Can I subscribe to apple music without losing my hi res files?

Nothing in your iTunes library on your computer should be altered. However, for matched songs, the version available from Apple Music may not be in as high quality format as your local copy; as such other devices that play or stream that track from your iCloud Music library will get the version available in Apple Music and not your Hi-Res version.

The tracks in your computer will remain your hi-res version unless you delete them and download them from the iCloud Music library. In which case you will get the version available in the Apple Music catalog.

For un-matched tracks, they should be uploaded as is, as long as they are less than 200MB in size and 256Kbps or less. Anything greater will be transcoded down to 256Kbps. Files larger than 200MB will not be uploaded. Uploaded files will be delivered to other devices in whatever quality they were uploaded or 256Kbps if they had better quality than that.

More info here: link-> Does the Match feature of Apple Music change files... - Apple Community

Hi,

Apple music and iTunes Match will match your music as 256 Kbps AAC or uploads non matched tracks as is but hi-res will be transcribed to 256 Kbps. It will not alter existing music that is on your computer unless you opt to remove track then redownload.

With Apple Music, matched tracks may have an lossless or hi-res equivalent. You can set your download or stream preferences from high quality 256 Kbps AAC to lossless or hi-res However, such tracks will have DRM and will only be available as long as you have an active subscription.

Therefore it is essential that you keep your own music backed up. I personally created a new library for Apple Music and kept my lossless music in a different library.

Jim