Aurorasound HFSA-01 Integrated Tube Amplifier

Shinobu Karaki-san's new hybrid is out - the HFSA-01 Integrated Amplifier, utilizing EL84 valves with an output of 14 Watts per channel.

HFSA-01 is a hybrid integrated amplifier utilizing the advantages of both vacuum tube and semiconductor. The tube EL84 delivers 14W + 14W power output. The model is equipped with bass and treble controls. The input stage has a built-in phono equalizer for MM-type cartridges, along with 3-channels of RCA unbalanced input terminals. This model accepts speakers with 4Ω to 8Ω impedance. In addition, it has a headphone output. HFSA-01 is designed with unconventional configuration, however, it fulfills the basic requirements such as sound quality and overall performance for a wide range source from high-resolution digital to analogue records that any generation and age demands. The front panel is ornamented with Mahogany wood on both sides to enhance the retro appearance producing a rather relaxing atmosphere for more enjoyable audio life.

The HFSA-01 now comes with Aurorasound's "Easy Compensator". That's a front plate overlay for the Bass/Treble controllers to adjust the phono input to various EQ curves (RIAA, DECCA, Columbia, AES, NEB). This hidden feature is a very useful tool for vinyl aficionados.

Features
The output vacuum tube EL84, a pentode equivalent to 6BQ5, is operated in push-pull configuration delivering extremely low distortion and excellent frequency characteristics with ultralinear connections. The driver for EL84 is a wellknown Texas Instruments OPA604A, a high precision audio Op-Amp. Aurorasound developed a perfect phase inverter circuit with OPA604A to drive the push-pull operation in the most ideal way. The tone-control section employs a CR-type for easy adjustments to achieve more rich bass and comfortable treble to meet listeners’ taste even with small-size speakers. The phono equalizer uses Linear Technology’s semiconductor to achieve an excellent S/N characteristic with NF-type circuit configuration. The power supply section is completely isolated between the vacuum tube and semiconductor to completely eliminating any interferences regardless of volume level and frequency range. The rectifier is of the super low noise Rohm’s silicon carbide diode. The output transformer and power supply transformer are custom designed by Aurorasound, and manufactured by a Japanese company. This model employs carefully selected high-quality capacitors and resisters, as well.

 - Input: RCA unbalanced - CD, LINE-1, LINE-2, Phono-MM (Gain 40dB, load resistance 47kΩ, RIAA +/-1dB)
 - TONE Control: BASS +/-12dB, TREBLE +/-12dB
 - Output: 14W + 14W into 8Ω speaker
 - Frequency response: 10Hz ~ 40kHz, -3dB, Flat
 - THD+N: 0.08％, 1kHz, 2W, A-weighted
 - SNR: 93dB, LINE IN-OUT
 - Functions: TONE control pass DIRECT SW, Stereo/Mono, Headphones output
 - AC voltage: USA model 120V, Europe/Asia model 220V, 240V
 - Upgrade to SR MASTER fuse available (+$250)
 - Power consumption: 150W
 - Size / Weight: W360 x D320 x H145mm / 10.3kg (14 x 12.5 x 5.7inch / 22.7lbs)

NEW: Ken Micallef of Stereophile wrote (March 2025):
"...the HFSA-01 played music with liveliness, buoyancy, and rhythmic drive. This smallish amplifier produced sound that was full-bodied, dynamic, and large in scale. With stereo discs, the little amp offered a wrap-around-the-head experience. Instruments were well layered and fleshed out; bass was surprisingly taut and extended. I heard fresh details, arranged in a beautiful, well-organized sound field..."

"...the HFSA-01's clearheaded, precise character makes it easy to enjoy. It delivers the heart and heat of music with a dancelike, easy on its feet, whirlwind intensity. As spirited as a pup, a first season baseball player, or a minty fresh sportscar, the Aurorasound absolutely zips through music with the kind of speed and dynamics I associate with well-made solid state amps but with the tonal flavoring of the best tube amps..." 
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Paul Rigby, The Audiophile Man:

Winner of StereoTime's Most Wanted Award 2023 - David Abrahamson writes (Jan. 2024): "...there’s a certain potency in the Aurorasound HFSA-01’s austere, retro appearance that just says "Amplifier: hold the frills." It quickly adds, "But I’m also adorable. Please take me home." And so, at the end of my review period, I did! When paired with sufficiently efficient speakers, it is illuminating, vibrant, detailed, and surprisingly dynamic, all wrapped up in just a hint of EL84 tube warmth. Bespoke Japanese transformers lend it among the jettest of jet-black backgrounds, and there is nary any electrical self-noise to speak of. If you can get away with (a feisty) 14 watts and think remote controls are for televisions and massage chairs, the Aurorasound HFSA-01 will thrill you with its operational simplicity, retro good looks, and sonic purity. A 30-day trial period and a selection of optional Synergistic Research fuse upgrades clinch the deal..."
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Winner of Twittering Machines Favorite Gear 2023 Award - Michael Lavorgna writes (Dec. 2023): "...as you may already know, those tone controls double as EQ Curves for pre-RIAA records!! What you may not know is listening to 78s is better for you than avocado toast. “When it comes to an integrated amplifier, especially in the HFSA-01’s price range, I like having a MM phono stage built in and even a headphone amp for good measure and I put the HFSA-01’s EQ Curves in the crazy-amazingly nice to have category. Add in its retro good looks, rich fit and feel, price, and performance that left me wholly satisfied, opening as big a door onto musical enjoyment as I need, I cannot sing the Aurorasound HFSA-01’s praises loudly enough to anyone looking for an integrated amp that will feed your love of music with endless delight..."CLICK HERE to check it out

