Compatible TV to audio receiver

AFAIK there are two standards for line level:  1.23Vrms (+4dBu) for Pro gear (and modern audio, I think), and 0.316Vrms (-10dBV) for older consumer electronics.  It is possible that both - your TV and receiver follow the older standard, so you should be OK.  Output is a little higher than input, as it should, while input to output impedance ratio is way higher than customary 10x minimum.

I figured phono was a bad idea.    

the inputs  for sound for video devices on my receiver says the "sensitivity" is 200 mV.    Its my understanding the lower the input sensitivity, the lower the output from the player device that was needed.    Note this is an older model receiver, we're setting up for my son.

No idea what sensitivity means in that sense.

S/N is a ratio. Changing input levels does not change the ratio. 

74 dB is actually just fine for a phono stage. You're thinking CD players where they can be anything up to and over 100 dB. But being CD players they sound like crap. Little hiss beats digititis, seven days a week.

Phono inputs are not just different in terms of gain. The signal on a record is cut with an RIAA equalized signal. The Bass is turned way down, treble way up. Then on playback this goes through a phono stage that equalizes it back by turning the bass way up and the treble way down. So you can plug your TV into the phono, but its gonna sound awful with massive bass and no treble. Not to mention distorted, because the .47volt input is gonna severely overdrive a phono stage that was designed for cartridge output that is in the range of a few millivolts.

Thanks for the explanation.  I thought since the "sensitivity" of the receiver was 200 mV, then we should have been fine.

I have a phono jack for a unit that needs preamp with 2.5 mV sensitivity but the S/N is a low 74db.   I would assume stick with the previous option.

Question, does increasing the voltage improve S/N value?  I would believe so.  But I imagine I could go too high.   the specs don't tell me the peak voltage output would be on variable.

No, that's right. Normal line level is around 1 to 3 volts. Your TV fixed is only half a volt (.47 to be exact) so of course you have to use variable and turn it up to get up over a volt where your receiver is expecting.

The position of the volume knob (or button, display, whatever) is one of the least relevant things in all of audio. Turn it up to whatever sounds best and forget about it.