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20 Khz constant signal in mix
Old 6 days ago
  #1
Gear Head
 

20 Khz constant signal in mix

hey there,
Curious if any of you have run into a mix that you are mastering where it seems there is consistently a low level signal of 20 Khz that doesn't really move all that much with the dynamics of the music, and there is drop off from 20 Khz to 15 Khz. Is this due to a converter issue on the mixing end, or something else? Just curious. Thanks!!
Old 6 days ago
  #2
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Nonlinear's Avatar
 

I haven’t seen that exact problem but I have seen similar. Most often, IME, it’s due to digital noise in the power supply to the A/D/A converters somewhere in the chain. Once it’s in the signal your only choice in mastering is to notch it out, AFAIK.
Old 6 days ago
  #3
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biksonije's Avatar
 

Your work or you're mix/mastering someone else's work? Could it be, if else's work, someone went overboard with "analogue" feel (noise)? ;-)
Old 6 days ago
  #4
Gear Head
 

Quote:
Originally Posted by Nonlinear View Post
I haven’t seen that exact problem but I have seen similar. Most often, IME, it’s due to digital noise in the power supply to the A/D/A converters somewhere in the chain. Once it’s in the signal your only choice in mastering is to notch it out, AFAIK.

Thats what I was thinking as well. I've heard strange things before from bad power. Thanks for the reply!
Old 6 days ago
  #5
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FabienTDR's Avatar
 

Verified Member
Probably a UV22 dither?

(narrow band HF noise)

AFAIK, early POW-R did similar.

These are also the primary reason for the dusty "don't dither twice" recommendation. It's irrelevant for the regular TPDF dither now favoured (due to the never ending reprocessing/re-encoding in today's playback realities). But these exotic dithers can show pretty nasty side effects, especially when applied several times.


There was a strange mania for dithers back in the 2000's, with full pages ads for dithers in magz, ppl accordingly dithering just everything, and even Waves adding dithers to all sorts of plug-ins, not just limiters. Maybe it's related.

Last edited by FabienTDR; 6 days ago at 01:23 AM..
Old 6 days ago
  #6
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John Moran's Avatar
 

Verified Member
It could be leakage from a video monitor around 15Khz. Yah, I know the OP said ~20Khz, but I've run into monitor leakage issues before.
Lovely little steady state vertical line on a spectrum analyzer.
Just tossing that out there as another source to consider. Probably not, but if you've never run into it, it does happen.
Old 6 days ago
  #7
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Adam Dempsey's Avatar
 

Verified Member
Heavily noise shaped dither would be more broad band and a distinctive rise, not a spike, but yes – noticed regularly from different converters, sometimes @16-17k, sometimes more than one frequency. And on many hits they've been almost lovingly retained without concern.
15.625kHz (PAL) or 15.75k (NTSC) precisely (give or take a bit if tape sources) for cathode ray tube monitor leakage.
Old 3 days ago
  #8
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polybonk's Avatar
I see that all the time.

Its from guitar effects. Especially ones that use a rate knob to lower the converter clock.
Chase Bliss mood does a lot of this and is very popular right now. A whole bunch of others.

I go in with RX and delete them.
Old 3 days ago
  #9
Gear Nut
 

Verified Member
Isotope RX Spectral De-Noise
Use the reduction curve, which lets you adjust what frequencies are targeted, and isolate the high end. To be extra careful unlink the static and tonal noise controls and just do static to prevent any loss of musical info.
Old 3 days ago
  #10
Gear Maniac
 
Ganglion's Avatar
ironic that i'm just seeing this thread - i'm in the middle of mastering a project where there about a 1/3 of the songs have a loud spike around 20k. It's coming from the vocals on this project. The spike only appears when the singer is singing (or right before and after). i have no idea what caused it (tube mic noise?!?), but i do know that notching it with Tokyo Dawn Labs Nova GE in surgical mode (and "insane" setting) did an excellent job of transparently taking it out with minimal change to the rest of the track.
Old 2 days ago
  #11
Gear Guru
 
Thomas W. Bethe's Avatar
 

Verified Member
Quote:
Originally Posted by Ganglion View Post
ironic that i'm just seeing this thread - i'm in the middle of mastering a project where there about a 1/3 of the songs have a loud spike around 20k. It's coming from the vocals on this project. The spike only appears when the singer is singing (or right before and after). i have no idea what caused it (tube mic noise?!?), but i do know that notching it with Tokyo Dawn Labs Nova GE in surgical mode (and "insane" setting) did an excellent job of transparently taking it out with minimal change to the rest of the track.
Same here. It is a very large spike at about 20KHz. The files I am working with are 32 bit float and 44.1 KHz and were mixed in Samplitude. It is only when certain samples are used. Very strange.
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