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Comparing two audio interace mice pre's for self noise.



 
 
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  #1  
Old November 1st 19, 01:50 AM posted to rec.audio.pro
Tobiah
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Posts: 615
Default Comparing two audio interace mice pre's for self noise.

How would you do it? I have one of those 150 Ohm terminators
that you guys told me how to make. Given two USB audio interfaces,
what would be your procedure for comparing the two units (like
deciding which one to keep) with regard to the mic pre's, mostly
for noise figures.

I have a pair of NT1A's, and am looking for low noise and transparency.


Thanks!
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  #2  
Old November 1st 19, 02:18 AM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,651
Default Comparing two audio interace mice pre's for self noise.

In article >, Tobiah > wrote:
>How would you do it? I have one of those 150 Ohm terminators
>that you guys told me how to make. Given two USB audio interfaces,
>what would be your procedure for comparing the two units (like
>deciding which one to keep) with regard to the mic pre's, mostly
>for noise figures.


Set the gain the same way, put the terminator in, read the noise floor on
the meters.

If you don't trust the gain settings, put in a tone, set the gain, then
replace the tone source with a terminator. So that way you know the gain
is the same on both.

>I have a pair of NT1A's, and am looking for low noise and transparency.


Low noise isn't always transparency... often people will do tricks to
bring noise down at the expense of coloration.

Since most of the mike preamp noise is at low frequencies, if you design
it to roll everything off at 60 Hz or so the preamp seems a lot quieter...
but it isn't.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #3  
Old November 1st 19, 12:46 PM posted to rec.audio.pro
Mike Rivers[_2_]
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Posts: 2,077
Default Comparing two audio interace mice pre's for self noise.

On 10/31/2019 8:50 PM, Tobiah wrote:
> How would you do it?* I have one of those 150 Ohm terminators
> that you guys told me how to make.* Given two USB audio interfaces,
> what would be your procedure for comparing the two units (like
> deciding which one to keep) with regard to the mic pre's, mostly
> for noise figures.


I'd keep the one you like best for other reasons - included features,
understandable user interface for its internal mixer if it has one,
range of the gain control, convenient input and output connections,
reputation of the company.

Don't worry about measurements. Unless you're doing some recording that
requires very high gain with very low noise - in which case you probably
should be using an outboard mic preamp - preamp noise shouldn't be a
problem. But if you really want to measure something, connect your input
terminator, turn the input gain up all the way, record what's coming
out, and take an eyeball average of the playback level meter when
playing your test recording. You may need to add 30 dB or so of gain to
the "track" before you can read anything.

If you want to compare gains to throw that into your decision, you'll
need a signal generator. There are a number of ways that you can get a
test tone. If you don't have a signal generator, you can make one from a
computer or even a smart phone, by recording a WAV file and playing it
back. Connect your test signal to the mic input of one of the
interfaces, adjust the level of the signal generator so that you get a
record level of around -6 dBFS, then switch over to the other interface
and, with its gain control turned up full, and see if the record level
is higher or lower than the first one. If you find that one has several
more dB of gain than the other and the noise level is very close for
both, that's the "better" one.

But, as Scott said, noise isn't transparency. Listening is the best
measure of that since you're looking for something that's a matter of
personal taste. But you can use the program Room EQ Wizard to measure
harmonic distortion with respect to frequency, and see which harmonics
are predominant over the frequency range. That could give you a clue as
to expected "warmth" or "clarity."

If Recording Magazine would get back to putting some useful technical
stuff into their articles, they might get back to running my apparently
abandoned (with the new editor) Trust But Verify series that explains
how you can test your gear with things you're likely to have laying
around the house, or that don't cost much.


--
For a good time, call http://mikeriversaudio.wordpress.com
  #4  
Old November 1st 19, 02:44 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,651
Default Comparing two audio interace mice pre's for self noise.

In article >, Mike Rivers > wrote:
>But, as Scott said, noise isn't transparency. Listening is the best
>measure of that since you're looking for something that's a matter of
>personal taste. But you can use the program Room EQ Wizard to measure
>harmonic distortion with respect to frequency, and see which harmonics
>are predominant over the frequency range. That could give you a clue as
>to expected "warmth" or "clarity."


Record a distant piano in a quiet room and it will become very very obvious
which preamp is quieter and which one is less colored.

>If Recording Magazine would get back to putting some useful technical
>stuff into their articles, they might get back to running my apparently
>abandoned (with the new editor) Trust But Verify series that explains
>how you can test your gear with things you're likely to have laying
>around the house, or that don't cost much.


