Equalisation for PC mic input/line input
 

QUESTION:
Do the PC mic and line inputs use the same equalisation (on the
frequency spectrum)?


BACKGROUND:
I have some noisy voice tapes from an old analogue dictation machine.
I'm reading the recordings from the "ear" socket of my dictation
machine into my PC and then coverting the recordings to MP3.

Later I will get some software to clean up the noise on the MP3s.

I didn't expect it but my PC allows me to set a decent recording
level whether I record through the mic input or the line input.

Until I clean up the sound, the noise from the original recording
makes it hard to tell if I'm getting a better result from the mic
input or the line input.

I was wondering if there was a different equalisation used by the PC
for the mic and line inputs. If so then I would make sure I used


ANOTHER QUESTION:
What is the input level at which the mic and line inputs are rated?
I had thought mic inputs were about 3 or 3 mV and line inputs were
200 mV.

-------

NOTE:
My PC motherboard chipset is VIA KT266A + VT8235.
A PC reporting utility says it detects a VT8233/A AC97 Enhanced Audio
Controller.

Equalisation for PC mic input/line input
 

"Mike Walsh" wrote in message
...


"David Peters (UK)" wrote:

QUESTION:
Do the PC mic and line inputs use the same equalisation (on the
frequency spectrum)?

There is not equalization with line input, i.e. it uses flat frequency
response. I am not sure about microphone input; the biggest difference
seems to be they operate at a lower signal level.

Microphone inputs are also flat, i.e. with no equalisation. As you say, they
operate at a much lower level, typically a few millivolts.


You should use the line input with the headphone output, as both operate
at relatively high signal level with flat frequency response.

Correct.

Back in the days of analog recording 0 db was 1 volt. Since this was
analog the 0 db level could be and was often exceed. With the advent of
digital CDs the 0 db level became the maximum level, which can not be
exceeded because of the digital format, and is supposed to be 2 volts.
Since these are maximum levels the average will much lower.
Microphone levels are lower and vary widely.

Not quite. Firstly, a dB is a relative level, not an absolute, so without
stating the reference, a figure of "xdB" is meaningless. Originally, 0dB was
referenced to a power of 1mW into a load of 600 ohms, and was referred to as
0dBm. Later, the same voltage level, but unloaded, that is, without
reference to a 600 ohm load became 0dBu (that is, unloaded) Note that the
voltage level is the same in both cases (0.775v, or 1mW into 600 ohm) There
was a strange semi-standard evolved of referring to 1V rather than 0.775v
and that was 0dBv.

Digital outputs are referred to maximum digital output (when all the bits
are 1) and that is called 0dBFS (0dB Full Scale). It has NO analogue
equivalent, as analogue can keep getting bigger without limit, digital can't
get any bigger than when all the bits are 1. In Digital-Analogue conversion,
a number of different conversion levels have become more-or-less standard.
The EBU (European Broadcasting Union) have defined 0dBFS digital to mean
+18dBu analogue after conversion. The USA prefers that 0dBFS = +24dBu
because that provides 20dB headroom above 0VU. A few dissidents prefer
+25dBu as that's 1dB better than +24...........

CD players have evolved a standard output of 2v analogue for 0dBFS, but as
far as I'm aware, there is no official standard for this.

S.

Equalisation for PC mic input/line input
 

In message , Serge Auckland
writes

(snip)

The EBU (European Broadcasting Union) have defined 0dBFS digital to mean
+18dBu analogue after conversion.


Interesting.
Can you let me have a reference to the technical paper for that.
Cheers,
--
Kevin Seal (at home)
FZS600 in Banana
{kevin at the hyphen seal hyphen house dot freeserve dot co dot uk}

Equalisation for PC mic input/line input
 

"Kevin Seal" wrote in message
...
In message , Serge Auckland
writes

(snip)

The EBU (European Broadcasting Union) have defined 0dBFS digital to mean
+18dBu analogue after conversion.


Interesting.
Can you let me have a reference to the technical paper for that.
Cheers,
--
Kevin Seal (at home)
FZS600 in Banana
{kevin at the hyphen seal hyphen house dot freeserve dot co dot uk}


EBU R68-2000. I'm emailing you a copy directly.

S.

Equalisation for PC mic input/line input
 

In message , Serge Auckland
writes

"Kevin Seal" wrote in message
...
In message , Serge Auckland
writes

(snip)

The EBU (European Broadcasting Union) have defined 0dBFS digital to mean
+18dBu analogue after conversion.


Interesting.
Can you let me have a reference to the technical paper for that.
Cheers,


EBU R68-2000. I'm emailing you a copy directly.

Received, thanks.

With 0dBFS as =18dBU, that would mean OVU (+4dBU) would be -14dBFS. Most
people I know line-up their Pro Tools rigs for -18dBFS for 0VU hence
OdBFS is going to be +22dBU.
Isn't it a lovely world!
--
Kevin Seal (at home)
FZS600 in Banana
{kevin at the hyphen seal hyphen house dot freeserve dot co dot uk}

Equalisation for PC mic input/line input
 

"Kevin Seal" wrote in message
...
In message , Serge Auckland
writes

"Kevin Seal" wrote in message
...
In message , Serge Auckland
writes

(snip)

The EBU (European Broadcasting Union) have defined 0dBFS digital to mean
+18dBu analogue after conversion.


Interesting.
Can you let me have a reference to the technical paper for that.
Cheers,


EBU R68-2000. I'm emailing you a copy directly.

Received, thanks.

