Review: Audio Note DAC 3.1 Balanced - Modified DA converter

Category: Digital


A Review of Audio Note's Official Factory/Dealer Modification to a 3.1 Balanced DAC

One of the painful realities eventually faced by anyone with an interest in so-called high-end audio is The Law of Diminishing Returns. Defined crudely, The Law says that beyond a certain point, sonic performance will no longer rise at the same rate as ticket price.

They dabble around for a few years upgrading first one component and then another, get hit once or twice by The Law, and most people begin to have lower expectations; taking comfort and joy from incremental changes in musicality and while at the same time perhaps expending considerable energy convincing themselves that although comparatively subtle, the benefits are worth the money.

And then, wouldn’t you know it? Along comes Audio Note (UK) and turns The Law on its head with its latest thinking on digital to analogue conversion (more on that shortly).

To many people, Audio Note’s founder Peter Qvortrup is already the bad boy of the audio industry with his purist valve-based approach to audio reproduction. Of course, there are a number of companies that would have us believe that valve is better than solid state, but Qvortrup’s doctrine goes much further, as anyone who has taken an interest in his Brighton-based company or explored its Website (www.audionote.co.uk) will already know.

Most audio sector vendors specialise in single types of component — speakers or turntables, for example. But Qvortrup reviles this componentisation of audio, claiming that it inevitably leads to much dissatisfaction because consumers are presented with an almost infinite number of mix-and-match permutations, many of which will be sonically incompatible.

Audio Note’s business model — which must be an utter nightmare to manage — contrasts starkly. Audio Note likes to sell complete audio systems. And complete means complete; turntable or CD front end, pre and power amplification, speakers, interconnects and cables. Most of it is hand-built in-house at the company’s UK or North American production sites; everything is an Audio Note design and some of it, according to audio industry convention, is quite idiosyncratic.

Audio Note offers systems in several price bands; each uses Audio Note components that are designed from the ground up to work together; each is meticulously voiced by Qvortrup and his team with the result that they share family sonic characteristics but become progressively more refined as one climbs the price ranges.

And so, people like me are potentially a bit of a problem: either through sheer cussedness, or lack of cash, we cherry-pick from the Audio Note product line. We don’t spend enough to seriously help the Audio Note business model work and, probably worse still in Qvortrup’s eyes, we also gratuitously unstitch all the care and effort that went into system matching and voicing. What’s more, there’s the possibility — albeit remote — that an Audio Note component introduced into a mix-and-match system might not simply unhappily co-habit, but actually trigger sonic Hell.

Of course, Qvortrup is a realist as well as an iconoclast, and one reason that he tolerates us cherry-pickers is that, ever the optimist, he hopes we will one day see the light (or a bigger bank balance) and buy an entire Audio Note system.

On amplification, Audio Note says it should be single-ended, directly heated triode, zero-feedback. This flies in the face of much mainstream thinking, even among the valve cognoscenti, but it is in reality little more than a return to an architecture that lost favour, so I am told, in the 30s.

It is on the matter of digital front-ends that Audio Note is really left-of-field. Audio Note (UK) was first to market with a D to A converter that applied no oversampling, upsampling or digital filtering to the native 16-bit CD data stream; passing it instead through patented I/V transformers and analogue filters to a single-ended valve-based output stage. The theory behind the development programme was that the digital processing and filters used by conventional DAC technology to achieve a ‘clean’ analogue output, as measured by spectrum analyser, essentially robbed the recorded data of its life force. They were the reason CD sounded so poor compared to (good) vinyl reproduction.

The Audio Note concept, first realised in the DAC 5, proved the point to the satisfaction of many purchasers, and to the small number of audio reviewers able to get their hands on a DAC5. Audio Note subsequently applied the technology to a family of progressively less expensive DACs, including the DAC 3.1 Balanced that I own and have reviewed previously here on this site.

The prime reason Audio Note’s approach to digital front ends raises hackles in the industry is because, as Audio Note itself cheerfully admits, all manner of distortion and ‘unwanted’ rubbish comes out of its DACs along with the audio signal. Plug a spectrum analyser onto the output and the hash is there, writ large. But put the same DAC into an audio system and all that’s there is music; or more correctly, all you can hear is music.

Convention says the measurements matter. But Audio Note says, ‘What’s the point of using trickery to remove distortion that you can’t hear if, in doing so, you suck the joy and life from recordings?’

This, then, is the point of collision. Audio Note is effectively suggesting that a measurement technique used as a benchmark of performance and quality by virtually the whole audio industry is, in the context of DAC output, leading us all up the garden path and away from musical Nirvana. The sniping and studied indifference this uncompromising view has triggered within the audio community has made one thing certain: Audio Note DACs are not bought by the Audio-Insecure.

