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20Khz noise sound

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Re: 20Khz noise sound

Postby James Perrett » Fri Jan 11, 2019 9:19 pm

Is there anyone else who used to notice the 19kHz pilot tone on FM broadcasts? Stereo tuners would filter it out but I had a couple of mono radios that you could hear it on if you listened closely.
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Re: 20Khz noise sound

Postby Hugh Robjohns » Sun Jan 13, 2019 12:55 pm

Yes, in my youth with a few tuners. Can't say I've noticed it in more recent times at all. I'd like to think that's because FM receiver pilot-tone filters have improved... ;-) But I fear it's just because my personal bandwidth is diminishing. :-(
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Re: 20Khz noise sound

Postby aviorrok » Tue Jan 15, 2019 10:24 pm

Ok I try to change everything (cables and microphones) and the noise come from the preamp (WA273) when I record without preamp the noise gone.
I connected a TRS cable from audio interface input to WA273 line output it's ok?
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Re: 20Khz noise sound

Postby James Perrett » Tue Jan 15, 2019 11:33 pm

Today I transferred some tapes recorded at Wessex Sound in the 80's which had a very similar spike around 23kHz - so this sort of thing isn't unknown even in professional studios.

I'm just wondering whether the Warm Audio preamp is fussy about output loading - does it expect to see a certain impedance?
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Re: 20Khz noise sound

Postby Hugh Robjohns » Tue Jan 15, 2019 11:50 pm

aviorrok wrote:Ok I try to change everything (cables and microphones) and the noise come from the preamp (WA273) when I record without preamp the noise gone.

Okay. Well it's a positive to identify the source of the noise. It's going to be harder to find the cause and cure!

It could be a fault in the preamp such as self-oscillation at an ultrasonic frequency. If so, it might change with different gain settings or input selections. Or if you turn down the output fader. Are both channels the same?

Or it might be related to a ground-loop problem.

I connected a TRS cable from audio interface input to WA273 line output it's ok?

Should be...
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Re: 20Khz noise sound

Postby aviorrok » Sat Jan 26, 2019 11:01 pm

The noise appears only when the analyzer button set to post, when the button set to pre there is no noise.
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Re: 20Khz noise sound

Postby hz37 » Sat Jan 26, 2019 11:44 pm

Are you saying you can actually hear this as noise? Because it appears to be very narrow band and 20 kHz means you have exceptionally good ears. Even my 8 year old daughter can only hear up to 19 kHz.

It would be interesting to render this to disk and watch it in a spectral editor, like Izotope RX. If there is a thin line at 20 kHz, then something is creating this harmonic as an artefact. I probably wouldn't worry too much about it, because only a handful of young people might actually hear it. And dogs, cats, bats and the likes.

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aviorrok wrote:The noise appears only when the analyzer button set to post, when the button set to pre there is no noise.
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Re: 20Khz noise sound

Postby James Perrett » Sat Jan 26, 2019 11:51 pm

aviorrok wrote:The noise appears only when the analyzer button set to post, when the button set to pre there is no noise.

I'd guess that the noise is still there but you can't see it on the display as it is 25dB lower at the input. Do you really need a 25dB boost?
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Re: 20Khz noise sound

Postby aviorrok » Sun Jan 27, 2019 12:22 am

hz37 wrote:Are you saying you can actually hear this as noise?

I’m not hear it but is very annoying.
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Re: 20Khz noise sound

Postby Dave B » Sun Jan 27, 2019 1:58 am

Dude, life is too short - move on and let go.

The fact that it is not there on the input means that the eq itself is more than likely causing the issue. The stock logic eq is fine, but not the be-all and end all of eqs. TBH, even if you are recording the odd _very_ high frequency content and even if that is getting summed by the time it gets to the master bus, you'd be fine with using a filter with a very steep slope to clean it up. I was always taught to both high- and low-pass the bus before any other processing to keep things tidy anyway.
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Re: 20Khz noise sound

Postby James Perrett » Sun Jan 27, 2019 2:05 am

Dave B wrote:The fact that it is not there on the input means that the eq itself is more than likely causing the issue.

There's a good chance that it is real but the analysis display doesn't really go low enough to see it on the input. As far as I can see, it comes up to about -40dB on the post eq display which would mean that it was 5dB below the minimum value on the pre eq display. I find it useful to be able to see down to -120dB or lower on a frequency analysis display. In a previous post I thought the cause had been narrowed down to the Warm Audio preamp.
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Re: 20Khz noise sound

Postby aviorrok » Sun Jan 27, 2019 5:48 pm

I discovered something new the noise sound appears only if the project set to 48Khz or more.
If I set sample rate to 44.1Khz the noise gone.
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Re: 20Khz noise sound

Postby Hugh Robjohns » Sun Jan 27, 2019 8:42 pm

As James commented above, I thought we had narrowed the problem down to the Warm preamp and a potential ground-loop or interference issue.

I suspect the fact that this ~20kHz tone appears only at 48k and higher as sample rates is due to unfortunate beat frequencies between the digital rig and something in the Warm preamp (switched mode PSU perhaps, or unintended self-oscillation maybe). Resolving any ground-loop problems may well make the HF tone disappear permanently.

H
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Re: 20Khz noise sound

Postby aviorrok » Mon Jan 28, 2019 8:55 pm

Hugh Robjohns wrote:As James commented above, I thought we had narrowed the problem down to the Warm preamp and a potential ground-loop or interference issue.

I suspect the fact that this ~20kHz tone appears only at 48k and higher as sample rates is due to unfortunate beat frequencies between the digital rig and something in the Warm preamp (switched mode PSU perhaps, or unintended self-oscillation maybe). Resolving any ground-loop problems may well make the HF tone disappear permanently.

H

I solved the problem I switch to line input 3/4 in the UR242.
1/2 inputs is a preamp inputs, so I connected a preamp to preamp and that make the noise.
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Re: 20Khz noise sound

Postby aviorrok » Fri Feb 08, 2019 1:46 pm

The problem is not solved but I know the cause.
When I disconnected the UPS (USB) cable from computer the noise is gone but the noise is happening only when the preamp is power on and the UPS USB cable is connected.
The UR242 connected to the preamp with TRS, how can I solve the problem?
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