My Vali came in yesterday and I've had some time to listen to my headphones with it.
First off, I bought it because I was curious after the rave reviews, and for $130 including shipping costs, it was cheap enough to warrant a listen. Also, I wanted to use it with my KEF M500 at work, despite hearing the noise floor problems with more sensitive headphones.
First thing like many noticed was the microphonics of the tubes. I've actually heard tube microphony before my Quickie preamp, but nothing like this. The ringing was very different. The Quickie microphonics was very analog sounding with a reverberation you could associate to tubes. The Vali microphonics was digital in comparison, sounding like a MIDI note. Perhaps this would foreshadow what was to come. Also, the persistence of the ringing last far longer than the Quickie. It would take a good 30 seconds before the microphonics are completely gone compared to less than 10 seconds with the Quickie.
I tried the Vali with the KEF M500 first, and being a portable high sensitivity headphone, the noise floor was apparent. However, once the music started playing, it was unnoticeable. Other than the really quiet parts of songs, I did not hear the background noise at all. As for sound quality, I have to say compared to driving through the Audioengine D3 alone vs. D3 + Vali, the Vali made the sound of the M500 much more dynamic and holographic in dimension. Better detailing as well compared to D3 alone, likely due to the improvement on dimensionality and imaging. I have to say I'm quite satisfied with the performance of the Vali and M500. I will probably get an attenuator to rid the background noise.
Now for the meat of this review: How it pairs with the HD800? Unlike the M500, the HD800 has no noise floor problems. But also unlike the M500, I'm driving the HD800 better than I was the M500. The Vali faces much stiffer competition against the gear I'm currently using with the HD800. Namely the Bottlehead Crack w/ SB. So how does the HD800 sound from the Vali compared to Crack? To put it bluntly, the Vali can't hold a candle to the Crack, at least when paired with the HD800. I found some better dynamics and details from the Crack, but the biggest difference by far was the sound signature. The Vali made the HD800 sound much too bright and thin. It was piercing and quickly fatiguing. I honestly could not stand it. It was pretty much like listening to the HD800 from my solid state D3 directly. This is probably mostly subjective and due to what I'm used to, but I can really understand now why people criticize the HD800 on its brightness and thinness.
I found out from Schiit that the Vali has a 50K ohm input impedance, so that makes it compatible with preamping with my Quickie. The Quickie has been known to me to add a very warm signature, whether it was plugged into the Crack or the Emotiva in my HE-500 setup. Adding the Quickie did help, and at first I thought it had fixed all of the Vali's brightness problems with the HD800. However, after some extended listening, it still got fatiguing, and I could hear the same brightness from the Vali alone. The Quickie may have added some bass and a more wholesome bottom end and gave a warmer sound, but it didn't tone down the highs at all. In the end, I could still hear the same brightness and thinness. I guess compared to the Crack, the Vali just accentuates the highs more, and other than EQ, there's no way around it. I cannot recommend the Vali for the HD800. At least if you're expecting a warm tubey sound, look the other way. The Vali sounds more like a SS amp than a tube amp. Then again, at $130 I don't know of any amp that could give you a warm, non-fatiguing pairing with the HD800. So this is not to hold anything against the Vali; it's not like there's anything in the same price range that could do any better for the HD800. For anyone thinking of getting the HD800, I recommend saving up a bit more and getting the Bottlehead Crack at the very least. And if you want more tactility and a richer bottom end, I recommend using the Quickie(w/ PJCCS) in conjunction with the Crack.
So overall, I think the Vali is definitely a competitive product, probably one of the best in its price range. It definitely sounded great for some headphones like my M500. But don't expect the Vali to be a panacea for a picky headphone like the HD800. Also, for any other headphones that are considered bright and you would like to use a tube amp to tone down the brightness and add warmth, I doubt the Vali is the answer either. This includes headphones like the Beyerdynamic T90, which I used to own. While I never tried out T90 with Vali directly, I would imagine it sound just as bright as using a SS amp.
In conclusion, admire the Vali for its technical strengths like detailing and imaging, especially considering the price and competition, but don't expect the Vali to change the signature of your headphones just because it has tubes.
Chains used in review:
Audioengine D3 -> KEF M500
vs.
Audioengine D3 -> Vali -> KEF M500
Audioengine D3 -> Bottlehead Crack w/ Speedball -> HD800
vs.
Audioengine D3 -> Vali -> HD800
vs.
Audioengine D3 -> Bottlehead Quickie w/ PJCCS -> Vali -> HD800
vs.
Audioengine D3 -> Bottlehead Quickie w/ PJCCS -> Bottlehead Crack w/ Speedball -> HD800