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No frills, no options, just great sound that defies the fact that it is non-oversampling.

A Review On: Metrum Acoustics Octave

Metrum Acoustics Octave

Rated # 22 in DACs
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Price paid: $1,023.00
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Pros: Great, non-fatiguing sound. Small footprint. Fantastic value for the sound quality.

Cons: NOS (Non-oversampling) so needs high-res files or high-quality up-sampling for best results. Coax input is only RCA. Only basic features.


This DAC came to my attention when I found a long thread about it on Stereo.net.au. While, in principle I wasn't interested in a NOS (Non-oversampling) DAC, due to their reputation for rolled-off and distorted (if pleasant) sound, some aspects of the design caught my attention. It doesn't use the old Phillips or BB chips that popular designs use, but industrial-grade high-frequency DACs. The designers also show graphs of it reproducing an impulse response perfectly, something that a regular DAC cannot do without pre- and post-ringing. These effects are, arguably, responsible for the "digital" sound that modern DACs have. Some modern designs, such as the AKM chips, claim to fix this by using a filter that removes the pre-ringing. Indeed, the DACs I've tried that use them sound very good, with critical instruments such as pianos and violins sounding more real and less like a digital imitation. 
According to the 6moons review, the designers specialise in industrial grade equipment and their DAC range is based on solid principles used in industrial equipment. The results in the design are apparent -- a no-frills case, only basic features, a high-quality separate power supply, heavily regulated and filtered (the numerous black capacitors in rows inside the DAC section), along with a complex 6-layer circuit board designed with a highly optimised layout.
I had expected the DAC to be somewhat larger when it arrived, so I was shocked to find out how small and light both it and its power supply are. Indeed, if I use it with my Triad Audio L3, I could sit the whole thing on my desk in quite a small space. Being used to having a large rack to hold everything, this was unexpected.
Initial disappointments in the design were that the coax digital input uses an RCA socket and not BNC and, via someone who is a hardcore DIY'er/modder, the isolation transformer on the digital input is not a quality part. Given that I dropped the coin for an Audiophilleo 1 to use with my DACs I'm sensitive to the quality of the digital input of DACs, so both these things are ones that I consider important and something I will consider rectifying in the future.
Despite those small issues, the Octave proved to be an interesting customer when it came to the sound. Initially it was similar to going from listening to Horowitz play Chopin to listening to Martha Argerich play it, or going from Miles Davis and Kind of Blue to Dave Brubeck and Take Five. Everything was so much more lively and intense. Even quiet notes stand out -- heck -- everything stands out. At first, it was all a bit much, but, similar to other gear I've owned that is a bit harsh at first, so was the Octave. After being left on a couple of days it began to settle down, though it hadn't lost all of the intensity with which it delivers music. Importantly to me, the digititis even the best DACs seem to have had wasn't there. I know what a piano sounds like and I feel I'm hearing what a piano sounds like despite listening through a non-analogue system.
With more expensive DACs, such as the Berkeley Alpha, part of what makes them special is the custom programmed over/up-sampling chips employed. What makes the Octave special is that one can use the software included in music playback programs to do up/over-sampling instead, using high quality algorithms such as iZotope.  The Octave only accepts a signal up to 176/24 (though some units apparently work up to 192). That allows one to effect the equivalent of 4x over-sampling, though makes straight playback of 192k files impossible. 
Running the DAC at 88.2 kHz, compared to just using regular CD-quality output at 44.1 kHz had both a measurable and audible effect. Measuring the output of sine waves of various frequencies through my Oscium iPad scope revealed the obvious distortion issues with non-oversampling DACs, which were rectified within the regular audible range by up-sampling or using high-res files. Audibly, this presented itself as an increase in clarity, though more of a subtle one than I had expected.
However, even without up-sampling, running from my MacBook using Amarra to an Audiphilleo 1 to the Octave makes for a very pleasant listening experience. There is an impression of clarity without harshness (except initially). It scares my Reference 7.1, by seeming, at least with headphones, to be almost equally as competent, without the huge footprint.
Going the full way to 176k with Pure Music, Audirvana Plus or Fidelia, the results were delightful.
Part of the reason for this likely has to do with the DA chips having no output stage, but sending the signal directly to the RCA outputs. The one downside to this is a slightly weaker bass when connected to some amps, at least in comparison to my Reference 7.1. However, mated to my hybrid Stacker II, which seems to give some headphones a bit of a bass boost, this is welcome as it balances things out nicely.
Now, after having listened with it in my system for some of weeks, the result, most often using 4x up-sampling, is that much like the long discontinued Parasound DAC1600HD, it manages to sound both detailed and smooth. The perceived soundstage is narrower but deeper than that of the Reference 7.1, even using high-res remasters. For example, in Muddy Waters album Folk Singer, an album recorded sounding like it was in a large space and containing considerable dynamic range, Muddy sounds further back with less intensity.  Briefly compared to the Benchmark DAC 1, the latter has that extreme sense of clarity while the Octave is more mellow and the Reference 7.1 somewhere in between. 
The Octave seems to be a little bass shy with my Stacker II compared to the Reference 7.1, though this is less noticeable with my Stax rig. I had felt for a while that the Stacker was overdoing the bass with the Sovtek re-issue tubes, but switching to using the Octave as a source solved this. Of course, breaking out the famous early Sylvania tubes that are more tonally neutral has the same effect.
Possibly one of the nicest things about the Octave is how fatigue-free listening with it in the chain is. It combines the best of being musical, detailed (especially if using high-res files or high-quality up-sampling) with natural-sounding reproduction. For £668 ($1023), if you only need one input and single-ended output and are happy with the no-fills design, for the sound quality you get this is one great bargain.


