I have to admit that I was surprised when I discovered the £18,650 asking price for Analog Domain’s Isis M75D integrated amplifier. Granted, it’s a lovely piece of engineering and the black surface has a rubbery coating that gives it a pleasing tactility, but nonetheless on size and looks alone I would have put it at around a third of the actual asking price. However, in audio, performance trumps all, and in that respect, the M75D has got it where it counts!
At seven years old, the German-based Analog Domain is a relative newcomer to the business. Until recently, the company almost exclusively concentrated on power amplifiers with outputs ranging from 550 Watts up to 4,000 Watts, with outputs that double into a four Ohm load. So, Analog Domain is no stranger to amplifiers, as it has made some of the most powerful designs an audiophile can buy. The Isis, with its 250 Watt into eight Ohm specified output, is relatively restrained in comparison, and at 25 kilos it’s fairly manageable, too.
The Isis M75D is a perfect reflection of company founder Angel Despotov’s uncompromising stance on amplifier design, which naturally extends to the choice of component quality and the level of build employed. Take the casework for example; it’s clearly custom machined, but what’s not obvious is that the top and bottom plates are internally machined in a latticework to give excellent rigidity without excess mass, lowering resonance in the process. The black parts are not painted or anodised but latex coated. This produces a deep matte finish, that is both ergonomically and aesthetically pleasing, and long lasting: Despotov make the point that his products are designed to last “at least 25 years”.
The actual component count under the lid is not apparently very different from other high-end integrateds at or beyond this level, but great claims are made for the amplifier itself. For a start, it is a fully balanced circuit with “exceptional current output capability” and output impedance that is “essentially zero” giving the Isis what Angel describes as an “insane damping factor”. The power supply is a class G type with separate voltage rails for high and low power outputs. This is an approach used with some considerable succes by Arcam, in its current range of larger amplifiers. According to Angel “the key here is to do it in such a way as to have minimal artefacts in the output signal.” He uses this topology because it keeps the amp’s temperature down, and yes, this is the coolest high power analogue amp I have used. The idea is that the lower the operating temperature, the longer the components inside survive in situ – apparently, every 10 degree Celsius drop in temperature doubles the life of “the most vulnerable components” in an amplifier. This gradual failure of components is essentially why older audio components tend to sound warmer and softer than they once did – it might often appear nice and benign, but this is the sound of your amplifier going out of specification, and ultimately beginning to die.
The price is related to the use of high-spec components, but Analog Domain admits that half of the Isis’s price tag comes down to the chassis, which is something one presumes about high-end components but it is nice to have it confirmed. And it is a superbly detailed chassis at that; the way that the heat sinks are concealed from the side but vent top and bottom gives it a clean appearance that doesn’t threaten to lacerate its owner, and the styling is reminiscent of Revox at its aesthetic peak, or Mark Levinson at its best. The back panel is also unusually well endowed on the switches front: chrome levers let you choose between bridged or stereo operation; separate pre-out/power in or internally connected on that rare connector the five pin DIN; and gain can be increased by 8dB on either of the two RCA phono socket equipped line inputs. The other two inputs are balanced giving the Isis just four line inputs in total, which doesn’t seem overly generous but probably enough for most situations.
Operation is mildly confused by the auto dimming of the input and level displays. This can be changed and you soon realise that a white indicator means it’s on, so even reviewers get to grips with it quite quickly. I was surprised to find a One4All remote handset in the box for the Analog Domain but am told that a suitably substantial matching handset is on its way and will be supplied to all purchasers of this amp. As the Isis is the first amp that requires control in AD’s range, this is understandable. On the amp itself, there are individual input buttons, power, mute and phase, plus a headphone jack with a limiter light above it. The latter is for the amp as a whole and indicates that you have maxed out the available unclipped volume. This indicator glows white if the limiter is active and red if protection has been activated, such as if the output has been shorted. Limiters are a rarity in high-end audio because they usually compromise sound quality but this amp doesn’t seem to be too compromised and a bit of protection is useful with this much power on hand.
The volume control consists of a discrete resistor matrix driven by solid-state opto-coupled MOSFET switches, in an arrangement that results in a constant output impedance at all attenuation levels. I was initially concerned that the level was approaching the nineties without the volume being that great, but discovered with some quieter recordings that it carries on past 100. It turns out that for some unstated reason, ‘127’ equates to 0dB, and every step represents 0.75dB. This, combined with good sensitivity to the remote, means you can make very small steps if required, or keep your finger down for bigger changes.
Perceived volume is quite different, too. The level rises but the distortion that usually accompanies it seems to be absent. This amp clearly has very low distortion of the usual variety and this results in outstanding transparency allied to total control. There is no sense of overhang or time smear in the usual sense because notes just start and stop without any trace of ringing. It’s quite uncanny to have this without the sense of grip usually associated with powerful transistor amplifiers. Such things generally have a subtle electric character, a water mark almost that lets you know that you are dealing with a high power amplifier. The Isis does not seem to have this. One example of the transparency of power on offer is that the sense of timing did not change noticeably when moving from the relatively difficult load of a Bowers & Wilkins 803D to the lower sensitivity but easier load of a PMC fact.8. With most amps, timing is superior with the latter speaker. Here, the same precision could be heard with both. And ‘precision’ is the word; this is not the ‘Pace, Rhythm & Timing’ of a Naim or the zest of a Rega, it’s a complete control of tempo with such a light touch that one’s attention is not particularly drawn to it.
