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Artifacts from VST eq plugins


cloud9blue

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First off, hello ;) Long time lurker here, but finally decided to make an account.

 

So my current setup has a late 2013 Macbook Pro Retina playing FLAC or Tidal HiFi through Audirvana Plus through USB to my two DACs, a HRT Music Stream II+ that I had since college (excellent for its price btw) and a Audio-GD NOS-11 I picked up just last week. The signal is then amplified through either of the 3 headphone amps that I have (NOS-11 built in amp, or Schiit Asgard 2, or Little Dot Mk. III) and played through the Audeze LCD-2 that I had for years.

 

With the new NOS-11, I am starting to hear A LOT more details than I used to able to with my older gears, particularly after some mild EQ through VST plugins such as BMG Equilibrium or TDR Nova that bumps up the treble by 3-5 dBs. However, I also started to notice that the EQ processing would create occasional artifacts, which sounded like a very faint popping noise. This tends to occur every minute or so during playback, and quite distracting for musics with high dynamic range and/or low volume sections.

 

This occurs during any EQ'd playback, either through using the VST plugins through Audirvana or just the through Soundflower and AU Lab, so I am inclined to this is caused by the noise on from the computer's motherboard and such. Problem goes away if I disable the EQ plugins, or just use my old Music Stream II+, which just aren't transparent enough for faint details such as this.

 

So I am just wondering if there is any way to reduce such noise/artifacts from occurring... LCD-2 sounds just so much better with some minor EQ...

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I would assume by clipping, you mean distortion from EQ. If that's the case, I would think these artifacts would be totally random.

 

To clarify, I sometimes rewind the songs by a few seconds upon hearing any noises such as these, just to figure out if it just poor mastering (which happens in some of recordings that got converted from old analog media) or it is actually random artifacts from the signal processing from my computer. In most cases, I would not hear the noise again at the same location.

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Yeah, then it would not be clipping.

 

The other weird thing is that in Audirvana, at least, the normal way to use AU plugins is to uncheck the box in preferences that says "Realtime Audio Units control and setup." If you haven't unchecked that box, give it a try. Then it does all the processing before playback (or very early into playback). (I use Dirac for equalization, and it turns out not to work as well for me if I uncheck that box, but for "normal" AU plugins, it should work better).

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One possible cause of the artifact you are describing might be if the DAC drops a few samples whenever its buffer (of input samples) overflows. The VST plugin could be disrupting the two-way communication of async USB, and forcing playback on the computer's clock. Or the computer's audio output system might drop the samples if the VST plugin is feeding it samples faster than the DAC wants them. With the DAC's clock slightly slower, overflows would occur periodically, but not at any particular place in the music. If that's the problem, then @wgscott 's suggestion should work (assuming there's a corresponding setting for VST), and otherwise switching to optical instead of USB (or to an older USB DAC with plain adaptive USB) would work by slaving the DAC's clock to the computer's.

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Yeah, then it would not be clipping.

 

The other weird thing is that in Audirvana, at least, the normal way to use AU plugins is to uncheck the box in preferences that says "Realtime Audio Units control and setup." If you haven't unchecked that box, give it a try. Then it does all the processing before playback (or very early into playback). (I use Dirac for equalization, and it turns out not to work as well for me if I uncheck that box, but for "normal" AU plugins, it should work better).

 

I typically leave that unchecked, expect for the time that I need the analyzer for fiddling with the eq settings. Doesn't seem to make much of a difference, the noises are still there as long as the eq is running.

 

One possible cause of the artifact you are describing might be if the DAC drops a few samples whenever its buffer (of input samples) overflows. The VST plugin could be disrupting the two-way communication of async USB, and forcing playback on the computer's clock. Or the computer's audio output system might drop the samples if the VST plugin is feeding it samples faster than the DAC wants them. With the DAC's clock slightly slower, overflows would occur periodically, but not at any particular place in the music. If that's the problem, then @wgscott 's suggestion should work (assuming there's a corresponding setting for VST), and otherwise switching to optical instead of USB (or to an older USB DAC with plain adaptive USB) would work by slaving the DAC's clock to the computer's.

 

That might be the case as well. Think I gonna give optical input a try then. My mac does have a mini Toslink output from the 3.5mm port, so I just gonna order an optical cable to see how that affects thing. Not sure if that would introduce a whole different set of problems though, since my understanding that async USB is always superior to optical output.

 

Would a digital (USB) to digital (optical) convertor down the line be superior to using on-board USB output from the computer though?

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