I already checked the speaker and it's ok, it measures me 6 ohms ... check the TDA again and it gets a 20V supply ... and in the TDA data sheet it tells me that the supply voltage is +/- 25V you say that it influences ?? .. by the way the TDA is the TDA7265..here I leave you the data sheet link
http://html.alldatasheet.com/html-pdf/25084/STMICROELECTRONICS/TDA7265/3247/2/TDA7265.html
If that tells you that the integrated one has a higher voltage range, check the positive and negative tracks if they arrive from the account with separate filters, one to negative and another one, if so, you need a voltage so that the integrated one works with greater power as you see in the data sheet each audio input is individual check if the audio is coming to the two channels equally from the volume with a homemade audio follower up to some headphones I could make them and check the audio input with watch out