Published On: August 15, 2011

Micromega AS-400 Integrated Amplifier Reviewed

Published On: August 15, 2011
Last Updated on: October 31, 2020
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Micromega AS-400 Integrated Amplifier Reviewed

Jim Swantko takes the new Micromega AS-400 which is more than just a stereo amplifier. It also functions as a preamplifier and a wireless media streaming option, which Swantko found to be quite impressive.

Micromega AS-400 Integrated Amplifier Reviewed

  • A veteran of, Jim Swantko also wrote home theater and audiophile component reviews for in the early days of the publication. His focus was on mid- to high-end audio brands like Mark Levinson, Classé, Noble Fidelity, Cary Audio, MartinLogan, and Paradigm.

MicroMega_AS-400_amplifier_review.gifThe Micromega AS-400 is the latest integrated amplifier from the French audiophile manufacturer and represents a paradigm shift among integrated amplifiers. The $4,595 AS-400 bristles with somewhat unexpected technologies such as high-power Class D amplification and a 24-bit/192 kHz wireless digital-to-analog converter. The AS-400 is aimed directly at those enthusiasts who have embraced computer-based audio and crave true high-end sound, yet eschew a rack full of components.

Additional Resources
• Read more stereo amplifier reviews by the staff at
• Look for a pair of bookshelf speakers or floorstanding speakers to connect with the AS-400.
• Learn more about the iPad 3G.

The AS-400 is essentially three high performance components in a single chassis: a preamplifier, a power amplifier and a state of the art digital-to-analog converter. The preamplifier incorporates several high-end design elements found in components costing significantly more. It is based around a very low noise design with its own dedicated power supply and R-Core transformer to eliminate cross coupling between the preamp and power amplifier sections. Ultra low noise regulators are also used to preserve maximum resolution of the delicate signals. Additionally, a digitally controlled resistor ladder is used for volume control, which is important for preserving phase equality between channels and imaging characteristics. This concept is very similar in design and function to my reference Mark Levinson N° 326S which also uses a digitally controlled ladder.

Operationally, the similarity continues in that the rate of change in volume is proportional to the speed in which the volume knob is turned. Turn the knob quickly and the volume steps are large; a slow turn results in smaller volume increments down to one-half decibel steps. Other notable features include preamp outputs for those who bypass the internal amplifier, nameable inputs, the ability to remove unused inputs from the input selector, and also a high quality MM phono section so turntable users can easily plug in.

The power amplifier section begins with a serious power supply consisting of a 1kVA toroidal transformer with fast recovery rectifiers and 40,000 micro Farads worth of smoothing capacitors in a dual-mono configuration. The amplifier circuit is a Class D design, which was chosen due to its compact size, high efficiency and sonic performance. The AS-400 generates 400 Watts of power into a four-Ohm load and we can only assume around 200 Watts at the industry standard measurement of eight-Ohms. Regardless, the AS-400 should have little problem driving most loudspeakers. The amplifier also features safeguards for under and over voltage as well as short circuit conditions and it also monitors for DC on the output to protect the loudspeakers from damage.

In my opinion, the most exciting aspect of the AS-400 is its integrated wireless DAC. The wireless AirStream module, based on the Apple Airport Express, has been completely redesigned since its original implementation in the Micromega WM-10 stand-alone wireless DAC. Utilizing the primary architecture of the Apple Airport express pays huge dividends in user friendliness and leverages the software might of Apple's iTunes software. The AS-400 is also able to take advantage of Apple's recently released AirPlay capability that allows for direct streaming of content from an iPhone or iPad - more on this later.

The new AirStream design utilizes three separate power supplies, one for the main module, one for the master clock circuitry and finally one for the D/A analog section. The master clock is also new and designed specifically to Micromega specifications, which provides astonishingly low jitter. Jitter is typically characterized as a smearing of the sonic image and Micromega went to great lengths in order to minimize it throughout the AS-400. The D/A converter is also completely new, based around a Cirrus Logic CS4351 chip that is capable of an impressive two Volt RMS output level. It's obvious that Micromega attacked every aspect of the digital circuitry and tweaked everything their engineers could think of.


