OK so obviously I cannot speak for your experience, however I might have an idea of what you're talking about, and I too blamed the amp....at first....
I was getting a lot of noise the first 2 days of owning this amp, it wasn't like it was malfunctioning, it was just slightly more than I'd expect, and I also realized there can be a whole lot of vibration pick up through the tubes, which is fine. However it wasn't until I started up a game(on my PC) while listening to some music (from my PC) and I was stunned to find out I could basically hear my GPU's power draw through my headphones. Direct correlation to the fps on screen, to the sound, turned out to be a ground loop, and it seems to have been solved by bringing an extension cord and changing outlets. That solved I also realized my RCA cable was picking up noise, and had to move some things that were along the path, however that too is pretty much solved. I also re-seated the stock tubes, and that helped as well to where the noise was only audible when impedance was set to 300+, or volume very loud. I don't know how sensitive Blon BL03's are, but they were pretty quiet (not set to 300 ohms though, obviously).
Not to say you don't know a ground loop from amp noise, but there are a LOT of things that can cause noise from this amp that I've realized in a very short time, and stock tubes have a fair amount of noise, considering, but a tube swap has brought this amp to THX amp levels of silence. It's really stunning to me, but for sure the amp itself has a very low noise floor, but it's sensitive to a lot of things, what's weird though is this amp caught the ground loop, but switching to my thx 887 from same dac (just from xlr outs), and I hear silence. The dac filtering for xlr but not unbal out? Odd... Or the ha1a-mk2 was the thing causing the ground loop specifically and therefore only heard when using it. I don't know, i'm not well versed in electrical engineering so it's all confusing to me.
Another slightly related thing to share......
I upgraded the driver tubes. Genalex Gold Lion ECC82 (12AU7). First off, the noise? gone, completely silent, even if set to 600 ohm OI, only when the volume is set past 12, does noise begin to appear, and only barely. I was shocked by what swapping 2 tubes did to the noise floor, it wasn't even very loud to begin with, but man.... The sound of them also significant change to the stock tubes, but this isn't about that.... Upon installing the new tubes, I found the right channel wasn't working, at all. Dead silent, even though both tubes were clearly seated fully, and warm. I re-seated the right tube and the right channel had sound again, however along with it, came noise. A lot of it, volume having no effect on it, unplugging the inputs as well. Clearly the tube was doing it, in addition this specific tube had massive vibration pick up, and is making a sound that is like a wave, growing in volume. Like an ocean wave kinda sound, someone told me that it's called tube rush, and I'm wondering what to do about it. The other tube in the matched pair I got works brilliantly, dead silent, no vibration pick up even, but this other one scares me with the noises it decides to make randomly, as in, it will be working great, no noise, no vibration pick up even, then out of nowhere it'll hit the right channel so loud with noise it scares you. Did I get a defective tube? Should I hit up the seller (was an amazon purchase) or is there some way of dealing with this. I quite like these new tubes, the sound is very nice, and the lack of noise (when working right) sounds on par with THX amp silence, truly impressive, but having one tube acting this way isn't good...
