June 2013

World Premiere!
Metrum Octave mkii
Updated Octave NOS DAC Including USB Input Option
Will this DAC be as highly acclaimed as its predecessor?
Review By Clive Meakins

  Anyone interested in DACs will surely know of the original Metrum Octave DAC released in 2011. This was a non-oversampling (NOS) two-box DAC which made a big impact on the market. Metrum have now released the Octave mkII; the core of the DAC is much the same as the original. There are still four industrial DAC chips per channel, whose identity is a fiercely guarded secret. There is still a direct connection to the output RCAs, there being no OpAmps to cloud or tailor the sound. The inputs include S/PDIF coax and optical and crucially there is now the option to specify a USB input based on the M2Tech USB-to-I2S module. As I'm wedded to computer-based digital music nowadays the addition of the USB option is an important addition which obviates the need for an external USB-to-S/PDIF converter. The Octave mkII with USB is priced at $1395 in the US and in Europe it is €1075 inclusive of a painful but unavoidable 21% VAT. Without USB the DAC costs $1230 or €950. The Octave mkII is available with front plate in either silver or black.

Metrum also make the lower cost Quad and the HEX which is 2.5 times the price of the Octave; the number of DAC chips in each is denoted by the product naming. The Octave mkII uses some of the upgrades developed for the HEX. The USB input was one of these developments though whereas the HEX powers the USB board internally, the Octave powers this board from your computer's USB port. Cees Ruijtenberg is the designer and here's what he told me about the power supply for the USB board; "Here we have used the raw power coming from the USB socket to create a new and very clean voltage. At the right side of the USB board you will see 4 capacitors which are a part of a huge filter. This filter is working as a low pass filter having a -3dB point at 15 Hz and -80dB at 10 kHz. From there a new voltage is generated by a regulator circuit below the USB board which is giving a clean voltage to the USB board. When looking at the noise the result is quite the same as in the case of the Hex approach. This part of the electronics is still separated from the DAC so there is no electric connection. To get the data from the USB part the data is sent to very fast (50 MHz) opto couplers as used in data transmission systems. This approach gives us full galvanic isolation and clean digital data."

Aside from the above changes the Octave now houses the DAC power supply in the main chassis so the DAC is now a single chassis unit. The mkII also now provides for 192kHz playback on S/PDIF and USB inputs, the final change is an increase in the depth of the input buffer which should result in reduced differences being heard between digital transports.

NOS is all very interesting but what about the sound?

Due to my computer setup needing a USB DAC I never got to hear the original Octave so when the offer to review the mkII arrived I leapt at the opportunity. The editor will tell you that he'd barely pressed "send" to email the offer to me when my affirmative reply hit his screen. The DAC actually came from the US to my home in the UK, it was a rather roundabout route as Metrums are built in the Netherlands. The reason for United States sourcing of the DAC is that it came from Fred Crane of StereoDesk who handles North America Metrum sales; the speed of shipping was impressive as the DAC arrived in only two days.

DAC reviews can be hard to write at times as many DACs are more similar sounding than they are different so getting at their unique characteristics can be challenging and time consuming. Refreshingly with the Metrum Octave mkII we have a DAC endowed with characteristics which stand out from most DACs. My initial reaction to the DAC was is one of very clear vocals, great space around instruments and sounds standing out extremely well within the soundstage. The DAC I'm told had only been run for a few hours before I received it and as the Metrum NOS DACs have a reputation for needing considerable burn-in I then fed it a diet of music all day for several days. As burn-in progressed I noticed the sound smoothed out though it was never remotely harsh, mid-burn-in I noted some mid-range leanness which was later eradicated.

Before going into details about the sound of the Octave mkII there are some aspects I found useful to extract the best from this DAC. These are a couple of tweaks which worked for me in my system. Feel free to try them or ignore them.

USB Driver (Windows)
The USB input being M2Tech based uses the HiFace driver as standard; this is supplied on a CD with the DAC. This driver is perfectly fine and it's simple to install. I know from previous M2Tech experience that the M2Tech driver for their Young DAC stood a chance of sounding just a touch better. I also know that installing this driver can be a pain as it's expecting to mate with the Young DAC. If you want to try this driver I have created some instructions. If you have problems please do not trouble Metrum or StereoDesk as they are not there to provide software support for a driver they do not support.

With other DACs I've found the Young driver gave a richer sound, with the Octave mkII this wasn't the case, possibly due to its deeper input buffer. What did improve was the sound stage which became a little more spacious.

Firmly PlantedI
It took me a while to spot this and I'm so glad I did. As my computer running Jplay resides on a wooden shelf and I find that short USB cables sound best, I just placed the Octave down on the shelf next to the computer. When I compared the Octave to another DAC I found the bass a little bloated. Hmm…shame I thought. I then wanted to try some other interconnects which are very inflexible so I had to move the computer and DAC. The DAC at this point ended up sitting on my solid floor. The bass immediately tightened up and became highly textured. You don't have to place the DAC on a solid floor but please to use it on a decent hi-fi rack.

