Does the CD‑recording software you use influence audio quality?
I was told that the quality of CD media and of the CD‑writing software package used can affect the sound quality of a recorded CD. Apparently, the results of Adaptec's Easy CD Creator are more compressed (in terms of dynamic range, not data) than those of CeQuadrat's WinOnCD. This seemed ridiculous to me at first, but then I remembered reading somewhere that two seemingly identical CDs could sound or appear different ('appear' referring to waveform analysis). The last I heard of this was that it was being looked into...
I know that the quality of media, writing speeds and the drive itself can affect the quality in terms of how well the disc will read but I call on your knowledge to clear up whether or not these factors can affect the actual audio quality of a CD.
Will B
Editor Paul White replies: Software should only affect the sound of recorded CDs if it does some kind of processing, such as sample‑rate conversion, gain change or a deliberate DSP process. Most editing packages allow you to edit data without 'changing the numbers', and providing you do this, the software has no mechanism for affecting the sound other than by introducing errors. However, the make of soundcard will affect the sound if you go in or out via the analogue inputs, and even digital I/O can produce problems if there's significant clock jitter in the system or if substandard digital cables are used.
Jitter also tends to get blamed for numerically identical CDs sounding different, because if you're storing the right data, one way it can be made to sound wrong is by introducing timing errors (right data but at the wrong time). Jitter leads to a subtle degradation of audio quality and many listeners also find it blurs the stereo imaging of a mix. Media does make a big difference too as some cheap unbranded CD‑Rs barely work on conventional CD replay machines — I suspect this means that the error correction will be working overtime, and once the error correction has to conceal serious errors by 'guessing' missing data the sound is definitely going to suffer.
The write speed of the media is also important, as different disc coatings are optimised for different laser exposure times — even though some CD‑R drives and recorders attempt to compensate for this, it usually varies with writing speed. I've had no obvious problems recording at up to 4x speed using quality branded media, but unbranded media are often rejected by my burner as being unsuitable, confirming the notion that it's better to buy branded product.
Another theory as to why 'identical' CDs can come back from a pressing plant sounding different is that some CDs are less concentrically pressed than others. The laser servo motors which keep the reading optics in your CD player aligned have to work hard to cope with non‑concentrically pressed CDs, and this can lead to the control electronics modulating the ground currents in the audio system, effectively superimposing noise and distortion on the wanted signal.
However, the jury is still out on the absolute causes of perceived differences between CDs with identical data. What is pretty certain, however, is that properly designed software shouldn't affect audio data unless you ask it to.