The Isis is a very clean amplifier indeed, and you hear extraordinary levels of detail in everything that’s played. This can make it sound a bit cool with a speaker like the 803D and I found it beneficial to seek out a warmer, highly refined source in the armoury to balance this out. I don’t think the AD has a particular tonal character – it seems extremely even handed, in fact – but the absence of overhang means you need to carefully consider the right balance of components in the system, rather than trust your luck. I found that the CAD CAT server and CAD 1543 MkII DAC fitted the bill better than my usual sources, perhaps because it’s the most expensive but also because it produces more resolution than the digital alternatives. My usual digital reference is a Melco server, Cyrus X-Stream network streamer, and Primare DAC 30, which as a rule delivers a strong sense of timing and plenty of detail in what seems an even-handed way when played through most systems. In the AD’s hands, however, it sounded a bit cool because it ultimately is a bit cool, although this rarely makes itself known when played through less revealing amplification. When you open the window wider, it’s inevitable that you hear both the good and the less good in a source.
That said, it was striking just how close this combination got to the recordings. The moment Gregory Porter’s ‘No Love Dying’ [Liquid Spirit, Blue Note] came on, the compression used was obvious, albeit in the context of good scale, maximum crispness, and dynamics. The percussion on Patricia Barber’s ‘A Touch of Trash’ [Modern Cool, Premonition] has never sounded so real and the timing never so taut. The double bass had power and extension, but was never allowed to get overblown. Barber’s voice was pretty special too, as was Melanie De Biasio’s on the song ‘With All My Love’ [No Deal, PIAS], where the subtlety of reverb, ‘inky black’ background, and virtual realism of the performance combined with eerie low frequency notes to tremendous effect. Did I mention that this amplifier is quiet? Because it’s very quiet indeed. It makes other serious amplifiers sound grainy, even decent, high-end examples that taken alone seem to have very low noise floors. But this isn’t a noise floor thing; it’s an absence of the usual sense of electrical power that is so hard to avoid in solid state amplification, and part of the appeal of valves. But valves have other characteristics and cannot deliver anything close to the sort of control on offer from this Analog Domain integrated.
I also used an analogue source in the form of a Rega RP8 turntable, Rega Apheta 2 cartridge, and Rothwell Signature One phono stage. This also sounded unusually taut and devoid of thickener, and it revealed an odd sound between tracks on a familiar album. This must be a sign of wear, but highlights the Isis’ clear cut, even-handed soundstage that appeared to have nothing added nor taken away. The dynamics of the drums on another Patricia Barber track, ‘Company’, were remarkably real and the voice was clearly recorded in a completely different fashion to the band. This sounds obvious yet is not always easy to define, and such image separation on this amplifier is in the premier league. The trumpet was bright and clear and the double bass remained as per the digital experience: taut and powerful. The only thing it lacked was a sense of presence; imaging is precise, reflecting both the depth, width, and height of the recording, but you don’t feel like the musicians are in the room in the way that other amplifiers present them. As both styles of presentation are very convincing it’s a case of figuring out which is the most accurate, but ultimately if it’s acoustic music then there shouldn’t be any grain evident, and that suggests Analog Domain is doing it right!
The majority of listening was done with the 803 Diamonds but I also used my usual reference the PMC Fact.8 and the results were equally as persuasive. The bass was superbly controlled and transparency remained in a class of its own. George Duke’s dulcet tones on the ‘smooth’ version of ‘Inca Roads’ as featured on the recently released Roxy by Proxy album [Frank Zappa, Zappa Records], have rarely sounded more real and intimate. Also, the low synth on the Hadouk Trio’s Live à FIP [Mélodie] was frankly gorgeous, dark, chewy, and full of texture.
In truth, everything I played offered up new insights into the performance and production: from Radiohead to St Matthew’s Passion it all had oodles of character and depth. The Analog Domain Isis 75D is a remarkable feat of engineering: it reveals the potential of doing things differently and opens the sonic window so wide that it’s hard to believe that this is an integrated amplifier. The presentation is so transparent that you need sources that are equally even-handed, resolute, and low in distortion to get a result that matches this amplifier’s capabilities. But it’s worth the effort in carefully selecting those components. There’s no doubt that Analog Domain is a force to be reckoned with, and that the price is well justified under the circumstances.
Type: Solid-state, 2-channel integrated amplifier with headphone amplifier
Analogue inputs: Two single-ended line-level inputs (via RCA jacks), two balanced inputs (via XLR connectors)
Digital inputs: N/A
Analogue outputs: One pre-power loop (via 5 pin DIN)
Input impedance (high-level): 20kOhms balanced, 10kOhms on RCA
Input impedance (power amp): 10kOhms [differential]
Output impedance (preamp): 10 Ohms
Headphone Loads: Any!
Power Output: 400Wpc @ 4 Ohms, 250Wpc @ 8 Ohms
Bandwidth: 2 Ohm, THD < 0.1% 5Hz – 50kHz
Distortion (THD+N): 20kHz BW, 8 Ohm nom. power < 0.002%
Signal to Noise Ratio: >120dB referenced to full power
Dimensions (H×W×D) inc. feet: 135 × 440 × 440mm
Manufacturer: Analog Domain
Tel: +49(0) 1608 173 193
UK Dealer: Choice Hi-Fi
Tel: +44(0) 20 8392 1959
UK Dealer: Concerto Audio
Tel: +44(0) 7751518404
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