Author Topic: DSD to PCM Conversion - roll off filter  (Read 5057 times)

dtc

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DSD to PCM Conversion - roll off filter
« on: November 07, 2014, 10:46:26 pm »
I am converting from 5.6 MHz DSD to 192K PCM. In some software there are options to apply optional roll off filters to remove high frequency noise.  Does VS apply such a filter? If so, what are its characteristics? Does it vary by PCM output sampling rate?

Thanks.

Tom

Paul Sanders (AlpineSoft)

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Re: DSD to PCM Conversion - roll off filter
« Reply #1 on: November 07, 2014, 10:50:45 pm »
Hi,

It rolls off at 48 kHz for DSD standard rate and 96 kHz for DSD double rate.  Any higher and you get a lot of noise in the converted signal.

dtc

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Re: DSD to PCM Conversion - roll off filter
« Reply #2 on: November 07, 2014, 10:59:41 pm »
So basically at the Nyquist frequency for the sample rate,  If I am going form2xDSD to 192K sample rate, it starts rolling off at 96 KHz.    What is the roll off rate, just for curiosity.

Paul Sanders (AlpineSoft)

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Re: DSD to PCM Conversion - roll off filter
« Reply #3 on: November 07, 2014, 11:03:47 pm »
It's pretty steep.  I'm not sure exactly what it equates to but we use a 96 pole FIR filter which was designed to have a reasonably sharp cutoff with good rejection above the cutoff frequency.

dtc

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Re: DSD to PCM Conversion - roll off filter
« Reply #4 on: November 07, 2014, 11:14:06 pm »
Thanks. Clearly I am not going to hear anything above that :)