Steven Stone is the former editor of AudiophileReview.com. He a longtime audiophile and home theater writer, as well as a musician and recording engineer. Steven has written for publications like Stereophile, as well as HomeTheaterReview.com, AudiophileReview.com, and The Absolute Sound.
Steven is plays guitar, mandolin, and Ashbory bass and is a collector of fine musical instruments.
When Oppo announced the HA-1, critics wondered why the company would bother, since the Oppo PM-1 and PM-2 headphones are so amplifier-friendly that an iPhone can drive them to head-banging levels. The answer is simple: the HA-1 is for all those other headphones that aren't as accepting or compatible with low-power sources as Oppo's cans. But the Oppo HA-1 isn't just a potent headphone amplifier, it's also a preamp with multiple outputs and a DAC that supports a wide range of formats and inputs. Plus, it has Bluetooth connectivity and iDevice compatibility and a level of fit and finish that ranks up with anything I've seen from other audio components, regardless of cost or where it was made. And the HA-1 is only $1,199.
At first glance, the Oppo HA-1 appears to be a stylish headphone amplifier, which it certainly is; but, for someone putting together a high-performance two-channel audio system, the HA-1 can be much more. With two pairs of line-level outputs on its rear panel (one balanced XLR and the other single-ended RCA), the HA-1 can also serve as a full-function preamp--one set of outputs can go to your main speakers' amplifier, while the second output can go to a subwoofer. That's how I connected the HA-1 in my nearfield computer audio system.
The rear panel of the Oppo HA-1 also has two pairs of analog inputs (one balanced XLR and one single-ended RCA), as well as four digital inputs (AES/EBU, RCA S/PDIF coaxial, Toslink, and USB 2.0). The rear panel contains a 12-volt trigger input and output, as well as an IEC AC power connector. All these inputs and outputs fit comfortably into the HA-1's 10-inch-wide chassis.
The HA-1 front panel features a 3.75 by 2.63 TFT LCD display occupying the center section. To the right is a large volume knob with an iPad/iPhone/smartphone input underneath it; to the left side is an on/off pushbutton with a quarter-inch headphone output directly below it. Closer to the center, the pushable Source knob sits above a balanced headphone output jack.
The analog section of the HA-1 features a fully balanced differential Class A amplifier circuit that uses a toroidal power transformer and linear power regulators with custom-made capacitors. According to Oppo's owner's manual, "Our emphasis was in keeping the audio signal in the analog domain once it leaves the DAC (section)." Both analog inputs remain analog, and although the volume control knob is motor-driven, it operates exclusively in the analog domain rather than using any digital truncation to adjust output levels.
The digital section of the HA-1 uses a 16-core XMOS chipset for both PCM and DSD formats. The central DAC chip is the ESS 9018 Sabre DAC that Oppo also uses in its Blu-ray players. The HA-1's Bluetooth implementation uses the aptX lossless digital codec, and its front-panel USB input supports direct digital output from iPhones, iPads, and Android phones.
The HA-1's overall fit, finish, and build quality are impressive. Between its 0.5-inch-thick front panel, the beveled edges on its ventilation screen, and its smoothly machined surfaces, the cosmetics and overall feel rank up with preamp and DAC designs that have at least one extra zero on their price tags. Nothing about the HA-1's build or feature set says, "I was designed for a price point." In many ways, the HA-1is a high-end product that lacks only the high-end price.
You can operate the HA-1 in three ways: from its front panel, from its dedicated remote, or from its iPhone/Android Bluetooth app. On the front panel, the source button can be pushed in to "enter" a selection. Options include source selection and your choice of three different home screens. The status screen supplies source, audio format, gain level, and current volume. The spectrum screen displays a dynamic spectrum of audio levels, and the VU meter screen gives you a pair of VU meters that measure the output signal levels. You can also select from three screen output levels, choose a high or normal preamp gain, put the HA-1 into home theater bypass, and select from two muting options via the source selector.
Instead of the usual credit-card-sized remote that's coupled with most modestly priced components, the HA-1 has its own dedicated remote that seems as if it was fashioned out of a solid slab of aluminum. The only thing it doesn't do is light up. The Bluetooth HA-1 control app has an identical layout to the remote and duplicates the remote's functions exactly.
Most DAC/preamps with headphone amplifiers follow a standard convention: when you plug a set of headphones into the front panel, the device automatically mutes the analog outputs. The HA-1 does not follow this scheme. Instead, when you attach headphones, the analog outputs remain active. To mute these outputs, you must first change the "mute all" default setting to "mute pre-out" via the source selector's menus. Now you can mute the analog output by pushing the "mute" button on the front panel, remote, or app. However, if you select the "mute pre-out" setting, it means that, when you are listening via headphones, you can't use mute to cut off the output. Instead, the only way to lower the headphones' output is via the volume knob or volume controls on the remote or app.
I did encounter one slight problem while using the remote. When adjusting the volume levels either up or down, the levels changed more than intended--even a light push often resulted in a large volume adjustment. The volume adjustments on the remote app weren't quite as twitchy; but, if you push for any length of time, you will also get a big output change. Fortunately for audiophiles who want to do matched level comparisons between different source components through the HA-1, it has calibrated volume numbers that make it easy to replicate a particular output level.
Bluetooth mating was easy. My iPhone 5 running the latest OS had no problem finding and linking with the HA-1. One nice feature of the remote app is that it gives you the current volume level; so, even if you can't see the HA-1 (it could even be in another room), you have accurate volume information. My only complaint with the Oppo HA-1 app was that it required a search through the Apple App store to find it. Oppo has four apps listed. The one you want is called "Oppo HA-1 Bluetooth remote control." The app called "Oppo remote control" is for the company's universal players.
