[Voyage-linux] Cubieboard 2 and MPD, (and NO external DAC)

[Joseph Chu]

Hello Patrick,
thanks your findings, i am little bit worry about high frequency burst
noise as i think it could jam the digital usb signal to dac.
could you try to measure the usb bus signal and check the interference
inside. preferably measure at the dac end.
Joseph


On 1 December 2013 00:27, superpat <patrick at byeslane.org.uk> wrote:

> Hi,
>
> As promised I tried 'scoping my Cubieboard 2 running MPD today. This is the
> frst time I have tried to 'scope a SOC board.
>
> No matter how and where I grounded my 'scope probes, I was unable to
> measure
> the noise on the analogue output stereo connector, because the whole area
> of
> the Cubieboard was swamped with bursts of HF switching noise, generated by
> the Cubieboard itself.  The noise was present when the Cubieboard was
> running, but the MPD app was not started.
>
> I even tried floating the 'scope and using two probes in differential mode,
> one to the ground plane, the other to audio signal, but I was still swamped
> by the HF clock noise of the A20, I think being picked up in the high
> impedance 'scope leads.
>
> I have NO idea how to achieve meaning full measurements of the noise floor
> for the ADC and audio output stages!
>
> All I can say it is a bl**dy wonder that MPD works as well as it does in
> that sea of noise, Power supply noise is minor compared with the SOC
> electrical noise.
>
> I will try to find the proper method of 'scoping SOC  boards, the
> literature
> must be out there somewhere.
>
> cheers
>
> Patrick
>
>
>
> --
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> Sent from the Voyage Linux mailing list archive at Nabble.com.
>
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