Interview with Pedja Rogic of Audial

Matej Isak talks with Audial Ltd. owner about digital audio. Pedja Rogic is well known in DIY circles an a man of deep understanding about contemporary audio technology and it's benefits and shortcomings.

Why and how did you start creating audio devices?

I’ve started tweaking the units I’ve had. And since undertakes got more and more serious, at one point I realized that it would be easier if I simply started from the scratch. And not only easier but also more honest, so I can face the truth about my basic postulates and actual abilities. Fortunately, results were good.

Did and do you have any influences of people in audio circles?

Purely technical approach, barely applying standard technical knowledge has never struck me at all. Yet, the other end, i.e. extreme subjectivism, and which often turns into some kind of religious bigotry, is too often only a scam, supported not by those who found technical knowledge insufficient, but by those simply lacking it.

In my view, a high quality music reproduction is quite demanding. It does requires technical knowledge, otherwise you don’t know what you are doing. Unfortunately, once you assume that the technical knowledge is everything, you are probably farthest away from this goal. Or, to paraphrase Nietzsche, supposing truth is a woman, how much does all the philosophy, especially dogmatic one, worth? The things in audio are just like that, and for the same reason that kind of technical dogmatism is worthless in itself. Technical research is highly needed and always welcome, but you need to look outside technical knowledge and to look elsewhere to know where you are at, and to know what you have to do. In other words, you need to listen to your work, seriously and carefully. Technical knowledge is always only a current state of technical knowledge. Hence, for technically oriented guys the only way to make something important is to move the boundaries of this knowledge.

It may look like the audio scene is full of smart people but it is not really like that. In fact, only a fraction of them fulfill criteria from above and makes the audio wheel spinning (or moves it forward, if you like). If I had to name some, people like Jean Hiraga would qualify like that (his work from 70s was generally way ahead of that time, even if you can spot there several flaws), as the Vacuum State guys do (Allen Wright and Joe Rasmussen). Regarding the digital audio, theoretical research done in 90s by Julian Dunn is simply the best one the digital audio world has seen so far. As for the practical engineering, many breakthroughs during the last 15 years or so are due to not that widely known guy called Patrick Digiacomo (Analog Research-Technology), though he is probably more known among DIYers as Jocko Homo. A DIY scene brought some very interesting audio designers recently. Actually, during last 10 years or so, and mostly due to internet, so called DIY community had, as never before, very important general influence onto the audio scene as a whole. Many designers (including myself) are in fact active in both DIY and commercial audio world.

You are quite known in DIY world. Where does the DIY ends and pro audio products starts?

I admit that I’ve had a vague idea that I can make some career in audio. And I knew that I can make good devices. Professional involvement started at the point where I realized that the fact I can make good or great unit is worthless unless I can produce it in series, and in a way that can make some profit.

That’s the main difference and that’s why Audial is actually still somewhere between the logic of DIY and logic of series production. I’m not fooling myself and I do understand that this approach can not last for too long. Audial DACs use the obsolete parts and some of them are not easily available anymore, and logic of efficient series production forces to give up of using such parts. If you however settle on them, you normally have either to make considerable own stock or to calculate this as a risk factor, which in turn increases the final price, and which again reduces your market. This also answers why, even if DIY TDA1541A DACs recently became popular more than ever, you won’t find many TDA1541A DACs in production around.

Would you explain what kind of philosophy stands behind Audial products?

As previously suggested, Audial units apply only solutions that sound natural and that make listening, and I mean here long term listening, enjoyable. They don’t and won’t apply solutions for their bare technical seductiveness and regardless of actual sonic consequences, since such an approach, more often than not, as a result, produces equipment that makes listening experience fatiguing and tiresome.

Why exactly DAC's?

That’s interesting. Some years ago I didn’t think that I could make better DACs than, say, amplifiers, or even loudspeakers. But it turned out that there was much more people who knew about amplifiers or loudspeakers than those who knew about DACs. During the time I actually discovered that there was practically only a handful of those who knew about issues we actually experience with digital audio.

