Does LiveProfessor2 always add some tiny noise?

takeshi
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Does LiveProfessor2 always add some tiny noise?

Postby takeshi » Wed Oct 11, 2017 10:58 am

Hi, I'm a new user of LiveProfessor2 and found it great!


I have been utilized ArtTeknika console
http://console.jp/jp/

It is good but have not been maintained more than 5 years
and only support windows 32bit VST2.

I'm excited about great functionality & flexibility that
LiveProfessor2 has!


But I encounter 1 strange behaviour in LiveProfessor2.


I check audio loop back characteristc and found that
I always got tiny noise even though I transmit no audio signal.
Maximum noise level is around -160dBFS.

I got no noise in ArtTeknika console in same H/W and S/Wsetting.


Is it the specification of LiveProfessor2? If yes, can you stop that?


Thanks in advance.




PC Win7 Pro 64bit(RAM:16GB)
Audio Interface RME Fireface400
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LiveProf_Noise.png
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Wed Oct 11, 2017 12:41 pm

Hi
No there is no part of the code designed to do this :)
How did you measure this ? could you please describe the setup ?
Could it be dither ?
takeshi
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Re: Does LiveProfessor2 always add some tiny noise?

Postby takeshi » Fri Oct 13, 2017 9:01 am

Hi nikolai, Thanks a lot for your quick answer!


My setting is as follows

HW : connect S/PDIF coaxial cable from SPDIF Out to SPDIF In(self loopback)
but I never send audio output to S/PDIF.

in Fireface400,
Audio In
S/PDIF(L) : ch 9
S/PDIF(R) : ch10

Audio Out
Monitor(L) : ch 7
Monitor(R) : ch 8
S/PDIF(L) : ch 9
S/PDIF(R) : ch10


SW : setting is same for both console / LiveProfessor2. TapeIt is audio recording plugin.

I record s/pdif in signal by 32bit float mono wav and
console -> no noise
LiveProfessor2 -> noise

I wonder some DAW add dither to avoid Denormal problem. But you said you don't add that,
so my guess is wrong.

Do you know what is the origin of this behaviour?
Best,

takeshi
Attachments
console_setting.png
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liveprof2_setting.png
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fireface400_connection.png
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Sun Oct 15, 2017 11:21 am

Hi
Ok, so you are recording a feedback..
I'll try to reproduce this setup, and see what I find.
What sample rate are you running (since the noise is at 38Khz?)
That said, what practical (non theoretical) issues are there at -160dB at 38K ?
takeshi
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Re: Does LiveProfessor2 always add some tiny noise?

Postby takeshi » Mon Oct 16, 2017 4:44 am

Hi nikolai

Thanks for the reply.

>What sample rate are you running (since the noise is at 38Khz?)

Fs = 44.1kHz. And please note that the the horizontal line of LiveProf_Noise.png means NOT kHz(frequency domain), But sample(time domain).
Sorry for less information and I attached frequency domain picutre this time.

>That said, what practical (non theoretical) issues are there at -160dB at 38K ?

I have utilized LiveProfessor2 as development purpose. And it is important to check the response differences among several version of our products
for quality management.


Best,

Takeshi
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Mon Oct 16, 2017 10:48 am

Hi
Ah, that makes more sense.
So what happens if you record only the input, with the output from Tapeit disconnected ?
Also this "Console" app (do you have a link?) Do you use ASIO or windows audio, is it the same in both apps ?
takeshi
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Re: Does LiveProfessor2 always add some tiny noise?

Postby takeshi » Mon Oct 16, 2017 12:42 pm

Hi nikolai,

>So what happens if you record only the input, with the output from Tapeit disconnected ?

I checked the attached setting but the tiny noise is still remained.

>this "Console" app (do you have a link?)

I have used v1.6.1 of console. Please refer following link
http://console.jp/en/

>Do you use ASIO or windows audio, is it the same in both apps ?
Yes, of course. I have used ASIO for both LiveProfessor2 and console. Driver setting is completely same.


Takeshi
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Mon Oct 16, 2017 1:09 pm

Aha, thanks
So it is coming from the input side then.
And from the first post, i understand that these are short noise "bursts" (since it is in the time domain)
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Mon Oct 16, 2017 1:37 pm

Sorry, I can't seem to reproduce this noise.
Maybe if I get a FireFace 400, but I don't have access to it right now.
I connected Voxengo SPAN:
http://www.voxengo.com/product/span/
To the inputs, and then up in the right corner of the plugin, click the settings icon, set lower range to -180 and then zoom in.
Also the peak meters say "-inf"
Can anyone else confirm ?
takeshi
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Re: Does LiveProfessor2 always add some tiny noise?

Postby takeshi » Mon Oct 16, 2017 4:22 pm

Thanks for your effort, nikolai.

Anyway what is your Audio I/O?

Voxengo SPAN is spectrum analyzer plugin, isn't it?

>And from the first post, i understand that these are short noise "bursts" (since it is in the time domain)
Exactly. the noise is periodic and very small. so I doubt LiveProfessor add tiny noise to avoid denormal problem.

*Denormal Problem : Alghough you might know, let me explain to make sure.

We sometime encounter high CPU usage with no signal because FPU exception is happened.
One of the dealing is adding tiny noise but the best way is described in intel site.

https://software.intel.com/en-us/articl ... e-zero-daz


Takeshi
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Tue Oct 17, 2017 10:13 am

Hi
I just used the digital input of the laptop i'm on. But that should not make any difference if the issue was inside LiveProfessor.
Voxengo SPAN is spectrum analyzer plugin, isn't it?

Yes, but it also have peak (hold) meters that go down to -180 so it should popup there, just not in the time domain.

*Denormal Problem
I have not added any code to "fix" this, I see that as something that should be fixed somewhere else.

I'll try again today with a RME MadifaceXT and see if there is anything like your noise
takeshi
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Joined: Thu Oct 05, 2017 3:45 am

Re: Does LiveProfessor2 always add some tiny noise?

Postby takeshi » Tue Oct 17, 2017 12:50 pm

Hi nikolai,


>I have not added any code to "fix" this, I see that as something that should be fixed somewhere else.
OK, thanks.

>Yes, but it also have peak (hold) meters that go down to -180 so it should popup there, just not in the time domain.
I also utilize another spectrum analyzer plugin. It also has level meter that can represent at most -999.9dB tiny signal.
This plugin shows -157 dB in LiveProfessor2 and -999.9dB in console.


Anyway, I checked my environment again and reach following conclusion.


1. tiny noise is added NOT by LiveProfessor2 BUT my hardware, S/PDIF cable or Fireface400.
if I pull out S/PDIF cable, then LiveProfessor2 shows -999.9dB
I change S/PDIF cable but the result is same. So I doubt Fireface400 now.


2. audio signal resolution in LiveProfessor2 is higher than console.
console -999.9dB because console cannot detect -157dB noise.


Thanks so much for your kind answeres. Although I don't know what is the true noise origin, it is not due to LiveProfessor2.
I will utilize LiveProfessor2 with confidence.


Best,


Takeshi
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nikolai
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Re: Does LiveProfessor2 always add some tiny noise?

Postby nikolai » Wed Oct 18, 2017 1:08 pm

Thank you for the update, glad you where able to figure it out.
Just for info, all internal processing is done as 32bit float, except in some very special functions where it is 64bit, so it should (internally) have a theoretical dynamic range of about 1500dB :shock:

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