Presumably the tapes available to download are from hardware, in which case we have the original and we can save it back out in MAME and compare.
It is true that the majority of the 300-baud and 2000-baud BASIC programs on ballyalley.com were recorded from real hardware. Usually this means that the recordings were made from tapes from the late 1970s or early 1980s. However, they these files were then all digitally archived using various audio archiving tools that are also available on the site here:http://www.ballyalley.com/program_downloads/tape_archive_tools/tape_archive_tools.html
What this means is that these are "perfect" WAV files. If anyone here would like to have a RAW WAV file recorded from real astrocade hardware in either 300-baud or 2000-baud, than me know and I can do that within the next couple of days. By "RAW" I mean that it will be a digital recording of an analog signal. The file will not have been processed in any way.