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When buying a portable amplifier, it’s easy to get confused by the complex array of options. From very low-end models to high-end audiophile models, there are simply too many choices. Sports stores offer a wide selection of equipment for every taste. But even among them, there’s one product that stands out for its stunning looks and high performance.
The HA-2 from OPPO, expand the American company’s line of portable USB DAC/AMP headphone amplifiers lineup. It features a special chip that converts the digital code (usually binary) into an analog signal, which decides the final sound quality.
Among the many capabilities of smartphones is playing music from digital files stored in memory or from online services, thanks to a built-in digital-to-analog converter and amplifier. However, smartphones and audio players don’t sound great when paired with high-quality headphones.
It’s because smartphones have strong sources of high-frequency interference, such as radio, Wi-Fi, and Bluetooth modules, on the same circuit board as the analog audio path. You can turn them off for an immediate sound quality improvement that makes the sound smoother and more natural. Yet, there will be other bottlenecks such as poor audio components, severe limitations on power consumption, which do not increase the amplifier’s power.
Because of the many nuisances of smartphones that stand between you and good-sounding music, advocates of quality recordings turned to over-the-ear headphones. In that regard, the OPPO HA-2 portable headphone amplifier tries to win back the attention of mobile audiophiles who want to listen to high-fidelity music on the go.
OPPO HA-2 Compact Headphone Amplifier + DAC Review
Oppo HA-2 Specifications
DAC: ESS Sabre32 ES9018-2M | Digital Audio Formats: 44.1 to 384kHz IRM, 16/24/32 Bit, DSD 2.8224MHz (DSD64), 5.6448MHz (DSD128), 11.2896MHz (DSD256, local mode only) | Frequency range: 20 Hz – 20 Khz | Recommended Headphone Impedance: 16 – 300 Ohms | Maximum headphone output: 300 mW/16 ohms, 220 mW/32 ohms, 30mW/300 ohms | Inputs: 3.5 mm stereo line input, Digital USB A (for iPod, iPhone, and iPad), Micro USB B (for smartphones with USB OTG, Windows, and Mac OS) | Outputs: 3.5 mm stereo headphone, 3.5 mm stereo line output (accepts 3.5 mm balanced cable) | Battery: 3000 mAh (13 hours for analog sources via line input, 7 hours for digital sources via USB) | Charging time: 1 hour 20 minutes | Quick-charge: 70% in 30 minutes | Weight: 175 g
The packaging is tastefully designed with a stylish print on a black background, giving it a modern look. Inside, you will find another package with the company’s logo on top. When you open it, you will find the main unit in a special box.
Here is what OPPO HA-2’s package consists of:
- A powerful charger that can provide fast charging.
- Mini jack to mini-jack cable.
- Micro USB to micro USB cable.
- Micro USB to Lightning cable.
- Micro USB to USB cable.
- Two rubber bands for smartphones/player.
- Instruction manual.
- Warranty card.
So far, this is a 5-star package.
Design & Ergonomy
The case is made of anodized aluminum. It is also lined with leather, which gives it a luxurious look. The design direction is based on a very familiar style, so the device’s appearance is clean and modern.
On the front panel, there is only the company logo. In the upper left corner is the volume potentiometer, which can also be used to turn off the amplifier. It turns with just the right amount of force, so you can’t accidentally turn the volume too high.
At the top, there are two headphone jacks and a signal cable for input and output. Also, on the right, you’ll find a toggle switch for accessing Bass+ and a slider switch for changing the level in the preamp (gain), as well as a button to activate the smartphone’s battery charging mode.
The gain function is typically found in conventional amplifiers. Its task is to reduce signals from different sources to a denominator that matches the sound.
Why do headphone amplifiers need Gain function? Because the input impedance of headphones can vary from a few tens of ohms to hundreds of ohms, it is necessary to deliver the correct signal amplitude to the headphones. The HA-2 supports headphones with an impedance between 16 and 300 ohms. In other words, if the input impedance of your headphones exceeds 150 ohms, set a high pre-amplification level.
Two gain stages are available for optimal coupling with headphones.
The high-gain mode (60 to 300 ohms) is suitable for standard over-ear headphones, while the low-gain mode (up to 60 ohms) is suitable for sensitive in-ear and on-ear headphones.
Also, it is possible to further increase the bass level without affecting the sound in the mids and highs while maintaining the linearity of the frequency response.
