RX-V373 tv input help

So my mom just got a RX-V373, I talked her out of getting an all in one so I'm pretty happy and we just got a pair of Wharfedale diamond 10.1's for it. I was also looking at the V473 but it just had networking and the same power so I went with the 373.

I had her TV connected to a boom box from the audio outs and it worked fine, could go super loud, had the volume on the boombox at like 1/4th but you could only control the volume from the boombox and it didn't have a remote. Now that we got a receiver and there is no coax in-put on receivers anymore, I'm again using the outs on the TV for cable audio (bluray/dvd is going all threw hdmi into the receiver) but when I connect the RCA's from the TV outs to Audio 1 or 2 I get nothing when selecting them and when I connect it to AV 4 or 5 it is supper quiet, the volume needs to be +10.0db of more to even hear it and you can hear background hiss? AV 3 which is labeled as "TV" is only optical in for audio.

My HK receiver is all assignable so the Yamaha is kind of confusing to me.

I can get a composite out for the cable box, I'm just wondering why this isn't working? I looked for a gain option or something but couldn't find it, the TV gain seems perfectly appropriate when connected to the boombox.

No it's from the local cable company and SD, it says aminio and dolby digital on it, as stated I can get a composite adapter but I would need to call the company and have them come out, It should work fine through coax and the TV outs? I have the adapter on my box and TV down stairs but somethings wrong with it and it looks all grainy so I use the RCA for audio and coax to my TV, if they come out I will have them replace it along with adding the other one upstairs but its no big deal sense there's no audio lag with the way I have it.

Figured it out, it was all the defective brand new RCA cable I had going from the TV outs to the receiver....

Almost blew the 10.1's out after I swapped cables as the volume was on max