By Peter Qvortrup
Ever since Digital Audio was introduced in 1983, I have seriously questioned the validity of the claims that the technology would deliver the "Perfect Sound Forever" that launched the technology. I, and many others with me, found analog reproduction far more "real", satisfying and authentic, not to mention less fatiguing.
The main criteria I have always used when evaluating any hifi system or component is that when playing different pieces of software (whether LP or CD) the better system or component is the one that individualizes the sound from each record the most, or in other words, makes you sense each recording as a different and individual musical "event".
The evaluation system is based on a fundamental analysis of recording in all its forms that concludes that we really know only one thing about recordings, and that is that they must sound different from each other, the conclusion is based on the indisputable fact that all we really know about each piece of software is that it was done at a different time in a different location, with different microphones, cables, mixers, tape recorders and they were recorded by different people to any other recording, furthermore the software was manufactured by different cutting and pressing machinery at different plants. We really do not know what the microphones picked up or what went on the tape, only that what was recorded must by definition have a character of its own.
I call this method "comparison by contrast" and with tool in hand (or should I say ear??), I have spent many years searching out the "best", more accurate audio components and technologies to improve the reproduction of my record collection. Please notice that the term used is more accurate, not accurate in its absolute sense, because total accuracy does not exist in recording or music reproduction- it is an unachievable goal- that will never be a reality, no matter how must the marketing men of the hifi industry would like you to believe.
I made this pursuit my livelihood in 1977 when I left my career as a broker with a large, multinational shipping company.
By the criteria outlined above, CD fails miserably compared against even quite cheap analog component hifi, and I have always thought that this failing was inherent in the medium itself, i.e. the fact that the musical signal is broken down into little "bits", with poor resolution at low levels. (It is often forgotten that music starts from silence, not from somewhere up the amplitude scale, the assumption is often made that what we hear at the beginning of a note is what was recorded and the words "I hear more detail" assumes that we somehow know what is supposed to be there, which we certainly do not, what the reviewer should perhaps say is I hear more contrast!)
The quiet background of the digital medium should therefore have the best possible low level detail, but it does not. Acoustic information like hall ambiance is almost completely lost on most digital recordings (it is a little better on good analog recordings transferred to CD, indicating that the digital recording process is to blame, at least to an extent), modern recording techniques do not help, as multi miking, digital mixing, and other technical gadgets used in the studio, "help" the recording engineers do their job speedily and within budget- a far cry from the simplicity, dedication and time that went into the earliest LP's. This real acoustic information is replaced by a varying degree of hard and bright electronic echo, which makes most CD listening fatiguing, unless of course the system used tailors the high frequencies to suit, at the price of severe information loss at high frequencies (which may be preferable to the alternative!) but does nothing for the idea a truthful system or signal.
I spent years in denial and despite commercial considerations of what my company required, I heard nothing from CD that encouraged much enthusiasm. As long as my favorite music was available on LP either new or second hand, I had no need for CD- at least until the late 1980s when a lot of interesting material suddenly appeared on CD-only releases.
My engineers and I had already spent a lot of time looking at the subject of digital to analog conversion, without achieving any real sonic improvements against the better converters already available. As it turned out, our initial approach was too conformist, as it too closely followed an already beaten track, which did not conform to our strong belief in a strict minimalist design approach.
In 1990 I put forward the idea that perhaps we should use an interface transformer between the converter ship and the analog filter, to try to match the output impedance of the chip better and, at the same time, to separate the digital and analog ground planes. The first experiments showed promise, but the matching impedance appeared to more critical than first assumed. Two years later we finally got it right and Audio Note launched its first digital product, the DAC3 D-to-A converter with patents awarded in the UK, the USA, Germany, Australia and elsewhere.
Since then we have progressed with greatly refined component quality (DAC3 Signature), power supply with a valve rectifier (the DAC4), and finally the output stage and ultimate component quality (the DAC4 Signature), and achieved even better sound quality than the original DAC3 offered, and considering that it celebrated it 6th birthday in March 1998, the improved versions did nothing to dent the original products price/ quality relationship to competing converters- no mean achievement for a digital product to stay at the top of its price range for that long in a market where model life generally is measured in months rather than years.
When we did the first experiments with the transformer coupled DAC-chip, I also wanted to remove the digital filtering. However, this proved beyond the capability of my engineers at the time, and would involve drastic changes in the interface transformer/filter configuration, which was considered too difficult.
The basis for my idea is that there has to be a price to pay in all attempts to "correct" or manipulate the signal, regardless of whether it is done in the digital or in the analog domain. I have always thought that the digital filters with their oversampling, reclocking, noise shaping, jitter reduction or whatever, are not different in their fundamental properties to the corrective feedback systems employed in the analog domain, in that they also try to "stop" or reverse time, so their effect on the sound must be similar.
In 1995 I proposed the no digital filter (1x oversampling) to my new engineer Andy Grove (fresh from Hifi World fame). Despite the fact that he had limited experience with digital designs, he did his homework, read books, did the math, and presto, a D-to-A converter with 1x oversampling and only analog filtering was born.
The first version had a fair bit of the sampling frequency breaking through, but even with this interference, the sound was freer, had more presence, immediacy, delicacy and contrast than any digital product I had ever heard. There is obviously more good information in the digital stream than previously though. In other words, it was clear to me and everyone else who heard this converter that its reproduction had moved us much closer tot he best analog and therefore had very serious potential, so we persevered getting the interface transformer and filtering right, and here we are, nearly three years later introducing the finished product, the DAC5 Direct Line D/A Processor with 1 x oversampling with not digital filtering, reclocking, noise shaping, jitter reduction or other such signal interference.
Despite its great and almost analog quality, I still find my AN-TT Three Reference with my IoGold excels with the best recording, but it is now a contest between the two rather than a race between a sports car and a bicycle!
The DAC5 uses the Analog Devices AD1862NJ chip with as little in the signal path between it and the input chip as possible, the analog filtering has been done in such a way that the carrier frequency is inaudible, although it will show up on the oscilloscope in abundance (another example of the hard to grasp reality of measuring and its correlation to sonic reality)!
The DAC5 has facility for 96KHz DVD technology, as well as the conventional 44.1 and 48KHz. It has high B C-core output transformers, with a 600Ohm balanced output using a professional Lemo connector (we can provide the silver cables with the Lemo plug for this) as well as a standard unbalanced RCA output.
There will be no patent applications or copy rights filed on this revolutionary idea, because that would limit its wider use by other manufacturers, to the detriment of the reproduction of music. Instead we are offering a small technical paper on the technology to anyone who wants to test the idea, and this included any of our competitors. All we ask is that you remember who though of it first.
Pricing and product availability information coming soon!
This page was updated on: 06 Aug 1998
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