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TOPIC: Asyncronuous sampling with ddrc88d and nanAVR's

Asyncronuous sampling with ddrc88d and nanAVR's 5 months 1 week ago #43919

  • jvdh1978
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Dear MiniDSP,

As a complete hobbyist I own nanoAVR HD, nanoAVR Dirac and the DDRC 88d. I have a full digital path from source through the DDRC to a 4.1 speakerset and use the internal DA converters of the speakers (B&O beolabs 17, 18 and 19 LFE). I use a modified OPPO player as decoder with 7.1 digital out and several signal converters (as B&O speakers are quite picky on their SPDIF signal format). So a lot of boxes and wires. As a purist (and someone with quite some experience in signal processing) I found out that a possible source of disturbance could be 2 many asynchronous sampling steps so I would like to find out if my setup has this and if I can minimize this.

I noticed that 99% of current hometheater content has 48kHz sampling. It is stated in the miniDSP specs that the products I own process internally at 48 kHz or for the nanoAVR HD at 96 kHz, so resampling could theoretically be avoided for this content. The DDRC manual specifically mentions asynchronous sampling at the IO, while the website says matched processing frequency. My question on the DDRC and the nanoAVR's is: When a 48kHz signal is on the input, what happen with the sampling and clock? Is that signal resampled and process at a 48kHz internal clock and is there then still some resampling of the signal? Or is the processing clock synced (or simply at a different frequency) with external the 48kHz signal so that no asynchronous resampling is used (keeping the signal as pure as possible)? In other words, when all filters are off and output volume is set to 0dB, will a 48kHz input signal be copied 100% bitperfect to the output?

Kind Regards

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Asyncronuous sampling with ddrc88d and nanAVR's 4 months 3 weeks ago #44181

  • devteam
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For a complete Hobbyist, that's quite an advanced setup that you have here!! :-)
We'd love to see some pics of your that install. :-)

With regards to your question, if the incoming clock is 48k, the ASRC will indeed lock to that clock and use it as reference.
I.e. you don't have to worry about conversion (even if our ASRC are running at 130dB SNR. :-)

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