Reply
 
Thread Tools Display Modes
  #3   Report Post  
Mike Rivers
 
Posts: n/a
Default


In article writes:

I suspect that the most common means for setting the gain of
systems with digital recorders is to adjust something in the
analog signal chain that preceeds it.


I'm sure you're right about that.

For me, that's always the mic preamp.


But good gain management tells us that this isn't always the best way
to do it. (and of course we always want to do our best, don't we?) You
want to get all the gain you need in as early a stage as you can, and
then keep unity gain past that. So you adjust your preamp gain so that
it's plenty high but safely away from clipping, and at point, your
peaks are at +20 dBu. If your A/D converter is calibrated so that it
clips at +14 dBu ("calabrated" to -14) then your nice clean and quiet
preamp will cause your converter to clip. The right place to reduce
the level is at the output of the preamp, not the input, or at the
input of the A/D converter.

Conversely, if your converter has lower sensitivity, you might be
tempted to increase the gain of the preamp until it's going into
clipping, in an attempt to "record a hot signal." We see that a lot
around here.

Indeed, if the individual channel recordings fail the first
test above, its probable that your gain staging through the
console is off and needs adjusting.


Exactly - and that's what you can't always adjust in the right place.
Most of the time, the only control you have over the direct output of
a console (or channel insert send) is the mic preamp trim control. You
can usually make the record level meters look right but you might be
compromising the signal-to-noise ratio or you might be driving your
mic preamp into clipping.

If you're smart, in the latter case, you'll recognize that it's
clipping and back it off (and complain that your preamp isn't "hot
enough." but most of the time probalby what will happen is that the
clipped signal will be reocrded and the A/D converter will get blamed.

--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo
  #4   Report Post  
Arny Krueger
 
Posts: n/a
Default

"Mike Rivers" wrote in message
news:znr1119976835k@trad
In article
writes:

I suspect that the most common means for setting the gain

of
systems with digital recorders is to adjust something in

the
analog signal chain that preceeds it.


I'm sure you're right about that.

For me, that's always the mic preamp.


But good gain management tells us that this isn't always

the
best way to do it. (and of course we always want to do our
best, don't we?) You want to get all the gain you need in

as
early a stage as you can, and then keep unity gain past

that.

My approach does just that.

So you adjust your preamp gain so that it's plenty high

but
safely away from clipping, and at point, your peaks are at

+20
dBu. If your A/D converter is calibrated so that it clips

at
+14 dBu ("calabrated" to -14) then your nice clean and

quiet
preamp will cause your converter to clip.


No, that's not how I do it, nor is it how I advise people to
do it.

I tell people to adjust the gain (in this case the mic
preamp gain) so that they have the desired amount of
headroom in the digital domain - by looking at the actual
display of an actual recording they make during rehearsal.

IOW, if the user manual says that the direct outs or
inserts are +4, then I set the input sensitivity on the
computer digital audio interface to +4 and then set the
trims or mic preamp gains so that the display in the DAW
software shows that the loudest part of the loudest music is
still recording at least 10 dB below FS. If I work on mixing
the tracks and see that the headroom for some channel is
less than 10 dB, I nudge the related trim down as required
before I record the next session.

The right place to reduce
the level is at the output of the preamp, not the input,

or at
the input of the A/D converter.


I think that's what I meant by: "For me, that's always the
mic preamp."

Conversely, if your converter has lower sensitivity, you

might
be tempted to increase the gain of the preamp until it's

going
into clipping, in an attempt to "record a hot signal." We

see
that a lot around here.


Hence my constant harping about maintaining about 10 dB
headroom over actual observed levels, as seen in the digital
domain.

Indeed, if the individual channel recordings fail the

first
test above, its probable that your gain staging through

the
console is off and needs adjusting.


Exactly - and that's what you can't always adjust in the

right place.

If your direct outs or insert points are running at the same
nominal level as your digital recorder's input sensitivity
is set for, then adjusting the mic preamp to make the
digital recorder happy automatically ensures that the rest
of the console will be happy, too.


Most of the time, the only control you have over the
direct output of
a console (or channel insert send) is the mic preamp trim
control.


Agreed.

You can usually make the record level meters look
right but you might be compromising the signal-to-noise

ratio
or you might be driving your mic preamp into clipping.


rant on

Where did I say *anything* about meters? I hate meters. I
never take them seriously when I am recording or mixing. I
ordered my new 02R96 without a meter bridge, and I hope to
*never* have any meters attached to it. I expect to make
minimal use of the 02R96 built-in metering. The output leds
on my Mackie SR32 are among its least-used features. BTW,
when I do look at them they look *right*, but that's a
natural consequence of good hygiene everyplace else.

rant off

If you're smart, in the latter case, you'll recognize that

it's
clipping and back it off (and complain that your preamp

isn't
"hot enough." but most of the time probalby what will

happen
is that the clipped signal will be reocrded and the A/D
converter will get blamed.


