• The streamer is 96khz/24 bit

    that's (theoretically) "high res" audio. I've not looked at chromecast, however it seems unlikely that you are getting this resolution on the majority output.

    FLAC is compressed CD quality so 16bit/64khz.

  • spotify says:

    Music quality details
    Check out a side-by-side comparison below.

    Free    Premium
    

    Web player AAC 128kbit/s AAC 256kbit/s
    Desktop, mobile and tablet
    Automatic - Dependent on your network connection
    Low* – Equivalent to approximately 24kbit/s

    Normal – Equivalent to approximately 96kbit/s

    High – Equivalent to approximately 160kbit/s

    Automatic - Dependent on your network connection

    Low* – Equivalent to approximately 24kbit/s

    Normal – Equivalent to approximately 96kbit/s

    High – Equivalent to approximately 160kbit/s

    Very high (Premium only) - Equivalent to approximately 320kbit/s

    Edit - formatting has got lost but essentially, normal spotify is 96kbs which I would suggest is below the level where hardware upgrades are going to help that much.

    https://support.spotify.com/us/using_spotify/system_settings/high-quality-streaming/

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