Aurorasound HFSA-01 integrated amplifier

Aurorasound is globally known and recognized for the quality of its Phono preamplifiers. A lesser-known fact, but one worth mentioning, is that Mr. Karaky has been offering high-fidelity amplifiers and preamplifiers of very high quality for several years. The Aurorasound HFSA-01 is the first integrated amplifier from the manufacturer to be offered outside Japan.

AURORASOUND HFSA-01: FRONT PANEL

This amplifier is unlike any other. The size of the casing is atypical, and its look is part of the brand's DNA, even though it resembles no other component offered by the brand. It retains the "modern" vintage design of the Aurorasound Vida.

The front panel in brushed natural aluminum is adorned with Mahogany side panels, reinforcing the retro look. There are four potentiometers managing tones (bass and treble), volume, and source selection.

On the strip below, we have access to the red backlit power button, a Tone Off switch, a mono switch, and a 6.35mm stereo headphone jack.

AURORASOUND HFSA-01: CONNECTIONS

The integrated amplifier HFSA-01 offers 3 high-level line inputs in RCA format. Additionally, there is an excellent phono input. Its impedance of 47k Ohms combined with a gain of 40 dB makes it suitable for MM cartridges with a minimum output level of 4mV. However, adding a "Step Up" transformer allows the connection of a low-output MC cartridge.

The speaker outputs accept speakers with an impedance of 4Ω to 8Ω. It is possible to connect banana plugs or forks.

The power cable can be advantageously replaced by a higher-quality product via the IEC socket.

AURORASOUND HFSA-01: TECHNOLOGY

The Aurorasound HFSA-01 is a hybrid integrated amplifier that uses the advantages of audio tubes and semiconductors. The power stage is designed with a push-pull of EL84 tubes. This vacuum tube is a pentode equivalent to the 6BQ5. In this push-pull (ultra-linear) configuration, it delivers a power of 14W + 14W under 8 Ohms with extremely low distortion and excellent frequency response (10-40,000 Hz).

The tubes are driven by a famous Texas Instruments OPA604A operational amplifier. Aurorasound has specially developed an optimal phase inversion circuit with this OPA604A for this amplifier, enabling the push-pull operation in the most ideal manner.

There is a large power transformer and, of course, two output transformers. They are custom-designed by Aurorasound and manufactured by a Japanese company. They are paired with high-quality capacitors and resistors, carefully selected.

The power supply is completely isolated between the tube and the semiconductor to eliminate interference, regardless of the volume level and frequency range. The rectifier bridge is designed with very low-noise Rohm silicon carbide diodes.

The tone control section uses a CR type to obtain richer bass and more present treble, catering to users' sound preferences. This can be interesting for small speakers.

The phono stage is designed around a Linear Technology semiconductor to achieve an excellent signal-to-noise ratio with an NF-type circuit configuration.

It also has a headphone output directly coupled between the preamp and the power drivers.

The Aurorasound HFSA-01 amplifier is entirely handmade in Yokohama, Japan. Each amplifier undergoes precise measurement tests and listening sessions before shipment.

AURORASOUND HFSA-01: PHONO EASY COMPENSATOR

The AURORASOUND HFSA-01 amplifier comes with a silk-screened plate that can replace the bass and treble tone knobs.

The tone controls of this amp transform into equalization curve adjustments for the phono input. This allows correct playback of pre-RIAA vinyl records. It offers the adjustment of different equalization curves (RIAA, DECCA, Columbia, AES, NAB, 78SP) on the phono input. This hidden function, in the absence of the plate, is a very useful tool for vinyl enthusiasts.

AURORASOUND HFSA-01: TEST AND LISTENING

First, don't be fooled by the advertised power! Once connected, the Aurorasound HFSA-01 integrated amplifier surprises with its ability to drive speakers with disconcerting ease.

From the start, to push it to its limits, we paired it with a set of speakers that we thought were oversized for it (3-way column, 4 Ohms/88 dB, > 9000 euros). We were completely captivated by the quality of reproduction and the ease demonstrated by the HFSA-01.

The midrange is clearly sublime in its transparency and neutrality. It offers an uncommon realism in vocals. The reproduction is full of details and nuances. The high frequencies are also particularly successful and perfectly integrated with the rest of the spectrum. The treble extends very high with surprising smoothness and finesse. This range is very close to what is found in some very high-end tube electronics. And what about the bass!? It is superb in its articulation and precision while remaining very organic. The dynamics are surprising and even unexpected given the advertised power! The whole benefits from a balance and elegance that few electronics currently can claim. It can be listened to for hours without any weariness or fatigue. It injects the music with that extra soul often lacking in many high-end electronics. It also appears to exhibit a certain "cheerfulness" that gives full meaning to the much-sought-after "musicality". This integrated amplifier is one of the best I have had the chance to listen to.

The Phono Easy Compensator plate is not installed as standard, and you can place it or not if you prefer the clean look of the HFSA-01 front panel.

However, it is worth mentioning that equalization curves play a crucial role in the reproduction process of vinyl records pressed before 1958. The proposed curves essentially reverse the RIAA equalization curve applied to records. The Recording Industry Association of America (RIAA) established this standard curve in 1954, which is used in most records produced since the late 1950s. However, before the RIAA standardization, record companies used various equalization curves, leading to the use of more than 100 different curves. Serious collectors of 78 rpm and mono records often prefer phono stages that offer selectable equalization curves to match these different standards.

It is important to note that selectable equalization curves remain the exception rather than the rule in quality phono stages, and are unique today in an integrated amplifier. Therefore, the addition of this function in the HFSA-01 integrated amplifier, in its price range, is quite remarkable and greatly appreciated.

This amp has reconciled me with the EL84 in Hi-Fi use, even though I have always appreciated these tubes for their dynamics and clarity in a guitar amp, for example! How is it possible to extract so much music from such a small tube?

Another advantage is that retubing this Aurorasound amplifier will be very economical (around 120 euros for 4 matched tubes). It has only one known competitor, also Japanese, but the latter is certainly less neutral. The HFSA-01 hybrid integrated amplifier is certainly the best quality/price/music ratio you can acquire!

Bravo again Mr. Shineo Karaki!

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