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audio issue - HDMI tv
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.



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Re: audio issue - HDMI tv [ In reply to ]
I'm a bit confused by your description of what device is connected to
what other devices, and how, but it sounds to me like a CEC issue.

CEC is the HDMI feature that allows control messages to be sent along
with the HDMI data, eg to switch on a linked device:

https://www.howtogeek.com/207186/how-to-enable-hdmi-cec-on-your-tv-and-why-you-should/

If I understand correctly, when it is powered, your TV is trying to
enforce use of the HDMI cable / device to which it is connected.


On 26 March 2018 at 11:44, Tim Draper <veehexx@zoho.com> 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.
>
>
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Re: audio issue - HDMI tv [ In reply to ]
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?

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Re: audio issue - HDMI tv [ In reply to ]
---- On Mon, 26 Mar 2018 12:15:25 +0100 Alasdair Macdonald <wewalkforonereason@gmail.com> wrote ----
> I'm a bit confused by your description of what device is connected to
> what other devices, and how, but it sounds to me like a CEC issue.
>
i thought that might be the case. currently i'm setup as follows:
rpi3 > HDMI > TV
rpi3 > usb audio > lepy external amp via 3.5mm.
also tried rpi3 > lepy amp via 3.5mm but same problem.



> CEC is the HDMI feature that allows control messages to be sent along
> with the HDMI data, eg to switch on a linked device:
>
> https://www.howtogeek.com/207186/how-to-enable-hdmi-cec-on-your-tv-and-why-you-should/
>
> If I understand correctly, when it is powered, your TV is trying to
> enforce use of the HDMI cable / device to which it is connected.
>
tried both HDMI CEC on and off. thing is, i can have the TV connected to the mains with tv remain turned off (remote control off, or physical rocker switch on the tv) and have the rpi3 unpowered and the noise is still present if the lepy amp is on. ONLY happens when i have 3.5mm and HDMI TV cable connected. theres something between the rpi and tv.
I've tried CEC on, and CEC off on both the tv and rpi3 /boot/config.txt file - no change.


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Re: audio issue - HDMI tv [ In reply to ]
---- On Mon, 26 Mar 2018 12:36:07 +0100 John Pilkington <J.Pilk@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.


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Re: audio issue - HDMI tv [ In reply to ]
On Mon, Mar 26, 2018, 8:17 AM Tim Draper <veehexx@zoho.com> wrote:

> ---- On Mon, 26 Mar 2018 12:36:07 +0100 John Pilkington <J.Pilk@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.
>
>
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Are you set up for simultaneous output to HDMI and line out?

>
>
Re: audio issue - HDMI tv [ In reply to ]
---- On Mon, 26 Mar 2018 16:08:35 +0100 Mike Carron <jmcarron@gmx.com> wrote ----
> This sounds like a classic case of a ground loop. Resolve it and the noise should disappear.
> mike
>

Looks like you might be right. tried using my laptop with DP>HDMI adapter and the same problem occurs.
Touch the ground of HDMI cable to any metal part of the TV and the sound occurs so definitely ground induced.

what options do i have to fix it? seems like internal TV issue and not fussed enough to resolve the issue to go buy a new one. Can i simply run a wire from a ground point down to the mains socket earth pin (3pin UK; green/yellow)?

mains connection is 2way wall socket > with 1 of the sockets to a 6way extension. all the kit connects to the 6way; tv, amp, rpi, laptop etc.
could a faulty mains socket cause this, or is it device issue?

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Re: audio issue - HDMI tv [ In reply to ]
> On Mar 30, 2018, at 10:38 AM, Tim Draper <veehexx@zoho.com> wrote:
>
> ---- On Mon, 26 Mar 2018 16:08:35 +0100 Mike Carron <jmcarron@gmx.com> wrote ----
>> This sounds like a classic case of a ground loop. Resolve it and the noise should disappear.
>> mike
>>
>
> Looks like you might be right. tried using my laptop with DP>HDMI adapter and the same problem occurs.
> Touch the ground of HDMI cable to any metal part of the TV and the sound occurs so definitely ground induced.
>
> what options do i have to fix it? seems like internal TV issue and not fussed enough to resolve the issue to go buy a new one. Can i simply run a wire from a ground point down to the mains socket earth pin (3pin UK; green/yellow)?
>
> mains connection is 2way wall socket > with 1 of the sockets to a 6way extension. all the kit connects to the 6way; tv, amp, rpi, laptop etc.
> could a faulty mains socket cause this, or is it device issue?
>
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There are several of these available, and I know there are some available with RCA ends on them because we used them occasionally in car audio applications.

