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Ultrasonic (48 kHZ+) signal boost to lower noise floor?
Old 1 week ago
  #1
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Ultrasonic (48 kHZ+) signal boost to lower noise floor?

Since most ADCs seem to use that technology (Delta-Sigma or similar sounding name) which raises the noise floor in ultrasonic frequencies, which is clearly visible in 192 kHz recording mode, and given that the intensity of ultrasonic frequencies in most audio content is negligible, I was wondering if it might be possible to effectively reduce the ultrasonic noise floor by boosting it by some 30-60 dB in the analogue domain before capturing the signal.

Is there any gear out there that can do this and do it without degrading the signal to a point where this whole endeavor becomes useless (read: in good quality)?

If not, how hard would it be to build something like this? Say, some kind of passive circuit which does this.

Then after recording, this EQ could be reversed, leading to a nice low ultrasonic noise floor.
Old 1 week ago
  #2
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UnderTow's Avatar
Quote:
Originally Posted by davorfilms View Post
Since most ADCs seem to use that technology (Delta-Sigma or similar sounding name) which raises the noise floor in ultrasonic frequencies, which is clearly visible in 192 kHz recording mode, and given that the intensity of ultrasonic frequencies in most audio content is negligible, I was wondering if it might be possible to effectively reduce the ultrasonic noise floor by boosting it by some 30-60 dB in the analogue domain before capturing the signal.

Is there any gear out there that can do this and do it without degrading the signal to a point where this whole endeavor becomes useless (read: in good quality)?

If not, how hard would it be to build something like this? Say, some kind of passive circuit which does this.

Then after recording, this EQ could be reversed, leading to a nice low ultrasonic noise floor.
The Ultra-sonic noise floor is intentional. It is noise shaped dither. It needs to be there to avoid quantization distortion. The dither is pushed into the ultra-sonic range because you can't hear it there.


Alistair
Old 1 week ago
  #3
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Quote:
Originally Posted by UnderTow View Post
The Ultra-sonic noise floor is intentional. It is noise shaped dither. It needs to be there to avoid quantization distortion. The dither is pushed into the ultra-sonic range because you can't hear it there.


Alistair
I understand, but if I push high frequency content first and then lower it after the AD conversion, I should get a lower effective noise floor while profiting from the dithering anyway. Of course I would get less dynamic range, but since ultrasonic content seems to be pretty low anyway usually, that wouldn't be much an issue.
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