How iZotope SRC Advanced Parameters in Audirvana+ affect playback of non-resampled and resampled PCM and DSD-to-PCM

[ToTo Man]

I've read the A+ user manual and several forum threads but I am still confused about how the iZotope SRC Advanced Parameters in Audirvana+ affects playback of straight PCM (non-resampled and resampled) and DSD-to-PCM conversions.

 

I have a Schiit Uber Bifrost USB DAC which natively accepts 44.1kHz, 88.2kHz, 96kHz, 176.4kHz and 192kHz PCM without applying internal non-integer sample rate conversion. This is what attracted me to this DAC, - I wanted a DAC that did not resample everything to 192kHz.

 

When I play music on A+, the display says INT and the displayed bit depth and sample rate matches that of the music I'm playing. I am therefore assuming that A+ is sending music to my DAC at the music's native sample rate, but I cannot verify this because my DAC does not have a sample rate indicator.

 

1) So my first question is how do I make sure A+ sends music to my DAC without any software sample rate conversion or other processing? Am I correct that all I have to do is make sure that 'Forced Upsampling' in the Audio Filter preferences is set to 'None', and that by doing this the 'Advanced Parameters' sliders have no effect?

 

2) What happens if I select 'Custom Upsampling' and make all the DAC sample rates the same as the native sample rates EXCEPT for 352.8KHz and 384kHz, which I choose to downsample to 174.6kHz and 192kHz? Does this mean the sample rate conversion parameters are only activated for these two sample rates, or do they become activated for all?

 

3) I am aware that DSD has a lot of HF noise that steadily rises above 40kHz. What is the most desirable method to remove this noise when playing DSD music via on-the-fly DSD-to-PCM conversion? Am I correct in thinking that the simplest method is to select '352.8kHz -> 88.2kHz' downsampling in the 'Custom Upsampling' settings, which I assume applies brickwall low-pass filtering at 44.1kHz. Or is it preferable to downsample to a higher frequency (e.g. 176.4kHz) and use the advanced parameter sliders to tweak the filtering?

 

4) When playing DSD music with on-the-fly DSD-to-PCM conversion, are the sample rate conversion advanced parameters always available, or does it depend on which DSD-to-PCM algorithm is chosen? And which algorithm is the preferred choice, e.g. Simple Decimation, Integer Multistage, 32bit Multistage, or 64bit Multistage?

 

5) If I add a DSD DAC and instruct A+ to use 'DSD over PCM standard 1.0', does this bypass all of the sample rate conversion advanced parameters referenced above?

 

Apologies for so many questions, - I'm just trying to get my head around it all!...

[ToTo Man]

275 views and no replies… was it something I said??!!

[wgscott]

1) So my first question is how do I make sure A+ sends music to my DAC without any software sample rate conversion or other processing? Am I correct that all I have to do is make sure that 'Forced Upsampling' in the Audio Filter preferences is set to 'None',

 

Yes

 

and that by doing this the 'Advanced Parameters' sliders have no effect?

 

I'm not sure they are dependent upon up-sampling.

 

2) What happens if I select 'Custom Upsampling' and make all the DAC sample rates the same as the native sample rates EXCEPT for 352.8KHz and 384kHz, which I choose to downsample to 174.6kHz and 192kHz? Does this mean the sample rate conversion parameters are only activated for these two sample rates, or do they become activated for all?

 

The only ones that are turned on are those where the numbers are not identical.

 

3) I am aware that DSD has a lot of HF noise that steadily rises above 40kHz. What is the most desirable method to remove this noise when playing DSD music via on-the-fly DSD-to-PCM conversion? Am I correct in thinking that the simplest method is to select '352.8kHz -> 88.2kHz' downsampling in the 'Custom Upsampling' settings, which I assume applies brickwall low-pass filtering at 44.1kHz. Or is it preferable to downsample to a higher frequency (e.g. 176.4kHz) and use the advanced parameter sliders to tweak the filtering?

I personally would sample to 88.2 kHz. But it is a judgement call.

 

4) When playing DSD music with on-the-fly DSD-to-PCM conversion, are the sample rate conversion advanced parameters always available, or does it depend on which DSD-to-PCM algorithm is chosen? And which algorithm is the preferred choice, e.g. Simple Decimation, Integer Multistage, 32bit Multistage, or 64bit Multistage?

 

Beats me.

 

5) If I add a DSD DAC and instruct A+ to use 'DSD over PCM standard 1.0', does this bypass all of the sample rate conversion advanced parameters referenced above?

 

Apologies for so many questions, - I'm just trying to get my head around it all!...

 

Durned if I know.

[wgscott]

275 views and no replies… was it something I said??!!

 

I think the only one who can answer your questions decisively is Damien.

[miguelito]

1) So my first question is how do I make sure A+ sends music to my DAC without any software sample rate conversion or other processing?

Audio Midi app (in Utilities folder).

 

2) What happens if I select 'Custom Upsampling' and make all the DAC sample rates the same as the native sample rates EXCEPT for 352.8KHz and 384kHz, which I choose to downsample to 174.6kHz and 192kHz? Does this mean the sample rate conversion parameters are only activated for these two sample rates, or do they become activated for all?

I doubt that the bitstream will be touched if the sample rate is the same as the source file, but of course I don't know. Should ask that question to Damien on the Audirvana forums.

 

5) If I add a DSD DAC and instruct A+ to use 'DSD over PCM standard 1.0', does this bypass all of the sample rate conversion advanced parameters referenced above?

I believe so. The point is to pass the DSD bitstream untouched. If the DSD bitstream bandwidth is not supported by your device (eg DSD128 sent to a DSD64 device) I would expect that PCM will be sent instead.

 

Mig

[Jud]

Your premise may be flawed (that the DAC's upsampling will sound better than allowing Audirvana Plus to handle the portion up to 176.4/192). Try it both ways - allowing the DAC to handle all upsampling, and allowing Audirvana Plus to handle part of it. See what you prefer.

[ToTo Man]

Yes

 

 

 

I'm not sure they are dependent upon up-sampling.

 

 

 

The only ones that are turned on are those where the numbers are not identical.

 

I personally would sample to 88.2 kHz. But it is a judgement call.

 

 

 

Beats me.

 

 

 

Durned if I know.

 

Audio Midi app (in Utilities folder).

 

 

I doubt that the bitstream will be touched if the sample rate is the same as the source file, but of course I don't know. Should ask that question to Damien on the Audirvana forums.

 

 

I believe so. The point is to pass the DSD bitstream untouched. If the DSD bitstream bandwidth is not supported by your device (eg DSD128 sent to a DSD64 device) I would expect that PCM will be sent instead.

 

Mig

 

Thanks!

[isquirrel]

Interestingly I have been messing around with the settings with up sampling set to zero, so it would be great to get clarification from Damien on the points raised as the user manual is not clear on this.

[goldsdad]

Interestingly I have been messing around with the settings with up sampling set to zero, so it would be great to get clarification from Damien on the points raised as the user manual is not clear on this.

 

Are you hearing differences between various iZotope parameters when upsampling is set to none?

[isquirrel]

I don't think so

[goldsdad]

I don't think so

 

Good.

[Jud]

Good.

 

Remember, it's no *forced* SRC, so there can still be sample rate conversion if the original rate can't be played by the DAC.

 

 

Sent from my iPhone using Tapatalk

[goldsdad]

Remember, it's no *forced* SRC, so there can still be sample rate conversion if the original rate can't be played by the DAC.

 

Yes, and I intended to ask isquirrel about the specific circumstances if he had replied affirmatively to my question.