It was only logical for an audio/video brand that has recently added serious headphones to its range to also make a specialised headphone amplifier. Especially since Oppo Digital specialises in high-end electronics, commanding respect for its Blu-ray universal disc players.
And so to partner the Oppo PM-1 planar-magnetic headphones, and the models that have followed, the company has designed its first standalone headphone amplifier.
Oppo HA-1 headphone amplifier meets PM-1 headphones
The Oppo HA-1 headphone amp is more than just a box with a volume control — it can serve as a system pre-amp, thanks to its on-board D-A convertor, its three digital inputs, and its two inputs for analogue sources like vinyl.
The HA-1 is a beautifully constructed midi-width separates unit, its visible high build quality surpassing others around the £1200 price. Your first encounter may be with the immaculate anodised finish in either lustrous black or natural silver; then experience its heavyweight chassis, packed with renowned components such as a Sabre ESS DAC chipset, feeding a fully balanced analogue architecture with XLR inputs and outputs; all powered by a linear power supply from a toroidal transformer.
Inside the Oppo HA-1: home to linear power supply, multiple voltage regulation, custom capacitors, and ESS Sabre 9018 D-A convertor
You’ll need to connect to a computer through its asynchronous USB digital input for best digital audio results, using the Type B USB port on the rear. This can accept PCM digital up to 32-bit, 384 kHz; and DSD audio up to 11.2 MHz — otherwise known as DSD256.
Pick a source, any sauce
Sources are selected from a front rotary-encoder knob. Or there’s a smart all-aluminium remote handset with reassuringly clicky buttons.
A total of eight separate inputs covers almost every option available today. For analogue sources, there’s one pair each of RCA and XLR balanced inputs, while digital is covered with AES balanced, RCA co-axial and Toslink optical.
In addition you can stream lossy compressed audio over Bluetooth — standard SBC or preferred aptX codecs available — or plug an iPhone into the front USB port. Going this way didn’t seem to support high-resolution digital though; we found 24/96 files were downsampled to 16/48 over a Lightning-to-USB cable, using the Onkyo HF Player app that’s ordinarily fluent with high-res audio files.
Oppo Digital HA-1: comprehensive rear panel includes XLR balanced output and inputs, and four digital inputs — AES, coaxial, Toslink and USB 2.0
The main volume control is smooth in operation but had a little play in its bearing. It’s a motorised potentiometer inside, and when operated by remote it would also frequently overshoot after releasing the button.
Whenever the main volume knob is used, the display switches to a round graphic with current setting ticked off around the edge, plus a level count from –80 up to +6 dB.
The large TFT display on the front offers a choice of three home screens. You can have a simple text list, of source, audio format in use, gain level, and volume. Or the look of an 18-band graphic equaliser, with pumping bars and peak hold. Neither axis is labelled to let you make sense of the animated graphics though, which is a shame.
Even more retro, only this time with what appear to be calibrated level, is the classic VU meter, arranged as left and right channels side-by-side. Or if you don’t wish to be distracted by the display, it can be dimmed or switched off entirely.
You can configure the HA-1 as just a fixed-level DAC, after delving deeper into settings in the easy-to-use on-screen menu. Other advanced settings include Home Theatre Bypass, selectable for any input, which fixes unity gain by sidestepping the pre-amp’s volume stage. The headphone stage is adjustable as usual. You can also set the Mute function to operate just the line-out, or line-out and headphone amp together.
Finally, there’s two gain setting for headphones, High and Normal, the latter more suited to sensitive in-ear earphones which could otherwise be overdriven. It must be said that the HA-1 is a very low-noise unit though, with only a trace of noise audible when tested with Sennheiser IE80 earphones.
It may be worth noting, in use the Oppo HA-1 runs slightly warm to the touch, almost reassuringly so, perhaps indicative of the Class A amplifier topology specified inside.
We listened to the Oppo HA-1 from a Mac mini using Audirvana Plus software, connected by Chord Co USB cable, and spent most time listening through the Oppo PM-1 headphones. In addition we also tried the Oppo as a DAC and pre-amplifier for a stereo system, with B&W 802D loudspeakers run from either Gamut or Chord Electronics power amplifiers.
