Volume 7 No. 3

Audiolab M-DAC
Brilliant, but slightly flawed.
Review By Chris Bryant

 

  This is the first Audiolab DAC since the 8000DAC was launched way back in 1992. In the meantime the brand has undergone a change of ownership, has appointed a new designer, and changed the location of production from the UK to China. One consequence is that this £599 M-DAC looks a far more convincing commodity product than its predecessor. The aluminium case is well finished in either black or silver, and the clear and informative display is a nonstandard size that makes it look more mainstream commercial than boutique audio. Not only does the display provide information about the input selection and lock status, but it also translates the sub-code transmitted over S/PDIF to display CD track number and time, and if required a precise read out of input sampling frequency. A digital level meter with peak hold has an attractive decibel read-out.

The DAC is designed by John Westlake, who has gained a reputation for creating good sounding and desirable products for several manufacturers over a couple of decades. He has squeezed quite a lot of technology into this product, which makes an interesting comparison with the main competition around at the moment. The M-DAC has a variety of digital filter options, which is a quite fashionable feature among today's DACs.

I haven't got space here to go significantly into digital filter technology but you would think there would be one correct way to implement a digital filter. Alas when you get one aspect just right, something else goes slightly wrong, and designers just have to compromise, or leave it up to the user to choose from a number of available compromises. The hardware processing power that is used to implement the digital filter algorithms can also be used to generate a volume function, and this is done here, but it can be deactivated should the customer be using an integrated or pre-amplifier.

This product has two co-axial, two optical and one USB input – all that's required to provide preamplifier function for a multiple digital source system if no analogue source is used. Both TosLink and coaxial digital outputs are available, and analogue outputs are provided on both true balanced (XLR) and single ended (RCA phono) sockets.

Inside, fully discrete Class A analogue amplifiers using J-Fets provide a high current drive potential with good immunity from RF demodulation. A 32-bit ESS Sabre 9018 digital-to-analogue chip is mounted on a multi-layer board, using both throughhole and surface-mount technology. A separate board, mounted at right angles, contains a bank of power supply reservoir capacitors.

The USB input is asynchronous, supporting 24-bit/96kHz with remote control of PC or Mac media players. Selected parts are used throughout with 0.1% MELF surface-mount resistors and both polypropylene film/foil and organic ultra-low-ESR capacitors. An external power supply keeps all the noisy bits away from the sensitive circuitry and offers future upgrade possibilities.

 

Test Results
The M-DAC's frequency response (and also its output level on some settings) varies with the filter settings. All the 'optimal transient' settings produced an early treble fall, starting at 3kHz and -0.7dB at 20kHz. The 'minimum phase' filter shows a slight rise above 15kHz, while 'optimal spectrum' is almost flat but with a slight high frequency ripple. 'Sharp roll-off' is flat almost all the way to 10kHz and is only 0.15dB down at 20kHz, but at 1kHz has a 0.2dB lower output as does 'slow roll-off' which is an audible 1.6dB down at 20kHz ref. 1kHz.

The jitter spectrogram is very clean, indicating very low levels of jitter, but there is a hint of 100Hz hum breakthrough down at -120dB. Harmonic distortion is very low indeed and the low level linearity test shows virtually no deviation right down to -112dB with the error value below this due to hum. When set at 0dB the output level is an audible 1dB above the industry's standard 2V.

 

Sound Quality
Using the coaxial S/PDIF input from a Naim NDS network player, we were quite enthusiastic about the M-DAC on first listening. We were seduced by its fine focus and soundstage construction, good bass weight and overall definition. The treble was airy with fine detail and the mid was nicely articulate. It appeared quite subtle, clean and spacious.

Next I tried the USB input from my desktop computer, and found it lacking here in both dynamics and timing. It was still quite spacious but dynamics lacked freedom irrespective of the filter setting. It sounds a little restrained and just doesn't have the full measure of dynamic expression necessary for a top class digital replay system.

With the digital data provided from a CD drive, it images very well and supplies a vast amount of detail, but it still doesn't have sufficient verve to earn a place in my own system. I played around with the filter settings, and preferred the 'slow roll-off' setting, but was still aware of an aural energy imbalance manifest in a slightly unnerving hardness in the upper mid/lower treble region that becomes tiring after a while. It does deliver lots of detail – more indeed than the vast majority of its peers – and must judged very transparent, but I still felt slightly uncomfortable by the balance of compromises found here. While it teaches the Rega DAC how to resolve minutiae, for example, it doesn't manage to structure music quite as naturally. I also tried it playing some high resolution material when connected to the Astell and Kern AK100 portable player, and although it is able to cope well with more information, the innate character of the sound doesn't change, and the same was true of music replayed from a memory stick, which often provides an improvement.

Finally I went back to where I started, connecting the M-DAC to the reference level Naim NDS S/PDIF feed, where we found that the M-DAC continued to sound rather restrained over a protracted listening session. Its dynamics are just not as convincing as the best of the current crop of DACs, and a slight metallic sheen makes it sound larger than life, leading to the false impression of true high end sound. Furthermore, it lacks some expressiveness, softening and compressing both macro and micro dynamics – the 'optimal transient' filter setting had better tonality, but sounded even softer and had 'slowed' timing.

We tried all the digital filters, and they do all sound different. But in one way or another they all shift the sense of timing away from my references: the closest to what I consider a 'normal' sound is the 'slow rolloff' setting. It's also noticeable that some filter settings have more treble energy than others, and these can sometimes sound a bit hard and glaring. This can add apparent extra detail, or is that lessened less masking when sounds are thus falsely separated?

After several extended listening sessions, I couldn't escape the feeling that I was listening to a more 'processed' digital replay than I was used to. I'd freely admit that I've been listening to a lot of analogue recently, but going back to other CD and DAC implementations that I habitually use, and after comparison with the others under test, I have become convinced that the Audiolab presents music a little differently. At times the M-DAC could sound very entertaining, but I have to conclude that it never sounds quite natural or convincingly expressed sufficient musical realism.

 

Conclusions
Considerable technical expertise has been applied to make this product what it is, and from a user point of view it's easy to get carried away, playing with the options and enjoying the effects of the various facilities. Lots of options are available through the menu and that rather decent remote control, but it must be remembered that the object of any piece of hi-fi kit is to fool the listener into thinking that the reproduction is close enough to live music to trigger the brain into believing that what's happening in your room is truly enjoyable, not just a cerebral exercise in hearing some extra micro-detail.

I'm sure that all HIFICRITIC readers will know that this state of mind varies, depending on experience and how your brain decodes music. I rely on comparison to remembered live music experiences, and also direct comparison with those bits of kit that I have found tend to fulfill those musical requirements. Make no mistake, I admire the thinking and the science that has gone into designing the M-DAC.

I like its utility and technical perfection. I like the display and I like the facilities. I also like the fact that it's available at a reasonable price. However, it failed fully to excite me musically, and on certain material and settings it even goes so far as to irritate. On balance it therefore achieves a sound quality score of 70. It is brilliant but slightly flawed, and not to my taste, though at this price, considering the facilities, and providing the slightly different presentation offered is acceptable, it does offer very good value.

 

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