HDtracks generally does not give specific source info about their downloads. They say they can't get this info from the labels.
There was an accusation that some of their downloads were upsampled cds and apparently this was true in a few cases (no content above the 22khz frequency). HDtracks says that doesn't happen anymore and I'd guess that someone out there checks to make sure that's true.
As with every other format, sound quality varies from album to album. TAS reviews a few and a few are discussed here. All I can recommend is that you ask about the sound quality of a specific album you're interested in and see if anyone has an opinion.
There was an accusation that some of their downloads were upsampled cds and apparently this was true in a few cases (no content above the 22khz frequency). HDtracks says that doesn't happen anymore and I'd guess that someone out there checks to make sure that's true.
As with every other format, sound quality varies from album to album. TAS reviews a few and a few are discussed here. All I can recommend is that you ask about the sound quality of a specific album you're interested in and see if anyone has an opinion.