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Author Topic: DSD Low pass filter in DOP?  (Read 977 times)

xexets

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DSD Low pass filter in DOP?
« on: May 17, 2020, 10:03:53 am »
Just a quick question: I understand that a low pass filter is needed when converting DSD to PCM, but do I also need it when I send DSD to the dac via DOP? DOP is not a conversion, it's DSD signal incapsulated into a PCM signal, so while the driver reports a 176khz PCM signal being sent the DAC reports correctly a DSD native 2.8000khz signal. So technically I wonder if I really need the low pass filter in case of DOP.

EDIT: Even though JRiver warns that it might damage the equipment I have been using DSD via DOP-WASAPI without low pass filter for a couple of days now and I cannot notice the difference. Should I hear more noise?
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Awesome Donkey

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Re: DSD Low pass filter in DOP?
« Reply #1 on: May 17, 2020, 10:08:18 am »
No, when bitstreaming DSD via DoP (or native DSD for that matter) you don't need a lowpass filter as it's only needed for the high-frequency noise when converting DSD to PCM. In fact, when bitstreaming is enabled all DSP is bypassed so you couldn't use a lowpass filter in MC even if you wanted to while DSD bitstreaming. ;)

That equipment damage warning is only when doing a DSD to PCM conversion without using a lowpass filter (which the high-frequency noise after the DSD to PCM conversion *could* damage some sensitive equipment if not filtered out). DoP IS NOT a DSD to PCM conversion, so you don't have to worry.

P.S. There was a bug in recent MC26 builds that erroneously reported that the lowpass filter was enabled when DSD bitstreaming (when it actually wasn't), this has been corrected so if you're seeing that make sure you're using the latest MC26 build which right now is 26.0.80.
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xexets

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Re: DSD Low pass filter in DOP?
« Reply #2 on: May 17, 2020, 10:49:51 am »
There you go! The bug coincided to my swapping WASAPI and ASIO and since before I did not see the low pass filter enabled I thought that WASAPI introduced it for the DOP, instead it's a bug! Thanks for clarifying
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dtc

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Re: DSD Low pass filter in DOP?
« Reply #3 on: May 17, 2020, 12:13:48 pm »
Yes, a bug in what Audio Path was reporting. Nothing changed in the actual processing. The data was always being bit-streamed without modification
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