As I promised before, I feel like ready to share my listening impressions of Folsom's 7297 chip amp.
First, let's clarify the costs. I reside in Israel, so the following table includes shipment and tax prices for Israel. The overhead is basically costs which are not directly related to the build (like tools, additional parts that were not needed, or solder tin that I bought a lot, cos you can't buy just a bit), or additional costs that could have been avoided, like additional boards components being sent. Here is the table:
Let's say, it's a $600 amp for me in parts (shipped to IL, $440 - no shipment, no tax) + my labor, which was about ~60 hours, as far as I can estimate it.
60 hours is a lot, but this is basically my first amp build, and it was a pleasure to do.
It's about 50 hours of burn-in passed now, and I'm mainly talking about 10-15 last hours of listening. You really need to burn it in at least 20 hours like Jeremy already wrote here, don't even listen to it before that.
SO, what does it sound like?
Well, in short, it's very nice, especially for the price! For me it sounds "sweet", with pretty much apparent solid state signature I was looking for.
My listening setup is DIY Troels Gravesen Discovery-12W speakers: http://www.troelsgravesen.dk/Discovery-12W_Ilia.htm
which are very nice 800 EUR alone in parts (no shipment no tax no cabinet no labor) desktop monitors
The source is digital - RME ADI-2 DAC https://www.rme-audio.de/adi-2-dac.html
I also own Audeze LCD-X headphones to "verify" what I hear. Together with the DAC's headphone amp, these are analytical monsters - https://www.audeze.com/products/lcd-x
I'm mainly comparing the build with my Nord ONE SE NC500MB MKII mono blocks, which are class D NCore 500 based power amps - https://www.nordacoustics.co.uk/product-page/nord-one-se-up-nc500mb-mkii-mono-block-single
(~$1000 each - ~$2000 for stereo)
I basically have a desktop setup, so I intend to use the 7297 on my desktop, and the amp has way enough power for this application.
So what do I mean by "sweet"?
I will do measurements later, but it looks like compared to my monoblocks it has those higher 2-nd and 3-rd harmonics, which make the sound rich, pretty dense hence still clear. It has very nice layering. Because of the presentation it's much easier to perceive it, as opposed to my monoblocks, which are sharper. Generally, my monoblocks are much more "analytical", while 7297 is more "musical", so it is pleasant to listen to. It sounds super great with soft rock, jazz, blues. Vocals are also great.
The downsides, well.. There are some. First, highs are (juuuust a bit rolled off?) not that crisp as on NCores. On the Ncores I even put an "SD Slow" filter on my DAC when I want a longer listening and not analytical session. On the 7297 amp I put "SD Sharp", otherwise it starts to be a bit "muddy". The base is not that tight as on NCores, it sounds a bit relaxed, that especially noticed with electronic music tracks. Though, it's not distorted, even on a decent volume. Few times while I was listening to some not thoroughly known tracks I heard a distortion and was like "Ahaa!", but after rechecking with my headphones it always turned out the distortion was in the record itself (and I was able to hear it "as is" with the amp!). I must also say the base improved a lot while the burn in. I was even setting +1.5 Db on the DAC to match my regular base expectation in the beginning, but now it is set back to 0Db, so I kind of expect it to improve a bit more, but the gap is still big. NCores are holding those D12s by the throat. Looks like the NCores have a sharper step response and a greater damping factor. I'm not really talking about the lower lower base cos my speakers don't really produce it. Still, the base is nice.
Summing up again, it's a very decent amp for the money! It sounds sweet on the midrange midbass, which was my main goal, the presentation I lacked with my NCores.
It's clear, the highs are precise hence not analytically bright, the base is pretty strong and also sweet and natural which adds up to the space perception and "drive" when is appropriate.
It's not a loud deep house party amp, but it was not meant to. In general, I'm indeed pretty much satisfied.
I'm looking forward to building Folsoms 7293 chip amp - https://www.diyaudio.com/forums/group-buys/357577-gb-2-folsom-ec7293-pvi-powered-frontend-amplifier-60-120w-8-4ohm-0-0005-thd.html
It was told to be "better in every single way" and I have no reason not to believe it. I suppose I would be able to drive floor standing speakers with inarguable base authority.
Jeremy, thank you very much for everything - your guidance, assistance, responsiveness and a great design!
Also, thanks everybody for the help and a great community we have.
I was very helped and inspired by other people's builds.