In addition to the above reply, it’s very worthwhile with Meridian gear to try and use digital outputs from any sources, rather than analogue. The digital processing is what they’re all about, really.

With the TV, sounds like you are connecting via optical output, but how is sound on the TV set to output? E.g., is it set to 2-channel PCM, or surround sound of some kind? For your application, set it to 2-channel if possible - surround might sound quieter and depending on the codec, the 218 might not be able to decode properly giving variable results.

HC: 861v4/ID40/LPS, DSP5000, DSP5000VC, DSP3100, SW1600, HD621, Oppo BDP-105, Sony VPL-HW55ES
2-Channel: TEAC VRDS-7/Trichord Clock 3/PSU, Avondale S100, Harbeth Compact 7ES-3
Previous Meridian: 5000C, 5200, 7200.2, 6000, 562V.2, 568.2mm, 800v4, 808.2i, 818v2/v3, 861v8, 551, 502