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iZotope vs SoX Upsampling in Audirvana Plus 3.2

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I wanted to start a topic that focuses on the parameters of these two upsamplers in A+ and perhaps even get some objective measurements of Fourier transforms (impulse response graphs) from those people who can capture them.  My experience comes from these software upsamplers as they are implemented in Audirvana Plus 3.2 - But I don't think there's anything keeping others with different players from chiming in here.

 

To kick things off, I'm using @copy_of_a 's extreme settings for iZotope as shown below.  In order to avoid aliasing with his settings, you have to use a software plugin to further lowpass the signal.  In my case, I'm using FabFilter ProQ2

 

steepness: 3

length: 500,000

Cutoff: 1.25

Anti-Aliasing: 50

Prering: 0.36

 

For SoX, I've chosen the below based solely by ear.  No LP filter is needed with an EQ plugin since the filter is much steeper it seems.  Admittedly I haven't put near a much time into SoX as I have with iZotope:

 

Bandwidth: 90 

samples: 500,000

Anti-Aliasing: 85

Prering: 41

 

Overall, the biggest difference between these is the inability to finely tune the filter steepness in SoX.  I've read some anecdotal things and tend to agree with most of them.  For instance, Sox seems to present a great image/stage/separation, but comes at the expense of some more ringing that can be heard in the "shimmering" highs on cymbals.  What's interesting though, is that the preringing doesn't seem too bad when I scrutinize the timing of a kick drum - hearing first its batter head which should be followed by its resonate sub bass thump.  I find that my setting in iZotope still perform best here - but the SoX isn't nearly as bad in the lows as with the high frequency "smearing/shimmering" I hear.  But this could just be my settings, more time will tell which is the better upsampler for me.

 

What else have other's experienced? 

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1 hour ago, Andrey said:

You can bring these diagrams, without increasing the sampling rate?

without resampling you are of course seeing the unaltered transition-/stopband of the original file (which makes sense since the resampler is bypassed when you select "none" in the upsampling section of A+'s prefs).

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11 hours ago, buonassi said:

For SoX, I've chosen the below based solely by ear.  No LP filter is needed with an EQ plugin since the filter is much steeper it seems.  Admittedly I haven't put near a much time into SoX as I have with iZotope:

 

Bandwidth: 90 

samples: 500,000

Anti-Aliasing: 85

Prering: 41

 

Overall, the biggest difference between these is the inability to finely tune the filter steepness in SoX.  

 

Maybe SoX adjusts the steepness according to the bandwidth? So you have a much higher steepness with a bandwith of 99% than with one of 90%.

Can you chose 500,000 samples with SoX?

 

Matt

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11 hours ago, copy_of_a said:

my experience with SoX in A+ 3.2.x is it's pretty much unusable:

 

I noticed similar aliasing and should've taken a screen shot of it.  It's weird as the aliasing pulses up to -45db but quickly falls.  This even happens with a bandwidth setting of 90.  But using fab filter, I can presumably remove some of that aliasing with a LP filter at 96db/octave.  Doing this, I still prefer your "extreme" izotope settings to any I could produce in Sox.  

 

Sox is initially appealing because it sounds "euphonic".  Perhaps this pulsing aliasing is causing intermodulation distortion that sounds good to some people?  Still I'm not sure I can hear the aliasing.  I'm more concerned that it could be damaging my electronics.  Is there any validity in this concern?  Also, what does aliasing sound like to you?  What cues should I be listening for? 

 

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53 minutes ago, matthias said:

 

Maybe SoX adjusts the steepness according to the bandwidth? So you have a much higher steepness with a bandwith of 99% than with one of 90%.

Can you chose 500,000 samples with SoX?

 

Matt

perhaps it does just that, good conjecture.  I'm able to select 500K on mine, yes.  

500k.jpeg

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On 1/14/2018 at 3:48 PM, matthias said:

 

Maybe SoX adjusts the steepness according to the bandwidth? So you have a much higher steepness with a bandwith of 99% than with one of 90%.

Can you chose 500,000 samples with SoX?

 

Matt

I can't on mine.  It maxes out at 30,000

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6 hours ago, Kilauea50 said:

I can't on mine.  It maxes out at 30,000

must have been a glitch.  I just relaunched and sure enough I now see 30K as the limit.  

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well, I think this topic is on hold until SoX is better understood, or at least the aliasing is better controlled.  

 

In terms of development and maintenance, does anyone have an opinion on which of these upsampling software products is leading the pack here?  SoX is open source, but that doesn't mean it has any less potential to go up against the "pro audio" products.

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On 1/14/2018 at 2:48 PM, matthias said:

 

Maybe SoX adjusts the steepness according to the bandwidth? So you have a much higher steepness with a bandwith of 99% than with one of 90%.

Can you chose 500,000 samples with SoX?

 

Matt

@matthias, you were right.  I was able to observe the rolloff steepness of the SoX filters at various settings using white noise and zooming in on FabFilter's spectrum analysis between 10 and 22khz.  At the highest setting of 99.5 it is a "brick wall", whereas at the lowest setting of 74, there is a definite rolloff.  What's interesting is that even at 74, the rolloff isn't very severe.  It kicks in at 18K, much higher than I'd expect since 74% of nyquist at 44.1 is 16K approx.  This is also what I'm hearing, zero loss of high frequency air, and I have verified up to 18K hearing by an audiologist (kinda freaky for my 38 year old hearing system).  