AudioXPress might run something like that.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #5  
Old November 1st 19, 10:17 PM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 451
Default Comparing two audio interace mice pre's for self noise.

Tobiah the Troll wrote:

------------------------
> How would you do it?



** This OCD ****ed fool never gives up, does he.


> I have one of those 150 Ohm terminators
> that you guys told me how to make. Given two USB audio interfaces,
> what would be your procedure for comparing the two units (like
> deciding which one to keep) with regard to the mic pre's, mostly
> for noise figures.
>
> I have a pair of NT1A's, and am looking for low noise and transparency.
>


** As you have been told before, condenser mics output noise form their internal electronics - way more than nearly any mic pre ever made !!!

The NT1A is no exception.

You are totally ****ing wasting both your and our time.

FFS get a life.


...... Phil


> Thanks!


  #6  
Old November 1st 19, 10:23 PM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 451
Default Comparing two audio interace mice pre's for self noise.

Scott Dorsey wrote:

----------------------
>
>
> Since most of the mike preamp noise is at low frequencies,
>


** No way.

Its white noise so mostly high frequency.

The noise level is proportional to bandwidth.

Noise between 10kHz and 20kHz is equal to that at all lower frequencies.


> if you design
> it to roll everything off at 60 Hz or so the preamp seems a lot quieter...
> but it isn't.
>


** Incomprehensible.

Mic pres do not have mains frequency hum.




...... Phil

  #7  
Old November 1st 19, 10:27 PM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 451
Default Comparing two audio interace mice pre's for self noise.

Scott Dorsey wrote:

-------------------

>
> Record a distant piano in a quiet room and it will become very very obvious
> which preamp is quieter and which one is less colored.
>


** The OP will need a damn quiet room.

Rode NT1As have a claimed self noise of 5dB A weighted.

Well below that of anything but an anechoic chamber.

FYI:

FFS stop feeing this seriously demented "Tobia" troll.



...... Phil
  #8  
Old November 2nd 19, 02:43 PM posted to rec.audio.pro
Scott Dorsey
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Posts: 16,651
Default Comparing two audio interace mice pre's for self noise.

In article >,
Phil Allison > wrote:
>Scott Dorsey wrote:
>
>> Record a distant piano in a quiet room and it will become very very obvious
>> which preamp is quieter and which one is less colored.
>>

>
>** The OP will need a damn quiet room.
>
> Rode NT1As have a claimed self noise of 5dB A weighted.


When you have mostly 1/f noise, it's easy to get a great-looking
specification on the datasheet by using A-weighting. But that does
not make it actually quiet.

You're right about needing a damn quiet room, because the room noise is
likely also worse at low frequencies.

> Well below that of anything but an anechoic chamber.


Above 1kc, sure.

I'll say that the piano test tells you about a lot more than just noise.
It tells you about how subjectively offensive the particular noise
spectrum is, and it tells you a whole lot about linearity. You should be
able to hear the piano note decay down slowly and hear room reverberations
well below the noise floor, and the tone should not change as they decay.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #9  
Old November 5th 19, 06:32 PM posted to rec.audio.pro
Tobiah
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Posts: 615
Default Comparing two audio interace mice pre's for self noise.


> FFS stop feeing this seriously demented "Tobia" troll.
> You are totally ****ing wasting both your and our time.


I'm sorry that circumstances have put you in a position in
life that causes you to be so miserable that you would feel
the need to find ways to hurt other people.

I've been on this list for 20 years or so and never had a
complaint. Is there anyone else on this list that views
my posts as a waste of our collective time? I normally
get helpful answers. Not sure why this one came out of
left field.


Tobiah


  #10  
Old November 5th 19, 09:26 PM posted to rec.audio.pro
Phil Allison[_4_]
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Posts: 451
Default Comparing two audio interace mice pre's for self noise.

Tobiah the Nut Case wrote:

----------------------------

> > FFS stop feeing this seriously demented "Tobia" troll.
> > You are totally ****ing wasting both your and our time.

>
>
> I'm sorry that circumstances have put you in a position in
> life that causes you to be so miserable that you would feel
> the need to find ways to hurt other people.
>


** LOL wot a ******.

> I've been on this list for 20 years or so and never had a
> complaint.


** Congratulations pal - you are sure getting them now to make up for lost time.

> Is there anyone else on this list that views
> my posts as a waste of our collective time?



** Most of the dopes here love having their time wasted.


> I normally get helpful answers.


** And you are still getting them too.

If only you were sane enough to tell.


> Not sure why this one came out of
> left field.
>


** Try reading what I posted over and over till it sinks in.

So far it has run right off you like water of a duck's you know what.

Quack, quack ....



....... Phil


 




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