitrax Sound Decoders in some of my E-units, I will say the sound is barely tolerable, even though I have installed air tight speaker enclosures on all of my sound installations.
I'm a big fan of both ESU and Soundtraxx...and in the past I prefer Soundtraxx Tsunami's over ESU Loksound for steam sound installations, but I prefer ESU for diesel sound.
I have been told that both ESU and Soundtraxx have new, improved sound files for their big steam engines, meaning Big Boy, Challenger, and FEF...as well as others I'm sure. I liked the old Soundtraxx sound file very much because of the rod clank and whistle...ESU's file being totally wrong for Big Boy, Challenger, and FEF whistles, which in real life are the same chime.
I also prefer Soundtraxx because of its integrated frequency equalizer, which allows manipulation of several frequencies to optimize the speaker you might be using...which for steam and all its low frequency sounds which cannot be replicated by tiny N-scale speakers, to be turned down so there's less distortion in the middle/high frequencies...improving the sound noticeably. I also really love the brake squeal...which is just right in my Soundtraxx Tsunamis.
However, I have an ESU equipped Kato FEF-3 that I haven't fully explored yet with the new steam sound file...and it seems to sound pretty good, although I am never happy with any sound decoder's default sound settings.
The point being that both Soundtraxx and ESU sound decoders are so advanced over what Digitrax makes that in my opinion, it's not worth the effort to make your Digitrax sound decoder sound better because it will never come close to what you'll get out of Soundtraxx or ESU...especially for the complex sounds emanating from an FEF-3.
However, since the tender is so big on the Kato FEF-3, I'd see if I could fit a larger speaker and enclosure in it than a Sugarcube, which will help optimize the sound of any sound decoder you may choose to finally stay with.
Cheerio!
Bob Gilmore
