Yes I own a few class 58s, yes I've seen inside them.
How big is the PCB recess in the class 58? W12.48mm x L32.3mm x D6mm. Now, compare that to the Loksound Micro v4.0...W10.6mm x L25mm x D3.8mm, and theres a 23mm x 8mm x 4-5mm recess at the other end which could readily house resistors with easily made redundant channels built into the chassis for wiring runs being as it would make sense (there is little other choice) to hard wire. Theres even a big capacitor beneath the chassis block in the fuel tank that can come out giving you a factory provided wiring route there for a speaker. Looks like half the works been done to me. Yes, I have looked into it...but my first and most important issue is its a complete waste of money so I won't waste my time or hard earned on it.
The sound given off by speakers limited to N Gauge sized enclosures (and 00 to be honest) are absolutely pitiful in their reproduction unless the real thing has a predominantly high tone. This is why the likes of 2 stroke EMD and the HST will generally work although extremely tinny, while other diesels just sound naff and always will. As beautiful as the Mercig 58 is, the sound absolutely ruins it. The class 58 was like being passed by a rolling thunder storm, a smaller scale (00 and N) model will
never get it right, and most of the video of them is taken using poor quality sound equipment so a true comparison is hard to find,
THIS is one of the better ones. To put a visual spin on it, I would compare DCC sound in N to the likeness that the Lima N Gauge Deltic has with the real thing; it bares a passing resemblance if you squint your eyes really tightly and look the other way, but thats as good as it gets. I've had 'modellers' using their bragging rights on their sound fitted models before - 'mines better than yours, its got sound' and all that tosh. My answer, 'it sounds very little like how i remember them, here, listen to this recording I have of the real thing' which usually shuts them up if not their god awful models too. If that fails then I get my D&RGW F3 ABBA set out and show them what
REAL DCC sound is about as it drowns out their rubbish whiney class 66 or similar, and every other locomotive on their tacky little shunting plank-cum-TMD.
Also one thing is worth remembering is that US N scale locomotives are a smaller scale to that used for British N, much in the same way as H0 is to 00 only not quite as large a difference. I believe British N is 8.12% larger if I am not mistaken, being made to 1:148 rather than the US which is at 1:160. The internal width of many US models actually dictates a PCB width of ~11mm, the class 58 PCB certainly doesn't fit inside the Atlas GP7 (I've tried), and MRC do a drop in sound decoder for that model.
By the way, I prefer this photo as a comparison between 12":1' Canadian and UK motive power...
http://www.railpictures.net/viewphoto.php?id=182313&nseq=3 