People like to (over)simplify and to promote such simplified views. And this inhibits the actual research. The digital audio was “perfect” right from the start for its linear frequency response, low harmonic distortion and lack of wow & flutter. Some 15 years later people were shouting about jitter (which is actually a form of the flutter) and they became, as still they are, prone to claim “if jitter is low, then the digital device is good”. The jitter is indeed another part of the puzzle and it is its real part, but the claim like that is again only another oversimplification. Cheap Sony CD players are low on jitter but they still sound quite digitally and cheap. Some articles and projects, as those published by Mr. Kusunoki, were eye opening, since they, in many or in about every aspect, were counteracting conventional wisdom, yet bringing a lot of subjective sonic qualities. It doesn’t imply that one must do the things exclusively the way Kusunoki did, but his work turned the red light on, pointing out disturbing fact of huge lack of real understanding of digital audio performance.

Another reason was that, when I made the first DAC projects public I was a bit surprised by the interest the DACs can generate. I probably could estimate better, since this was the weak point of audio chain for decade or two.

What is your opinion about USB vs SPDIF?

It is normally the best if you avoid both, but external protocols are needed for practical reasons. S/PDIF is now, two decades after it’s been introduced, relatively mature, whereas USB audio is still relatively new. USB gets constantly better and at this point it is probably the simplest yet decent way to connect external DAC to PC. Its audio performance already has some advantages over that of S/PDIF, but it still has to improve, and I believe it will improve. But it is a bit huge topic so I’d rather direct to the article you may find on Audial site.

Please tell us more about USB to I2S conversion. What is the gain and difference?

USB is external, coded protocol, while I2S is internal 3-wire protocol. Today’s DACs normally require some 3-wire protocol to work. The first version of The Model, as well as the AYA II, convert USB directly to I2S, avoiding any intermediate conversion. Many devices on the market, prior to conversion to I2S, perform conversion to S/PDIF. The reason may be simply historical one, since USB to S/PDIF converters came first, and USB decoders with I2S output came later. Conversion to S/PDIF may have benefit of more convenient galvanic decoupling (you would need 3 transformers to galvanically decouple I2S), however it is not what most of manufacturers actually do. And you then anyhow must go to some 3-wire internal protocol, whether it is I2S or LSBJ/EIAJ. But, for the record, some tests we ran confirmed that a galvanic decoupling between PC and the DAC may be sonically more important than avoiding S/PDIF.

Recently I read that PSA audio is preparing new high end optical DAC. It's a common thinking that for optical digital transfers there is no place in high end. How do you see this?

I normally can not comment on this particular device (yet). Generally, one may want to use optical link for its non-compromise galvanic decoupling, however it regularly sounded inferior to the classic electrical connection. Optical transfer needs additional hardware which also brings own problems, and industry has never offered the parts one should be keen to use. And measurements confirmed relatively poor jitter performance of normally available parts.

What is importance of quality digital cable? There is a lot of overpriced cables on the market. What is good enough in you opinion?

Every digital cable has (at least) own tonal balance, soundstage, dynamics, resolution and definition. In some way, some conventional 75 Ohm antenna cables can work well. There are more expensive cables which will do better but it doesn’t mean that one has to go crazy spending the money. DH Labs Silver Sonic D-75 works well for me these days.

Still, a digital cable is the part of transmission line which includes the other parts as well, and these are the output stage of the source and the input stage of the receiving unit (usually DAC). Suitability of particular cable depends on how well it fits this environment. So, even if every cable has own nature regardless of environment, it is not really possible to give a final recipe. And, as always, something also depends on the rest of the system.

Can you please tell us more about Aya II and Model?

AYA II is the current embodiment of all those TDA1541A DIY DAC projects released since 2003 through www.pedjarogic.com, so now it is not only a DIY project but is also a commercial device.

The Model, on the other hand, was never meant to be released as a DIY project, and it wasn’t only because I considered necessary to keep something confidential, but also because it is a bit beyond capabilities of typical DIYer.

General topologies of AYA II and The Model are still not that different though. Both are non-oversampling DACs based on TDA1541A, both comprise S/PDIF and USB inputs and use the same decoders, supply regulators are very similar, and layout strategy is practically the same.

Yet, many things are released by different means. For example, I/V stages of both the AYA II and The Model are zero feedback transimpedance stages. The difference is that the AYA II uses integrated circuits whereas The Model employs discrete transistors. With ICs you use what’s available and there is actually not a lot of chips you can use this way, and that’s because such stages do not fit the way semiconductors manufacturers think. The OPA861 is one such IC, as is the AD844 used in the previous AYA. Such a stage is in my opinion superior to any opamp based or resistor only I/V. This solution, as good as it is, however still uses the (monolithic) circuit which is not optimized for such a purpose. The Model hence uses the circuit accomplished by discrete transistors and optimized to achieve better linearity in this application. The upcoming version of The Model will make another step in this direction, combining the good sides of monolithic circuits (matched active parts, thermal coupled on one substrate) and using transistors where monolithic circuit appears a bottleneck.