Maxwell Geiger of Audiophilia.com wrote (October 2023):
"...the Aurorasound HFSA-01 offers a pure musical performance, and just as importantly, it delivers music with a purity of purpose. It’s not a solution to a problem but rather a realization of a particular vision of musical enjoyment. For analog enthusiasts willing to work within the surprisingly minor constraints of its power rating, the Aurorasound HFSA-01 should bring a lifetime of musical engagement. A passionate recommendation and an Audiophilia star are in order..."
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 HiFi-Bargain Award by Twittering Machines, Michael Lavorgna writes (October 2023): 
"...I bet you saw this coming. The HFSA-01 is the second product from Yokohama, Japan’s Aurorasound to hit the Favorite/HiFi Bargain double header, joining the Aurorasound VIDA Prima Phono Stage. One of the lovely tricks up the HFSA-01’s sleeve is the inclusion of EQ Curves to properly play back 78s, a rather rare feature in a sub $4k integrated amp. Of greater importance is the HFSA-01 is a killer integrated amp with a killer MM phono stage, using 2 pair of EL84s run in ultra-linear push-pull mode for 14 Watts of output power per channel. Enough to drive the DeVore O/96 to Barn-filling heights. And you get all of this wood-trimmed goodness for $3,680 making the Aurorasound HFSA-01 Vacuum Tube Integrated Amplifier a genuine HiFi Bargain..."
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Follow-up review on Twittering Machines writes (October 2023):
"...I am even more impressed by the lovely Aurorasound HFSA-01 now that I’ve heard what it can do with 78s and it drove the DeVore O/baby like a dream. A big, beautiful joyous dream that kept me enraptured and happy every moment music played. All told, at $3,680, the HFSA-01 is a screamin’ bargain, and I do mean screamin’, and if you’ve ever had a hankerin’ to play some 78s, or if you already have a stash but no way to properly play ‘em, I can’t think of any other integrated amplifying option anywhere near the Aurorasound’s price..."
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Michael Lavorgna of Twittering Machines concluded (September 2023):
"... I choose my hifi gear based on everything—looks, build quality, company, performance, features, and price. When it comes to an integrated amplifier, especially in the HFSA-01’s price range, I like having a MM phono stage built in and even a headphone amp for good measure and I put the HFSA-01’s EQ Curves in the crazy-amazingly nice to have category. Add in its retro good looks, rich fit and feel, price, and performance that left me wholly satisfied, opening as big a door onto musical enjoyment as I need, I cannot sing the Aurorasound HFSA-01’s praises loudly enough to anyone looking for an integrated amp that will feed your love of music with endless delight..." CLICK HERE to read the entire review

Janine Elliot of the HiFi Pig Magazine writes (September 2023): 
"...this was a highly engrossing product giving me tons of fun per watt. Everything was harmonious with excellent clarity and a fair amount of dynamism for such a small output. Mids were sublime and top end was pin sharp and fast. The unimposing exterior hid within it a product of excellent calibre, and well worth exploring if you perhaps don’t want to annoy the whole street..."
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David Abramson of The StereoTimes wrote (August 2023):
"...he has created an op-amp/tube combo circuit that really does combine the best of solid-state low-end punch and drive with the (not at all overdone) punchy/spacey liquidity of EL84 tubes in the mids and highs, resulting in a lively, spacious, punchy sound which occurs within expansive spaces that suggest much pricier ‘purist’ tube or solid-state amps..."

"...String textures here were readily apparent, and the HFSA-01 resolved detail better than most any amp I’ve had through here, clarifying and illuminating and generally bringing this beautiful collection of heretofore unfamiliar (to me) symphonic pieces to life in my listening/living room..." 

"...'Exactly Like You' from Best of the Ray Brown Trio showcased two of the special attributes of the Aurorasound; namely, it is especially dynamic (macro and micro) and especially well defined in the mid-bass. On 'Freddie Freeloader', Ray Brown plays a descending scale on the standup bass, and you can hear the string texture and woody resonances as separately defined notes descending down into the lowest reaches of the scale just as clearly as you can on the higher end..."

"...my hat is off, and my head is bowed to Shinobu Karaki-san. This one is special. If amplifiers were akin to people, the Aurorasound HFSA-01 might be Garland or Sinatra, born and bred to perform. In answer to your next question, yes, of course, I bought the review sample. I can’t let this one go..."
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Wojciech Pacula of HighFidelity.pl wrote (July 2023):
"... FOR A LONG TIME, THERE WAS NO small, tube amplifier on the market that would work as well with loudspeakers as with headphones. The Aurorasound HFSA-01 fills this gap perfectly, as if it's always been there. It plays with an open, clear sound of extraordinary energy. Its sound is not muddied or lifeless, as it happens with large devices. At the same time, it has enough authority at the bottom of the band to show the scale of events, the volume of instruments and the depth of the soundstage... A beautiful example of minimalism in the spirit of zen combined with modern solutions. From us, a saturated, full of red color award the RED FINGERPRINT..."
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