My Hypex Nilai500DIY amplifier kit did in fact arrive yesterday as expected! I spent a couple hours in the afternoon building it, and then the entire evening listening obsessively in wonder.
It's packaged and set up beautifully, in order to get everything ready to go quickly. Minimal tools are required by the end user, just a pair of needle-nosed pliers, a small flathead screwdiver, a 12mm wrench, and a 7mm socket wrench. The quality is unquestionably present, in all kit components. The amplifier boards themselves are gorgeous and mounted on thick, polished aluminum. I more than half wish they were visible! The modules light up when powered, incidentally, which is slightly but attractively visible through the tiny holes in the top panel. The case is robust aluminum.
There is included an install guide. It's pretty good; there were a few steps where the Ikea-esque pictures confused me for a minute or two, but nothing I did couldn't be undone, and then redone properly, easily enough. The one step that was definitely unclear in the booklet is that you have to snap off the little board for the front panel LED from the left channel balanced connector board, but it obvious what to do, when you get there.
I won't say the build for me was exactly easy-peasy, but only because so many fasteners are tiny, and I'm 52 and not simply not very deft with tiny screws and such, and also I need some magnification to be able to manipulate them all into place. The design itself is as neat and clean as anyone could ask for, so if you're comfortable handling small objects, it should be a breeze. Even for myself, I'm guessing that, if it happens that I assemble any more of these, it would take me less the half the time it did yesterday, now that I get it. All in all I would say it was a fun assembly.
Of course what everyone wants to know is, did it work? How does it sound?
It works, with zero issues, and zero trouble-shooting required.
As for the sound, well I was going to make an crack involving my wife coming running from the kitchen, but actually something just as dubiously clichéd actually did happen. My dog, normally totally indifferent to anything coming out of my speakers (except the sound of other dogs barking), kept getting startled! And not because or just when I had the music turned up nice and loud. It's cute, really. I'm sure he'll get used to what's different about what he's hearing soon.
My old amp, in service for 23 years, is a Hafler DH500, itself originally a kit from around 1980. It's been refurbished, and honestly I've loved it. For its vintage, it's been outstanding. But it is unquestionably old technology. It has a fan, which is audible. Just gentle white noise, but still: that alone I'm glad to dispense with. It also draws a lot of current, even while idling. After all, it's rated at 250 watts per channel into 8 ohms, and it's class A/B, heavy on the A.
Probably the Hafler measures well for its age, but the Nilai500DIY undoubtedly measures way better. The question in my mind was, better enough that I'd notice?
Well. It's a subjective response, with zero blind testing, but absolutely, to me, it's noticeable!
Ok, I know how this works. It is easy without blind tests to be sure you're hearing a massive improvement where there in fact might not be anything actually distinguishable, outside of sighted testing. Yet, I'm a professional musician with conservatory training, who has also worked in the electroacoustic and recording/mastering realm for decades, so if there's an audible difference, I hope I'd hear it. And I say there's a difference.
The Nilai500DIY is actually far more of a improvement than I had expected! Among things I think I've noticed, beyond the indisputable absence of minor fan noise: the new amp has absolutely zero added hardness or harshness, even when cranked. It's like a window so transparent and without reflections, you can't even tell that a window is there at all.
Obviously, take all that with a healthy degree of cautionary skepticism.
Short answer: I am well pleased.
Incidentally, my dad is a professional (now retired) cabinet maker. He's going to be working on a replacement faceplate in some kind of exotic wood. We're going over some designs. The stock faceplate is fine, but I don't love it.
To be fair, I still have a UcD400 that about 15 years ago, you helped me with, which included replaced capacitors, and a special arrangement of caps in the driver power supply. It still works and sounds as good as it ever did though 