In addition, The Model employs more serious power supply filtration (it is the only device on the market that internally comprises isolating mains transformer with balanced output), and some better passive parts.

How important is use of top quality components?

The parts do matter a lot, both active and passive ones. Not all expensive parts are good though, nor do all cheaper parts are bad.

Under certain circumstances you avoid using transformers in the output path. What is your preferred way of coupling and why?

I do advise transformer as coupling device. But if the following device comprises the input transformer, then the output transformer of source device is not only redundant but is also unwanted, since its windings resistance adds to the output impedance. And every transformer sounds better when you feed it by the low impedance source. This low impedance of the source will additionally somewhat reduce importance of the cables, but there are also two other reasons to prefer a scheme with transformer at the end and not at the start of the interface. The first, as pointed out by Bill Whitlock of Jensen Transformers, a common mode rejection is better, and second, the input transformers are, in my experience, often sonically better than the output ones. I do know that many people don’t differentiate between the input and output transformers but there is important difference; in a goal to keep the output impedance as low as possible, windings of the output transformer must be of low resistance. As you normally want high inductance, this makes some design constraints and it is not any easy to make a good output transformer. Input transformers, on the other hand, have no such a demand, and you can easier wind them for required inductance.

Capacitors don’t do that well as transformers do but we still have some Black Gates, which work excellent given their price. Yet in the price tag of audiophile film caps I’d again rather think about using transformers, since some fair transformers are actually not more expensive.

Still, once you solve interconnections, a direct coupling is the best in my opinion, but it is not a universal solution.

Is The Model truly balanced?

No, it operates as single end device. The balanced output is accomplished by the use of transformer.

What are the real benefits using balanced outputs?

A ground connection is not used for audio signal (in other words, cables get less important) and common mode rejection is better.

Why do you avoid upsampling in your products?

Up-sampling, and I assume you are referring to asynchronous sample rate conversion (which is a conversion to the sample rate that is not the multiple of original frequency, so for example conversion from 44.1kHz to 192kHz, as opposed to classic over-sampling which converts to 176.4kHz or 352.6kHz), is needed when you have to convert between 44.1kHz string and 48kHz string of sample frequencies. This is usually needed in professional recording systems. It is not the process that brings any gain but only problems. Also, unless you remove the jitter before you feed the input of ASRC, you embed it into the data. Upsampling in my opinion has no place in home audio chain, and in practice it does makes things sound worse.

Many DAC's can sound harsh and cold. How do you avoid this?

Well, I worked on this... ;) Seriously, there are many sources that can cause such a result. So I tried (and still working on) to detect as many of them as possible, and I did found them almost everywhere: in the D/A part (and associated oversampling), in some forms of jitter, in supply, in the feedback (especially improperly used feedback) of the output stage, to name a few. But it is still not enough in itself. You sometimes have only to add one wrong passive part and result won’t be good anymore.

What bring musicality into DAC's?

There is nothing you can throw on them to make them sound that way. Musicality is rather what you get solving the problems mentioned above. And the rest is on musicians and recording engineers...

How do you refine them?

Improving is one of the trickiest parts of the audio game. You immediately hear what’s better but you usually need some time to detect if something is missing or wrong. That’s also why tweakers too often announce improvements. Some improvements are normally that huge so they are obvious, but in most cases the main element of success is the time.

What do you think about analog vs digital?

I moved to digital long time ago. Unfortunately, there is no way back and there is not such a choice anymore.

Who are your clients?

Audio devotees, by vast majority. Be it good or bad. ;) Sociologically, as per rule, they are males, 25-55 years old.

Do you consider yourself an audiophile?

As an owner of company which targets the market mostly made of audiophiles, I’d be probably better to say “yes, I do”. The things are not that simple though and my honest answer is rather that “I do not”.

I do listen to the music all my life, and exactly for this reason (and not for external and only technical reasons) I started dealing with audio equipment very early. I finally started making this equipment, and I still do share major audiophile approach, preferring subjective performance to the technical one, and I still do listen to the music most of my time.

