[Listening test] Amphion Amp700 professional Class D power amplifier

Product name: Amphion Amp700
Manufacturer: Amphion - Finland
Approx. price: $2000 USD
Reviewer: M.L. Gneier - TNT USA
Reviewed: October, 2023

I must confess that I searched a long time for an amplifier like the Amphion Amp700. And, once I found it I was fairly sure I wouldn't be able to get one to review. I mean Amphion is a hybrid pro sound high end company that's based in Finland. Still, it was worth a try. Much to my surprise, mere hours after sending my email I got a reply by from Amphion's US rep, none other than Colin Liebich, a legendary Los Angeles-based engineer in his own right. Mr. Liebich had an Amphion Amp700 sitting right next to him and I was invited to borrow it for review.

Why the Amphion Amp700? Well, it's a Class D amp. But, it's not just another Class D amp. It's a Class D amp that's designed and built to a higher, dare I say, truly high-end standard, than are many of the other Class D offerings. To be clear, I have nothing against inexpensive gear. But the fact is that full implementation of any topology is not as easy as buying a chipset. Might that day come? Certainly for the mass market it may already be here. But it's not for high end audio. Loyal readers of TNT already know that high end does not always mean high priced but it does mean that a product is built with high ambitions, rather than with a low price being the primary consideration. I wanted my first experience with Class D to be a product that was designed to be something more rather than just something that's simply inexpensive. The next thing that's considered good just because it's cheap holds almost interest to me.

All of that said, this is a ridiculously low priced amp when you honestly consider its power, musicality and transparency. The Amp700 is a 350 watt stereo amplifier into 8Ω. Into 4Ω it doubles its power to 700 watts per channel. Of at least equal is just how quietly the Amp700 operates. The stated specification is a dazzling 117dB dynamic range [it uses an IcePower 700ASC2 module, see bottom of this page for more info].

Amphion doesn't define whether that spec is referenced to full power but I can say that this is easily the quietest amplifier I've used in a long time, maybe ever. Pro gear always induces a little anxiety when it comes to listening. In the same way that mid-fi and consumer gear is designed to work without a lot of functional compromise, pro gear is designed to be exceptionally rugged and reliable. The Amphion Amp700 certainly covers both bases. It looks like a typical two-rack-space product. While not exceptionally deep it is very light at only 5 kg. There's a single blue LED that forms an illuminated ring on the on the front panel. It's not obtrusively bright, thank goodness, and the feel of the power button is exceptionally smooth and positive. Befitting its Class D topology there are no external (or internal for that matter) heat sinks. The rear panel is simple but shows a great deal of thoughtfulness in its design. The XLR inputs sit far to one side directly adjacent to the Amp700's input stage on the other side of the rear panel. The speaker connections are fantastic and I assumed they were proprietary to Amphion. But, I learned later they were made by Argento. They are very high quality, three-way connectors. The plastic knob allows for the easy use of bare wire or spades. Remove the knob and you have properly dimensioned banana sockets (which I used exclusively) that satisfy EU requirements on spacing and separation between jacks. It is the model of simplicity and makes it all the more curious that so many other products makes such a simple task as connection of speaker cables such an ordeal. The Amp700 is the first product I have ever reviewed where a comment on the IEC 320 connector is in order. The Amphion's has two interesting features. First, there's a small master power switch. There's also a locking tab and a corresponding tab on the female AC cord that Amphion provides. Do you want to be a smart audiophile? Use the AC cord that Amphion supplies. They've put a lot more thought into how to use their product than you will.

Have you forgotten what I wrote about anxiety when it comes to pro gear? Well, it's a thing. Pro gear can sound, well, like pro gear. Any time you can hear into a product's origins you have a problem. You end up listening to how the product was designed rather than the music. Never one to let anxiety rule me, I started with two difficult and revealing recordings. Laurel Zucker & Susan Jolles / Images for Flute & Harp / Sonatine for flute & harp Victor Frost (1952-) (Cantilena Records 66016-2) Moderato e deciso. This track will reveal any tendency to make the sound of the flute sound overly whispy and will bleach away the fundamentals of the harp. If the Amp700 had a problem I would be able to hear it quickly. Instead, dead cold, the sound was fantastic with a great retrieval of the fundamentals of both instruments and a superb sense of space. Talk about a noteworthy start.

