Reddit reviews FiiO L21 3.5mm - RCA Digital Coaxial Cable

Well you've got a subwoofer, and an amplifier that isn't meant to work with a subwoofer, so that's the bulk of the problem.

The TV has a headphone and an optical out... the Headphone output you can use with a 3.5mm to stereo RCA cable, which is good... but The BasX S8 has line level in and out, but that's only going to work with one source, so no matter what there are going to be sacrifices made, here.

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Here is my proposed method:

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• This optical cable out from television ($9)
  
• To THIS DAC ($20)
  
• This Chromecast Audio ($35) (or you could use a bluetooth adapter to play your phone, with lower quality audio)
  
• Using THIS Cable plugged into Chromecast Audio and to DAC ($12)
  
• TWO Sets of THESE RCA Cables ($9 each), one from DAC to Subwoofer's LINE LEVEL IN, one from Subwoofers LINE LEVEL OUT, to Yamaha AMP input
  
  Total cost: $95
  
  But you'd need to run an aux cable/bluetooth/chromecast audio to have phone input on the yamaha anyway. Obviously if you have any of these cables you can save the money. RCA cables are pretty easy to find. So are optical cables.
  
  If music is more important to you than tv sound, you could run the optical cable to the chromecast and the 3.5mm rca to coaxial from the headphone output of your tv... your choice.
  
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  The dac needs to exist because your amp lacks bass management and a subwoofer output.
  
  You will then use the subwoofer's crossovers to control the bass it receives and what it is sending out to the amplifier, and your Q100's will get the rest.
  
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https://www.amazon.com/FiiO-L21-3-5mm-Digital-Coaxial/dp/B019OWCID6