Generally speaking, when we refer to bit-perfect soundcards, we mean the soundcard is capable of being bit-perfect within the greater chain of gear used for transfers. All links in the chain must perform bit-perfectly to achieve a bit-perfect transfer. Failures may occur in any number of links in the chain:
- damaged/faulty tape
- misaligned or dirty DAT playback heads
- digital connector/cable problems
- soundcard hardware issues
- soundcard driver configuration
- recording software configuration
- operating system configuration
- RAM usage
- virtual memory configuration
- hard drive health (e.g. fragmentation) and/or spin rate
- CPU health (e.g. overheating) and usage
There are probably other links in the chain, but you get the idea. Problems in any one or more of these areas may contribute to a bit-imperfect transfer, and only when all these links in the chain are operating properly do we achieve bit-perfect transfers. And as Luvean suggested, most artifacts or bit-imperfection issues are often related to a link in the chain other than the soundcard.
If we all really want to ensure our transfers are bit-perfect, we should transfer twice and compare the resulting WAVs (the odds of the same sample being misplaced/dropped in exactly the same way and exactly the same place on both transfers is astronomically high). Of course, transferring every DAT twice is a major PITA.
Since it is a reality that not everyone has the time, knowledge, or skill to perform every transfer twice and compare, or even to test a single time the exact combination of links which make up their particular transfer chain, we all invariably rely on testing performed by others - fellow tapers, manufacturer support and tech reps, even retailers. Hence, Luvean's mention of the previous tests posted to DAT-Heads.
To address the original point of the thread, we need a lot more information:
- How was SHN > WAV performed?
- Did the operation complete without errors?
- How were the WAVs transferred to DAT? (i.e. what were the exact links in the chain, per above*)
- How was the DAT transferred back to PC? (i.e. what were the exact links in the chain, per above*)
* Your original post lists the following:
Using: Win XP, DA-20, 75ohm coax, Latest Driver, Sound Forge7.0, Samplitude6.0, EAC, CDWav
[/list]But more detailed information would be useful. For example, for what purposes was EAC used? Did you use SF7 or Samplitude 6 for conversion? When and how was CDWave used? How is your WinXP machine configured? When was the last time the heads on the DA-20 were cleaned and/or aligned? Specifically what kind of coax cable? Latest Driver = ...what version? How was your soundcard configured, etc.?
So, yeah...that's a lot of information to provide. My initial reaction is that the issue is not related to bit-perfectness, but more likely a soundcard configuration issue during WAV > DAT or DAT > WAV transfer.
Some additional questions:
- What do you mean when you say the copy distorts at higher volumes before the downloaded original does?
- How are the copy and master each being played back?
- I'm not sure what you mean by the copy's wavform "loses texture" before the original - please explain?