And now things are about to get even more interesting. Audio Note has refined its thinking on D to A conversion still further and, starting with the latest versions of the DAC4, is shipping product with a redesigned analogue stage that omits the previously included filters (cue much slapping of thighs and tears of laughter from the audio establishment).

What’s more, for a fixed price of the local currency equivalent of just £300, including return shipping, the tweak is available retrospectively to owners of other balanced DACs in the Audio Note range (cue violent slapping of forehead and tears of grief from Audio Note’s bankers). Audio Note will be shipping part kits to selected local distributors authorised to carry out the modification. DAC owners should deal direct with them.

But why would anyone bother?

Simply, because the modification makes a stunning DAC sound…utterly stunning. It also turns on its head The Law of Diminishing Returns, delivering for £300 an improvement in musicality that has to be worth, oh, what? Let’s say at least three times that much.

It’s probable that most purchasers of Audio Note DACs came to that point having auditioned a range of products from different vendors. They’ll have found no audio magazine reviews to validate their decision. It will have been made simply on the back of how the Audio Note product sounds.

This was certainly the case on my part. I found that ‘conventional’ DAC technology, including that employed in the much reviewed and much-lauded Musical Fidelity 3D CD, sounded comparatively mechanical, whereas even a mid-range Audio Note DAC rendered music with a palpable sense of organism that made it more enjoyable and more believable. I bought a 3.1 Signature and later up-graded to a 3.1 Balanced.

The DAC did sterling service in my system, almost invariably triggering appreciative noises from visitors to our household, particularly those musicians among them. They were hearing what I also heard: a defining naturalness in the timing and pitch of the music that is normally absent from CD playback. Anyway, you get the picture: I was very happy with my purchase.

And then, a few months ago, I detected a level of hum on the right channel that had not been apparent before. When swapping the output tubes around failed to move the hum, I returned the DAC to Audio Note for attention. Shortly after, I phoned Peter Qvortrup to enquire when I might have the box returned. I also, just idly, asked whether there had been any further developments on Audio Note’s DAC thinking. “Funny you should ask that,” was Qvortrup’s response. He then went on to reveal the work on filters and ended by asking with an audibly wolfish grin, “How do you fancy being a guinea pig?”

I should explain. Qvortrup knows the only Audio Note components in my system are the CD transport and DAC. All cables and interconnects are Kimber; amplifiers, pre and power, are 25 BP and 7B ST Bryston; speakers are Vandersteen 3A Signatures. The ensemble is therefore far from Audio Note’s ideal. “We’re not in production with it yet, but I’d be very interested to hear from you how the modification works with all that stuff you’ve got,” said Qvortrup. Did I detect a polite sneer in his voice?

I must hold my hand up and confess to having felt feeling a degree of uneasiness at his suggestion. Damn it, I’d paid good money for those analogue filters and the idea of them being removed, and other surgery taking place, made me hesitant. Qvortrup read me correctly: “Try it. If you don’t like it, we’ll reverse it.”

Within two days the DAC was back in my system and switched on. Frankly, I was not expecting £300 value to sound like very much. I set a CD spinning and left the living room to make a pot of tea. The first bars of Improvisations Part 1 from David Kikoski’s Combinations (Criss 1226) percolated through our house to the kitchen. I left the tea unmade and hurtled back. The sound I heard was definitely not my DAC. It could not be. Surely there’d been a mistake? Someone in Audio Note must have re-built my DAC using boards from the much more expensive DAC4.

Those readers familiar with Combinations will know that Improvisations Part 1 is simply solo piano played by Kikoski in a particularly reflective and lyrical mood. I can’t guess at the number of times I’ve played this disc and yet I am still moved greatly every time by Kikoski’s meditation. Through the modified DAC, Improvisations Part 1 took on new and more profound meaning for me. The piano, closely miked, stretched between the Vandersteens, seemingly life-size. So faithfully was the recording transcribed that the sound of the damper pedal mechanism, never obvious before, was clearly heard. But what really amazed was the way the DAC revealed the exquisite timing in Kikoski’s playing.

I swapped the Kikoski for something musically more complex; Haydn’s piano concerto No. 3 played by Norwegian pianist Leif Ove Andsnes and the Norwegian Chamber Orchestra (EMI 5 56960 2 ). I sat spellbound, hearing, as I had with the Kikoski, musical information and spatial cues in the recording that I had never heard before.

This was not a step-change. It was a night and day transformation. The DAC as originally conceived by Audio Note had won me over for its remarkable ability to retrieve low-level information and for its astonishing fluidity. Now, though, it was as if not one but several veils had been lifted on the Haydn. A hugely extended top-end had appeared, effectively removing the walls and ceiling of my listening room and replacing them with the much larger recorded space of Lommendalen Church, Oslo.

