If there was some mysterious type of "inharmonic" distortion, other than IMD or jitter or aliasing which are all known and understood, I’d have seen it by now in an FFT. There is no such thing. If you believe otherwise, please post an FFT showing that distortion, and explain how you created it.Thanks for your explanation. So the specs you quote are from your own measurement?
Inharmonic distortion is a form of IMD, in this case related to the scan frequency. Its called that as the distortions are not related to harmonics of fundamentals, and differs from regular IMD as it can occur with only a single tone being recorded. IME, its most likely to show up on the record side, and can’t be detected with static tones. You have to use an analog sweep generator (using static tones, or tones generated digitally allows the technician to be unaware that there might be a problem). Set to sweep 20-20KHz, record at just below 0VU and in playback, listen for the ’birdies’ (this is radio parlance for subtones and supertones that vary with the changing frequency of the sweep tone; obviously you will want to set the speed of the sweep to a slow rate so its easier to experience the birdies). It might be a record-only artifact; the problem is you have to play back the sound file at some point and I’ve not investigated the issue enough to ascertain how much of a role the playback systems play. This problem seems to have improved over time- it was horrendous only 15 years ago!
First, the makers of "high end" CD players do whatever they think is needed to convince people to pay handsomely for their stuff. That they "isolate" their transports means nothing. They probably claim to use some BS over-designed power supply too. More important, if you believe normal amounts of vibration can affect audio quality, why don’t you test it for yourself? I’ve done that, which is why I know isolation for CD players is BS. It’s not a difficult test! If you design audio gear, surely you have a sine wave generator, a CD burner, and a way to record the player’s output as you shake it around while playing your test tone CD. Or just watch the output on a ’scope as you shake it. Or just listen. Sheesh!I do design audio gear, but never gotten to the point where I take digital seriously. I show with digital gear at shows of course, but if I have the same track on LP its always a very easy thing to demonstrate how much better the LP sounds than the digital. The worst system we’ve used at shows was a Tascam DV-50; Tascam is a major supplier of CD transports so you would think their machine would be pretty competent, but I found it irritating enough that usually I could not play an entire track with it (and I have found this pretty repeatable with other examples so I know it was not due to a malfunction). By contrast I find the less expensive Oppo players to be more musical.
The way I see it, if digital is working properly you won’t hear any difference from one machine to another, but we hear differences all the time, which says that the digital is falling well short of the ideal.
The most expensive setup we’ve shown with was also the best (although a close runners up is much more affordable!) by a country mile over any setup I’ve heard anywhere (I have customers with the dcs setups, which have been a benchmark in high end for a long time). When the designer was in the room playing a cut, I asked him if he would like to hear the same thing on LP; he said yes and upon hearing the difference, turned to me and said "digital has such a long ways to go". Its that pragmatic approach on his part which I credit for his gear being one of the very best I’ve seen.
Now I should make a distinction here- if the sound file is stored on a hard drive or the like I find it robust. It should not be that when you change a CD transport that the sound should change but it does. That simply says to me that CD playback is variable, and is a proven topic that has endured for decades on the web. In a nutshell, its not robust while hard drive performance is. This is why there are programs like ’CD Paranoia’ (an older bit of software for Linux) because Redbook simply does not allow for complete data recovery.
Its very easy to show that vibration can affect a CD transport. Just tapping some machines can cause the CD to drop out or stop playing altogether! So it would appear that reducing vibration, such as on a platform, could have an effect. Personally I feel that the sooner we get rid of the CD format, the better.
