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A client has asked me if I can sort out a TV audio feed into his Loxone audio system so that he can play his TV sound through the ceiling speakers in his room. I have managed to convert the TV optical audio out to coaxial audio and send it via a Cat 6 cable between the TV room and the Loxone "hub". At the hub I feed the coaxial audio into a DAC and have connected the stereo phono out from the DAC into "Line 2" on the Loxone miniserver. When "Line 2" is selected on the app, we can hear very faint TV sound through the ceiling speakers, but only when the volume level is set to 100%. Please note that I tried this setup at home first, feeding the output of the DAC into my Marantz stereo amplifier and it worked perfectly. I have also tried the Line 1 input, and there is no TV sound, just a small amount of "noise". The other issue we noted is that when using Line 2, there is quite a large amount of delay in the audio processing, so the sound lags picture by a second or two.
Is there any way to increase the audio level of Line 1 or Line 2, and also reduce the delay ?
The cause of your low to none existent audio on the line ins is very likely due to a drop in the line level due to the amount of conversion happening from your source. The likely reason that it worked on the Marantz unit is that this is probably an integrated amplifier with a built in pre-amp on the line in.
If the audio line level drop is due to voltage drop lower than line level then a pre-amp should help to rectify this part of the problem.
The second issue with delay will always be present as the Music server has to process the audio, plus as you are using a digital output from the TV, through a DAC this would have also be subject to a processing delay.
If the audio is before the video you will have to see if the video processing delay can be reduced on the TV side, if the audio is after the video you will have to see if there is an audio delay option on the TV. There is no ability for adjusting the delay on the Music server to compensate, also please bear in mind that different sources e.g Blu-Ray, Sky etc… will have different processing delays. As such we would normally not recommend using a music system for processing of TV audio.