With 0dBFS as =18dBU, that would mean OVU (+4dBU) would be -14dBFS. Most
people I know line-up their Pro Tools rigs for -18dBFS for 0VU hence OdBFS
is going to be +22dBU.
Isn't it a lovely world!
--
Kevin Seal (at home)
FZS600 in Banana
{kevin at the hyphen seal hyphen house dot freeserve dot co dot uk}

Standard are great, that's why we have so many of them!

S.

Equalisation for PC mic input/line input
 

On Sun, 12 Mar 2006 13:41:15 GMT, "David Peters (UK)"
wrote:

QUESTION:
Do the PC mic and line inputs use the same equalisation (on the
frequency spectrum)?


BACKGROUND:
I have some noisy voice tapes from an old analogue dictation machine.
I'm reading the recordings from the "ear" socket of my dictation
machine into my PC and then coverting the recordings to MP3.

Later I will get some software to clean up the noise on the MP3s.

I didn't expect it but my PC allows me to set a decent recording
level whether I record through the mic input or the line input.

Until I clean up the sound, the noise from the original recording
makes it hard to tell if I'm getting a better result from the mic
input or the line input.

I was wondering if there was a different equalisation used by the PC
for the mic and line inputs. If so then I would make sure I used


ANOTHER QUESTION:
What is the input level at which the mic and line inputs are rated?
I had thought mic inputs were about 3 or 3 mV and line inputs were
200 mV.

-------

NOTE:
My PC motherboard chipset is VIA KT266A + VT8235.
A PC reporting utility says it detects a VT8233/A AC97 Enhanced Audio
Controller.


The short answer is that for best results you should:

- use a quality tape deck with line-out, not the earphone
jack of a dictation system

- use the line-in on a fair quality sound card, not
integrated motherboard audio with a really cheap codec.

Equalisation for PC mic input/line input
 

On 12 Mar 2006, Serge Auckland wrote:


Back in the days of analog recording 0 db was 1 volt. Since
this was analog the 0 db level could be and was often exceed.
With the advent of digital CDs the 0 db level became the
maximum level, which can not be exceeded because of the digital
format, and is supposed to be 2 volts. Since these are maximum
levels the average will much lower. Microphone levels are lower
and vary widely.

Not quite. Firstly, a dB is a relative level, not an absolute,
so without stating the reference, a figure of "xdB" is
meaningless. Originally, 0dB was referenced to a power of 1mW
into a load of 600 ohms, and was referred to as 0dBm. Later, the
same voltage level, but unloaded, that is, without reference to
a 600 ohm load became 0dBu (that is, unloaded) Note that the
voltage level is the same in both cases (0.775v, or 1mW into 600
ohm) There was a strange semi-standard evolved of referring to
1V rather than 0.775v and that was 0dBv.

Digital outputs are referred to maximum digital output (when all
the bits are 1) and that is called 0dBFS (0dB Full Scale). It
has NO analogue equivalent, as analogue can keep getting bigger
without limit, digital can't get any bigger than when all the
bits are 1. In Digital-Analogue conversion, a number of
different conversion levels have become more-or-less standard.
The EBU (European Broadcasting Union) have defined 0dBFS digital
to mean +18dBu analogue after conversion. The USA prefers that
0dBFS = +24dBu because that provides 20dB headroom above 0VU. A
few dissidents prefer +25dBu as that's 1dB better than
+24...........

CD players have evolved a standard output of 2v analogue for
0dBFS, but as far as I'm aware, there is no official standard
for this.


I can't say I understand all of what you write but the parts I do
understand are very useful to me. Thank you for posting.

Are there any web sites or documents which explain this sort of thing
for a beginner: rigorously but not going too fast.

Equalisation for PC mic input/line input
 

"David Peters (UK)" wrote in message
...
Lots snipped

I can't say I understand all of what you write but the parts I do
understand are very useful to me. Thank you for posting.

Are there any web sites or documents which explain this sort of thing
for a beginner: rigorously but not going too fast.

I don't know of any specific websites that explain all the ins and outs of
analogue and digital audio. I've learned all this during my professional
life in audio. There used to be a great magazine called Studio Sound, which
had technical articles explaining the basics in rigorous but understandable
form. Sadly SS has been extinct for several years, but you may find copies
in larger public libraries.

You may also want to look at Jim Lesurf's web sites -
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html

He's got a lot of useful information, and what's more, it's correct!

Canford Audio have useful information in their catalogue, you may want to
contact them and see if they'll put you on the mailing list for the
catalogue. www.canford.co.uk

S.

Equalisation for PC mic input/line input
 

In message , Rich Wilson
writes

"Serge Auckland" wrote in message
...

"Kevin Seal" wrote in message
...
In message , Serge Auckland
writes

"Kevin Seal" wrote in message
...
In message , Serge Auckland
writes

(snip)

The EBU (European Broadcasting Union) have defined 0dBFS digital to
mean
+18dBu analogue after conversion.


Interesting.
Can you let me have a reference to the technical paper for that.
Cheers,


EBU R68-2000. I'm emailing you a copy directly.

Received, thanks.

With 0dBFS as =18dBU, that would mean OVU (+4dBU) would be -14dBFS. Most
people I know line-up their Pro Tools rigs for -18dBFS for 0VU hence
OdBFS is going to be +22dBU.
Isn't it a lovely world!

Standard are great, that's why we have so many of them!

Decibels, to me, seem to be overused, particularly with digital audio. And
particularly because silence is negative infinity decibels, which isn't a
lot of good if you're writing a computer program that can only cope with
real numbers. What's wrong with plain old 0% to 100%?!
(Rhetorical question, don't feel obliged to answer...)


Are you trying to put us out of a job? :)
--
Kevin Seal (at home)
FZS600 in Banana
{kevin at the hyphen seal hyphen house dot freeserve dot co dot uk}