Fostex HP-A3 Review – High Value RCA Digital-to-Analog Converter with Headphone Amplifier

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Some devices were launched several years ago and are still in production, even though competitors continue introducing the latest technologies. Meanwhile, some Chinese manufacturers are improving their offerings and releasing new drivers and amplifiers every year. But as a consumer, is it more cost-effective to opt for new audio equipment than to buy timeless equipment?

In this article we’ll talk about Fostex HP-A3, a high-value 32-bit amplifier + DAC with a USB power supply and RCA connectors. It’s a compact desktop headphone amplifier with convenient controls and an attractive model with multiple connectors: USB, optical, headphone output, and speaker.

This allows it to be used with headphones, integrated into a home audio system as a stand-alone DAC, used in the studio with active monitors, and can even be used as a USB-S/PDIF digital converter.

1. Overview | 2. Quick Review of Fostex HP-A3 | 3. Package | 4. Design & Ergonomy | 5. Technology | 6. Connectivity | 7. Sound Quality | 8. Conclusion

Fostex HP-A3 Best-value Desktop Headphone AMP/DAC Review

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1. Overview

DAC: AKM 32bit DAC AK4390 | AMP: TPA6120 and Burr Brown OPA2134 op-amp | USB: Tenor TE7022L | Headphone Outputs: 20 Hz to 20 kHz ±0.3 dB (32-Ohm Load, 100 mW) | Line Outputs: 20 Hz to 20 kHz ±0.3 dB | Headphone Output Power: 100 mW into 32 Ohms (Max) | THD: 0.01% or less (100mW @ 1kHz, 32-Ohm load) | Power consumption: 2.5 W | Weight: 450 g


USB interface sampling rate 16bit-24bit/96kHz
Full speed USB interface
Optical digital square port
S/PDIF format (32kHz-96kHz)


Phone jack: stereo phone
Maximum power: 100mW (32Ω load).
THD 0.01% or less (100mW @ 1kHz, 32Ω load)
Frequency response 20 Hz / 20 kHz +-0.3 dB (32Ω, 100mW)
Analog input RCA pins
Reference output level -10 dBV
Distortion factor of 0.01% or less (at 1 kHz)
Frequency response 20 Hz / 20 kHz +-0.3 dB
Digital connectors Optical, square
S/PDIF format (32 kHz to 96 kHz)

General Information

General Information
Power supply DC5V (via USB)
Power consumption 2.5 W
Accessories USB cable (1.0 m) x 1, rubber feet x 4, user manual
Dimensions 108mm (W) x 36mm (H) x 140mm (D)
Weight: about 450g



2. Fostex HP-A3 Review

To be completed

Beyerdynamic Aventho Wireless On-Ear Headphones

3. Package


The Fostex HP-A3 is delivered to the buyer in a standard box without decorations. In addition to the amplifier itself, the following parts are included.

  • A quality USB cable
  • 4 soft rubber pads
  • Documentation
  • Warranty

The no-frills packaging suggests that this model is intended for professional use and is characterized by high quality. From the first glance, you can see that you are getting a reputable product with beautiful packaging.

4. Design & Ergonomy


On the front, there are LED indicators, a 6.3 mm headphone jack, digital input selection buttons, output selection buttons, and volume control. The buttons and “dial” are made of high-quality plastic and feel good in the hand. The volume controls are also very easy to use, with soft keys.

On the back panel are more power outlets. On the back, there is a USB port (power input/output), optical input/output, and two RCA connectors for speakers (the USB cable is remarkable for its thickness and durability, as it is quite long and interesting silver color). For receiving digital signals. There is no analog input (which is logical since there is a high-end DAC inside). But there is an optical output that allows you to connect, for example, a recorder.

What I like about the Fostex HP-A3 is the input/output switch and how it works. If you press the left button, the signal is received via USB; if you don’t press the button, the signal is received via the optical connector. The same goes for the right button: press it, and you get RCA; don’t press it, and you get headphones. The latter is great; just two buttons and two positions for four connection options.

