I was lucky to get to try once a '70's Dumble ODS 50. I still haven't tried another amp yet nearly on that level (haven't tried a real Trainwreck yet though). You could just play one high open e and be amazed at everything going on in the one simple note. With most amps once you hear the note come out of the speakers that's as good as the sound will be, but with that ODS it kept evolving and getting better, more detailed as it rang out. For other amps I'd call 3D, this was 5D. And the way notes connected to each other on leads would probably have made my iic+ sound sterile and disconnected like an UU if I had compared them lol (I hadn't). What amazed me too is that clearly it's not at all a metal or shred amp, so it seemed like there wasn't nearly enough gain or compression to play sweeps or shreddy type leads, yet it was glorious for that somehow. The notes somehow still all carried through with sustain and distinction. It doesn't make sense, but you just play it and it's there
My dad and others were there who didn't even play guitar were all blown away and I'm not a great player nor the "right" type of player for that amp either. It wasn't though that great until it got loud enough, kinda muffled, but once it was it was very obvious why the demand is there. This clip shows some hints of good stuff about it, but I think especially with special amps like this it doesn't even scratch the surface of what I heard with it (same IME with the Klon or best classical guitars I've tried). I didn't really get the hype from clips until I tried that one '70's ODS. Like Tiago said also, I've played lots of clones including Bludotone's, several 5 figure Two Rocks, Smarbelle, lots of Fuch's, etc. and if the Dumble is an orange or apple, the Bludotone would be a medicinal tasting orange candy or cough syrup. Sometimes I think you have to be as nuts as a guy like Dumble to create something exceptional. Some great artists are just very weird and Dumble I'd think clearly had to be an artist (whether he could play well or not), not just a great technician like many amp makers it seems