I want to begin my "review" by saying that this is the best amp I have ever had, both visually and technically speaking. It is beautiful.
I decided to get the HA-6A because I saw the review of
@Relaxasaurus (Midfi Guy on YT) and he's one of a very selective few that I trust on YT
My unit is already 1 year old, so the valves already have x hours of use
The very first time I plugged it in, there was a very noticeable hiss, the cursed hiss I've read a lot here about the HA-6A so instead of crying like a baby I removed all the tubes, plug them back again, but not KT88. I used the EL34, moved the switch behind the amp to EL34 position and voila: 0 hum, 0 hiss, 0 noise, very very black background, you can
hear there's something but it is very black. After checking out about the fact that the hiss was gone, I plugged KT88 back again and no noise at all either. ("Fixed" by restarting I guess)
Sound impressions with KT88, default valves, I preferred TR to UL with these:
(D8000 Pro, no EQ, volume at 9:00 position most of the time. RCA+SE, low impedance position)
Big sound, big body, never boring, every single instrument has its own personality, its own place and its own position within the soundstage... Layering and depth is impressive when the music allows it. Very holographic.
Every single instrument has texture, you can feel it, it is virtually solid in front of you, you can't see it but it is there, has its own importance and relevance...
Bass is amazing, going very low and with this valves sometimes a bit boomy but very sweet, the midrange is there, vocals are really good, a bit forward to me but never too intimate and the treble is on pair, very detailed and never strident
Resolution compared to let's say the Kinki is like going from 1080 to 4K, the naturality and organic sound of instruments makes you smile like a child, like how is this possible? this is just headphones!!
The quality of what you're hearing is so detailed that you can even know how big the concert hall is because the reproduction of the air between the instruments, the echoes, resonance etc.... It is like you are really there, very very hard to really get this feeling on headphones. Never felt any brightness.
Sound impressions with EL34, default valves, I preferred UL to TR with these:
(D8000 Pro, no EQ, volume at 9:00 position most of the time. RCA+SE, low impedance position)
Sound is not as big or full as with the KT88 valves but this time we're going for surgical accuracy and precision of the sound, while still being a romantic and funny mix of tubey sound and SS, never sterile or boring
Again, every single instrument has its own texture but with even more resolution than KT88, I could say EL34 for classical music might be the best if you want to experience the ultimate detailed experience
The soundstage gave me the impression of being a little bit smaller than KT88 but with more coherence and maybe, realistic. I know my music and I spent many hours everyday listening to it so I'm not afraid to say that
Bass is amazingly detailed and linear, never boomy and never too much, even if I give 8dB+ to 20-60hz it will still sound very precisse and never loose
Midrange is to die for, I had never listened to voices with this resolution, detail and realism, specially women, you can even draw their faces, it's like they are in front of you singing for you haha
Strings are simply amazing, it is so very very very detailed and accurate than a simple guitar can transform your listening experience
Piano, for the first time sounds like piano, from the very first keystroke you know that is a real piano, I've heard many live and I know how they're supposed to sound, you can get that experience with this amp and EL34
Treble is never strident either with this valves, very detailed and sweet. Never felt any brightness.
Cons:
- (Not Cayin's fault) I will probably have to change the EH 12au7, one of them is probably dying and I get an interference in the right channel (after many hours of use), which is where the valve is and I tested it by hitting it with a pencil and
you can hear is not a solid hit, like something vibrates inside more than it should. Luckily they are very cheap so I might try different brand, I wonder if buying valves with low power needed will reduce any hiss even more
- 100 watts of use, compared to the 10-20 watts of the Kinki, still I don't really mind, I get pleasure for 100 watts and the room gets heated, not really a 'con' haha
The amp made me have to buy a new table to place it on, we're talking 20-25 kg of weight it is no joke, but it looks so very beautiful....
Final notes:
I never expected to have this kind of amp, I've always wanted to get the best sound by spending the less possible, I was close to it with THR-1 or Elise but somehow decided to try this and while it's not end game for me because I know I will end my journey with SS, this is worth it for real, this is not a joke of an amp.
You can really play with it using all the tubes you want, adapters, TR, UL, different impedances,
any headphone you throw at it will work, SE, 4.4 or XLR..... And whatever you do, the quality of the sound is going to be superb
Again, this is my first Cayin, I don't care where they come from or where they are, I'm just honored to have a piece of gear designed by beings that made me enjoy my music even more and provided joy in the darkest of times
José
(Thank you to @ThanatosVI for his inestimable help)