The character is on the whole lean but neutral. The Oppo HA-1 impresses by its extremely wide span across the octaves. It seemed to give a very level and open sound with adding much of its own fingerprint.
Both 24-bit PCM and DSD64 were handled with aplomb, and switching between formats from the same computer playlist was fast and virtually click-free. We also heard DSD128 sounding its incredibly realistic self, the vaguely subliminal softening effect of 2.82 MHz DSD effectively erased out of the background. We had less success with DSD256, unable to play via Audirvana software without being downsampled to DSD128.
There are two headphone outputs available, the usual 1/4-inch stereo jack socket, plus a 4-pin balanced output. Sadly they can’t be used at the same time, which removes the chance for any sociable listening. For the most part we used the regular jack input, but also tried the latter balanced connection, using a custom balanced cable available for the PM-1 headphones. This proved a none-too-subtle upgrade, and we were rewarded by a more muscular, tighter sound that really added more grip on bass and seemingly expanded dynamics.
If you plan to use the HA-1 amp with PM-1 headphones, you really must try the combination. It’s not perhaps so relaxing a ride, putting the music more forward in perspective and seemingly closer to your ears — helped by the greater output volume of course — but we suspect in playing this way it’s getting closer to the original sound performance.
The Oppo HA-1 gave an overriding impression of a very low distortion source, with limpid clarity that stretched right into the ultrasonics. In comparison with our Mytek Stereo192-DSD, another digital pre-amp with a respectable headphone stage, the OPPO had the sweeter, more shimmering sound that drew attention away from bass and midrange, toward its crystalline treble rendering. Given the mildly damped quality of the PM-1 headphones’ upper reach, that’s a handy asset.
The comparison between these DACs is particularly apposite as they’re based on almost the same D-A chipset, an ESS Sabre 9018 for the Oppo and ESS Sabre ES9016 for the Mytek. In our experience this Hyperstream digital architecture (a proprietary variant of pure sigma-delta conversion) can have a deliciously revealing character, with fewer traces of the amusical artefacts of 1-bit conversion.
In treble detailing, the HA-1 allowed organ harmonics and strings in clear relief, with other higher-range musical details typically standing proud in the mix. If you like to count out the component strands of a recording, the HA-1 should certainly aid your enumeration. Lower down the registers though, we preferred the more solid yet agile bass playing character of the Mytek.
Stereo width and instrumental separation were first-class, just edging out the Mytek here, which placed more focus between the ears in headphone listening, where the Oppo could stretch that bit wider and out of the head.
Sometimes that leaning toward higher-frequency exposition could prove a little distracting, with some of our favourite progressive rock losing its musical focus in the name of a squeaky clean hi-fi sound. But nonetheless there remained that sense of sound stretching up to the stratosphere, open and free of ceiling – with DSD material especially, where this headphone DAC really shone.
The more we listened, the more we were reminded of the best of Japanese high-end audio and the more careful focus placed on finely sculpted treble.
To get a better idea of the contribution of the DAC section versus just its headphone section, we put the Mytek on exclusive DAC duty, feeding balanced into the Oppo’s balanced analogue input. Here the intense detailing heard from the Oppo DAC was calmed somewhat, and the HA-1 became firmly established as the better headphone stage.
The 100 Words or Less
The Oppo HA-1 is an extremely insightful headphone amplifier and D-A convertor. Its build quality and luxury touches fully warrant a four-figure price tag. But the HA-1 importantly proved itself a particularly versatile digital pre-amp, able to take on many different modern and legacy sources. Its digital capabilities are right up to date, and its talent with external sources through the analogue inputs will likely seal the deal for anyone looking for an upmarket headphone amplifier to take on any hi-fi source.
Headphone amplifier with digital-to-analogue convertor (DAC) and analogue pre-amp; 4.1-inch TFT display; 32-bit 384 kHz / DSD256 (11.2 MHz) ESS Sabre ES9018 DAC; Class A balanced headphone amplifier; 1x AES, 1x RCA coax, 1x Toslink optical digital inputs; 1x Type B USB 2.0 port; Bluetooth A2DP with SBC and aptX codec support; USB input for iPhone; analogue volume control; XLR balanced and RCA single-ended analogue outputs; 254 x 80 x 333 mm; 5.9 kg