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Can I bypass the DAC oversamplingfilter? 1 month 4 weeks ago #63088

  • asx77
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Great - thanks a lot 

This is really appreciated, I also contacted the MiniDSP development team. And they kindly explained how the ASR graphs are wrong, like it is explained in this thread.

Best regards
Alfegutt:-)


@alfegutt
Did support explain how ASR came to get it wrong? As @mdsimon suggests, did they say it was the source ASR was using? Presumably set up to send a signal with a brick wall filter on it. Always thought Amir was pretty thorough. Goes to show everyone makes mistakes. 
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Last edit: by asx77.

Can I bypass the DAC oversamplingfilter? 1 month 3 weeks ago #63098

  • alfegutt
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The full answer from the development team is attached below:
"
a) That ASR measurement was actually an artifact. The 2x4HD will "always" process at 96kHz. It will always roll off at 48kHz (i.e. nyquist). We had chatted with Amir back then about this. He didn't have the platform. That was more than 4years ago (older measurement AP). 
b) So to answer your question, the 2x4HD will indeed use the DAC brickwall filter since it's running at 96kHz. "

However, as shown by @mdsimon2, the filter seems to be steeper when feed an 192 kHz signal (filter at 48 kHz) compared to feeding 44 kHz (filter at 20 kHz), is that correctly spotted or is it just that the scales on the graphs trick me?
 
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Can I bypass the DAC oversamplingfilter? 1 month 3 weeks ago #63103

  • mdsimon2
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IMO the apparent steepness of my 192 kHz input measurement is the log frequency scale. Here is the same 192 kHz white noise input measurement using a linear scale like the 44.1 kHz measurement. This probably gives the best characterization of the bandwidth of the 2x4HD and what the combined ASRC / DAC reconstruction filter looks like.

 

Also, the reason my previous 192 kHz measurement was "fuzzy" was I was overloading the filter with too high of level. This measurement is done at an appropriate level to show the true response of the filter.

Michael
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Last edit: by mdsimon2.
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