Time For Serious Listening
With the Octave mkII well burnt-in I played a lot of music and made notes for this review so here are some thoughts as they developed as immediate reactions to what I heard. My system comprises Computer Audio using Jplay, 2 record decks (Garrard 301 and Trans-Fi Salvation), preamp was the AVC-1 by John Chapman, a selection of power amplifiers; 300B SE, T-amps / chip-amps and Valvet Er1 SE solidstate power amps feeding Open Baffle speakers (hybrid Bastanis / Trans-Fi), there's DSP correction on the bass with 2 x 15 inch bass drivers per channel being actively driven courtesy of XTZ amplification. Using a two computer (streamer/audio) setup with Jplay here are some examples of what I heard with a few tracks:

Jennifer Warnes Famous Blue Raincoat "Bird on A Wire" – some NOS DACs suffer at frequency extremes; any deficiencies should be obvious with this track. What I heard is that Octave mkII has better vocal focus & more bass impact than I was used to. Treble is well balanced, it's not over-sparkly and is sweet. Instruments and vocals have greater presence than is typical, there being more space around them and they have excellent depth.

Mary Chapin Carpenter Hometown Girl "Hometown Girl" – I noticed that the DAC doesn't over-emphasize leading edges and decays are well reproduced. There's great musical flow & expression without forced aggression. Bass guitar notes somehow sound "deliberate" or purposeful. When the there is a pumping rhythm it pumps for sure but only when the music intends this.

George Martin In my Life "Golden Slumbers" Phil Collins – this track has tremendous drums in the middle which are totally thunderous with the Octave.

Genesis Live "Watcher of the Skies" - Power and space, this sounds track better than it has any right to.

The Who Who's Next "Behind Blue Eyes" – Vocal focus was excellent and frankly hard to improve on. With Octave the steel guitar strings sound like steel and the instruments have lots of space around them. Certainly the depth with the Octave is greater than most DACs I've used; it's more of a vinyl-like front-to-back depth.

The Rolling Stones Forty Licks "Brown Sugar" – This is not the greatest recording but the Octave allows it to breath, it almost feels like a live performance.

The Rolling Stones Forty Licks "She's Like a Rainbow", "Paint it Black", and "Satisfaction" – These are all vintage sounds but all the better for it; they sounded really great, plenty of energy and atmosphere. Hardly precise sounding in the way many modern recordings are but these vintage sounds came across wonderfully. Vibrant.

Ben Harper Welcome to the Cruel World "Whipping Boy" – This is really well recorded but with bass that can be hard to resolve with detail texture. No such problems here. It's easy to hear both drums and bass guitar and importantly the interplay between them. A fabulous demo track.

Sonny Rollins Saxophone Colossus "Moritat" – Sonny's sax comes over with a wonderful tone and realism, add to this the quality of the double bass… I love it! I want to mention here that I've had great jazz discussions with the supplier of the Octave, Fred Crane of StereoDesk; he has a tremendous heritage with jazz that clearly helps him select great products to offer his customers. He really knows about musical reproduction and what makes it emotional.

Diana Krall Girl in The Other Room "Love me like a Man" – Wow…Diana's vocals, the double bass, piano and drums; sublime. I play this a lot on vinyl, I've not heard it anywhere near this good previously and this is in comparison with a Garrard 301 deck and London Reference cartridge. Note to self – buy Keith Jarrett's Koln Concert on CD, given the piano performance I hear on this Krall track the Koln Concert will be totally stunning.

To try out the S/PDIF coax input I used OPPO BDP-103 and BDP-105 for playing my ripped CDs. The sound of the OPPOs with their internal DACs was more forward in presentation than the Octave and aggressive too. Some of this character remained with the Octave acting as the DAC so the OPPO transport was adding its own character to the sound I was hearing. Clearly the S/PDIF input on the Octave works as you'd expect, the more pushy sound due to using the OPPO isn't for me. With coax, optical and USB inputs on the Octave you have plenty of options to find your preferred transport.

USB Power
Cees has done a tremendous job refining the computer USB power line to run the USB converter board, these boards are very sensitive to power quality; this becomes especially apparent when feeding a very high quality DAC such as the Octave mkII. My inquisitive nature demanded I try something here; as I had a suitable power supply on hand which could supply a less polluted 5V than my computer USB, I had to try it. This is the $199 iFi iUSBPower; reviewed last month. What happens here is that the USB data feed from the computer is used as normal but the 5V power now comes from the iUSBPower. The in-built power supply filtering Cees provides then gets an even better start taking a more pure 5V feed.

Powering the USB board from a separate supply opens up a second option which I find brings benefits. I'm not a fan of hyper-expensive USB cables; what I find works well are short USB cables and where possible splitting the power wires from the data cables. You still need the ground wire to accompany the data cables but removing the +5V wire from the USB cable I find provides a performance lift. Initially I used an ISOLATE cable from Australia based Elijah Audio feeding into the iUSBPower, data and power are then fed from the iUSBPower via a standard USB cable. Elijah Audio cables include Peter Belt treatments in their manufacture.

