This is a long time coming, but with the corona virus, I've finally got time to do this. This is my review of the KGSSHV Carbon I had commissioned from @joehpj (thanks!). I've purchased a pair of Stax L300 Limited to replace the Stax Lambda Pros I had been using for some 25 years before Hurricane Harvey flooded my house and destroyed my old headphones. I've upgraded the pads on the L300 with L700 pads--these make a noticeable difference for me, as the thicker pads allow me to get a decent seal even when I wear headphones. I've been driving them with a Stax SRM-252s, and it has become apparent to me that the amp was the weak link in the chain. After seeing photos of various builds on head-case forums, I decided that the ones joehpj was putting together looked among the nicest I have seen. I decided to take the plunge, despite Joe being in Taiwan, half way around the world from me. Working with Joe remotely was extremely pleasant. He is extremely professional, and allowed for/suggested various changes, from using the venerable Alps RK501 potentiometer, to upgrading the capacitors, to various colors for the chassis. I decided to stick with the stock black chassis to keep the looks similar to my existing equipment. I stuck with the default potentiometer Joe uses--I believe it's sourced from China, and I had heard good things from other people on these forums about it. I also stuck with the stock caps. The one customization I did ask for was to add the delay on power-on for the HV power supply, as I am intending to build a Grounded Grid amp in the near future, and figured I could use this power supply to use as a reference for comparison as I build the GG. Despite some hiccups during construction (Joe's amp-building partner apparently had a severe illness that added delays), Joe was always very clear with me about the delays and offered a full refund for the amp. Also, when the amp first arrived, something happened in transit that ended up compromising the power supply. After some investigations on the problem, Joe requested that I send the amp back for analysis. Unfortunately, the post office wasn't very kind to me, and ended up damaging the chassis and bending the heat sink slightly on one side. When sending an amp across the Pacific Ocean three times, I suppose this might be expected, and it doesn't bother me at all. The Carbon amps that Joe builds come in two chassis, one for the amp and one for the power supply. The cases are very nice, simple, and elegant, and very much look the part of a professional high-end amp. I'll post photos of them shortly. The inerts of the amplifier and power supply look as beautiful and professional as I can expect. My music tastes are all over the map. I'm a software developer, and typically use my headphones 4+ hours per day, usually listening to acoustic jazz (especially Blue Note--Miles Davis is a personal favorite); singer/songwriters (such as Damien Rice, Thom Yorke, and Nick Drake); rap, hip-hop, and rap fusions (including Beastie Boys, Eminem, Dr Dre, Rage Against the Machine, and Ozomotli); classic rock and prog rock (old Genisis, Yes, Pink Floyd, and the like); EDM (Chemical Brothers, Daft Punk, and Deadmau5); Alternative (R.E.M., Radiohead, and U2); and loads more. Basically, I like all styles of music, aside from country/western (unless you consider Johnny Cash country) and most bubble-gum pop music (although I might have a soft spot for my daughter's Taylor Swift music...shh, don't tell anyone). I listen to some classical, but rarely as a critical listener--usually when I'm trying to get some coding done. The sound is, as expected with a Kevin Gilmore design, stunning! Doing comparisons between my Stax amp and the KGSSHV shows that the new amp has substantial "authority" in the bass. The "air" in the midrange is closer to what I hear when listening to SR-Omega/SRM-T1S, the pairing that first brought me to the Stax world, even though it was far outside of my price range until recently. I'm afraid as I get older, my previously excellent high-end hearing isn't what it used to be--I used to have hearing through to 22kHz, whereas from my current testing it appears I'm only able to hear closer to 18-19kHz--still excellent for a male of my age (49). Despite that, this pairing between the L300 Limited and the KGSSHV Carbon is never the slightest bit fatiguing. In fact, with the higher quality front-end, I'm now finding that I don't turn the volume as high as I did on the SRM-252s, which ought to help my ears over the coming years. The noise floor on the amp, even when turned all the way, is non-existent, even though for actual listening I rarely turn it above about 15%. Balance between channels on the stepped pot is, to my ears at least, perfect, although I haven't measured it yet. I've not heard an amp with the Alps RK501, so I don't have a good reference here, but I am very happy with the Chinese pot that Joe used. The downside? I've always found Stax to be extremely revealing headphones, and they exaggerate poorly mastered music, and they are even more so with a better front end like the KGSSHV (old Genesis and Peter Gabriel--I'm talking about you). But on well recorded music, there's nothing better, in my humble opinion. The imaging and separation on old Miles Davis is absolutely superb--Sketches of Spain and Kind of Blue are regulars for me to evaluate equipment, as the simple mic placement, and quality of mics, used by Rudy Van Gelder can be extremely revealing, despite the recording being made 60 years ago. I've got a binaural recording from Stax--a sample disc they produced back in the 90s to show off their at-the-time new binaural microphone--that is absolutely stunning. There's one spot where a door is slammed...every time I hear it, I turn around to see who has come into the room. Likewise, the binaural bits on Pink Floyd's The Final Cut also make me feel like I am there in the room. These were stunning before with the SRM-252s, but they are more...involving, for lack of a better word...with the KGSSHV Carbon. To be honest, I'm afraid the pairing of the Stax L300 Limited with the KGSSHV Carbon has rekindled my never-ending hunt for higher quality sound. I've already determined I'm going to need a new DAC, and I've started experimenting with 24-bit and 96kHz or 192kHz sampled music. To be honest, now I'm beginning to look at higher-end Stax, like the SR-009s. I'm also looking forward to experimenting with tubes on a Grounded Grid. But I've definitely reached the point of severely diminishing returns. Thank you, Joe, for rekindling my old audiophile tendencies!