The Hookup
The Micromega AS400 arrived double-boxed and well insulated with foam suspension packaging. Included with the unit was a somewhat flimsy multi-function remote control designed for use with other Micromega products. The remote was a bit of a tactile letdown as I expected something more substantial and to be honest, it felt downright cheap. To the remote's credit however, I must admit that I have never used a remote with better range and power than this one. Regardless of where I aimed the remote it operated the AS-400 without fail. In fact, at one point the AS-400 was turned around, facing the wall and it was still able to control it flawlessly. Oddly, I found that some of my DirecTV remote control signals also operated the AS-400. For example, pressing the volume up button on the remote would cause the AS-400 to power on. As I learned, there is no way around it due to a industry wide lack of codes, which results in overlap; thus this is a nuisance to anyone with DirecTV. I would assume this behavior is related to the sensitivity of the receiver that gave the AS-400s remote such amazing range, but at this price point it's something that needs a fix.

The operating manual was a brief two pages yet seemed to cover all the relevant points needed to get the AS400 up and running. One warning in the manual stated that nothing was to be placed on top of the unit and one should allow for at least thirty centimeters of ventilation above, which shouldn't be a problem considering the AS400 is about the size of a standard CD player, although significantly heavier than one. The specifications list the AS-400 at thirty-three pounds, but it felt much heavier.

My first impression of the Micromega case was that it was incredibly rigid and solid - think military grade. But Military grade finished with an eye towards beauty. Micromega uses a unique sandblast procedure that creates a surface that can't be characterized as smooth or rough, it's somewhere in the middle and has a very interesting feel. The top of the case was adorned with three rows of vents in the center, which not only break up the large surface but are necessary for venting the copious amounts of heat generated within the circuitry. My review unit was silver and pushed all the right visual buttons. The AS-400 is also offered in black, should it better suit your décor.

The eye is naturally drawn to the center of the unit where the large volume knob is surrounded with the only bit of bright work on the unit: a rectangular chrome surround printed with the model number, and the fact that it was proudly crafted in France. The chrome adds a bit of visual flair to an otherwise understated style. To the right of the volume is a large vacuum fluorescent display which provides source and volume information. Below the display is a row of buttons for input selection, monitor, mute, and headphone functions as well as a standby. The left side of the face has a convenient iPod input and headphone jack. Overall, the units styling is modern and elegant befitting a high-end product.

Moving to the rear of the unit, the space is dominated by a pair of large gold plated binding posts generously spaced for serious cables. They accepted my large Audioquest Colorado speaker cable spades with ease and felt as solid as any I have ever used. I would love to see other manufacturers follow Micromega's lead and stop with the cheap feeling plastic covered posts, which are unfortunately used everywhere with the exception of some mega-buck amplifiers. Moving right across the rear panel are placed several RCA connectors for preamp out, processor in and subwoofer out. The AS-400 provides a unity gain setting so its amplifiers can be used in conjunction with an A/V processor and also adds a subwoofer output for 2.1 configurations crossed at 400 Hz. Three sets of analog inputs round out the connection options. I was disappointed that no XLR balanced inputs were offered, as all I use are balanced cabling and assume many prospective buyers do too. The rear also houses the 802.11n antenna, which is a protruding semi-circular lump of plastic. Surprisingly, there was no digital input to let traditional sources take advantage of the fancy new DAC.

Integrating the unit into my system was simple once I dug out the RCA Audioquest cabling which I keep for occasions such as this. I connected my aging but still excellent sounding Esoteric DV-50 disc player, as well as my DirecTV HD-DVR and Sangean HDT-1X HD radio tuner.