However I don’t think that I share common audiophile approach and audiophile way of thinking, at least not anymore. In many ways they lead you astray, and push to the dead end of listening to “details”, “microdynamics” and alike, making you forget to listen to the music. In that way the term audiophile can have even a pejorative connotation. It is not that I don’t think the terms like details or microdynamics have no meaning or their use has no purpose, but when you start dealing with sound instead with the music, even if you apparently still deal with audio, it doesn’t have real content anymore, and it consequently doesn’t have much sense, if any. In that way, though I do admire recording quality achieved by, say, ViTaL Records, for me those are ultimately simply recordings that I normally don’t listen to.

What would be your dream product?

Integrated CD player with my own discrete DAC. And I believe it will come true in a reasonable term.

What kind of music do you listen by the end of the day?

My interests and taste have been changing over the time. My first serious interest in music was associated to the studio recording revolution of 80s, and that time there was probably the most systematic approach to so called pop-rock music ever. A lot of the work and talent were put into the records (and concepts, if you like) made back then. The works of Peter Gabriel, David Bowie, Sting, Bryan Ferry, David Sylvian (and I am very glad that Sylvan is again very creative) were the most important to me, but there were many relatively different authors that I listened to, as Robbie Robertson or Propaganda, and also Lou Reed or Tom Waits. In 90’s my interest moved to the jazz, though it was again rather contemporary than some classic jazz... In my opinion the most of ECM recordings are awesome. I do know that many people believe that the jazz is passing over but for me musicians like Jacky Terrasson and Brad Mehldau keep it alive and worth attention.

It would take some time to name or even sketch the music I’ve ever listened to, and now I have no firm favorites. I can listen to about any genre, and what I’m actually listening to simply suits particular day. And, for the reasons previously explained, there is no real difference between some official test material and my personal preferences.

What kind of equipment do you use for your reference work system?

All the stuff gets checked through my home system. My preamp is EF86 (Amperex) triode mode based, and it obviously counteracts the common audio wisdom, which teaches us that the good sounding device must be a high transconductance device. The power amplifier is chip based and with input stage most similar to the recent Vacuum State’s solid state buffer. The speakers are also my made and these are three way, 1st order (electrical) crossed, with open baffle midrange. They work practically across the whole audio range (-2dB at 20Hz and 20kHz) and were made as a compromise between technical theoretical consistency on one, and sonic transparency of simple speaker systems on the other side. Other than Audial interconnect cable, occasionally I’m also using AudioQuest interconnects and previously mentioned DH Labs digital cable. My speaker cables are designed by Dusko Stijepcic (the same guy behind Audial interconnect cable, iCon.S).

What you think about stereo vs multi channel audio?

Music is still mostly recorded in stereo, whereas multi channel is associated to the home theater world. I can not guarantee this won’t change in the future but for now Audial won’t enter this segment of the market.

There is a lot of competition from China manufacturers. Where do you see yourself in a global audio race?

Some finished Chinese products cost less than what we have to pay for the parts, so there is no way to rival prices like that. It is however still not hard to design and make the units better and to provide better support than most of them do. Of course, it is a high pressure and it is sad to see some neat and established companies closing the doors for this reason.

For one decade manufacturers have been reducing the costs by economizing on the parts used, the next decade they made saving by decreasing the costs of the labor, and now the price apparently drops by discarding own research and development. Customers are normally happy to pay less, and I do understand that many times they get annoyed by hugely overpriced equipment they can find around, and it is good to put the things down to earth sometimes, but this situation may kill any serious research, simply because it won’t be economically justified.

Also, since this whole audio game essentially depends on the software, which is the music, the way the things went with music industry are the same worrying, since they also do not support creativity (decreasing recording quality, mp3 which dominates in everyday use, illegal downloads). All this may be extremely destructible in the longer terms.

How do you see the future of high-end audio and your role in it?

As always, predicting the future is not easy but it is sure that the high-end audio will continue to change. Two main issues that will determine the future are exactly these two, the quality of future recordings, and the place the Chinese manufacturers will ultimately take (since this may easily dictate general approach).

Audial will continue to design good sounding and well designed devices at fair price. Audial is a small enterprise that wasn’t started expecting the huge profit, but I hope the company will grow slowly but continuously. I do believe that there will be always some interest in seriously designed and manufactured equipment.

Any last words for our readers?

Audio can make your life better but it often becomes pointless mess. If you learn to separate one from the other, and make you decisions accordingly, you did half of the work.

Audial web site