HDACC’s headphone amp is a mix of good and bad. First the bad. It’s got loads of noise, more so than any mains-powered amp I’ve tested this year. Which is a shame. HDACC tracks evenly from 0 to -80 in half decibel steps. There is no problem finding perfectly balanced channels even with an Ultrasone IQ or Shure SE846. But through either, and even through Audio Technica’s ES7, the background noise varies from noticeable to noisome. Second, it struggles slightly supplying enough current into low-Ω loads, distorting signals, dropping frequency pressure, and more.
To its credit, HDACC keeps stable dynamic range and noise no matter the load. And, while measurable, its frequency response deviates by a mere 1dB at 5.000Hz when driving the Earsonics SM2. Respect. Plug in Oppo’s wonderful PM-2 or a DT880, however, and HDACC’s headphone amp struts its stuff. While it is slightly more detail oriented, it shares similar output power to my favourite DAC, the Lynx HILO. That is: warmish, full, with good y-axis stereo detail.
And just like Hilo and ALO Audio’s wonderful CDM, HDACC’s headphone output isn’t capable of resolving 24-bit audio. Which makes me wonder if HDACC splits output duty between two DACs, one for headphone output, and one for line out.
As long as you stay away from sensitive earphones and portable headphones, the HDACC has more than enough power and drive. For best performance, you’ll want to plug something in the 60Ω – 300Ω range. It’s no Mojo, but it’s got verve of its own. HDACC comes with six impedance settings: 16, 32, 64, 200, 300, 600. Noise doesn’t amplify based on the setting, and the volume jump from one to the next is meagre and studied. I’ve found no major difference in current stability from one setting to the next.
The DAC behind HDACC’s XLR outputs is brilliant. With my amateur setup, I measure 111dB of dynamic range, -111dB of noise, 0,0017% THD, 0,011% IMD, and a whopping 109,5dB of stereo separation. Channel balance is great, and the signal is both steady and flat from 20 to 20.000. They feed either a flat 4VRMS, or their voltage can be controlled by the attenuator, or included remote control, which makes them great for use straight with amps.
Which, is probably where Bob wants you to turn. Essence’s DPA-440 Class D Amp appears to fit the bill. Small, powerful, and in need of a pre-amp, the couple should work together like peas in a pod.
The point is that if you want performance, HDACC is more than capable. Its XLR output is wonderful. Its headphone out is decent. And, lo and behold, so is its front line input. That input measures -110dB noise, 109dB dynamic range, and tracks faithfully to the performance you can expect from HDACC’s XLRs. Wonderful. In other words, if your mates bring over iPods and want to listen to their tunes, both they, and you, can, in exceeding quality.
Finally, the star of the show: HDMI, is brilliant. It performs audibly as well as USB input, and passes back out so that simple Blu Ray players as well as the new Apple TV can still hook up to quality downstream audio equipment. Better yet, you can fire up HDACC with the included remote control, by which you can switch its inputs around, change volume, and mute the volume.
I should also mention that I’ve detected none of the USB-input anomalies that stymie Chord’s Mojo or ALO’s CDM, when switching USB input from iPhone to iMac.
HDACC outputs a slightly warm signal that errs toward neutrality and stereo detail. It’s not as low distortion as it gets, but it kicks up solid pre-amp/DAC performance for the price.
Because its XLR output keeps harmonic distortion and noise low, you’ll have to make sure to choose an amplifier whose noise levels are low.
While it doesn’t output signals devoid of distortion, through its headphone output, it metes out 3x less THD and IMD than Onkyo’s DP-X1 (DP-X1 RMAA) in single-ended mode. Even loaded with an Earsonics SM2, it keeps frequency deviation to within +/- 1dB, which is respectable. If only HDACC hissed less.
Stereo balance is very good across the range, from bottom to top. Again, if for some reason you’re listening through earphones, you may find HDACC favours the upper midrange (around 5K or so), but if you’re running any normal headphones, by and large, stereo detail is even from 20Hz to 20.000Hz.
Which may be why I’m tempted to call its sound stage ‘round’. Stereo details don’t piddle out at the sides, nor are they thin. HDACC spits good y-axis depth into every headphone with which I’ve paired it.
HDACC’s overall good to excellent performance, and Swiss Army bevy of connections, make it a brilliant part in a home theatre system. Not only can you pass an Apple TV HDMI signal out to it, and onto a TV, you can do the reverse and still end up with a DAC that spits great signal quality to downstream power amps.
Having lost its toslink connection, the latest TV completely buggers clean wireless living room setups. Until now.
If like me, you depend on streaming devices for home entertainment, you can’t do better than HDACC for 500$.
Quibbles about Bob
I’m not sure why but Bob insisted in seeing my review before it was published. It came back marked up. I had to say this, or had to say that. I had none of it. This is a review, not an advertisement. I will write it the way I see fit, and I will be as honest as I can. I won’t make claims I can’t back up, nor do I take kindly to a manufacturer’s wishes to massage important parts of the review (hiss, for instance) in a device’s favour.
Bob’s insistence on marking up my review aside, my experience with HDACC has been positive. Not, it’s not pretty. Yes, it wears HDMI like a Best Buy Boss. That this unit made it to a reviewer’s office with a shifted faceplate is tacky. I won’t hold the final bit against HDACC. It could just be a poor sample.
Whatever. Especially for its asking price HDACC is solid. It sounds good. It plays very nice with downstream equipment. And despite higher levels of THD, IMD, and headphone amp background noise, its headphone amp performs well.
It can route any analogue or digital input into any of its outputs, and is easy to use which makes it a good choice for the living room. If there were less Best Buy in it, it would be a beautiful partner to the TV.