I was very eager to take advantage of the AirPlay feature of the Micromega but was apprehensive of the complexity of making it all work. My research told me that it creates its own WHiFi (very cute, Micromega) network that will show up as a wireless network named "MUSIC". This network is used only for streaming music to the AS-400. In my laptop's Wi-Fi utility, I simply connected to the MUSIC network and opened iTunes. In iTunes you will find a new icon at the bottom right of the window in the shape of a small rectangle with a triangle at the bottom. Click the icon to choose the playback device, which in my case was either the laptop speakers or the AS400. Once the AS400 is selected you are free to stream anything from you iTunes library. It's very slick and works flawlessly. After a little encouragement from Mr. John Bevier of Audio Plus Services, the distributor of Micromega, I decided to push my luck and link my iPhone 3GS to the AS-400. I was running an older version of Apple's iPhone OS so I had to upgrade it in order to take advantage of the recently released AirStream feature. Once completed, I camped the iPhone onto the WHiFi network, selected it as my playback device and was streaming directly to the AS-400. I cannot overstate how cool this is, and how it encourages you to enjoy your music more often. When my wife wasn't looking, I put her iPhone on the network and told her to play a song. Her eyes lit up when she heard The Cure's "Pictures of you" (Fiction Records) from the Disintegration album start playing from the system. She spent the rest of the evening sampling her library and gushing over how good it all sounded. Maybe she'll finally get this whole audiophile thing after all. I was very pleased to see her having so much fun with the AS-400 and my all too manly hobby of audiophilia.

Read about the performance of the Micromega AS-400 on Page 2.


I began my review with "I Love Being Here With You" from Diana Krall's Live in Paris album (Verve) played on my Esoteric player, a combination I am intimately familiar with. This was done so I could get a handle on the sound of the AS-400's preamplifier and amplifier section without introducing the DAC as a variable. What I heard was a little shocking, to be honest - in a very good way. The AS-400 created a massive soundstage, easily extending beyond my walls right and left with stage depth to match. Not only was the soundstage large, the imaging within it was pinpoint precise and laser etched. The long guitar solo beginning around the 1:10 mark of the track occupied a distinct location on stage, but beyond that seemed to create an image of the instrument and the musician playing it. Lesser equipment can usually get the location information realistically, and even make the notes of the instruments sound right, but the real trick is integrating all the pieces together. The Micromega had this down cold. The acoustical interaction of the guitar with the Olympia Music Hall was palpable. Subtle reflections working in tandem with the musician created an illusion of authenticity that my brain happily processed and accepted as legit. The chords were rich and complex, delivered with weight and energy and hung in the air as they slowly decayed. I can only assume all the work that Micromega did to keep noise to an absolute minimum played a large part in creating an illusion so lifelike.

Jumping to the next track "Let's Fall in Love," I was impressed with how the AS-400 was able to project Ms. Krall's voice front and center while never forcing the issue. Her contralto vocals are matched by the amazing work of John Clayton on the standup bass. The Micromega was able to drive my power hungry Aerials to extreme depths while never sacrificing musicality in pursuit of excursion. The bass was played deep, but always kept its organic quality and warmth. After skipping around through a few tracks, I had a good feel for how the AS-400 performed as a traditional integrated amp, which was outstanding.

Next, I synced the same tracks in iTunes and on my Esoteric so I could switch inputs to easily compare and contrast the sources. The album was ripped via iTunes into WAV format and then streamed from my Dell laptop. What I noticed was that when streaming, there was a slight compression of the sound stage compared to the Esoteric. It wasn't massive, but it was noticeable. The laser-etched edges of the instruments softened a bit and while the detail was still there, it wasn't quite as vivid as with the Esoteric. These comparisons are given not to bash the AS-400; on the contrary. I think Micromega should be extremely proud of the fact that their integrated amp can offer ninety percent of the performance of my player, which alone cost about the same as the AS-400. I believe that it may be the air interface, which accounts for these subtle differences, but without a digital input I can't say for sure.

