You're wrong Kohlrabi. Webshops sell transcodes as well. I bought several transcodes at Beatport, Juno and Trackitdown.
Do I still have to convince you? What if waves have very specific distortions, that let's you even guess what encoder was used?
@ Kohlrabi - if you have just 2 copies of the same track (of course one is just excerpt from mix CD, other is full lenght) and one of them has permanently visible lowpass applied - would you still believe webshop? Other thing is that after my complaints certain track was resupplied by label. Original copy looks like it was encoded to 128 kbps mp3 and then decoded to wave, and resupplied copy has perfect spectrals. Sorry, this is genuine evidence.
There is simple way to distinct mastering lowpass and encoding (transcoding) lowpass. Filters used in lossy encoding are very steep polyphase IIR filters (transition band is very narrow). ...