DSD low pass filter needed for transfer to PCM

[Gazjam]

Converting a bunch of DSD to 24/176 PCM, I know a low pass filter is required, usually around 30K or so, but I'm wondering if my DAC has a hardware low pass filter built in, I know the DSD dacs do and my Young was a pretty advanced bit of digital kit when it came out?
Probably not, but curious.

If so, would save me applying the filter in software, potentially keeping the DSD file as intact as possible before hitting my dac.

Maybe Keith (Young dealer) can comment, forgot his Username on here or I'd PM him. :)


Thanks.

[Stratmangler]

Maybe Keith (Young dealer) can comment, forgot his Username on here or I'd PM him. :)


Thanks.

http://www.puriteaudio.co.uk/

[Gazjam]

That's the one, cheers Chris. :)

[Gazjam]

Big thanks to Keith for asking my question directly to M2Tech.
He emailed back within a couple of hours, great customer service from him.

As it turn out the original Young dac HAS the low pass filter, meaning I can send the converted DSD "untouched" to the Dac, apart from adding 6db of gain.
Keeping bitdepth the same so not applying dither.

One less stage of processing done to the original file, always good news. :)

[Audio Advent]

I'm confused about this... Isn't the filter an automatic part of the conversion process? This for example shows that the filter is applied by the software: http://archimago.blogspot.co.uk/2015/04/analysis-dsd-decoders-2015-windows-mac.html Unless you can turn the filter off during the process it's going to be double filtered (that's fine with some beer..)

Are you therefore turning off the filter in the conversion process somehow and then thinking that the on-the-fly filter in the dac applied to PCM is going be better? Will the DAC be applying the filter on PCM? Surely it will only apply a filter applicable to DSD noise to a DSD signal?

PCM requires it's own filters and for 176.4 won't the filter applied by the Young DAC be much higher than that needed by DSD and therefore a lot of noise will still be there above 20Khz up until the PCM 176.4 filter kicks in? Or have you been told that the Young dac applies the very same 30K filter for all PCM and DSD alike?

I'm sure you know what you're doing, just I'm not quite understanding it....

[StanleyB]

I am still confused about why so much filtering needs to be applied, since incorrect filtering can adversely affect the sound. Anyhow, the noise level above 20kHz will probably be less than -100dB in a good design.

[Gazjam]

Hiya Sam.

I had a lot of stuff to convert so I spent a bit of time listening to different files created to get what I thought sounded best to me.
Looked at a few variables: Different combinations of low pass filters switched on and off applied by different software, which method of dither (and does it improve things?)...all that jazz.

Hear what your saying about >20K noise being present.
I contacted M2Tech and looked into the Youngs filters for DSD and PCM, and was told the low pass filter was built into the Young.
Its not the DSD dac I have but was still told the filter was there.

In all this, the final arbiter of what was "best practice" when starting the conversion process was sitting down and listening. :)
Turned out (to my ears) that applying the low pass filter in software robbed the music of some of its "air" and sounded better without the filter applied at all.
Bit of a knock on effect though..some albums mastered "hot" on DSD led to some clipping when I applied the 6dB gain when converting to FLAC.
Discovered this early on though, so knocked back the gain a couple of points which took care of it.

You can switch the filter off in Jriver's DSD plugin when converting, which is what I did before converting to 24/176 FLAC in another program which I found did a better job than Jriver.

Then the tagging nightmare begins, be happy when all the music is converted, its all backed up and I can call it done.







I'm confused about this... Isn't the filter an automatic part of the conversion process? This for example shows that the filter is applied by the software: http://archimago.blogspot.co.uk/2015/04/analysis-dsd-decoders-2015-windows-mac.html Unless you can turn the filter off during the process it's going to be double filtered (that's fine with some beer..)

Are you therefore turning off the filter in the conversion process somehow and then thinking that the on-the-fly filter in the dac applied to PCM is going be better? Will the DAC be applying the filter on PCM? Surely it will only apply a filter applicable to DSD noise to a DSD signal?

PCM requires it's own filters and for 176.4 won't the filter applied by the Young DAC be much higher than that needed by DSD and therefore a lot of noise will still be there above 20Khz up until the PCM 176.4 filter kicks in? Or have you been told that the Young dac applies the very same 30K filter for all PCM and DSD alike?

I'm sure you know what you're doing, just I'm not quite understanding it....

[Audio Advent]

I am still confused about why so much filtering needs to be applied, since incorrect filtering can adversely affect the sound. Anyhow, the noise level above 20kHz will probably be less than -100dB in a good design.

Kind of.. For DSD64, noise level keeps increasing and can reach -70/-60dB at about 80kHz but under 30kHz yes is more than -100dB down. So I guess you have to filter or risk those very high frequencies interfering with electronics further up the chain. That for a 1Khz tone at -60dB.

I'd say that Grimm AD1 DSD A/D converter is probably a good design and that's their noise component - it's inherent to DSD.

But manufacturers are often a little afraid of being ridiculed or maybe are technical zealots themselves and so will insist that there MUST be a filter involved to make their design correct whether it sounds good or not.

[Audio Advent]

Hiya Sam.

I had a lot of stuff to convert so I spent a bit of time listening to different files created to get what I thought sounded best to me.
Looked at a few variables: Different combinations of low pass filters switched on and off applied by different software, which method of dither (and does it improve things?)...all that jazz.

Hear what your saying about >20K noise being present.
I contacted M2Tech and looked into the Youngs filters for DSD and PCM, and was told the low pass filter was built into the Young.
Its not the DSD dac I have but was still told the filter was there.

In all this, the final arbiter of what was "best practice" when starting the conversion process was sitting down and listening. :)
Turned out (to my ears) that applying the low pass filter in software robbed the music of some of its "air" and sounded better without the filter applied at all.
Bit of a knock on effect though..some albums mastered "hot" on DSD led to some clipping when I applied the 6dB gain when converting to FLAC.
Discovered this early on though, so knocked back the gain a couple of points which took care of it.

You can switch the filter off in Jriver's DSD plugin when converting, which is what I did before converting to 24/176 FLAC in another program which I found did a better job than Jriver.

Then the tagging nightmare begins, be happy when all the music is converted, its all backed up and I can call it done.

I wonder how steep their filter is and where it sits. With high rez PCM there shouldn't be much noise (unless converting DSD) and so for 176.4 for example you can get away with a shallow filter a fair bit below the half way point and still filter out the images without the ringing of brickwall filters. So if the low-pass filter you're relying on is that for 176.4 then I'd think you will still be getting a lot of DSD noise from 24Khz onwards which is now not filtered out.

But if it sounds ok, that's what matters as a lot of that noise will be very low level anyway as Stan says - sounds like that's where you've tested things.