How to increase the audio power out to amp from tv
This idea / suggestion of mine was not elaborate enough to be written as an "answer", but it's the only way to insert a drawing in the post.

I also strongly suggest you research about "dummy load".

First, try take the audio output signal from the circuit WITH the headphones plugged in (the first dashed box in the drawing below). This test will prove if the load (heaphones) indeed make the soundlevels output be higher enough to drive your audio system input.

If it suceed, next step ir try replacing the headphones with resistors (I would start trying with 100 ohms resistors) as in the rightest dashed box in the drawing). Maybe you'll need to try lower resistors (but not less than 47 ohm). 

Please note that some headphones models have an impedance so low as 8 ohm, but the fact that the impedance of headphones is measured in ohms doesn't mean that you can replace the headphones with 8 ohm resistors! They're both measured with the same unity, but resistence and impedance are somewhat different things, so you should be safe using resistors higher than the phones' impedance.







simulate this circuit &ndash; Schematic created using CircuitLab