Since the analog amplifier section of the HA-1 is a Class A circuit, it generates a certain amount of heat. It has a nice large heat vent grille on the top of its cabinet; as long as you don't cover the top and leave some room underneath (don't put the HA-1 on top of a fluffy pet bed), the natural flow of air through the unit will prevent excess heat build-up. Even after a day of use, the top of the HA-1 was merely warm to the touch.
The Oppo HA-1 is a very good-sounding DAC/pre. It's so good that, during my listening sessions, I was constantly aware of the weak links in my audio system, such as they are, and the weakest link was never the HA-1. Most of the time, the first thing I noticed when listening to a recording, whether it was an old fave or a brand new release, was the way it was recorded. Through the HA-1, I could effortlessly follow the different parts of the music and concentrate on one particular instrument or vocalist easily. Image placement, whether I was listening through speakers, such as the Audience 1+1s or headphones, including Oppo's own PM-1, was precise. On my own recordings, the HA-1 consistently and reliably placed instruments exactly where they should be within the soundstage. Even the subtle room acoustics came through without any reduction in depth or low-level detail.
While I hesitate to call the HA-1's overall sound "sweet," since that implies some amount of extra warmth or euphony, I will readily admit that--regardless of how high the volume was set or how difficult to drive a pair of headphones might have been--I never heard additional hardness or edginess during dynamic peaks. The HA-1 sounded as effortless at zero dB as it did at -30 dB. Dynamic contrast was also impressive and was more limited by my choice of headphones than by any limitation imposed by the HA-1.
I tried out a wide range of headphones with the HA-1 and found the vast majority mated quite well with it. Power-hungry headphones such as the new HiFiMan HE-560 or the Beyer Dynamic DT-990 600-ohm version were well-served by the HA-1's high-gain setting. Even the normal gain setting had enough output so that the usual listening levels were between -5 and +2 dB. With efficient headphones like the Blue Microphones Mo-Fi headphones or Oppo's own PM-1s, even at the normal gain setting, normal listening levels were usually more than -20 dB.
One sonic issue I had with the HA-1 was that, with extremely sensitive earphones like the 115dB-sensitivity Westone ES5, there was a slight but constant low-level hum. Even Oppo's own PM-1 headphones had an extremely low-level background hum that I could hear during breaks in the music. As I mentioned at the beginning of the review, the HA-1 was designed to handle hard-to-drive and low-sensitivity earphones. If all you use are hyper-sensitive and easy-to-drive earphones, the HA-1 may not be your ideal headphone amplifier.
The only other sonic issue I noticed with the HA-1 is something I'll call "the phantom whine syndrome." Using Oppo's own PM-1 headphones attached via Oppo's balanced cable (available as an accessory for the Oppo headphones), I noticed an occasional low-level whine that would change pitch. The whine would come and go. I notified Oppo of the issue, but their techs were unable to duplicate it at their repair and test facility. During the review I switched computers, from a MacPro 1.1 to the latest MacPro 5.1, but the problem was present with both computers, so the source of the whine was not the computer. With the regular quarter-inch single-ended cable, the problem never appeared. I suspect that something in my office was the source of the whine, but I was never able to pin down the cause of the problem.
• The HA-1 is beautifully built.
• The HA-1 supports all current digital formats.
• The HA-1's sonic character doesn't change as the volume goes up.
• The HA-1 can power even hard-to-drive headphones to satisfying volume levels.
• The line output does not automatically mute when a headphone is plugged in.
• The remote volume control is over-sensitive.
• The Class-A amplifier section runs warm and requires adequate ventilation.
• With highly sensitive earphones, the HA-1 may produce a low-level background hum.
Comparison and Competition
At $1,200 or less, there are very few options that offer a similar combination of features and sonics as the HA-1. The Wyred4Sound mPRE comes the closest in features to the HA-1, but it lacks Bluetooth or digital iPod inputs, a balanced headphone connection, and gain-level options, and its USB implementation isn't quite as transparent. In terms of sonics and ergonomics, the HA-1 competes with the Wyred4Sound DAC-2 DSD SE ($2,495) or April Music Eximus DP-1 ($2,500) DAC/preamps, both of which are twice its price. But even these two excellent-performing DAC/pres lack a balanced headphone output.
When audiophiles use the term "high end," they are usually referring to a component's performance AND its price. Ever since The Absolute Sound's Harry Pearson initiated the "I have the best toys, and you don't" gambit, high-performance audio gear has continued to rapidly escalate in price from three to four to five figures or more with no end in sight. Of course, the problem with this high-end arms race is that it makes it seem like, unless you have boatloads of money to spend on the hobby, your sonics will be second-rate. During the last couple of years, though, companies like Oppo, Fiio, HiFiMan, Schiit, Geek Out, Ressonessence Labs, and others made components whose performance competes directly with much higher-priced options. The Oppo HA-1 accomplishes this with aplomb.
You can tell most budget-priced audio components are less expensive merely by their looks, but the Oppo HA-1 is an exception to that rule. It looks slicker and is more beautifully finished than any DAC/pre near its price. The HA-1 also has more features and performs at a level that I haven't heard before from a DAC/pre priced under $1,200. So, if you are looking for a DAC/pre/headphone amplifier to drive your difficult headphones, you should consider the Oppo HA-1--regardless of how much money you are "willing" to spend--because it is one heck of a high-value, high-performance component.
• Oppo PM-1 Over-the-Ear Planar Headphones Reviewed at HomeTheaterReview.com.
• Oppo BDP-103D Darbee Edition Universal Disc Player Reviewed at HomeTheaterReview.com.