Re: [LAU] Focusrite Scarlett 18i8

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To: <linux-audio-user@...>
Date: Friday, January 10, 2014 - 11:20 pm

On Fri, Jan 10, 2014 at 10:48:15PM +0000, James Stone wrote:

> > Do you mean the spectrum analyser showed a trace at -90 dB ?

It means something... but what it means is another question.

Assume

* the noise is more or less white (if not: real trouble)
* the spectrum analyser uses an 1024 point FFT (typical),
* and a raised cosine window (also typical),

Then the full bandwidth (1/2 Fs) is covered by 512 filters,
and each of these has a bandwidth that is 1.5 times that of
a rectangular filter.

So each filter sees 1.5 / 512 of the total power.

10 * log10 (1.5 / 512) is -25.3 dB

So the noise level would be around -93 + 25 = -68 dB.

You could check this with jnoisemeter.

> With further testing, I think I can detect a similar change in gain

That could as well be due to the random alignment of the signal and
the periods of the analyser.

> I think

Unless you pay at least 10 times more they will analog pots, and they
all show this effect to some degree.

Ciao,

--
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Messages in current thread:
[LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Tue Jan 7, 3:10 pm)
Re: [LAU] Focusrite Scarlett 18i8, Robin Gareus, (Wed Jan 8, 4:06 am)
Re: [LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Wed Jan 8, 1:41 pm)
Re: [LAU] Focusrite Scarlett 18i8, Robin Gareus, (Wed Jan 8, 2:52 pm)
Re: [LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Wed Jan 8, 3:43 pm)
Re: [LAU] Focusrite Scarlett 18i8, Robin Gareus, (Wed Jan 8, 4:04 pm)
Re: [LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Wed Jan 8, 10:21 pm)
Re: [LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Wed Jan 8, 4:24 pm)
Re: [LAU] Focusrite Scarlett 18i8, Jeremy Jongepier, (Wed Jan 8, 8:40 am)
Re: [LAU] Focusrite Scarlett 18i8, James Stone, (Fri Jan 10, 8:42 pm)
Re: [LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Fri Jan 10, 10:20 pm)
Re: [LAU] Focusrite Scarlett 18i8, James Stone, (Fri Jan 10, 10:48 pm)
Re: [LAU] Focusrite Scarlett 18i8, Fons Adriaensen, (Fri Jan 10, 11:20 pm)
Re: [LAU] Focusrite Scarlett 18i8, James Stone, (Sat Jan 11, 10:20 am)
Re: [LAU] Focusrite Scarlett 18i8, Tim Goetze, (Wed Jan 8, 9:37 am)
Re: [LAU] Focusrite Scarlett 18i8, James Stone, (Thu Jan 9, 9:23 pm)
Re: [LAU] Focusrite 2i4, Tim Goetze, (Fri Jan 10, 10:33 am)
Re: [LAU] Focusrite 2i4, James Stone, (Fri Jan 10, 10:40 am)
Re: [LAU] Focusrite 2i4, Tim Goetze, (Mon Jan 27, 2:34 pm)
Re: [LAU] Focusrite 2i4, James Stone, (Mon Jan 27, 2:44 pm)
Re: [LAU] Focusrite 2i4, Tim Goetze, (Fri Jan 10, 11:33 am)
Re: [LAU] Focusrite 2i4, Kees van Veen, (Fri Jan 10, 4:30 pm)
Re: [LAU] Focusrite 2i4, Tim Goetze, (Mon Jan 13, 8:58 am)
Re: [LAU] Focusrite 2i4, James Stone, (Mon Jan 13, 10:49 am)
Re: [LAU] Focusrite 2i4, Tim Goetze, (Mon Jan 13, 12:25 pm)
Re: [LAU] Focusrite 2i4, James Stone, (Sat Jan 11, 7:52 pm)
Re: [LAU] Focusrite 2i4, Jeremy Jongepier, (Sat Jan 11, 10:22 pm)
Re: [LAU] Focusrite 2i4, Kees van Veen, (Sun Jan 12, 9:19 pm)
Re: [LAU] Focusrite Scarlett 18i8, James Stone, (Wed Jan 8, 10:55 am)
Re: [LAU] Focusrite 2i4, Tim Goetze, (Wed Jan 8, 12:07 pm)