⌈ ACCUPHASE launched its first stereo amplifier half a century ago, in 1973. Since then, the Japanese brand has become one of the most recognized and respected around the world. The company has earned its reputation by offering primarily high-end amplifiers (including class A), preamplifiers, CD and SACD players. We are testing the A-48S power amplifier, operating in class A. ⌋

I DO NOT REMEMBER A SITUATION LIKE THIS, i.e. one related to an “S” added to the symbol of a device by the Japanese company Accuphase. Just to be sure, as memory is not reliable, I reached for the "Product museum" tab on the manufacturer's website and it turns out that I was wrong about being mistaken. In the past, in the 1970s, 1980s and partly the 1990s, the company differentiated its products like that, attributing an additional letter to the symbols of previously produced devices. As far as power amplifiers are concerned, the letters used were “S”, “X”, “L” and “V”, as in the P-300 amp, “V” in the A-20 and A-50 models, “A” in the E-250 integrated amp, or “B” in the CD DP-90.

If we were to pay attention to what kind of products these are, and note that the new versions were created every three or four years, we might be tempted to make some assumptions that would allow us to understand how these particular products differ from other Accuphase devices. The P-300 power amplifier was the first product treated with such attention and its design was modified the most. It was the premiere product of Accuphase, then still Kensonic Laboratory, so it was especially significant to the company. Therefore, my first guess is that it is all about attachment, and thus emotions.

My second guess is purely technical, however, as it can be added with a high degree of probability that these are products whose design was so successful, so perfect, perhaps even futuristic, that its change to a completely new one was simply impossible in this period of time. After all, the manufacturer introduces new models on a regular basis, but only when it manages to significantly improve at least a few technical aspects, e.g., widen the frequency response, reduce distortion or noise, increase output attenuation, or sometimes improve functionality. So, this would be a reason related to a cool view of the matter, i.e. intellect

The A-48S, if we agree with what I wrote above, would thus be a power amplifier whose basic model, launched in 2019, i.e., six years ago, proved difficult to replace and close enough to its creators that they decided to make important, but not crucial, changes to its design, thus keeping its name. At the same time, this would be the first such case in this company in twenty years, as the last “tweaked” power amplifier was the A-20V model from March 2000.

▌The A-48S

LET'S START FROM THE BEGINNING. The A-48S is a stereo power amplifier operating in class A, push-pull mode. It yields 50 W at 8 Ω, i.e., 5 W more than the A-45, doubling it at a 50% decrease in impedance. So, that would be 100 watts at 4 Ω, 200 at 2 and as much as 400 at a 1 Ω (!) load. The device can operate in both stereo and mono modes; its power then rises to 800 watts at 2 Ω. At the same time, the manufacturer points out a 6% drop in noise, compared to the original, and an increase in the damping factor by as much as 25%, to an exceptional level of 1000.

It retains the most important solutions known from other devices with the Accuphase logo, such as class-A operation, balanced circuitry, current feedback with balanced equalization signal routing, instrumentation amplifier topology, MCS+ multiple summing circuit, output relays on MOSFET transistors, and sophisticated overload and short-circuit protection circuits. I don't even mention the layered, very solid chassis and high-carbon steel feet.

Even though the device has the same dimensions as the A-48, it weighs two more kilograms. It's probably about a larger transformer, since the power amplifier has an almost identical design. The signal path is fully balanced and has been designed using a technique called Instrumentation Amplifier. This is a type of a circuit that allows for a high common mode rejection ratio (CMRR), yielding high precision amplification. This is one of the key techniques of this manufacturer.

It is still an amplifier working with six parallel MOSFET transformers per channel in the current section and bipolar transistors in the voltage section. In doing so, the company's engineers focused on a special way to divide the overall gain between the two sections. The former amplifies it 12.6 times, and the latter just twice. The company materials read that “allocating high gain (12.6×) to the input section drastically reduces output noise.”

A very important parameter that engineers from this Japanese company pay attention to is as low output impedance as possible. It translates directly into a parameter called the damping factor, describing how well the amplifier handles the speakers, how well it controls them. For the last two or three generations of amplifiers from this company, shorter and shorter signal paths and output protection based on MOS-FET transistors are supposed to be responsible for its increase. This is the case with the A-48S as well.

The amp still looks like a classic Accuphase device: a gold front panel, large outgoing VU-meter indicators, balanced and unbalanced line inputs, absolute phase change for XLR inputs, and large custom-made speaker terminals - here double, allowing bi-wiring. There's also optional gain change, making it easy to match it to a particular system. Setting the switch to lower levels reduces noise. Accuphase wouldn't be itself if it hadn't gently remodeled the shape of the buttons. Both the power and input change switches are now more angular than before, the latter now square rather than round.

