Front channels (CH1, CH2) not working

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Front channels (CH1, CH2) not working

Post by bartl » Thu Nov 02, 2017 9:19 am

Hi I have set up the octo sound card so far. I am running libreelec in the newest version. The audio configuration is available in kodi - (2.0 <-> 7.1).

My problem is, that CH1 and CH2 is not working. I have only sound on CH 3, 4, 5, 6 (rear, center and sub woofer). Both front channels have only a very low static noice. (I also think, that ch7 and 8 are not working / muted as well - I have checked with a headphone - no output.)

Any idea how to debug this issue or how to unmute ch1 and 2?

Best regards


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Joined: Thu Nov 02, 2017 8:48 am

Re: Front channels (CH1, CH2) not working

Post by bartl » Fri Nov 03, 2017 4:35 am

I have figured out some further details. Contraire to my previous thoughts channel 7 and 8 are doing fine (I have only the misplaced resistor issue with channel 8).
I have chosen a stereo source and switched on the up-mix feature (then all channels are playing stereo sound). Here channels 3,4,7,8 are playing fine. Channels 1 and 2 (front) are not working.

Any hints where to look and which settings to check? Thanks for any ideas to help me out with my problem.

(A workaround idea: perhaps I can reconfigure channel 7 and 8 to be the front channels? How to proceed here?)

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Joined: Thu Nov 02, 2017 8:48 am

Re: Front channels (CH1, CH2) not working

Post by bartl » Sat Nov 04, 2017 3:28 am

After some further internet research and try&error testing I now believe, that my audio injector octo is faulty.

What I have done:
I have used the speaker-test -c 8 command to play a sample sound on each channel seqentally. Each time channel 1 or channel 2, default configuration of Front Left and Front Right, have been triggered no sound output was available. All other channels have played the sound correctly.
Afterwards I have reconfigured the Front Left and Front Right to be channel 7 and 8 (see below). I now can play sound from the front channels but no sound was played on channel 1 and 2 being now the Rear Left and Rear Right in my 7.1 test setup.

Reconfiguring the channel is a quite simple task (after figuring it out) in libreelec:
Just place a file asound.conf into the /storage/.config directory. (As a template just take that one form the topic)

Then just change there the channel definition, I have currently the following:

Code: Select all

ttable {
           0.6 1
           1.7 1
           2.2 1
           3.3 1
           4.4 1
           5.5 1
           6.0 1
           7.1 1
My question now: How can I debug/test where the failure with my audio injector octo is. Perhaps it is a misplaced component or a broken wire.
At first I would like to figure out if the problem is on the sound board or on my breakout board.

Please advice.

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Joined: Sat Jul 23, 2016 11:39 pm

Re: Front channels (CH1, CH2) not working

Post by flatmax » Sat Nov 04, 2017 9:16 pm

Hi there,

In the first iterations of these breakout boards there was an assembly error which makes one of the channels very low in level, check here : ... 3080#p5206

Your problem however is different I Think because you have two channels which aren't working.
Can you eyeball the breakout board and see any problems ?

Do you have an oscilloscope ? Can you play audio out and measure the pins on the output header of the sound card ?

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Check out our new forum on github :

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Joined: Thu Nov 02, 2017 8:48 am

Re: Front channels (CH1, CH2) not working

Post by bartl » Tue Nov 07, 2017 6:19 am

will try (my dad has the equipment, but it take some time - I have to visit him (170km away))

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