It’s an unfortunate thing when different equipment (and, in this case, I’ll blame the Lepy amp) decide on how they will implement chassis ground differently, and that’s the case here. We don’t hear of TVs and home receivers having issue, so I’m going to blame the Lepy amp for sure. However, an isolator like this should do the trick.

It’s a cheap trial if it doesn’t work, anyway. Good luck!


https://www.amazon.com/Mpow-Ground-Isolator-Stereo-System/dp/B019393MV2/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1522434713&sr=1-1-spons&keywords=ground+loop+isolator&psc=1 <https://www.amazon.com/Mpow-Ground-Isolator-Stereo-System/dp/B019393MV2/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1522434713&sr=1-1-spons&keywords=ground+loop+isolator&psc=1>

Mike
Re: audio issue - HDMI tv [ In reply to ]
Tim Draper <veehexx@zoho.com> wrote:

> Touch the ground of HDMI cable to any metal part of the TV and the sound occurs so definitely ground induced.
>
> what options do i have to fix it? seems like internal TV issue and not fussed enough to resolve the issue to go buy a new one. Can i simply run a wire from a ground point down to the mains socket earth pin (3pin UK; green/yellow)?
>
> mains connection is 2way wall socket > with 1 of the sockets to a 6way extension. all the kit connects to the 6way; tv, amp, rpi, laptop etc.
> could a faulty mains socket cause this, or is it device issue?

Is the noise a low frequency (50Hz) hum ? Which devices have 2 pin (or core) mains and which have 3 pin (or core) ?

Lots of kit only has a 2 wire mains connection - and hence no earth connection. The input filters typically are two capacitors connected L-chassis and N-chassis, which with an unearthed chassis means a potential divider pulling the chassis to half the mains voltage !
Thus it's easy to end up with units earthed through the connecting leads, with obvious problems.

Connecting the chassis of each unit to the same earth as they are plugged into should deal with that - and it's a cheap thing to test.

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Re: audio issue - HDMI tv [ In reply to ]
---- On Fri, 30 Mar 2018 19:35:21 +0100 Michael A Weber <mweberjunk01@gmail.com> wrote ----
>
> On Mar 30, 2018, at 10:38 AM, Tim Draper <veehexx@zoho.com> wrote:
> ---- On Mon, 26 Mar 2018 16:08:35 +0100 Mike Carron <jmcarron@gmx.com> wrote ----
> This sounds like a classic case of a ground loop. Resolve it and the noise should disappear.
> mike
>
>
> Looks like you might be right. tried using my laptop with DP>HDMI adapter and the same problem occurs.
> Touch the ground of HDMI cable to any metal part of the TV and the sound occurs so definitely ground induced.
>
> what options do i have to fix it? seems like internal TV issue and not fussed enough to resolve the issue to go buy a new one. Can i simply run a wire from a ground point down to the mains socket earth pin (3pin UK; green/yellow)?
>
> mains connection is 2way wall socket > with 1 of the sockets to a 6way extension. all the kit connects to the 6way; tv, amp, rpi, laptop etc.
> could a faulty mains socket cause this, or is it device issue?
>
> _______________________________________________
> mythtv-users mailing list
> mythtv-users@mythtv.org
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> http://wiki.mythtv.org/Mailing_List_etiquette
> MythTV Forums: https://forum.mythtv.org
>
>
> There are several of these available, and I know there are some available with RCA ends on them because we used them occasionally in car audio applications.
> It’s an unfortunate thing when different equipment (and, in this case, I’ll blame the Lepy amp) decide on how they will implement chassis ground differently, and that’s the case here. We don’t hear of TVs and home receivers having issue, so I’m going to blame the Lepy amp for sure. However, an isolator like this should do the trick.
> It’s a cheap trial if it doesn’t work, anyway. Good luck!
>
> https://www.amazon.com/Mpow-Ground-Isolator-Stereo-System/dp/B019393MV2/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1522434713&sr=1-1-spons&keywords=ground+loop+isolator&psc=1
> Mike

i was actually looking at something like that last night. My experience of isolators in car applications haven't been worth squat however. My dad thought about an optical to RCA DAC. It'll definitely isolate.