Next up was The Cowboy Junkies / The Trinity Sessions (RCA 8568-2-R): Mining for Gold. This classic traditional tune, sung a cappella by Margo Timmons will tell you more about what your system can and can't do than any other minute and a half of recorded music can. It was recorded using the famed (notorious?) Calrec Ambisonic microphone in the Church of the Holy Trinity in Toronto. This is a recording that should bloom with the actual space where the music was captured. But, with lesser amplifiers I have heard the space shrink and become airless. But, that recorded space is real. It is part of the music's signature and as such is critical to a system's fidelity. The Amp700 truly shined on this music. Timmons' voice was warm and beautiful and alone in the reverberations of the church and the effect was so essentially musical that I played the track again and again to hear it.

Gabriel Fauré The Two Piano Quartets / The Ames Piano Quartet (Dorian DOR-90144). The entire CD is the very pinnacle of the genre in both performance and recording. A good amplifier has to place each of the three string instruments in their own sound field with the piano well focused, yet expansive. The Amp700 handled this very well with astonishing focus that could, occasionally, almost be rendered as slightly etched. Still, the woodiness of the piano and strings were always presented in a way that preserved their fundamental acoustic qualities and warmth.

I have saved my discussion of the Amphion Amp700's power until last. You might be asking what 350, let alone 700, watts per channel means to the average high end system? In the past, high-powered Class AB amps could suffer from a lack of finesse. End users were left with a choice between finesse and dynamics if their budgets were limited, which most were and are. Smart listeners always erred in favor of finesse while those who were less-wise went for power. The Amp700 makes this balancing act, the one between finesse and power, moot. In use, its power seems both effortless and unlimited. In a way, I wish I still owned some genuinely power-hungry speakers like my Martin Logan CLS to see if they would stress the Amp700. I rather doubt they would. When you turn up the sound with the Amphion things simply become louder. There's no perceptible shift in the Amp700s sonic character whether the music is loud or at the edge of silence. Not surprisingly, dynamic peaks of all kinds of music were recreated with a sense of relentless ease. Bass was always full of impact and precision in both the recreated attack and pitch. The Amp700 always sounded and behaved as if was loafing, because it obviously was. The Amphion's power provides the kind of energy that's good for music of any kind. Its authority is always there, waiting, to provide exactly what the music needs.

A couple final operational notes. The Amp700 functioned perfectly at all times. It was utterly silent in operation and free from any kind of annoying power-off or power-on pops or thumps. I drove the amp from a balanced source. During my evaluation I also tried listening to the amp from an unbalanced source and while things still sounded fine it seemed to me the Amp700 lost that little something extra when driven from an unbalanced source. I'm not talking about a big difference here but I would gently advise that you consider this observation and use the A700 as the fully balanced design it is. At $2000, if you can find one to audition, the Amphion A700 is an absolute bargain. It's truly an amplifier you could buy and keep forever. No matter your age, my guess is the A700 will outlive you. As a seriously well-built Class D design it doesn't have rows of bipolar or MOSFET transistors or capacitors the size of soda cans both of which will eventually wear out. If you made the wise investment in the Amphion Amp700 you could simply forget about amplifiers and live the rest of your life enjoying your music. And that, sounds pretty damn good to me. Take my advice. If you are in the market for a balanced stereo amp, take your time and find a way to audition the Amphion A700. Depending on where you live an audition may not be all that easy for you to arrange, but I'm confident you will be as rewarded as I have been. At its price Amphion Amp700 is truly a ground-breaking high-end amplifier.

P.S. Technical note (by L. Cadeddu)

This Amphion AMP700 is based on an IcePower 700ASC2 module, the company's powerful two-channel solution with an output power of 2 x 700 W in 4Ω or 2 x 350 W in 8Ω. The amplifier utilizes ICEpower's patented HCOM modulation and control technique to produce audiophile sound quality with very low total harmonic distortion (THD) and noise levels. Its cost, for a standard customer (like me and you) is around 250-360 USD but, of course, members of the industry can purchase these modules in large volumes as OEM supply at a much lower cost. Amphion has put this module into their cabinet and just added a proprietary buffer stage (the small board at the top right in this image). Whether or not this justifies the 2000USD request is up to you to decide.

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Amphion Amp700

The Amphion Amp700 defines power, finesse and fulfills the promise of Class D.

P.S. Technical note (by L. Cadeddu)