Very useful, detailed and informative review Currawong. This DAC just went back on my "maybe" list!
Did you mean to write "non-digital" in this clause: "I feel I'm hearing what a piano sounds like through a non-analogue system"
I've clarified that line, thanks. That review has been sitting around my computer for ages, so I wanted to get it finished off. I don't think my writing is as good as it could be.
Great review, thank you for sharing your impressions!
Thanks for the review. Fascinating that you just reviewed this, as I just came across a reference to it and am wondering about it. Couple of things:
I wonder if a better quality transformer on the SPDIF input would let the thing lock onto higher sampling rate signals.
With 4 DAC chips, it would seem that balanced outputs would be very easy to offer, wonder why they don't.
I think they are concentrating more on headphone users and balanced headphones are neither popular nor very much better than unbalanced. PLus, as Currawong titled his review, this is supposed to be a 'No frills, no options, just great sound' DAC.
milosz: The chips are stacked for NOS operation, not set up as dual differential. Even so, it probably helps that both amps I was using, the Phoenix and Stax amps don't lose anything when using their single-ended inputs.
Yes I understand they are watching costs. Balanced line users are a minority.
I don't know that they are concentrating on headphone users; none of the reviews listed on the manufacturer's site even mentioned headphones ( http://www.6moons.com/audioreviews/metrum/1.html , http://www.nosminidac.nl/downloads/octavehificritic.pdf and http://www.tnt-audio.com/sorgenti/metrum_octave_e.html )
Came to read about the Metrum left lusting for the 7.1. Again. Thanks.
The more I look at what's inside various $1,000 to $2,000 DACs, the more I appreciate Audi-Gd designs. I don't know if the engineering philosophy that is exemplified in Audi-Gd builds actually results in better sound- I'd have to do a listening comparison for that- but I sure do admire the attention to detail (and the parts and workmanship!) that results from Kingwa's approach.
well done currawong....am also considering a octave..but am also doubting about an eastern electric minimax plus..that one blows much more expensive dacs out of water acording to very renowned reviewers..they all three bought one after reviewing one..lolz...did u ever heard that dac?
Very useful review as I am shopping for a sub-$1,000 DAC.  Thanks.
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