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Re: audio issue - HDMI tv [ In reply to ]
---- On Fri, 30 Mar 2018 20:33:33 +0100 Simon Hobson <linux@thehobsons.co.uk> wrote ----
> Tim Draper <veehexx@zoho.com> wrote:
>
> > Touch the ground of HDMI cable to any metal part of the TV and the sound occurs so definitely ground induced.
> >
> > what options do i have to fix it? seems like internal TV issue and not fussed enough to resolve the issue to go buy a new one. Can i simply run a wire from a ground point down to the mains socket earth pin (3pin UK; green/yellow)?
> >
> > mains connection is 2way wall socket > with 1 of the sockets to a 6way extension. all the kit connects to the 6way; tv, amp, rpi, laptop etc.
> > could a faulty mains socket cause this, or is it device issue?
>
> Is the noise a low frequency (50Hz) hum ? Which devices have 2 pin (or core) mains and which have 3 pin (or core) ?
>

theres actually no hum. the Lepy amp clicks (sounds like a pair of relays clicking inside) every second or so and sounds very similar to power-on speaker thump. Only does it when HDMI is connected to the TV *AND* 3.5mm/RCA connection to the amp. can touch the metal casing of the HDMI connector to any metal part of the TV and it'll make the noise. I even get a small arc on either the HDMI > TV casing metal or on the sound cards USB cable ground into the rpi too so obviously a volt difference is present somewhere; thus ground loop issue.
works fine if i only have 3.5mm/RCA to the amp and far more of a typical setup for 99% of users, so i think it's working correctly in terms of product design.

> Lots of kit only has a 2 wire mains connection - and hence no earth connection. The input filters typically are two capacitors connected L-chassis and N-chassis, which with an unearthed chassis means a potential divider pulling the chassis to half the mains voltage !
> Thus it's easy to end up with units earthed through the connecting leads, with obvious problems.
>

Most likely the lepy amp (someone else in the thread mentioned they thought it was that) as all other cables are 3pin. Lepy amp external PSU is L&N with full plastic earth pin.
iirc i tried swapping the lepy amp with headphones and didnt get any undesirable issues so i'd go with the TV ground is ok and the issue is on the amp side. isolating the audio line (optical is my preferred method due to car-audio RCA isolator experiences) seems like the way to definitely resolve the issue.


> Connecting the chassis of each unit to the same earth as they are plugged into should deal with that - and it's a cheap thing to test.



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Re: audio issue - HDMI tv [ In reply to ]
On 03/04/18 08:41, Tim Draper wrote:
> ---- On Fri, 30 Mar 2018 20:33:33 +0100 Simon Hobson <linux@thehobsons.co.uk> wrote ----
> > Tim Draper <veehexx@zoho.com> wrote:
> >
> > > Touch the ground of HDMI cable to any metal part of the TV and the sound occurs so definitely ground induced.
> > >
> > > what options do i have to fix it? seems like internal TV issue and not fussed enough to resolve the issue to go buy a new one. Can i simply run a wire from a ground point down to the mains socket earth pin (3pin UK; green/yellow)?
> > >
> > > mains connection is 2way wall socket > with 1 of the sockets to a 6way extension. all the kit connects to the 6way; tv, amp, rpi, laptop etc.
> > > could a faulty mains socket cause this, or is it device issue?
> >
> > Is the noise a low frequency (50Hz) hum ? Which devices have 2 pin (or core) mains and which have 3 pin (or core) ?
> >
>
> theres actually no hum. the Lepy amp clicks (sounds like a pair of relays clicking inside) every second or so and sounds very similar to power-on speaker thump. Only does it when HDMI is connected to the TV *AND* 3.5mm/RCA connection to the amp. can touch the metal casing of the HDMI connector to any metal part of the TV and it'll make the noise. I even get a small arc on either the HDMI > TV casing metal or on the sound cards USB cable ground into the rpi too so obviously a volt difference is present somewhere; thus ground loop issue.
> works fine if i only have 3.5mm/RCA to the amp and far more of a typical setup for 99% of users, so i think it's working correctly in terms of product design.
>
>> Lots of kit only has a 2 wire mains connection - and hence no earth connection. The input filters typically are two capacitors connected L-chassis and N-chassis, which with an unearthed chassis means a potential divider pulling the chassis to half the mains voltage !
> > Thus it's easy to end up with units earthed through the connecting leads, with obvious problems.
> >
>
> Most likely the lepy amp (someone else in the thread mentioned they thought it was that) as all other cables are 3pin. Lepy amp external PSU is L&N with full plastic earth pin.
> iirc i tried swapping the lepy amp with headphones and didnt get any undesirable issues so i'd go with the TV ground is ok and the issue is on the amp side. isolating the audio line (optical is my preferred method due to car-audio RCA isolator experiences) seems like the way to definitely resolve the issue.
>
>
> > Connecting the chassis of each unit to the same earth as they are plugged into should deal with that - and it's a cheap thing to test.

This is getting to sound either expensive, dangerous or both. The
classical ground-loop was a millivolt-level thing. Here you appear to
have several DC power supplies, probably with 2-core mains leads, with
at least two having some sort of leakage (maybe capacitative) to the
live pin. I would perhaps put your amp psu as the chief suspect. Be
careful.

Of course an optical coupling would be a 'modern' solution to a hum
problem, but that doesn't really fit your descriptions.

John


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