No longer were performers simply sharply-drawn in space and relationship to one-another, but the air between the individual point sources of sound seemed to vibrating too. I struggled for several days to rationalise what I was hearing there — and it took that long because I was enjoying CD so much. Realisation only dawned when after oh, I don’t know, 50 or so CDs, I stuck on some vinyl. On good recordings, the same effect — point source plus ‘aura’ of sound — was there too. What I was hearing from the modified Audio Note DAC — and for the first time from any CD front-end — was this crucial element of the full-on vinyl experience.

What was more, everything I played through the modified DAC; everything; had much more drive, energy and life to it than before. It has an ability to make a lot of material sound faster and more intensely rhythmical while at the same time resolving more completely the complexity of the music. I am struggling here, but I guess some sort of visual analogy might be the feeling one gets upon wearing prescription spectacles for the very first time: suddenly, one regains a sharpness of vision that had been lost. So was with the modified Audio Note DAC. My reaction was to shout to no-one in particular, “Yeah! THAT’S what music sounds like!”

I felt I owed Qvortrup some feedback, and especially felt I need to tell him that he wouldn’t be getting my DAC back to un-modify. “Peter,” I said. “Here’s what I heard.”

“Mmmm. That’s what we hear too.”

Apparently, on the test bench, when the first DAC4 with the modified circuit was run up, it sounded better in many respects than the flagship DAC5, at £19,500.00 more than two and a half times more expensive. That would be a heart-stopping moment for any company with a complex and wide-ranging price-book to justify and it certainly caused Audio Note some serious head-scratching. Much engineering work later, the changed DAC 5 is ‘nearly there’, but it’s clearly been a hard furrow to plough. It seems that trickle-down of the filter-less technology proved easier to achieve than trickle-up, thanks to the (relative) complexity of the DAC 5 and its money-no-object build.

So what is the circuit change now in production on the DAC4, soon to be available on other balanced DACs in the Audio Note range and also as an after-market modification?

All D to A conversion chipsets (and few, if any, DAC vendors use their own silicon) output the original full-bandwidth recording, plus multiple images at progressively higher frequencies. Mainstream DAC vendors typically employ digital brick-wall filters to remove these images. Audio Note’s original patented filter uses a resistor-capacitor network to attenuate much more gently in the analogue, not digital, domain. The analogue filter is a major contributor to Audio Note DACs sounding, in the view of this reviewer, head and shoulders above anything so far heard that uses ‘conventional’ technology.

However, that was then, this is now. Last year, as part of a personal pet project, Qvortrup and Audio Note designer Andy Grove began experimenting with transferring 78s to CD. They were deeply disappointed with the initial results. Something was obviously sapping the energy of the performances and eventually it was found that filters — the Audio Note Analogue filters — were the culprit.

Audio Note’s work in the field of 78 transfers will shortly see the light of day as a series of commercially available CD releases, but the experience also had the side-effect of making Grove and Qvortrup re-think the whole process of D to A conversion; eventually asking themselves the hitherto unthinkable. ‘We know analogue filtering is better than digital filtering. But what if we did away with filters altogether?’

Qvortrup: “They do something to the music that we can’t measure in the traditional frequency domain. The problem is that when you are dealing with something that you can’t measure and don’t really understand, the only thing you can do is play around, try with and without, and then make a judgement based upon how it sounds.”

Heh, heh! Audio Note’s industry peers will love that. Can’t you just hear the sound of knives being sharpened and lips being drawn back in anticipation of the bloody kill?

Qvortrup is not saying how much time was spent ‘playing around’, but the resulting circuit changes are essentially thus. The analogue filters are taken out of circuit (on new-build DACs, they’re simply omitted) and resistors are used to place an active dynamic load on the output of the DAC chip. The patented iron-core Audio Note I/V transformers then carry out wideband impedance conversion on each channel as before. The only restraint on the multiple musical images is supplied by the natural filtering properties of these patented iron-core windings, and it is even less aggressive than that previously delivered by the now absent analogue resistor-capacitor network.

As of now, the process is proving resistant to tidy mass production ideals because appropriate resistor values within a known range have to be selected by informed trial and error while the engineer watches the display of an oscilloscope. However, Audio Note’s bankers will be pleased to know Grove and Qvortrup are confident that a solution is on the horizon.

So what’s going on? Why does the changed DAC sound so very, very good? “There’s obviously a difference between the way transformers and resistor-capacitor networks filter. We’ve looked at this and even we don’t understand it,” confesses Qvortrup.

Of course Qvortrup and Grove would very much like to know why the DAC modification generates the sonic benefits that it does, but isn’t it refreshing that they’re quite prepared to admit being baffled by the disconnect between objectivity and subjectivity?

Associated gear
Audio Note CDII transport, Bryston BP25 pre-amp, 7B ST powers amps, Vandersteen 3A Signature speakers. All interconnects and power cables Kimber.

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