That's one reason why I tell people to set levels based on
the individual channel display(s) at full magnification in
the DAW software. Then, there's no question about how much
headroom there is between peaks and FS, and there's no
question about how meter response relates to the music you
are recording.


  #5   Report Post  
Mike Rivers
 
Posts: n/a
Default


In article writes:

IOW, if the user manual says that the direct outs or
inserts are +4, then I set the input sensitivity on the
computer digital audio interface to +4 . . . . .


One of my all-too-often points is that many computer digital audio
interfaces have no way to set the input sensitivity unless you do it
externally. "External" could be an output level control on the mic
preamp, or, if you have no other choice, the input gain of the preamp.
But that only works if you have to turn the level to the converter
down, not up, to achieve the desired amount of headroom.

It can all be workable, and I know that you have the understanding to
make it work. But most of the time when people are faced with this
problem, they don't have time to learn what's happening, they work on
instinct (or just turn knobs until the meters read right, not
listening to what's being recorded) and then ask on r.a.p. after the
fact what was wrong with their mic preamp.

If your direct outs or insert points are running at the same
nominal level as your digital recorder's input sensitivity
is set for, then adjusting the mic preamp to make the
digital recorder happy automatically ensures that the rest
of the console will be happy, too.


But that "if" isn't universally true. If there was in interface
standard to which the industry adhered, we'd have an easier time with
this, but marketing pressures more often that not at least on gear
that might be somewhat lacking) cause this to be moved around for the
sake of the best advertiseable numbers.

Where did I say *anything* about meters? I hate meters.


Meters are good, but you have to know what they're telling you. I
woudln't want to be without a meter bridge on my console because it's
a quick look at what's working and what needs some attention.

That's one reason why I tell people to set levels based on
the individual channel display(s) at full magnification in
the DAW software.


I can't think of a program that allows you to do this in real time
though. It takes a test recording (or several), and faith that the
setting you've established during your test will represent what
happens in an actual take. Leaving 20 dB of headroom is usally safe,
but on a graphic display, that just looks like a skinny wiggly line. A
waveform display is really only useful when you're close to the limit.

Keeping a watchful eye on the meters allows you to make adjustments in
real time if necessary. But then this is a skill that you have to
develop, along with others.



--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo


  #6   Report Post  
Arny Krueger
 
Posts: n/a
Default

"Mike Rivers" wrote in message
news:znr1120045997k@trad
In article
writes:

IOW, if the user manual says that the direct outs or
inserts are +4, then I set the input sensitivity on the
computer digital audio interface to +4 . . . . .


One of my all-too-often points is that many computer

digital
audio interfaces have no way to set the input sensitivity
unless you do it externally.


Well *many* is one of those vague words that seems to mean
something... ;-)

Almost all of the pro interfaces I've used (over 30) have
had at least -10 and +4 as options. One recent big nasty
surprise was the fact that the AP 24192 lacked the slectable
input sensitivity feature that graces virtually all of the
rest of the M-Audio line. But, it does a pretty credible
+4, and that is *the* pro standard, right?

"External" could be an output
level control on the mic preamp, or, if you have no other
choice, the input gain of the preamp. But that only works

if
you have to turn the level to the converter down, not up,

to
achieve the desired amount of headroom.


The way almost every audio interface stacks up is that the
the stated sensitivity is way under FS. IOW a -10 input will
generally put FS someplace around 2 volts, and a +4 input
runs from 2.5 to about 8 volts for FS.

It can all be workable, and I know that you have the
understanding to make it work. But most of the time when
people are faced with this problem, they don't have time

to
learn what's happening, they work on instinct (or just

turn
knobs until the meters read right, not
listening to what's being recorded) and then ask on r.a.p.
after the fact what was wrong with their mic preamp.


That's one reason why I keep telling people to match up the
specified numbers on the preamp and the interface, and then
*look* at what they are recording.

If your direct outs or insert points are running at the

same
nominal level as your digital recorder's input

sensitivity
is set for, then adjusting the mic preamp to make the
digital recorder happy automatically ensures that the

rest
of the console will be happy, too.


But that "if" isn't universally true.


Nothing is universally true, but what do you call a console
that gets bent of shape if you take its specs at face value?
I call it unprofessional junk. Its not like the console
market has a sole source...

