Upon first listen, it was very obvious this amplifier had virtually no mid-bloom effect at all. Vocals seem set up on the same physical plain of existence as the bass and treble, meaning the amplifier is not U shaped and not suited for intimate vocalist headphones like the Audeze LCD3 or AKG K267 / K812. Despite that, the sound stage in general feels wider than tall with excellent stage presence overall. The HA-1 presents a neutral setup. The Bass, Treble and Mids do not compete against one another. Everyone plays together nicely and nobody is vying for attention. This could be a problem for certain headphones with that more intimate midrange appeal.
Overall clarity is again, 2nd best in the price tier and a step behind that darn Conductor SL from Burson. I don’t find this at all something to complain about, due to Oppo offering so many features and inputs on their HA-1. The vocal experience is a bit snappy and nasal on the upper most reaches of the midrange, but nothing to fret over. Once again, purist snobs shouldn’t really be using the HA-1 anyway, so I have no problem in excluding them from the review entirely. Much like a person who wants a tank for pure bliss and enjoyment ( musical sound, something fun ) vs someone buying a lush and smooth Porsche or sports car that handles like butter, but can’t go off road nor can compare to that tank driving experience ( refined, purist sound ).
Also I find the HA-1 a bit too exaggerated with coloration and tone, once again because of that 9018 factoid looming behind my eyes and in my brain. The 9018 is pure, but the HA-1 isn’t a pure sound. It has some coloration, so that means some of the components inside are crayoning the tone of the HA-1 up a bit, but not much. Again, pick your poison here: Musicality vs Purity. The HA-1 is definitely closer to musical than pure so the vocals tend to be exaggerated just a bit. Sennheiser HD800 owners won’t be happy with this sound (unless you are an HD800 owner like me who enjoys the warmth and coloration some amplifiers can produce with the HD800, taking away that raw sound and substituting it for a gently colored experience). If that is the case, then by all means grab this HA-1 because the sound signature accentuates the HD800 VERY well. The HD800 has a nice big, flat sound with neither the bass, mids or treble appearing more or less forward than anything else. There is no bloom on that HD800 and it instead relies on the track to provide the setup and presentation. You wouldn’t want an amplifier or DAC that has a bloom (when any set frequency range sounds more or less forward than the rest) to be used with the HD800 or any headphone like it. You’d want a highly dynamic, wide and deep source or amp that will not bottleneck the staging qualities the HD800 is capable of.
In this case, thankfully, the HA-1 is more than satisfactory for usage with the HD800. With a flattened staging quality, good depth of field and a good sense of width, the HA-1 seems nicely suited for the HD800 in general. Both the AKG K812 or Audeze LCD3 simply sound more yummy on the Burson, which has that midbloom effect that only makes the midrange and vocal experience pop even more.
I don’t really find the treble experience to be anything special. As with everything else in the HA-1, the upper region is a bit laid back and somewhat neutral. I guess you could argue it has optimal tonality and quantity for playing well with the majority of headphones out there. If you aren’t looking for a specialized amplifier for your Hifiman HE-6 let’s say, the headphone that I feel to have the best treble of any top of the line headphone, then you should be opting for something with this sound signature. Not too much, not too little but still enough to be interesting.
The Hifiman HE-xxx series is generally known for having excellent treble response, as is the Stax 007, something sparkling and wildly engaging, but never harsh or slamming. P.R.A.T is a bit of an issue with this HA-1 and I don’t feel it is at all able to produce excellent summit level treble response, although it does not falter in the slightest in this area, it just doesn’t really seem like treble masters would feel at home here.
Sets with a more neutral, dry or laid back treble experience, such as the Audeze LCD3, PM-1 or similar will be right as rain with the HA-1. With no real amazing treble on these headphones to emphasize, the HA-1 will mow through without any problems on these types of headphones. I would certainly avoid usage with likes of the HD800 and Beyer T1 as well, but that is my opinion and only holds merit if you are a treble head. I don’t feel the HA-1 to have sufficient quantity and styling in the treble to properly accentuate what these few headphones with stellar treble can offer. Now, that is not to say it does a bad job, it doesn’t. It just isn’t the optimal sound type to fit well with them. One interesting thing I was privy to was that the AKG K812, a headphone with treble problems, was relatively calm and enjoyable on the upper end through the HA-1. I feel like the HA-1 tamed the K812s ravenous and unforgiving treble, inverting it into something very similar to my Audeze LCD2, something more dry and neutral, but also something more listenable and far more enjoyable than what it usually tended to be.
K812 lovers are going to enjoy the HA-1, not only for taming that treble problem it has, but also for the general shape of the presentation. It is almost perfectly suited to headphones like the Stax 007 or the K812, sets that have a wider feel to the stereo void that are very well defined from left to right. Combined with the HA-1’s naturally good stage depth and separation qualities, these headphones excel and pair exceptionally well with the HA-1. I find myself enjoying Classical music with headphones I really didn’t enjoy the genre with before. As a pure DAC, the HA-1 combo’s nicely with the Woo Audio GES and Stax 007. Three peas in a pod, all three offering the same general sound type: Wider than tall, good depth but nothing special or stellar and taking a back seat to depth potential in comparison to the Burson Conductor SL. Overall, it is a solid sound staging machine and most headphones will sound more than spacious enough to satisfy sound stage nutbars like myself.