The goal of designing amplifiers has remained the same since the early day of audio: to deliver an appropriate amount of gain and current with minimum distortion. Today we know that the goal can be approached in countless ways, none of which can do without compromises. There are alternatives for every amplifier topology, staging, the structure of the power supply, biasing, negative feedback, component choice etc. Possibilities are practically unlimited.

Why I’m telling you all this? Isn’t it rather obvious that there is no one truth in these matters, and that the so-called “right” choice always depends on the case in hand? I’m bothering you with this because I want to make it clear at the outset that although I like Audionet’s AMP MAX monoblocks very much in many respects, and eventually bought a pair for my own purposes, I don’t want to put forward a claim that they’re the only route to an outstanding sound.

Audionet’s vision is “to provide the listener with direct access to music and film. To provide an authentic listening experience in which one forgets that the heard sounds and the seen images are being reproduced by machines”. Not very original, perhaps, but the idea is sound. And it guided me through this review.

AMP MAX is Audionet’s current reference amplifier. It was launched a couple of years ago despite its immediate predecessor’s - AMP II MAX – success both in press and among the audiophile community. Naturally, AMP MAX makes a good use of the techno side of the AMP II MAX. The difference is, according to the manufacturer, that the AMP MAX monos deliver more bandwidth, speed and precision.

MAXIMIZE MAXES

The AMP MAX monoblocks feature Audionet’s ULA (Ultra-Linear-Amplifier) technology. As far as I know Audionet originally developed this complex circuit topology for the purposes of medical engineering. Here’s a list of what goes in the AMP MAX:

• Magnetically and capacitively optimized construction.
• The massive aluminum cabinet avoids harmful influences of subsonic noise.
• The signal paths are completely DC coupled and kept to a minimum and contain no sound-impairing components such as coils, chokes or power relays.
• A special double cascade decouples the source signal from the driving and output stage.
• The driving stage linearizes distortion of the output circuit locally with a unique, cross-linked correction circuit in real time.
• The input and driving stage are separately powered by an oversized 80 VA toroid-core transformer with separate windings for positive and negative operating voltage.
• Discrete, extremely fast and stable driver and output stages. The output stage is equipped with eight hand selected power MOSFETs with actively controlled bias current amounting to 0.6 A.
• Two individual 1000-VA toroid-core transformers feed the positive and the negative half-cycles of the mains.
• The supply voltage is stabilized as rapidly as possible by optimized discrete MOSFET regulators.
• Four special, fast and impulse-resistant high-current capacitors with filtering capacity of 156,000 uF.
• Special care of the component selection is taken. Only the highest order ones are accepted.
• Bi-wiring terminal with two pairs of WBT nextgen connectors.
• Large-size, two-line VDF-display featuring a screen saver.
• Timer.
• Automatic mains phase detection.
• Microprocessor unit controls all functions and permanently monitors DC, HF, temperature and overload.
• Remote activation over Audionet Link (optical waveguide) and via input signal.
The output is 400 W into 8 ohms / 700 W into 4 ohms / 1.100 W into 2 ohms, ie. enough! The frequency response is said extend from 0 to 500,000 Hz (-3 dB), - zero Hz? The damping factor is above 1.800 @ at 10 kHz, and > 10.000 at 100 Hz.

Audionet also publishes info on the harmonic spectrum: k2 typ. -117 dB for 25 Watts @ 4 ohms / k3 typ. -123 dB for 25 Watts @ 4 ohms. Intermodulation and distortion are expressed in dBs: Intermodulation: < -110 dB SMPTE 100 Hz : 20 kHz, 4 : 1, 50 W @ 4 ohms, and THD + N: < -106 dB at 1 kHz, 25 Watts to 700 Watts @ 4 ohms. The SNR is better than 125 dB. The input impedance for RCA is 37 kOhm, 100 pF, and for XLR 3 kOhm, 100 pF. The max. power consumption is 2000 W. Dimensions: W 215 mm * H 285 mm * D 500 mm; weight: 38 kg/mono block. Finally, the price in Finland is around 15.000 euros per pair.

AMP II MAX VS. OTHER POWER AMPS

Before the time I made my final decision to purchase the AMP MAXes, I compared the AMP II MAXes with several high quality power amps: McIntosh MC-501 monoblocks, Burmester 911 Mk III, Plinius SA Reference and Pass Labs X-350.5 stereo amps. I also did try a couple of stereo tube amplifiers but very soon noticed them to be unsuitable for my setup’s power requirements, and my preferences, despite their exceptional tonal richness.

