I have a arcam a75 and monitor audio speakers. When playing from turntable via amp the sound quality is great. When I plug my phone in via aux I can't get the sound right at all. Toggling phono/line, trying diff inputs etc
Any ideas of what is wrong?
Not clear what the issue is. Where are you plugging the phone in? should use CD, Tape, DVD, AUX, basically anything but Phono.
That should sound OK. Your limitation will be the rubbish DAC that phones tend to have. If you have a USB (or iphone equivalent) out, you could connect that to a DAC such as an Audioquest Dragonfly, or Cyrus Soundkey.
Finally, you could forget the phone and use a streamer such as a WiiM Mini. This will stream directly from your wifi, and just use your phone as a controller.