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Metrum Acoustics NOS mini DAC Octave

Almost analogue

[Octave DAC]
[Italian version]

Product: Octave DAC
Manufacturer: Metrum Acoustics - The Netherlands
Cost: 795 Euros, factory direct
Reviewer: Maarten van Casteren - TNT UK
Reviewed: February, 2012

Some products are more inspiring than others and for non-audiophiles it can be a little bit difficult to understand our enthusiasm for equipment that only looks just like a box to anybody else. DACs are particularly uninteresting to most people, even if they look expensive with buttons and little shiny lights at the front. Even messages that jitter has been reduced to the absolute minimum through innovative reclocking, or that some kind of special filter has been applied are now so commonplace that you don't really score many brownie points with them anymore. For that reason I was very interested in the Metrum Acoustics Octave DAC, as that really does use some new technology.

At first sight there's nothing special about the Octave DAC, except for the fact that it is very small, and consists of two boxes. One box contains the actual DAC, and the other one houses the power supply. Even together these are much smaller than most other dacs on the market and very easy to accommodate. The casing is fairly standard and the connections at the back are limited to optical or coaxial spdif input and phono output. There's no USB input, no balanced output and no settings for sample rate or filters at all. The only switches are the on/off switch and the one that selects optical or coaxial input. That's it.

The interesting story starts inside. This DAC doesn't do any upsampling or oversampling, hence the NOS in its name for Non Over Sampling, and no anti-alias filtering either which is not that unusual, to be honest. But it also doesn't have an output stage, which is quite unique as far as I know. Basically, the digital signal goes straight into the DAC chips, and then from there straight to the output connectors. No messing about with sample rate converters, complicated filters and fancy output stages here. If you like your DACs straight and simple, then nothing will beat this.

There's a little more to it, obviously. You cannot do this with any old DAC chip, and the ones used in the Octave are completely unique, for audio applications that is. The DAC chips are actually not intended for audio at all, but for much higher frequency applications. Metrum Acoustics uses this in more DACs, with the simplest version, the miniDAC Duo, using one DAC chip per channel. Then there's a better version, the Quad, which uses 2 chips per channel, and finally there's the Octave, with 4 DAC chips per channel. There's also a progression of power supplies, with the simpler models using basic wall mounted power supplies and the Octave using a more powerful and higher quality solution in a separate case.

In use, I had no issues with the Octave at all. It always behaved itself, whatever the source or the circumstances. It's simple, but also extremely reliable and robust. I have to admit that my first impression was that it was perhaps a bit too basic, but I soon learned to appreciate the qualities of the Octave as it's such a solid performer. There's something to be said for keeping things simple, after all, and DACs rarely come in a more simple form than the Octave.

[Octave DAC]

The sound

This DAC immediately makes a good impression. The sound is warm, focussed, clean and basically without any obvious flaws. It's a very easy DAC to listen to, and also one that never pushes you in one or another musical direction: it works very well with all sorts of music, and is even relatively easy on lesser recordings. When fed the digital signal from my Astin Trew AT3500+ CD player it sounds very much like the analogue output of that player: switching from one to the other is almost undetectable at first listen, except for a slightly more friendly top end with the DAC, perhaps.

After a bit more listening it becomes clear that the Octave indeed has a slightly less bright top end than the Astin Trew, but shows a vitually identical tonal balance over the rest of the spectrum. Perhaps this is also the reason that the Astin Trew seems to reproduce slightly more detail than the Octave, although I have to say that the difference is small and only detectable with very good recordings and in direct comparisons. The Astin Trew also produces a little bit more air around instruments.

Having said that, the Octave certainly doesn't seem to leave anything out, even at the top end. If anything, this slight softness seems to have more to do with the absence of distortion or digital 'edge' than with the absence of actual signal. Other players might show a bit more extension at the top end, the Octave scores bonus points with its extremely clean presentation and lack of smear.

Compared to the Astin Trew the sound is ever so slightly more detached from the speakers, with a nice and relaxed character. The soundstage is a little bit more towards the front, but there's nothing 'forward' to it. The CD player simply projects a little bit further to the back. There's no difference in width, layering or focus, with both sources doing a fine job.

It is certainly not the case that the warm overall character of the Octave is caused by an emphasis on the bass, but rather by this slight softness at the top end. The bass is actually well controlled and only the midrange shows a hint of added richness.

The Octave does hold the sound together exceptionally well when the going gets tough, even better than the Astin Trew, probably because of that friendly top end and the appealing richness to the sound. Whatever the reason, this DAC really sounds rock solid and totally composed without any edge, aggression or other nastiness. Pretty much perfect, I'd say, but if your taste is more for ultimate detail and absolute neutrality then the Tentlabs b-DAC I reviewed earlier would be the better choice, being a DAC that is pretty much perfect too, but in a different way.

[Octave DAC]

I also took the Octave to a friend with a Naim CD5 CD player, with flatcap power supply upgrade. He uses a squeezebox with a BenchMark DAC as well. I've used his setup to assess other DACs before and the Octave turned out to be one of the best ever. It basically matched the Naim player and the BenchMark DAC quite easily and did feel completely at home in this company. The Naim is obviously strong with rhythm and pace, but the Octave had no problems keeping up and showed no weaknesses at all. In the end we couldn't really agree on which one of these three sources was the best, but I strongly suspect that, given enough time, we could well have chosen the Octave. Given the natural advantage of the Naim player, working in an all Naim system through the preferred DIN connection, this is high praise indeed, certainly if you take into account that this player is over twice the price of the Octave.

I then took it to another friend to be compared to his new Rega DAC. The Rega is somewhat more affordable than the Octave, by a small margin, but a very impressive dac for the price. Definitely a recommendation, but I still thought the Octave sounded more natural and coherent. The Rega had a bigger soundstage and deeper bass, but also sounded more mechanical and artificial. It left a bit of a gap in the middle of the stage and was less at ease with good live recordings. The Octave was slightly dryer, but more refined and convincing in its presentation. With more processed recordings the Rega seems to do a bit better, but with more listening the inner qualities of the Octave will shine through, and the Rega can even become a little bit tiring.

Both of these comparisons have been made on digital transports of perhaps less than optimal quality: a Squeezebox and a PC. It was fair in the sense that the other DACs used the same source, but unfair in the sense that the Octave definitely deserves a top quality transport. I couldn't do the direct comparison, but I'm absolutely convinced that it sounded much better at the end of my Astin Trew than being fed by either the Squeezebox or the PC. It was fine with the lesser sources, but only when it was being fed the digital signal by the Astin Trew did it sound really exceptional. Make sure you audition it with a good digital source!

What is very clear is that this is a DAC that is more focussed on preventing any nasty digital additions to the sound than to make sure every last bit of information is reproduced. Not that it leaves out much, but its main mission is clearly not to irritate or distract and to communicate the music in the most natural way. It succeeds brilliantly at this.

[Octave DAC]


I suspect the Octave will appeal very much to people with preferences that go in the direction of vinyl rather than digital, as this is one of the most 'analogue' sounding DACs I know. Not that it sounds like vinyl, of course, but it certainly lacks everything that vinyl lovers dislike in digital, while still possessing virtually everything that digital has to offer.
Virtually? Does that suggest that it doesn't offer everything that digital is capable of? If that is supposed to mean that there's no better digital source available, then no, because I know there are CD players and DACs that are even better. But for the asking price, the Octave is quite amazing and if you like its personality then I don't think you will be able to better it at double or perhaps even triple the money. Very highly recommended.

Copyright 2012 Maarten van Casteren - maarten@tnt-audio.com - www.tnt-audio.com

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