The effect of the power tweak was certainly audible in my system, there wasn't a night and day improvement due to the well-designed power supply treatment Cees implemented but bass was deeper and tighter, the space around instruments became a little larger and even better defined.  I would also describe the sound as being more composed too. When I've heard the difference iUSBPower makes powering an entire USB DAC the improvement has been more significant. Of course your computer is bound to have a different USB noise signature compared to mine so I can't begin to know what benefit or otherwise you may find.

The ISOLATE cable worked well enough for me to ask Michael at the Elijah Audio to make me the next cable I wanted to try based on his ISOLAATE BL cable but with a longer power cable (50cm); these cables cost $155 to $200 depending on the length you select. This is a twin-headed USB cable; one head comprises a USB Type A plug with data and ground wires, this plugs in to the computer; the other head is a USB Type A plug with ground and +5V wires, this plugs into the iUSBPower. Both sets of wires then meet at the USB Type B plug which connects to the DAC. We now have the +5V separate from USB data wires until they meet momentarily in the USB plug and socket. The big question is would this segregation of data and power bring additional benefits. If it did this might due to the power wires not now being able to mess with the impedance of the cable, which should be 90 ohms; this is one explanation I've seen for such effects.

The ISOLAATE BL cable configuration built on the ISOLATE + standard USB cable benefits. The first improvement I noticed with that the sound was yet more "composed", the music was even more at ease and more natural. How can I better explain this? I'll have to use an automotive parallel; the more composed sound I'm talking about is as if I'd swapped from a car with a highly tuned but smallish capacity engine to a car with a big torquey V8. I also found was even better stage depth and separation of instruments. Treble, as in hi-hats, was better defined and more real sounding. As you might imagine I was swapping between configurations listening to a piece of music for about 3 minutes at a time until I noticed with the ISOLAATE BL I'd reached the end of a 7 minute track. This says it all; it's a very worthwhile improvement.

If pushed I would say the ISOLATE + standard USB cable and iFi IUSBPower gives 60% of the improvement of the ISOLAATE BL twin-headed cable + iFiiUSBPower. The twin-headed solution is the one I'm now living with.

ISOLAATE BL is functionally close to the Gemini cable iFi have designed for the iUSBPower, whether these two cables have an identical effect on sound quality I cannot say as the Gemini wasn't available during my auditioning.

Conclusions
The Octave mkII has a mid-range which is very spacious and natural with realism being especially strong due to image depth and impressive tonality. Treatment of overly sibilant recordings is amongst the best I've heard. You must ensure the Octave mkII sits on a suitable rack if you are to hear the DAC close to its best. With this optimized there's a lot of bass drive, I find I'm drawn more strongly to the bass line and rhythm than is normally the case, pacing is dictated by the music; depending on the music it can be very infectious, it makes me move to the music. The bass does not dominate but the Octave does ever so slightly highlight the bass. Is this 100% neutral? Possibly not but I don't know many people who would complain about this, most will welcome it.

A tweak I recommend for USB users; get yourself an iFi iUSBPower with a twin-headed cable, you won't look back. Just do it. While you're at it give installing the Young driver a try, you may just like it and what's more it's free.

Even without the power tweaks I find the sound of the Octave is particularly natural; it gels with the sound of my record decks which from me is a huge compliment. It is not at all "in your face, aren't I impressive?" sounding. It is an affair of the heart, not the head. In some ways the Octave mkII mid-range reminds me of single-ended amplifiers, ones which are especially lucid with vocals and instruments such as saxophone.

Given that I run two record decks and the music that moves me the most I have on vinyl, how I can justify the purchase of the Octave mkII? Instead of buying so much vinyl in future I can buy lower cost CDs and there's a lot of very affordable second-hand CDs out there. With the Metrum Octave mkII I can achieve a sound equivalent to vinyl and I can throw fabulous hi-res digital into the mix too. The Octave mkII will be a great investment as it will save me money on my music purchases. Or will it? I've just worked out that I'm going to be buying a whole lot more music.

There can be no doubt that the Metrum Octave mkII is a superb DAC by almost any measure; it will suit those who prioritize natural and realistic presentation over a hyper-analytical sound.

Specifications
Type: Digital to analog converter
Power: 15 VA internal power supply 
Inputs: Optical, S/PDIF coaxial, USB (option)
Optical: 44 to 96 kHz
Coaxial: 44 to 192 kHz
USB (option) 44 to 192 kHz.
Outputs: Two gold RCA connectors 
Max Voltage Output: 2 Volt RMS max. : 
Slewing Rate: 35 Volt/uS
Dimensions: 190 x 60 x 245 (WxHxD in mm)
Weight: 4.2 lbs.
Price: No USB $1230, including USB $1395
         No USB €950, including USB €1230

Company Information
Metrum 
All Engineering
Ambachtsweg 4k
3953BZ Maarsbergen
The Netherlands

Voice: +31(0)343437331
E-mail: info@metrum-acoustics.nl
Website: www.nosminidac.nl

North America Sales
AudioPrana LLC
69 Boston Ave.
Medford, MA 02155

Voice: (617) 669-3275
E-mail: audioprana@gmail.com
Website: www.stereodesk.com