On the rear panel, next to the XLR input polarity switch, there is a switch with which we set how the power amplifier is supposed to operate. The standard setting is “Normal”, which means the device working as a stereo amplifier. On the right is the “Bridge” setting, in which the amplifier is bridged and works as a mono monoblock. And on the left is the “Dual mono” setting, which also makes the amplifier work as a monoblock, but not in a bridge, but with two separate amplifiers to power two speaker sections in the bi-amping mode. It is then sufficient to feed the signal from the preamplifier to one of the inputs.

On the user’s side only two details have changed. One is related to the outgoing power indicators mode of operation switch. Instead of two buttons, as in the previous model, the A-48S has a rotary switch, allowing the user to choose from three measurement options or turn off the indications altogether. The second noticeable change is the way the user is informed about the choices. Now, instead of LEDs, it is illuminated lettering located between the indicators.

▌ ODSŁUTHE LISTENING SESSIONH

THE WAY WE LISTENED • The Accuphase A-48S power amplifier was tested in the “High Fidelity” reference system. It was compared to a two-part reference amplifier, i.e., the Soulution 710 solid-state power amplifier and the Ayon Audio Spheris III line-level preamplifier. During the test, I used the Ayon Audio CD-35 HF Edition SACD player and the Lumin T3 file player as sources.

Signal between the preamplifier and the monoblock was sent via the Siltech Single Crown RCA interconnect. The Accuphase amp was powered by the Harmonix X-DC350M2R Improved-Version cables, and signal to the speakers was supplied by the Crystal Cable Da Vinci speaker cable. The amplifier was driving the Harbeth M40.1 speakers, and during the test it stood on its feet on the top carbon shelf of the Finite Elemente Pagode Edition Mk II rack.

» ALBUMS USED IN THE TEST ⸜ a selection

⸜ BENNY CARTER, Jazz Giant, Contemporary Records/Craft Recordings CR00500, „Contemporary Records Acoustic Sounds Series”, SACD/CD (1958/2023).
⸜ ART PEPPERArt Pepper Meets The Rhythm Section, „Contemporary Records Acoustic Sounds Series”,Contemporary Records/Craft Recordings CR00392, SACD/CD (1957/2023).
⸜ BILL EVANS, You Must Believe In Spring, Warner Bros./Craft Recordings CR00455 SACD/CD (1972/2022).
⸜ DIANA KRALL, This Dream of You, Verve Records UCCV-1181, SHM-CD (2020).
⸜ JASON ISBELL, Foxes in the Snow, Southeastern Records/Tidal, FLAC 24/96 (2025).
⸜ ZOE WEES,Traitor, Valeria Music/Tidal, FLAC 24/44,1 (2025).
⸜ GROVER WASHINGTON Jr., Winelight, Elektra/Tidal, FLAC 24/192 (1980/?).

» HIGH FIDELITY playlist: Accuphase A-48S is available in TIDAL → HERE

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I DON’T KNOW IF IT’S APPROPRIATE TO SAY SO, but Accuphase has recently reached the spot where the technical perfection of measurements has met something that many other manufacturers practice in listening sessions. That does not mean that this company's equipment played “technically” before, that's not the point at all. Listening sessions have always been an important part of this company's design practice.

Accompanying it for the last twenty years, however, I notice something that the “listeners” camp rejects a priori, namely that improvements in selected technical aspects translate directly into positive changes in sound. This would not have happened, I believe, without the involvement of musically sensitive engineers who translate technical prowess into the sound of recordings, or without the participation of all the people involved in the projects of this company from its beginning. Without them, even the best intentions of the company's contemporaries would probably be only 50% satisfied.

For what we get with the A-48S is a straightforward transfer of the operation of small and very small companies, which tinker with a project for a number of years, reaching for sophisticated, often exotic components, with which they appeal to our sense of beauty. But this is usually inner beauty, as their products normally look as if they were made by a gifted second-grade student of a high school of mechanical engineering. That's it.

In the case of the A-48S, we have a combination of superb construction, a design that has been refined over the past forty years, and an exceptional musical message, as the sound of this company's new amplifier is deep, warm, smooth and velvety. At the same time, it is also dynamic, open, fast, transparent and sonorous. It reads like a combination of two “traditions” intertwined in the history of this manufacturer's products for years. However, if I had to point out the more important component of this set, it would be the first one.

