LIME - Harmonics Question

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LIME - Harmonics Question

Post by markgalup » Sat Feb 10, 2018 5:27 am

Hey all,

So I recently purchased a Black Box Analog HG-2 (fucking love it) and decided to go back through my mixbuss and see the structure of my harmonics/saturation throughout, and I noticed something rather strange.

I have Lime and Sand on my mixbuss, and Sand, with compressor C in insane mode, using the buss comp C preamp, with filters engaged in the sidechain, generate nearly no visible harmonics (inspecting with Span Plus down to like -150 dB). Lime, with no preamp, Comp C in insane mode, and filters engaged on sidechain, generates a huge amount of harmonics. Without insane mode it goes completely NUTS. Can anyone confirm this is happening with them, or seems somewhat reasonable? I’m a bit concerned. Screenshots are attached.

First photo is with insane mode on:
LIME-harmoincs-insane.jpg
Second photo is without insane mode on:
LIME-harmonics-no-insane.jpg
Thanks in advance,
MG
Last edited by markgalup on Tue Feb 13, 2018 6:31 am, edited 1 time in total.
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Re: LIME - Strange Harmonics/Aliasing?

Post by Phelix » Sat Feb 10, 2018 5:47 pm

Compared to Lime, I will say Sand creates more harmonic content -and aliasing. ~ 6dB GR @ 44.1kHz
Perhaps check levels again?
Lime-Sand_insane_44kHz.jpg
Great piece of hw you got! Occasionally I like using the Bl*ck Box plugin in m/s matrix.
Have you compare it with Crimson? Here’s Crimson+SuperSatu and HG2 to the right.
CrimsonSuperSatu-hg2.jpg
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Re: LIME - Strange Harmonics/Aliasing?

Post by markgalup » Sat Feb 10, 2018 10:23 pm

Thanks for chiming in, Phelix. I haven’t tested it yet, but I’m almost positive I know why my tests are wrong for Sand and that they’ll show what yours showed. Reason is likely because I had Sand sidechained to only listen below 300hz or so, and I was using a 1k tone at -18dB. I’m sure once I bring the sidechain up past 1k it’ll read similarly.

My main concern is why the aliasing? I haven’t checked in the past, but I thought Insane mode mainly did away with this. I’ll test some other channel strip comps as soon as I can but other acqua EQs/pres don’t show this Aliasing.

MG
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Re: LIME - Strange Harmonics/Aliasing?

Post by Sheikyearbouti » Sun Feb 11, 2018 12:28 pm

Hey Mark,

I wouldn't call the harmonics in any of the presented measurements 'a lot'. Quite low and normal levels. The amount of harmonics generated will depends a lot on the frequency of the test tone used. If you use a LF sine tone with fast attack/release values on the compressor you may be chopping that waveform just around where it peaks (1/4 or 3/4 of the wave). If you do so this will generate a lot more harmonics. It is how compressors work - when you have amplitude modulation you have harmonic distortion. And indeed this is the initial reason why you have attack/release controls on compressors - to reduce the distortion levels.

Now, the aliasing is another story, but still very much related. It is just the nature of digital audio to have it, especially if you are not using oversampling. Harmonics generate HF above Nyquest = aliasing. It is the same with distortion and strong saturations. But from what I can see the level of aliasing here is actually very low and I would simply ignore it. And also at 96k the aliasing should be even lower in level

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Re: LIME - Strange Harmonics/Aliasing?

Post by Phelix » Sun Feb 11, 2018 1:38 pm

Totally agree Sheikyearbouti,
With insane mode the aliasing towards Nyquist is very low in the audible range. Different story if using ‘economy’ mode.
For the record, this measure is at a gainstage around -18db rms. As the mix finalises STN will of cause increase.
Also it can be interesting to see what happens if using a sine sweep.

@Mark, I haven't observed any aliasing from preamps either.
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Re: LIME - Strange Harmonics/Aliasing?

Post by markgalup » Mon Feb 12, 2018 4:52 am

Hey Phelix and Nik,

Thanks for your assistance and input here. I’m fairly new to this realm of analysis so I’m very happy to get schooled a bit. Glad to hear that these plots look as you would expect them to - that was my main goal here. Honestly, I’m tempted to delete these posts since I was incorrect in calling the harmonics and aliasing “strange”, but perhaps someone with similar confusion will find this post and realize they have nothing to worry about.

Phelix, I have not yet compared the HG-2 to Crimson but I will as soon as I can. One of the huge pulls in using outboard on my mixbuss (beyond the unpredictable “magic” going on especially in the HG-2) is the fact that I don’t have to use as much heavy CPU plugins on my mixbuss, which is where the biggest hits happen. I have been tempted to demo the HG-2 plugin however to see if it stood up to the hardware at all. Once I have some time to do more testing I’ll let you know what I find!

Cheers,
MG
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Re: LIME - Strange Harmonics/Aliasing?

Post by [email protected] » Mon Feb 12, 2018 10:05 am

Audio analysers can be, today, very dangerous in inexpert hands.
Seeing curves and plots is very different from fully understand them.
But is also true that it could be a good instrument to start to discover the audio physics (leaving apart sensationalized forum titles, that can kill, maybe, in one word an entire company work).

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Re: LIME - Strange Harmonics/Aliasing?

Post by Sheikyearbouti » Mon Feb 12, 2018 10:50 am

Hey Mark, No, no need to delete anything. If someone sees the same and wonder it is good that this is here.

And of course, I meant to Nyquist, not Nyquest.
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Re: LIME - Strange Harmonics/Aliasing?

Post by Phelix » Mon Feb 12, 2018 2:41 pm

Yes of cause Nik, and below nyquist (half the sample rate), not above.

Mark, when you do, try look at the even and odd harmonics and the distribution on different settings. It’s fun!

I see many wrong attempts using advanced analyzers. Correct calibration is fundamental and plenty of factors come into play for a usable plot, it isn’t just slap on. And first and foremost, it does not reveal the actual sound from a given plug-in in context, which is for the ears to decide.

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Re: LIME - Harmonics Question

Post by Sheikyearbouti » Tue Feb 13, 2018 1:30 pm

Yeah, looking at measurements doesn't exactly tell you what it will sound like. But when it comes to harmonics think of the first few in the order, which are the highest in magnitude.

1st - fundamental (lets take note C)
2nd - octave / even (C)
3rd - perfect fifth / odd (G)
4th - octave / even (C)
5th - major third / odd (E)

So if you put a pure C sine tone into a device that gives 5 harmonics you get a C major triad chord :D
And as you can see the balance between these is different for each signal path.

And of course octaves sound the cleanest.
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