I suppose another question is does the sample rate conversion happen through the Interface and interface drivers or does it happen independently within Sonar? If Sonar depends on the interface, we may all get different answers as to whether a filter is applied and how the filter is applied.

Heck plugins upsample and downsample. Its called oversampling and I doubt dither is used for that. All high sample rates do is increase bandwidth.  

The filtering you are asking about is already an intrinsic part of any competent SRC (Sample Rate Conversion) process, and Sonar's is quite competent. So there is no need to do it manually as it is already being done.
 
 
And dither has absolutely nothing to do with sample rate reduction - it is used when reducing bit depth.

drewfx1
The filtering you are asking about is already an intrinsic part of any competent SRC (Sample Rate Conversion) process, and Sonar's is quite competent. So there is no need to do it manually as it is already being done.
 
And dither has absolutely nothing to do with sample rate reduction - it is used when reducing bit depth.

 
+1. This is my understanding also on both counts.

mudgel
Whenever you reduce sampling rate you should be dithering

I'm sorry to say I wrote this in error. I typed up some info then copied n pasted the wrong part. Didn't realise till later when other comments made. Don't want to correct the post because others have since commented on it.
Dither when reducing bit depth not sample rate is what I should have said.

If final target output sampling rate is 44.1kHz (for CD Audio), then it is better to record/mix at 88.2 or 176.4 (if available) rather than at 96 or 192, as this simplifies SRC processing and can yield better results.

Also, if source audio is 24-bit, then enable the 64-bit DPE when performing SRC to avoid audible artifacts due to insufficient precision in filtering DSP employed.

drewfx1
The filtering you are asking about is already an intrinsic part of any competent SRC (Sample Rate Conversion) process, and Sonar's is quite competent. So there is no need to do it manually as it is already being done.
 
 
And dither has absolutely nothing to do with sample rate reduction - it is used when reducing bit depth.

Thanks, DrewFX1. This again was my assumption. I was just asking for confirmation - thanks for providing it.
 
Nika Aldrich says dither helps when the division of the sample rate is not even. So for example, that it should be used when going from 96 to 44.1 but it should not be used for 88.2 to 44.1. For this reason, up sampling and down sampling done by a factor of 2 does not require dither.
 
I can find the page number and quote the book if you would like. I know that many of the forum members feel strongly that going from 96 to 44.1 doesn't require dither, but I don't know their source of information on this and I have trouble accepting the assertion without knowing the source and that the source is more respectable than Nika's book published by Sweetwater.
 
 

brundlefly

drewfx1
The filtering you are asking about is already an intrinsic part of any competent SRC (Sample Rate Conversion) process, and Sonar's is quite competent. So there is no need to do it manually as it is already being done.
 
And dither has absolutely nothing to do with sample rate reduction - it is used when reducing bit depth.

 
+1. This is my understanding also on both counts.

That is why I was confused and asked in my first post. I have never had a spectrum analyzer that goes that high (and honestly do not see the logic in it), and often because one sees something, then it is a "problem." I have always just trusted SONAR to do what it "needs to," and never thought anything beyond that. I guess it just proves that "ignorance is bliss" for me... but if it came out as an audible artifact in a final copy, then I can hear it, which makes it a problem (for me).

gswitzNika Aldrich says dither helps when the division of the sample rate is not even. So for example, that it should be used when going from 96 to 44.1 but it should not be used for 88.2 to 44.1. For this reason, up sampling and down sampling done by a factor of 2 does not require dither.
 
I can find the page number and quote the book if you would like. I know that many of the forum members feel strongly that going from 96 to 44.1 doesn't require dither, but I don't know their source of information on this and I have trouble accepting the assertion without knowing the source and that the source is more respectable than Nika's book published by Sweetwater.

 
I would indeed be curious what his argument for dithering is. Perhaps it refers to SRC algorithms that process at a higher bit depth?

That's the first I've heard of dither being required for (or having anything to do with) SRC, but it's been quite awhile since I read Nika's book. If you can cite a page from the book, I'd like to read what he has to say about that.
 
Of course, the question is moot in most cases, because downsampling during export is usually done in conjunction with wordlength reduction, which is where dither comes into the picture. That may be the source of confusion.