BENNY CARTER, playing with his colleagues on the album Jazz Giant, wonderfully recorded in 1958 by Roy DuNann and remastered in 2022 by Bernie Grundman, sounded sophisticated. Spread across the channels (extremely spread out, we should add), the instruments were not isolated, but rather “blended” with each other. There were interactions between them, even between the extreme channels. After all, we know that these recordings were made in the same room and at the same time.

So, when the drummer hits the snare drum harder from time to time, a short reverb is heard in the second channel as well. The Accuphase amp rounds the sound attack – not much, but still – resulting in an even more velvety sound than the reference amplifier. However, it does not lose sight of dynamics and detail by doing so. The leader’s trumpet, opening the track ˻ 2 ˺ I’m Coming Virginia, is thus sharp, biting and open. But it's still warm sound.

Also, the double bass in the right channel hits from time to time in a more contoured way. It is not because the amp tells it to, however, but because the sound engineer positioned the microphone close to the sound box, and in this particular track he let it out more during the mix – live mix, we might add. The A-48S is transparent also because the fine clearances accompanying Carter playing, but also immediately Webster, who plays tenor saxophone in the same channel, are clear, distinct and unambiguous, but also subordinated to the whole, never “by themselves”.

The year before, at the same studio in Los Angeles (the warehouse and packing room of Contemporary Records) DuNann recorded ART PEPPER and his RHYTHM SECTION, i.e., Red Garland, Paul Chambers and Philly Joe Jones. The difference in sound between these records was clear, as Pepper's record has a lower midrange and is also more focused on the midrange. This difference was more pronounced with the reference amplifier, more strongly marked, which makes me conclude that the Accuphase amplifier has its own agenda and plays music in its own way.

As far as I can hear, the idea is to show the instruments in as tangible a way as possible. The double bass and percussion in the right channel in the album's opener ˻ 1 ˺ You’d Be So Nice to Come Home To was thus powerful and almost jumped out of the column. And the Harbeths can show this kind of natural “drive” and “power” like few other designs. With the Accuphase amplifier it was closer to the listening position and a bit warmer. The mid-bass was heavily saturated and sort of “turned up” with it - it makes the sound so jumping, so rhythmic.

Remastered and released the same year (2020) by the same label (Craft Recordings), incidentally also on SACD, the album You Must Believe in Spring by BILL EVANS confirmed these observations. Recorded in 1972 for Warner Bros. at Capitol studios, it sounds completely differently. The sound producers chose for it is warm, thick and focused on the midrange. So, the leader's piano sounds as if it is covered by something, with distance, warmth and gentleness – just like the percussion. The double bass, on the other hand, sounds like a warm bass guitar, which only at the end of the first minute, with the solo, becomes a double bass.

There was no problem with momentarily recognizing this change, as the tested amplifier is a very resolving device, differentiating the sound well. In some respects, however, it played it the same way as the previous two albums, with a stronger mid-bass and a rounded attack in the midrange. The highs were warm – just like with the Soulution 710 amplifier – but they also had a sort of golden “halo” added to them. At the same time, they were not put out, which is interesting. They came out of the background strongly, unambiguously, and the ride hit by Eliot Zigmund had the energy and power that I expected from it.

The sound was extraordinarily saturated and exceptionally tangible, and Eddie Gomez's double bass I mentioned was within reach of my hand. So were DIANA KRALL's vocals from the album This Dream of You (2020). Produced with Tomy LiPuma, who died in 2017, and had co-produced the album by Bill Evans played earlier, it sounded in a way that could be described as a combination of tangibility and energy.

It is because energy is the key word for understanding this amp. This is not wild, unleashed energy, but a force under (clear) control. The bass, that incredibly low electronic bass in the track Traitor by ZOE WEES, descended very low and was explosive in its mass. It didn't have some very clear contours, but it wasn't dragged either. This is because the Accuphase amp plays music with larger sound planes rather than details.

This also worked out great with the excellent song Foxes in the Snow by JASON ISBELL, played only on acoustic guitar and sung. The producers placed these two elements very close to us. They wanted us to almost enter the vocalist's head, to see what he sees and feels, which was conveyed by the amplifier. In doing so, the A-48S did not forget to “look at” Isbell's peculiar diction, with “closed” and “wrapped inward” hissing voices, without brightening or isolating them.

▌ Conclusions

LISTENED TO BLINDLY, the A-48S could “do” as a high-powered tube amplifier. It's open at the top of the range, doesn't play in a closed way, and it's also resolving. However, the way it shows the midrange, palpable and close to us, as well as the way it shapes dynamics and shows mid-bass, sends us back to amplifiers like the McIntosh Mc275, only in a more resolving and energetic version.