If there was in interface
standard to which the industry adhered, we'd have an

easier
time with this, but marketing pressures more often that

not at
least on gear
that might be somewhat lacking) cause this to be moved

around
for the sake of the best advertiseable numbers.


I don't see a lot of marketing grease in fudging specd
output levels.

Where did I say *anything* about meters? I hate meters.


Meters are good, but you have to know what they're telling
you.


Plan B: forget about what the meters say and trust the most
relevant and accurate empirical results. In the race between
ears and meters I'll take ears every place they work.

I woudln't want to be without a meter bridge on my
console because it's a quick look at what's working and

what needs some attention.

If you haven't noticed, I recommend a paradigm for recording
that really doesn't require a lot of attention during
tracking. Someplace around 16 tracks one meter per track
starts becoming more of a light show than a relevant tool.
I'll take the ability to listen to the track with headphones
(a la Mackie's grotesquely misnamed solo buttons) over a
meter, any day. Thats one reason why consoles have headphone
jacks - so you can listen! ;-)

That's one reason why I tell people to set levels based

on
the individual channel display(s) at full magnification

in
the DAW software.


I can't think of a program that allows you to do this in

real
time though.


It's very hard to do metering right in real time. So, why
make it a critical sucess factor?

It takes a test recording (or several), and faith
that the setting you've established during your test will
represent what happens in an actual take.


Admittedly you have to know something about the work habits
of the talent and the equipment. Getting along with and
having a feel for talent is one of those big advantages of
using flesh and blood technical staff as opposed to relying
on machines for that.

Besides, level setting need only be very approximate during
tracking - that's one of the things that headroom is for.

Having 20 dB of headroom is usally
safe, but on a graphic display, that just looks like a

skinny
wiggly line.


Hence my repeated advice that people only seriously judge
waves based a full-screen view per track. Besides 20 dB
headroom is pretty excessive in most cases. Did someone say
10 dB headroom? ;-)

A waveform display is really only useful when
you're close to the limit.


Agreed, so there's no reason to make the waveform display
during recording, a critical sucess factor, either.

Keeping a watchful eye on the meters allows you to make
adjustments in real time if necessary.


Real time adjustments make mixing more confusing and more
work later on. Bad form for tracking except in dire
emergencies.

But then this is a skill that you have to develop, along

with others.

I see real time adjustments as a skill I only practice when
I'm doing live sound.

I think I made my last real time adjustment for recording
levels during tracking about 3 months ago... That ruined the
whole day for me! ;-)


  #7   Report Post  
Mike Rivers
 
Posts: n/a
Default


In article writes:

Well *many* is one of those vague words that seems to mean
something... ;-)


That's why I used "many" rather than "most."

Almost all of the pro interfaces I've used (over 30) have
had at least -10 and +4 as options.


Yes, but what digital level is represented by -10 dBV or +4 dBu?
That's where you need the missing control, so you can set it for
-20, -18, -14, -12 or whatever you want.

One recent big nasty
surprise was the fact that the AP 24192 lacked the slectable
input sensitivity feature that graces virtually all of the
rest of the M-Audio line. But, it does a pretty credible
+4, and that is *the* pro standard, right?


Right. What's its calibration? Put in +4 dBu and how many dBFS do you
get? Whatever it is, you take it or leave it (or compensate for it
elsewhere). That's my beef.

The way almost every audio interface stacks up is that the
the stated sensitivity is way under FS. IOW a -10 input will
generally put FS someplace around 2 volts, and a +4 input
runs from 2.5 to about 8 volts for FS.


Well, for the "+4 input" that's about a 10 dB range in calibration -
not very standard, is it?

I don't see a lot of marketing grease in fudging specd
output levels.


No, but they want to make the S/N and noise floor numbers as good as
they can. One way to do this is to eliminate any unnecessary gain or
gain control element on the input or output.

If you haven't noticed, I recommend a paradigm for recording
that really doesn't require a lot of attention during
tracking.


It depends on what you're tracking. You can get away with that
sometimes. If it works for you, fine. But not everyone will be happy
with set-it-and-forget-it.

It's very hard to do metering right in real time. So, why
make it a critical sucess factor?


Program? Metering? I thought we were talking about real meters here.

Besides, level setting need only be very approximate during
tracking - that's one of the things that headroom is for.


No, headroom is so that you can accommodate dynamic range of
performance, not accommodate unpredictable performance. One good
example of wanting to ride a fader (or preamp gain) is when a
performer goes from singing to talking. There might be a 20 dB
difference that it's good to make up at the front. It's just good
engineering practice.

