This is a copy and paste from the Linn forum, following the link that Cno posted.
Hi Guys,
Just to clarify, the MP3 version is encoded from the CD master, where as the Studio Master stands alone.
Quite often the Studio Master and the CD versions are the product of separate mastering sessions.
Typically the CD master is made in line with the requirements of the Red Book and generally trys to make the most of what the format allows. It's also made in the knowledge that it will be the master that will be distributed to all download services through an aggregator; transcoded to a myriad of lossy formats.
Without these constraints for the Studio Master, the engineer is free to give it his best, and is afforded the dynamic range to give the best representation of the album possible — losing the shackles of the CD master.
This is indeed the case with Trashcan's album, a record I know intimately by the way, having been part of the management and label team that produced it. We discussed the master with the band and with Calum Malcolm — the mastering engineer — and tried our best to achieve what we felt was the perfect master of 'In The Music' with no concerns or constraints. One of the beauties of Studio Master.
Hope that clarifies things,
Jim
Interesting, while this is a better answer than the drivel Colin from Linn posted, it still leaves me with some questions. I wonder why Linn feel the need to master the CD and Studio Master (is that what they call the 24bit version?) differently? Why not just downsample the Studio Master version? The sentence "Without these constraints for the Studio Master, the engineer is free to give it his best, and is afforded the dynamic range to give the best representation of the album possible — losing the shackles of the CD master." doesn't make much sense to me, the dynamic range of any piece of music ever recorded doesn't approach the limits of CD as a format. It still smells, to me, of trying to artificially provide a reason to purchase the 'Studio Master'.