5. Technology


Inside the HP-A3, the designers delight us with the unit’s neat layout and the high build quality characteristic of Fostex products. The headphone amplifier uses a TI TPA6120A2 chip and two high-quality Class AB amplifiers. The line outputs use TI’s OPA2134 (Burr Brown) op-amps, which are interchangeable via a PA variant mounted on the DIP board, which can be useful for op-switch enthusiasts. The board houses an AKM Japan AK4390 DAC chip and a Tenor TE7022L USB controller.

In fact, unlike the HP-A4, the Fostex HP-A3 can only receive 24-bit/96kHz via USB, although it has a 32-bit DAC. According to the manual, 32-bit files can be processed via the optical connector; if the signal comes from a computer via ASIO or WASAPI (i.e., without operating system processing), it must have a sampling rate of 96 kHz. No more, no less. So if you want to listen to music via ASIO, you have to use DSP splitting. This generally reduces the theoretical audio quality advantages of ASIO to zero.

However, it should be noted that Fostex designers have achieved a sound that is not always possible with similar operational amplifiers from other manufacturers by using a high-quality circuit design and properly selected parts such as Nichicon Gold capacitors.

6. Connectivity


When you connect the Fostex HP-A3 DAC amplifier to your computer, the driver is automatically installed within seconds, and you can start listening to music immediately. It is convenient for those who are not interested in technical connection issues, whose only concern is the sound, which, in the case of the Fostex HP-A3, it sounds much better than listening directly to your computer with headphones.

This amplifier can play music through headphones (full-size 6.3mm jack) or through speakers/amps via two standard RCA outputs. In other words, this combo can also be used as a preamp. If you want to connect speakers, it is best to use active speakers. You can also connect your computer to this combo via USB, connect your TV via optical, or headphones and speakers. Then you can choose what you want to listen to and through what output. It’s pretty simple. As long as the cables are long enough, that’s all that matters. In any case, the Fostex HP-A3 did a great job of demonstrating its versatility.

The Toslink optical input provides high-quality sound with no apparent weaknesses. When listening to acoustic music or jazz, you can naturally enjoy the music, especially the instruments.

7. Sound Quality


Fostex is a mid-level amplifier with a decent DAC for any type of headphone, provided it has low impedance and high sensitivity. Fostex HP-A3 offers a good soundstage and detail throughout the audio spectrum, without any loops or artifacts. It reproduces sound correctly.

The Fostex HP-A3 desktop amplifier provides enough power for standard low-impedance headphones and high-impedance headphones like Beyerdynamic DT-770 250-Ohms (although they can be difficult to handle and lose detail). For high-impedance headphones, you’ll need a better amplifier; the Cambridge Audio DacMagic Plus, Music Fidelity MX-DAC, or Marantz HD-DAC1 are good choices.

When I plugged the headphones into the Fostex HP-A3, the acoustic music gained depth, the piano sounded sharper, and the hip-hop drums were more energetic. Put heavier music with thundering drums or powerful guitars into the player, and the DAC reproduces the full dynamic range of the recording without messing the recording. Overall, the Fostex HP-A3 is versatile and capable of playing almost any type of music and reproducing the music the listener wants to hear.

Compared to the Fostex HP-A4, there is virtually no difference in sound, although the DAC chips are different; here, we have AKM AK4390. The HP-A3 offers all the same detailed, smooth and dynamic sound, which is pleasing to know since HP-A4 offers first-class sound for reasonable money, whereas HP-A3 has a similar sound and is slightly cheaper.

8. Conclusion


With this desktop dac+amp combo, the music flows nicely, is smooth and beautiful, with a rich, rhythmic sound. What the Fostex HP-A3 lacks is a pair of gain and filter switches, as well as DSD support. It’s also worth noting that the maximum sampling rate (PCM audio) is 96 kHz.

Nonetheless, the headphone Amp/DAC is a must-have for anyone who regularly listens to songs with headphones on their computer for its price. If you have decent headphones and speakers and want to listen to high-quality music but can’t afford a high-end DAC or amplifier, you should get the HP-A3 headphone amplifier from Fostex.



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