Hi All.
I have a Sony KDL-40W5500. I have a problem with the way the line out of this TV functions.
The problem is that the Line Out is always controlled by the volume control. This is a pain because it means that when I want to use my HiFi speakers (such as when watching a movie) I have to go into the menu and mute the TV speakers manually.
Now on my newer TV in the other room I can set the line out to be a true non-volume controlled line out in the settings menu, then I simply just press mute on the TV and turn on my HiFi amp. However the older TV does not have this option. If I mute the TV the Line Out is also muted.
I have had a look at the service manual and notice that the Line Out is driven by the 'AMP1' section of a CXA3785R. It appears this IC has a I2C programmable gain control so I assume this is where the 'volume' is controlled from?
I am thinking there is a way I can tap the signal out from the AMP1 inputs.
I can see the input pins labelled AMP1INL_P and AMP1INL_N and also AMP1INR_P and AMP1INR_N.
The data sheet of the CXA3785R shows what appears to be a simple balance (positive and negative) audio input into an op-amp which is outputting an unbalanced signal.
This is as far as my understanding really goes.
I am wondering, could it work taking a wire from the AMP1 inputs to this IC and tapping them into another pair of op-amps (TL072 or similar) for a line-out that isn't affected by the volume control?
Then I could just add a panel 3.5mm jack socket to the rear of the TV and be happy with a real Line Out!
What do you all think? Could this work?