˻ 1 ˺ Just the Two of Us, a track from GROVER WASHINGTON’s album on which Bill Withers sings, also showed that the device is excellent at stretching planes across but also pulls them up into the depth. That's why the sound is so palpable and at hand with it. Withers' vocal, positioned far away in the mix, was thus closer to me and clearer than with the reference amplifier.

The Accuphase is an amp with a distinct sound “of its own”, on the one hand reminiscent of the sound of small, specialized companies' designs, and on the other hand of powerful tube monoblocks. This is absolutely smashing because, after all, this is an engineering company, and what you hear is not the result of selecting some components or “tuning” the circuit, to give you the most obvious examples, but of reducing distortion and noise, and improving the speed of signal transmission. They've done this wonderfully, really wonderfully.

▌ DESIGN

THE ALUMINIUM THICK FRONT WALL anodized in gold, which is also referred to as “champagne”, multi-layered chassis, large (here: very large) VU-meter gauges, the rigid, solid and resonance-resistant steel-aluminium chassis and high-carbon steel feet, these are all the ABC of Accuphase products, which you also get in the A-48S power amplifier.

THE OUTSIDE • The front is made of a thick slab of aluminum with a “window” made of tempered glass at its center. Underneath it are signal level indicators and illuminated lettering informing about selected functions. The latter are reminiscent of the way Air Tight did it in its phono preamplifier → ATE-3011, and, historically, of industrial products from the 1960s.

The metal part has been divided into three parts, with a “control panel” protruding in the middle. It features a large mechanical power switch (there is no standby mode), a rotary selector for active outputs: A, B and A+B, the same VU-meter mode switch, an input selector and a knob for setting the circuit gain. All the knobs and buttons are aluminium and have a precise tripping point.

The speaker outputs are dual, so that proponents of bi-wiring speakers can conveniently use two separate speaker cables per channel, separately for, say, the tweeter and woofer sections. The terminals are solid, easy to screw on and have gold-plated contacts. Both banana plugs, fork plugs and “bare” cables can be attached with them. The VU-meters are really big, and we can choose how we want them to show peak indications - momentary, stop for three seconds or keep the highest level permanently. The indicators can also be turned off.

THE INSIDE • The XLR sockets are gold plated, while the RCAs have only gold-plated ground. They have been soldered to a vertically aligned board on which there are small relays – noticeably smaller than in the A-48 version. On the same board there are also MOSFET transistors, part of the protection of the output circuit, and it is to this board that the speaker sockets are screwed. Also here we can see the desire to shorten the signal path.

The power amplifiers are attached directly to powerful heat sinks. They look cast and are covered with paint, which is pleasant to the touch, more so than “bare” aluminium, and does not interfere with heat dissipation. The board features surface-mount transistors (SMD) in the input circuit and classic large output transistors. The former work in a double parallel circuit, which is supposed to reduce noise and harmonic distortion, theoretically by up to 30%.

Current transformers also operate in parallel – these are 1H01AF + 1H05AB (36P15 + 28N15) complementary pairs by the Chinese company Shenzhen Haolin Electronics Technology. Accuphase uses the same components in more powerful versions of its power amplifiers. The circuit boards themselves with gold-plated paths look high-end.

The PSU takes up the most space, i.e., first of all, a large, shielded power supply transformer and two very large capacitors, with a total capacity of 68,000 μF, whose negative screwed outputs are connected by a gold-plated jumper. These capacitors bear the Accuphase logo, but are known to be custom-made by Nichicon.

The entire circuit, as is the case with this company, is clear, clean and excellently made. ●

▌ Technical specifications (according to the manufacturer)

• Maximum output power (RMS): 50 W/8 Ω, 100* W/4 Ω, 200* W/2 Ω, 400* W/1 Ω
* Musical signal
• Frequency response:
- 20-20 000 Hz (+0/–0.2 dB) at full power
- 3-160 000 Hz (+0/–3 dB) for 1 W

• Intermodulation distortion: 0.01%
• Damping factor: 1000
• Damping: MAX, –3 dB, –6 dB, –12 dB
• Amplification: 28 dB, 25 dB, 22 dB, 16 dB
• Power consumption: 0.3 W (standby), 200 W (without input signal), 220 W (IEC 60065)

• Dimensions (W x H x D): 465 × 211 × 464 mm
• Weight: 44.8 kg

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THIS TEST HAS BEEN DESIGNED ACCORDING TO THE GUIDELINES adopted by the Association of International Audiophile Publications, an international audio press association concerned with ethical and professional standards in our industry, of which HIGH FIDELITY is a founding member. More about the association and its constituent titles → HERE.

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