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Thoughts on Computer Audio

post #1 of 4
Thread Starter 

Digital audio has been around for almost 30 years since the launch of the first CD player back in 1982 in Japan. In the early days, CDs were issued alongside with LPs, recordings were done mainly by analog gears. The criticisms on quality of early CDs due very much to the immature technology by then. Time moves on, digital technology turns better and better and now digital audio becomes the mainstream not only in means of storage, the recording and mixing industry rely heavily on digital technology, analog gears are way too expensive.

  

Comparisons between LPs and CDs remain hot topics, traditional audiophiles normally take LPs for serious listening session, CDs just for casual and convenient listening. Authentic analog LP's are rare, new releases are produced from digital master files and their sonic footprint is quite different from traditional pure analog ones. Even the pure enthusiastic LP fans have to buy CDs in order to listen to music of late. As a matter of fact, LPs and CDs are not always compared apple to apple. If recording is done by analog gears, LPs are always better; if recording is done digitally, LP then may not always be a winner. Of course, CD is a general term here, DVD audio, HDCD, SACD are in the same category, all being family members of digital music. 
 
People tend to distinguish "digital" sound from "analog" sound. This is somewhat ambiguous indeed. Sound is vibration of air, there is no such thing as digital vibration, probably this is stereotype. Digital=non-musical; Analog=musical. For those with open mind, digital audio has long been their prime source of music. Having said that, good old analog recordings are best heard with vinyls. 
Problem with digital audio on the side of domestic users being play back media. CD player has a long history associated with copyright protection. Digital files are encoded on compact disc, extract of these files are extremely difficult, if not possible. Mechanism of CD player to a certain extent inherits from vinyls. Loading the disc properly, disc starts spinning at a high speed, signals being picked up for further processing. Both have the same problem of physical vibration leading to degrading of sound quality. Like it or not, CD player is considered the only proper way of playing back digital audio.
 
Up until the time when ripping CD is no longer a difficult task, era of computer audio comes. At the very beginning, compressed audio in the form of MP3 dominates the trend. It's really the Dark Age of music industry, people listen to music of inferior quality, download MP3 from internet, intellectual property right infringed to a large extent. Portable MP3s are everywhere while the young generations never experienced the same sonic quality as walkman and discman in the last century. New player formats like DVD-audio, HDCD, SACD, DTS never have the same popularity as CD.
 
After a while, some people realized that computer may be able to produce better audio than the compressed MP3. Plenty of music playing softwares comes into the market, mostly are free ones. The ugliness of using PCs is the very restriction on operating environment. GUI (Graphical User Interface) is good for multi-purpose usage, for pure audio applications, there are far too many tweaks to play around. On hardware, noise, vibration, audio interface, storage..are the targets to deal with; on software, latency, bulky and unnecessary program tasks, drivers...are complicated for ordinary people. The real problem being: the everyday PC (both hardware and os) is designed for multi-purpose use, they are far too bulky for pure audio application. Even a purposely built PC still has excessive parts on mother board, operating system always comes with excessive services. 
 
Linux may be another story. This has nothing to do with Window like Ubuntu, these desktop applications are as bulky as their counterpart. The real deal is terminal operation. MPD (Music Player Daemon) is by far the simplest yet powerful music player and it comes with an excellent sever function. On operating environment, voyage linux is a tiny one that fits perfectly for minimalist. Indeed there is no other readily available program come close to this gem. Limitation is still on hardware side, the Alix board suggested by official Voyage web-site is ok, but not exceptionally good. Having said that, it's the best pc audio without tweaks of this kind or that. And the best part is......CHEAP. There are a number of commercial applications using MPD or voyage mpd, Bryston BDP-1 is probably the first to use MPD well received by consumers.
 
People may recall a few years back, music player manufacturer Linn announced the drop out from CD player market and the launch of Linn DS, a network player. Some may query why CD player is being abandoned while Vinyl players are still on production line. There is a fundamental difference: vinyl player plays analog music; CD player plays digital music. Vinyl remains the most mature technology by far, CDs can be replaced by digital files, with better quality. This strategic move declared the beginning of the end of CDs and CD players, an era that will be missed by many of us.
 
Is there any product good for playing digital audio? People often ask. 
 
The answer may be yes when a project in diyaudio emerges. The SDTrans 384 developed by two Japanese Chiaki and Bunpei.
It's an ugly DIY looked thing with a beautiful design and implementation. The rationale is simple, minimalism. 
8 bit MCU+FPGA+ultra low jitter oscillator+SDCard reader=SDTrans384.
Lowest voltage is required, only 5v.
As a result, no stupid bulky os, just configuring FPGA. SD card stores huge amount of CD's but no vibration at all at time of reading.
It can read PCM files(wav only) and amazingly DFF files (DXD) in native form, as different from those converted into PCM.
It has no DAC. DAC is another topic. Remember even traditional CD player splits down into two parts, CD transport and DAC.
SD Trans 384 demonstrates the possibility of good standalone digital music player in the simplest form, a perfect replacement of CD players.
Quality of music playback is at least comparable with good CD players on red book format, if not better than. 
Sadly though this is just a DIY project already finished, yet many want to see a commercial product building on their design.
 
post #2 of 4

Check out Nyquist frequency. Digital audio has the ability to perfectly replicate an analog soundwave, and therefor exceeds analog in sound quality. That being said, LP's have a rather pleasing sound signature.

 

I'm not really sure how old of a computer you are using where bulky programs and the OS gets in the way either... bitperfect audio is quite easy to achieve. Latency is quite irrelevant in playback, unless you're really anxious to get that first song playing and can't wait another 500ms.

post #3 of 4
Quote:
Originally Posted by chewy4 View Post

Check out Nyquist frequency. Digital audio has the ability to perfectly replicate an analog soundwave, and therefor exceeds analog in sound quality. That being said, LP's have a rather pleasing sound signature.

 

 

It's not as much about the ability as what you do with it - check out the loudness war. Digital audio is notoriously being destroyed by attempts to record audio as loud as (or louder than) possible. The effect is lack of dynamic range, compression and clipping.

 

The funny thing is that recording as loud as possible was much more important for analog recordings than it is for digital (to ensure decent S/N ratio), yet it is digital recordings driving it to insane levels. But at the same time analog recordings have much better tolerance for exceeding nominal levels - that's probably why a lot of people prefer them over digital.

post #4 of 4
Thread Starter 
Quote:
Originally Posted by chewy4 View Post

Check out Nyquist frequency. Digital audio has the ability to perfectly replicate an analog soundwave, and therefor exceeds analog in sound quality. That being said, LP's have a rather pleasing sound signature.

 

I'm not really sure how old of a computer you are using where bulky programs and the OS gets in the way either... bitperfect audio is quite easy to achieve. Latency is quite irrelevant in playback, unless you're really anxious to get that first song playing and can't wait another 500ms.

It's true that sampling theory is the very foundation of digital audio, but implementation differs from theory. 

LP vs Digital being the everlasting debate but as i said it's never apple to apple comparision, and that's why vinyls remain favorable choice by quite some audiophiles.

If powerful pc can generate bit-perfect audio so easily, latency an irrelevant issue, then it's definitely a good news to all of us. 

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