Converting analogue source to digital stream on the fly

[nickc]

Can anyone offer information or advice as to how one might go about creating a high quality digital stream from an analogue source? I have an old Thorens turntable connected to an Arcam amplifier and I would like to be able to convert the output to digital so that it could be recorded and/or streamed, ideally, say, by MinimStreamer running on a RaspberryPi. The idea solution would be an A/D card for the Pi, similar to the Hifiberry DAC, but no such product exists and the people behind the Hifiberry card say there isn't sufficient demand to merit producing such a thing, which would be challenging anyway. I thought I had a relatively low cost solution in the Roland UA-55 Quad-Capture Audio Interface, but it turns out it uses a proprietary software that is only Windows or Mac compatible. Can anyone recommend something of similar specs that would be Linux compatible?