[mythtv-users] audio issue - HDMI tv

[Tim Draper]

 ---- On Mon, 26 Mar 2018 12:36:07 +0100 John Pilkington <J.Pilk at tesco.net> wrote ---- 
 > re-sent to list: probably not as good as fixing a cec issue... 
 >  
 > On 26/03/18 11:44, Tim Draper wrote: 
 > > While strictly not a mythtv issue, it is to do with one of my FE setups. 
 > >  
 > > my conservatory has in-floor speakers by the previous owner and figured i could use them with an external amp (ebay/amazon Lepy T-class amp). This works fine from my phone/laptop. 
 > > It doesn't work when i have the 3.5mm jack connected to my rpi3 AND is connected to the TV with HDMI cable. even with the rpi3 unpowered, the lepy amp seems to see some sort of fault and (i think) enabling & disabling itself every few seconds. - internal relays clicking and speaker popping as it switches. disconnect either end of the HDMI cable form the rpi3 and the issue goes. Plug rpi3 power in and problem remains. swapping HDMI cable has same effect. 
 > > problem occurs both on the rpi3 3.5mm jack and a USB sound card. 
 > >  
 > > i'm not really sure exactly what or how, but something in the TV is upsetting the external amp. happens with the tv on, soft-off, or turning the physical switch on the side of the tv off. only way to stop it is to physically unplug the mains cable. 
 > >  
 > > TV is a 2009-era LG 32". 
 > > Is this a case of i'm outta luck or is there something i can do to stop it? I've tried to disable the tv speaker via the menu and cant see anything else in there that could help. 
 >  
 > If your tv can get audio via hdmi, can you feed your amp from a tv  
 > headphone socket? 
 >  

didnt think to try that; noise still present though when using HDMI audio to the TV, and then using headphone socket on the TV to the lepy amp.
use headphones on the TV headphone port no issues.
at this point it kinda points towards the lepy amp, but it acts fine if i use any other device with it; laptop, the same USB audio dongle on laptop, mobile phone, disconnect the 3.5mm cable from tv/rpi3.