Real time adjustments make mixing more confusing and more
work later on. Bad form for tracking except in dire
emergencies.


Good real time adjustments make mixing easier. Good tracks practically
mix themselves.

I see real time adjustments as a skill I only practice when
I'm doing live sound.


I'm ALWAYS doing live sound, even when recording in the studio.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo
  #8   Report Post  
Arny Krueger
 
Posts: n/a
Default

"Mike Rivers" wrote in message
news:znr1120063521k@trad
In article
writes:

Well *many* is one of those vague words that seems to

mean
something... ;-)


That's why I used "many" rather than "most."

Almost all of the pro interfaces I've used (over 30) have
had at least -10 and +4 as options.


Yes, but what digital level is represented by -10 dBV or

+4
dBu?


Something like 12 to 16 dB below FS.

That's where you need the missing control, so you can set

it
for -20, -18, -14, -12 or whatever you want.


But, we don't have that. What we do have gets us within a
few dB of a standard.

One recent big nasty
surprise was the fact that the AP 24192 lacked the

slectable
input sensitivity feature that graces virtually all of

the
rest of the M-Audio line. But, it does a pretty credible
+4, and that is *the* pro standard, right?


Right. What's its calibration? Put in +4 dBu and how many

dBFS
do you get? Whatever it is, you take it or leave it (or
compensate for it elsewhere). That's my beef.


Nothing's perfect. OTOH, close is fine when it comes to
setting headroom.

The way almost every audio interface stacks up is that

the
the stated sensitivity is way under FS. IOW a -10 input

will
generally put FS someplace around 2 volts, and a +4 input
runs from 2.5 to about 8 volts for FS.


Well, for the "+4 input" that's about a 10 dB range in
calibration - not very standard, is it?


I guess we need to put this on our wish lists for audio
interface vendors.

I don't see a lot of marketing grease in fudging specd
output levels.


No, but they want to make the S/N and noise floor numbers

as
good as they can. One way to do this is to eliminate any
unnecessary gain or gain control element on the input or
output.


Agreed, and that's pretty much how the whole industry went.


If you haven't noticed, I recommend a paradigm for

recording
that really doesn't require a lot of attention during
tracking.


It depends on what you're tracking. You can get away with

that
sometimes. If it works for you, fine. But not everyone

will be
happy with set-it-and-forget-it.



Paradigm shift is pretty well guaranteed to make *someone*
unhappy. Better, easier speaks to me.


It's very hard to do metering right in real time. So, why
make it a critical sucess factor?


Program? Metering? I thought we were talking about real

meters
here.


On top of everything else they do suboptimally, real meters
cost money! Bahhh!

Besides, level setting need only be very approximate

during
tracking - that's one of the things that headroom is for.


No, headroom is so that you can accommodate dynamic range

of
performance, not accommodate unpredictable performance.


There's plenty of evidence that headroom suits both
purposes.

One good example of wanting to ride a fader (or preamp

gain) is when a
performer goes from singing to talking.


Thing is, you can handle that common situation far better
after the fact.

There might be a 20 dB
difference that it's good to make up at the front.


If it could be done as well in real time, but it can't.

It's just good engineering practice.


What constitutes good engineering practice changes with the
state of the art.

Real time adjustments make mixing more confusing and more
work later on. Bad form for tracking except in dire
emergencies.


Good real time adjustments make mixing easier.


Due to the well-known failings of human omnisicence,
real-time mixing is very limited in terms of precision and
accuracy. Because it always has to happen in real time, it
can be far more time-consuming than is necessary.

Due to the well-known superiority of hindsight to foresight,
mixing during the mix is generally the better way to go.

Good tracks practically mix themselves.


The mix is the best time to mix. That's why they call it the
mix. ;-)

I see real time adjustments as a skill I only practice

when
I'm doing live sound.


I'm ALWAYS doing live sound, even when recording in the

studio.

Show me how to make foresight as accurate and reliable as
hindsight, and you've got a deal!


  #9   Report Post  
Bob Cain
 
Posts: n/a
Default



Arny Krueger wrote:

That's one reason why I tell people to set levels based on
the individual channel display(s) at full magnification in
the DAW software. Then, there's no question about how much
headroom there is between peaks and FS, and there's no
question about how meter response relates to the music you
are recording.


It's really just a different kind of meter, a fast one with
history. I agree with you, by the way.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein
Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
on topic: we need a rec.audio.pro.ot newsgroup! Peter Larsen Pro Audio 125 July 9th 08 06:16 PM
Artists cut out the record biz [email protected] Pro Audio 64 July 9th 04 10:02 PM


All times are GMT +1. The time now is 03:34 AM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"