On the bottom side, there are two ports – USB and micro USB – and a switch mode. This allows the portable amplifier to be connected to a smartphone or computer (special drivers must be installed under Windows), such as Apple (using the standard USB Lightning cable for iOS devices) or Android (with USB OTG support).
Mobile devices can be connected via analog inputs as well as USB ports. In this case, the micro-USB port is used for Android devices and computers running Microsoft Windows and Mac OS, and the normal USB port for all other devices. Note that Windows computers require a driver, which can be downloaded from the official website.
The device can operate in two modes, the first of which is the analog input. In this case, only the input signal is amplified and sent to the headphones. The second mode uses the digital input, which activates the built-in digital-to-analog converter to convert, amplify and send the signal to the headphones.
The line output can also be used to connect external amplifiers, speakers, or powered speakers. In this case, the sound volume is fixed. Also, if you connect both headphones and speakers, only the headphone audio output will work.
It is worth mentioning that Oppo HA-2 amplifier works in AB mode. The amplifier is built on an integrated circuit that uses carefully selected discrete transistors and is set to operate in the linear part of the voltage amplifier characteristic.
Now that we’ve covered the construction, operation, and connections, let’s look at the device’s internal design. The DAC consists of a two-channel ESS Sabre32 ES9018-2M chip. This chip is a mobile version of the eight-channel reference chip used in the OPPO BDP-105D Blu-ray player and the OPPO HA-1 desktop headphone amplifier.
The HA-2 is capable of decoding PCM signals up to 32-bit/384kHz and DSD256 at sample rates of 2.8, 5.6, and even 11.2MHz.The gain path is Class AB and provides a 16Ω load with 2x220mW power. The volume control is analog and is done via the digital volume control built into the DAC. Bass amplification is also done in the analog section, so no signal processor is used.
This attractive, compact, and portable headphone amplifier surpasses the playback quality of any smartphone: We tried several pairs of headphones (ranging in impedance from 24 to 250 ohms) into the HA-2, and the amplifier had no trouble handling them. We were pleasantly surprised by the way the bass was controlled and the realistic midrange reproduction.
Another advantage of the Oppo HA-2 is that it can be used as a portable smartphone battery. For someone who uses his phone often, this “power-bank” feature actually enticed me. The built-in 3000mAh battery can operate for 13 hours when connected to an analog network and 7 hours when connected to a digital network. However, if you listen to it gradually, it will last you longer. 30 minutes is enough to charge the battery, so you can use it immediately. An indicator on the side of the case will tell you how much power is left in the battery.
To test the OPPO HA-2 headphone amp, we had to try some demanding high-impedance headphones that could challenge the HA-2, including the Beyerdynamic DT-990 Pro 250Ω, the Sennheiser HD 660S, and the Sennheiser HD 650. The low gain is high enough, but you’ll need to turn the knob almost all the way up on some recordings. However, if you set the gain switch to High, you’ll get a good sound stage, denser bass, and a warmer sound. There is no need to activate the bass boost system. If there is enough bass and the amplifier boosts it, even more, the bass control deteriorates, and the bass becomes muffled and loses definition.
If you test the OPPO HA-2 to rigorous hi-fi standards, there is a slight tightening of the treble that is especially noticeable when playing back hi-fi files. These differences from standard 16-bit/44.1 kHz recordings are obvious. As the bit depth and sampling rate increase, the sound becomes more detailed and credible. Assuming, of course, that these high-resolution files are real and not the result of sampling.
The frequency response balance is nearly perfect, with the exception of the brighter soundstage that characterizes ESS’ Sabre32 chip. Nevertheless, the music is convincing, and its emotional character is correctly conveyed. On the other hand, the symphony has a sense of scale, with instrumental sections clearly separated rather than blended. The colors of the instruments are also accurately rendered, without any coloration.
When testing multiple headphones, we were able to get a more in-depth evaluation of the sound quality of the portable amplifier. Our conclusion is that OPPO HA-2 sounds very good. The sense of dynamics is evident compared to a smartphone and has enough volume reserve for more pretentious headphones.
The OPPO HA-2 headphone amp disproves the common belief that the sound of a smartphone or player alone is sufficient and does not require additional equipment such as an external amplifier. The OPPO HA-2 is a portable amplifier that I would recommend to anyone who loves good sound. This compact DAC/AMP sound is excellent, and the extra features are useful, especially the smartphone charging feature, which I enjoyed a lot.