Lots of Blu-rays have "Linear PCM uncompressed" tracks. In the menu system it may be listed as "LPCM" or "Uncompressed" or something. When you bring up the on-screen display it shows a constant bit-rate of 4.6mbs or something close. It's 5.1 or higher.
Dolby TrueHD is a "lossless compression" and uncompressed are just raw data. It's like taking a computer file and putting it in a zip folder. So they should sound the same assuming the same original "master" was used, TrueHD is just more space-efficient.