Next, I cued up my iPhone with Dark Side of the Moon (Capitol) from Pink Floyd and jumped to the track "Time." Again, the size of the soundstage that filled my room was massive. I felt as though I could get up, walk over to one of the ringing clocks and turn it off should I choose. The center clock ticked through the long introduction well in front of the speaker plane, hovering higher than I ever remember it. The heartbeats had punch that felt like a fist to the chest, and on those occasions when Roger hit a bass note, the room nearly pressurized. The AS-400 delivered near Krell-like bass performance that was taut and extended down through the floor. My listening sessions were typically loud, with the volume cranked up near the eleven mark and the little integrated never flinched or got edgy. All the while, the background singers blended together to create the ethereal atmosphere that Floyd is known for. If it sounds like I am smitten with the AS-400 - it's because I am. This integrated kicks out music as though it thinks it's a stack of mega-buck equipment. To say it punches above its weight class doesn't even come close to doing it justice.

For kicks, I decided to play with it in a two-channel theater application as I'm assuming most owners will use it as such. Knowing that it delivered the low frequency goods, I decided "Das Boot" (Columbia) was a natural film for it. The classic WWII submarine film offers some of the best low frequency information ever recorded as torpedoes explode around the German U-boat. As expected, the Micromega had a Kung-Fu grip on my Aerial's woofers, which seemed to defy physics with the speed at which they could start and stop. The transients were explosive and hard-hitting. During more subdued portions of the film, such as when the Captain pushed the sub to untested depths to avoid detection, the squeaks and groans of the submarine's shell coping with the incredible pressures were crystalline and vibrant. The whispers of German dialog were clear and anchored in the center of the action.

I have had some very large, very expensive amplifiers come through my system and this little integrated from France stood toe to toe with them and really held its own. Does it have the ultimate refinement of, say, a Krell Evolution or Pass XA amplifier? No, but the Micromega AS-400 gets you in the ballpark and considering its sub $5,000 dollar price, it is quite an accomplishment and highly relevant in today's market.

Competition and Comparison
When considering a high end integrated amplifier, there are several players which immediately come to mind such as the Krell S-300i, which does not offer wireless streaming like the AS-400 does, yet received high praise from Jerry Del Colliano and will lighten your wallet by about half that of the Micromega. If you are a fan of class-D amplification like that used in the AS-400, you should also consider the Bel Canto e.One S300iu. Like the Krell, it is less than half the price of the Micromega but does not provide streaming capabilities. If tubes are more your cup of tea then certainly check out the Cary Audio Xciter integrated that offers five Watts of glorious Class-A Triode goodness.

For more on integrated amplifiers including the latest news and reviews please visit Home Theater Review's Stereo Amplifier page.

The Downside
The Micromega AS-400 is a solid performer but does have a few chinks in its shiny armor. First of all, I found out first hand that it is very sensitive to ground loops. My reference Mark Levinson N° 326S preamp has zero problems when connected to the same pieces of equipment used in this review, using the same cabling. The Micromega emitted a noticeable hum which I could not resolve until I used a cheater plug on the power cord. Once done however, the AS-400 was dead quiet. It may be more of a knock on my electrical system than the Micromega, but regardless it did create an unforeseen problem, which I have not experienced with the countless pieces of gear that has passed through my system.

Secondly, the Micromega, while utilizing class-D amplifiers, generates about as much heat as a class-AB amplifier. I assume the majority of the heat is from some heavily biased transistors in the preamp section, but I repeatedly measured temperatures on the top of the case at over one hundred degrees while playing and mid nineties in standby. Al Gore would probably not approve. Be sure to leave lots of breathing room in your equipment rack when you do your installation.

As I mentioned earlier, there are overlapping IR code issues with the Micromega AS-400 and DirecTV that there is currently no known solution for.

The Micromega AS-400 is one of the most impressive products I have had the pleasure of reviewing. At its asking price of $4,595 you are essentially getting three top-tier components all wrapped up in a single beautifully constructed chassis. I challenge anyone to assemble a system for the same price and compare it to the Micromega. I predict that comparison will result in a lot of bruised egos. For the enthusiast who wants a hassle free system that fits on a single shelf, sounds fantastic and allows seamless integration with their existing iTunes audio library, the Micromega should be at the very top of the audition list.

Additional Resources
• Read more stereo amplifier reviews by the staff at
• Look for a pair of bookshelf speakers or floorstanding speakers to connect with the AS-400.
• Learn more about the iPad 3G.

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