** 2 page regular Digital audio / 1,485 words **
** Side banner: Falcon pro audio gear **

Adventures in hi-fi

Tired of "multimedia" sound quality? Shiuming Lai examines the problem and recommends a solution to make that Falcon really sing...

8-bit stereo audio was a sensible choice for the STe. At the time, the cost of RAM and disk storage needed to handle the application scope of 16-bit was too prohibitive for a home computer. In terms of quality it was streets ahead of the STFM, but still some way short of high fidelity. So what about the Falcon, with its eight 16-bit channels? The proof is in the listening, and even a reasonably competent amp and speakers easily reveal its lacklustre performance. The input and output are set for direct connection of microphone and headphone, the bass swamps the overall sonic image, headroom is restrained, warbling background noise...

Why? Isn't it 16-bit?

The answer is as simple as that to why does one CD player sound better than another, even if they're playing the same discs. Forget the numbers for a moment, we're concerned about what comes out at the end, analogue. Television, video, hi-fi and computer; they are all abstractions of a collection of electronic components, which can vary in quality. Being a product for the highly competitive and cost-conscious consumer market, the Falcon's components had to be chosen accordingly. In the case of its audio I/O, a cheap CODEC chip was put in with only functional testing. When it comes to recording and playback quality there is a large tolerance band.

CODEC stands for enCOder/DECoder, as the name implies it contains the circuitry for A/D and D/A in one package. Such integrated devices are generally used in low-cost applications or where PCB real estate is limited. Top-end equipment tends to keep the two sections separate where possible.

For argument's sake consider another type of CODEC you'll have learnt to use at school, a ruler. When you use one to measure something you're performing A/D, and when you use it to construct something from a specification, you're performing D/A. Naturally, the higher its resolution the better its theoretical capability, so a device calibrated in mm has ten times the precision of one in cm. It's important to know the difference between precision and accuracy; suppose you're trying to draw a line of 65mm, but you have a blunt pencil, the table is vibrating, loud noise is distracting you, and the ruler itself isn't correctly dimensioned (say, after 20mm the markings are spaced randomly). Despite the digital information, 65, being present, you have little chance of drawing this line accurately! That is, translating a logical value to something of true proportion in the real world. You should now see, the numbers are a significant part of but by no means the whole story.

In much the same way, it's not of exclusive importance that the Falcon's CODEC processes 16-bit resolution audio. Physical factors, both internal and external, have a marked bearing on its performance. To make things worse, Atari piped it through a hard-wired bass boost in the analogue output stage, to compensate for speakers with weak bass reproduction. Besides tackling a problem not its responsibility anyway from the wrong end, partner this with modern trendy active-sub computer speaker systems and there you have a recipe for acute nausea.

It's a fallacy to believe the Falcon, or any other so-called multimedia computer, is a serious digital recording machine in its unadulterated state.

Some companies recognised the Falcon's potential in pro audio and carried out modifications to remove the bass boost and adjust the I/O to line level. C-LAB in Germany made these standard in its badge-engineered Falcons, created for the music market. None of these, however, got to the heart of the problem; the CODEC chip is simply a means to an end, Atari's engineers knew this and left an upgrade path open. Since the infrastructure to manage 16-bit was already there, it would have been self defeating to keep that closed in. They wisely incorporated a signal routing matrix in the Falcon (figure 1), allowing audio to pass in and out digitally, through the DSP expansion port, so external ADCs and DACs could be used. External conversion is better isolated from the noisy Falcon motherboard, and a wide range of more refined converters can be used - money being the only obstacle, and of course we have the possibility to give each channel its own output socket.

The sound's saviour

Line Audio's Falcon audio I/O expanders have made a good name for themselves in studios across Europe. Each is hand-built and individually tested to guarantee the published specification. Various configurations are available, all are based on the same core of high speed 1-bit converters with 18-bit resolution. It started with Jam, a family of professional input and output units with balanced connections, essential for preventing ground loop hum in studio environments containing a lot of equipment. Jam PRO IN and OUT come as individual boxes, or, you can get Jam PRO OUT in a smart 19" 1U rack-mount case and add Jam PRO IN 2 or 8 as an upgrade. Derived from Jam are the FAD (Falcon Audio Digital) units, simply without the balanced connections.

How does it sound? Imagine smelling your favourite food again after a long bout of flu. My first reaction to Jam was one of absolute joy. It turns in a sparkling performance with its extreme linearity of frequency response and ultra low noise (figure 2), music from a Falcon never sounded so pure. In A/B listening tests, the sound stage immediately opened up showing an articulate and coherent mix, delivering an authoritative slam when required yet still revealing subtle detail hopelessly lost by the Falcon's CODEC. This does mean bad recordings will be shown for what they are, remember: Garbage In, Garbage Out. Run an 8-bit sample through this piece of kit and the noise floor is revealed in horrifying detail, even some sample CDs are really laid out warts and all - you have been warned!

Playing decent material, the investment is handsomely rewarded. Every breath of a singer, every pluck and twang of acoustic guitar and the awesome impact of an orchestra are all beautifully and convincingly rendered. Bass presence is strong but not intruding and mid-range is not forgotten either. Treble has bite and sting with cymbals, yet doesn't lose control with complex electric guitar twiddling or energetic violin passages.

Klaus Heyne's CD Reader program will allow Jam to work similar wonders for the even worse sound of CD-ROM drives (maybe I'm being harsh, since they don't try to pretend their analogue outs are anything but an afterthought), as it will read an audio CD over the SCSI bus and route the data to the Falcon's DSP port. If you really must use your computer for playing CDs then this is the way to do it, so avoiding the motor and servo noise that afflicts even premium-priced writing drives.

Jam scores on recording as well, producing crisp, faithful copies of NICAM television broadcasts (from a Panasonic NV-HD650 edit deck) and other quality sources. This is real hi-fi sound and I love it, so with that I'm going to finish here and listen to some more.

** Boxout **
Jam technical

Output frequency response: 10-22,000Hz +/- 0.1dB
S/N: 93dB A-weighted
THD: 0.005%
Channel separation: over 85dB

For more information:
http://www.lineaudio.se
UK: System Solutions

According to Roger Jonsson of Line Audio, "Jam PRO will soon be available in a new version with 24-bit converters. These new converters lower the noise even further, by about 6dB. The S/N ratio will be about 99dB A-weighted (close to 96dB non-weighted). It's impossible to get lower noise out of a 16-bit system and it gets very, very quiet, with these new converters!" That's not to say the current Jam PRO is at all noisy, far from it. I can't wait to hear the new version.
** /boxout **

** Boxout **
Compatibility

All the major professional audio software will automatically use external DACs on the DSP port, including Cubase Audio, Zero-X, the Electronic Cow, Softjee and SoundPool ranges. It's easy to do, so I hope more programmers will realise the advantages.
** /boxout **

** Images and captions **

** MATRIX.GIF **
Figure 1: This style of interconnect topology is also known as a crossbar switch.

** FALKCURV.GIF **
** Please don't scale below 1:1 **
** Let me know if reproduction  **
** problems are likely          **
Figure 2: Frequency response of a Jam OUT compared to a stock Falcon. The lower graph signifies poorer S/N ratio and the large bump dominating the sub-1KHz range is caused by the Falcon's bass booster.

** CDREADER.GIF **

** FAD.JPG **
FAD is a popular choice among home recording enthusiasts.

** JAMPRO.JPG **
Data and sync lines are filtered to reduce effects of clock jitter, although Jam's converters are much less sensitive to this than the Falcon's internal chip anyway.