First of all, the above transistor amps sounded excellent, and I could have easily lived with each of them, even though I fully enjoy the performance of the AMP II MAXes. But each of the amps also turned out to be a personality with a mixture of characteristics. It should be kept in mind in particular that my comments below are relative to Wilson Watt/Puppy 7 loudspeakers (Audio Aero Capitole Mk II SE CD player; Transparent Reference MM (MMI) interconnects and speaker cables; Transparent Reference XL (MMI) Balanced interconnects; Transparent Power Isolator XL (MMI)).

The McIntosh MC-501s delivered the most tube-like performance I have ever heard from transistor monoblocks, with many favorable qualities and some minor defects. They produced a bit richer and warmer sound than the AMP II MAXes without giving up in over-all purity of the sound. I only would have preferred slightly more power and extension.

The Burmester 911 Mk III sounded tremendously clean, airy and revealing, but could not quite compete with the AMP II MAXes in authority over the bass frequencies and in blackness of the background. It also added a bit more bottom noise during the silent moments of music.

The Plinius SA Reference shone in resolution as well as delivered exceptionally dimensional soundstage and very neutral overall sound, especially in Class A mode. However, it not have the same punch as the AMP II MAXes, and the sound wasn’t equally gentle.

The sound with Pass Labs X-350.5 was tonal rich and pleasurably soft plus the amp gave an extraordinarily punchy presentation. With respect to those characteristics it equaled or even bettered the performance of the AMP II MAXes. On the other hand it was rather general in the organization of the soundstage and the background wasn’t quite as black as with the AMP II MAXes. The Pass Labs X-350.5 was the only amp in the group that could compete with the AMP II MAXes in punch and overall bass performance.

AMP MAX VS. AMP II MAX

Next thing to find out was how the advanced technical step-ups improved the sound of AMP MAXes. Associated equipment: Wilson Sasha W/P and Burmester B-100 loudspeakers; Audio Aero Prestige SE and Capitole Mk II SE CD players; Transparent Reference MM interconnects and MM/XL speaker cables.

Common to both amps was their ability to provide an ultimately unconstrained sound. No matter what kind of speakers were fed, what genre of music was played or how demanding the recording was, both amps reproduced music with a sovereign ease and purity. In this regard, the AMP MAXes added only very little to what the AMP II MAXes were already capable of.

Believe or not, the AMP MAX monoblocks have a killer bass! Even in the most critical investigations I couldn’t find any flaws in this respect. Besides the tremendous subjective treble extension the quality of the bass is likely the first feature, which will jump out for the listener. In comparison to the AMP II MAXes, the AMP MAXes seemed to offer a tad richer, detailed and uniform low end. I can assure you that if for some reason you don’t feel that the AMP MAXes are you thing, the reason won’t be its bass.

Reproduced music will touch me only if the soundstage is transparent and life-like, faithful to the source. AMP II MAXes are very good at this, but having set up the AMP MAXes in my system I felt the background of the soundstage was even blacker and every musical event was presented with greater clarity. Otherwise the soundstage was well organized and showed a good dimensionality.

The way in which the AMP MAXes reproduced subtle musical and instrumental details was surprisingly impressive. Massive power amps are sometimes criticized for sounding rough, hard and edgy, and that this effectively prevents them from successfully revealing fine textures of music. Not the AMP MAXes. They let the nuances of music to come through cleanly and coherently without compromising life-likeness of tone colors and harmonic expression. Chamber music and sonatas were the best indicators of this character. I felt that the AMP MAXes were slightly better in reproducing correct timbres.

CONCLUSION

In the end of the day I was very convinced of the AMP MAXes’ performance, also believing them to be a step forward from the AMP II MAXes. But as I said earlier on, in a wide pool of preferences and system characteristics, there is no single best amp. The AMP MAX monoblocks were my choice, and they surely deserve my highest recommendations. These monoblocks can master all kinds of music. They can command every loudspeaker I can imagine while being practically insensitive to the speaker load. And only a very monstrous monoblocks can handle music’s subtle textures in the way in which the AMP MAXes do. What can the engineers at Audionet possibly do next, except scratch their head?

www.audionet.de