 

Also, the ringing doesn't seem to be reduced by very much even at the 74 setting.  Sometimes I think I like SoX, other times I'm convinced that I'm getting the better staging and separation of instruments at the expense of a sloppier kick drum attack.  I guess we can't have our cake and eat it too, huh?

sox74.jpeg

sox99-5.jpeg

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Initially I thought I preferred  the new SoX setting. Now , not so sure ? SoX can sound slightly artificial and euphonic at times to my ears . Does seem quieter with more clarity though when listening to my Classical  and Jazz piano recordings .

Some of these negatives are somewhat mitigated though when I use SoX without oversampling . With oversampling  activated I find the treble through my Invicta DAC can sound somewhat thin and glassy or strident  with a loss of mid- range tonality due to an increase in euphonics . 

I’ve never tried the custom settings though as I’m not at all computer savvy and it seems rather complicated . 

Still deciding . 

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Well I seem to have fixed my issues with SoX . Mainly buy adjusting the phase values . I adjusted the default setting of 73 to about 46 . This was very big improvement . I won’t be going back to iZatrope . Thank you Damien - great upgrade . 

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I've given SoX some more time and I like its staging (width) and liveliness, for lack of a better term.  There's more shimmer in the highs and it's not as dry as iZotope.  I agree with @Noodle that SoX can sound euphonic, reminds me of the "exciters" on DAWs that add some sparkle by increasing the overtones/harmonics of cymbals.  It seems to spread a bigger canvas over my head (I'm a headphone listener).  

 

I've actually been enjoying it a bit more lately.  While I acknowledge that it may not be as "pure", I do seem to become more immersed in the performance.  

 

I've been using these settings - which is odd for me because I tend to like min phase better.  But something really opens up with the lin phase:

 

 

sox.jpeg

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Well I seem to have fixed my issues with SoX . Mainly buy adjusting the phase values . I adjusted the default setting of 73 to about 46 . This was very big improvement . I won’t be going back to iZatrope . Thank you Damien - great upgrade . 

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I’ve adjusted to the SoX sound now . Prefer a phase setting of about 60 with power of 2 oversampling switched on . 

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2 hours ago, RunHomeSlow said:

I think your safe volume reduction should be set at -3 when upsamplinh to DSD... don’t ask me why 😀

yes, according to the Audirvana manual, this is to prevent the DAC from clipping.  But my DAC has analogue filters that activate when DSD is sent to it.  It has 3 positions:  0,-3,-6 db approx.  I have it set to -3 currently.  

 

Also, in my EQ software, I leave a little headroom to ensure no clipping, so that's an added layer of protection. 

 

According to A+ manual, unless you get channel dropouts or hear distortion, you should be ok to leave at 0.

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Hi Buonassi,

 

I'm a long time A+ user and have tried many different filter settings over the years.  I gave your iZotope setting a try and must say that it sounds fantastic.  I'm exclusively listen to loudspeakers and have owned Magnepans for over a decade  a now currently have a pair of 3.7i's with a REL sub.  I state this as so many now are exclusive headphone listeners.  

 

I saw your screen shot you posted regarding your SOX settings and noticed that had a DSD DAC.  Do you feel that the SOX filter should primarily used with DSD?  It seems that the SOX filter lacks just a touch of warmth.  When I did audition a DSD DAC a few months ago, my impressions were that it was a touch on the warm side of things so I've come to the conclusion that SOX is a better fit for DSD.  Do you agree with this assessment?

 

I'm currently using a PS Audio Perfectwave DAC II and have been thinking about upgrade it.  

 

On a different note, I noticed the I can no longer adjust filter setting by directly inputting settings into the box to the right of the sliders in A+ but must us the slider to make changes.  Have you noticed this as well?

 

Again thank you so much for posting your filter settings.  

 

Hoshi

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NEW Settings

steepness: 3

length: 500,000

Cutoff: 1.25

Anti-Aliasing: 50

Prering: 0.36

 

I was previously using:

steepness: 22

length: 500,000

Cutoff: 0.95

Anti-Aliasing: 100

Prering: 0.86

 

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12 hours ago, Hoshi said:

I've come to the conclusion that SOX is a better fit for DSD.  Do you agree with this assessment?

Well I’m not sure. Sox is a resampler that performs interpolation. If it’s better for dsd I can’t say. It does sound a bit more shimmery and glaring composed to izotope. 

 

12 hours ago, Hoshi said:

noticed the I can no longer adjust filter setting by directly inputting settings into the box to the right of the sliders in A+ but must us the slider to make changes.  Have you noticed this as well?

Yes I have. I reported it, but it persists after some incremental updates. It is a pain, but not a dealbreaker for me. 

 

11 hours ago, Hoshi said:

was previously using:

steepness: 22

length: 500,000

Cutoff: 0.95

Anti-Aliasing: 100

Prering: 0.86

 

This isn’t a bad setting if you’re concerned with aliasing and want to suppress it. I have actually gone back to using this setting (or very similar) and do like it. 

 

Welcome  to the club. Glad you’ve joined us here on CA!

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9 hours ago, buonassi said:

Well I’m not sure. Sox is a resampler that performs interpolation. If it’s better for dsd I can’t say. It does sound a bit more shimmery and glaring composed to izotope.

I think that's a bit too much of a generalisation. The Sox and iZotope resamplers both have a multitude of settings. Most of what one can do, the other can too. If they sound different even with the same settings, that would be interesting.

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On 4/7/2018 at 7:17 AM, Hoshi said:

NEW Settings

steepness: 3

length: 500,000

Cutoff: 1.25

Anti-Aliasing: 50

Prering: 0.36

 

I was previously using:

steepness: 22

length: 500,000

Cutoff: 0.95

Anti-Aliasing: 100

Prering: 0.86

 

 

I'd like to try your settings, but I'm not seeing some of the preferences you're referring.  Check out my SoX preference page, attached.

SoX-Pref.jpg

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