If it's a digital signal from the HDMI cable, then essentially what you're doing with this cable is splitting audio out of the HDMI cable and sending it through a SPDIF connector, which is still digital audio, which will not work with an analog amp. --You will need a DA/ converter, of which I don't know if they exist for consumer audio.
Pro audio your options will be multiple, however the analog signal passed through Pro Audio cables is quite often +4db, while the signal passed of Consumer, and some crossover 'ProSumer' gear is quite ofter -10db, which will cause distortion overload issues if trying to run pro audio signal through circuits designed for consumer audio. Conversely, there will also be gain attenuation issues if trying to run a -10db signal through a system that wants a +4db signal. -- At least with the latter,, you'll have plenty of dynamic headroom to spare, though it might be a bit noisy.
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