[peter]

Is there any portable mixer/pre-amp for microphone with an AGC that works
almost as well as a human operator?

It should allow the operator to set the maximum gain limit so that
background noise does not become noticeable when nobody is talking. But if
the input is too strong, it should reduce the gain automatically, and
gradually increase it (perhaps this rate of increase is also adjustable).

I heard of a feature called a "soft limiter". I'm guessing this reduces the
gain to avoid clipping, but the moment the strong signal is gone, it
instantly returns to its previous gain. I want the gain to return
*gradually*.

This would be useful for shooting video when I already have too many other
things to adjust. The built-in AGC of camcorder usually increases the
background noise to an annoying level.

[Mike Rivers]

peter wrote:
Is there any portable mixer/pre-amp for microphone with an AGC that works
almost as well as a human operator?

No, and in fact, a lot of human operators don't work all that well.

It should allow the operator to set the maximum gain limit so that
background noise does not become noticeable when nobody is talking. But if
the input is too strong, it should reduce the gain automatically, and
gradually increase it (perhaps this rate of increase is also adjustable).

This is what a compressor does. But it's not an automatic gain control

I heard of a feature called a "soft limiter". I'm guessing this reduces the
gain to avoid clipping, but the moment the strong signal is gone, it
instantly returns to its previous gain.

A "soft limiter" is one that doesn't suddenly flatten out the output
vs. input curve at a certain level (as a hard limited does) but rather
starts reducing the gain slowly over a range of input level so that the
change from no limiting to limiting is gradual..

I want the gain to return *gradually*.

This is adjustable on many compressors and limiters. It's known as the
"release time."

This would be useful for shooting video when I already have too many other
things to adjust.

That's when you need an audio engineer to help you out (or a cameraman,
if your primary interest is with the audio). There's no such thing as
an ideal automatic level control. One thing that a human can do that a
circuit can't is see what's happening and anticipate what adjustments
will be necessary.

The built-in AGC of camcorder usually increases the
background noise to an annoying level.

Best to just turn it off, record at a level that doesn't overload, and
make volume adjustments in production. But of course when you have to
turn something up, expect the background noise to come up along with
it. But at least the background noise won't come up when there's no
input.

[Steve King]

"Chel van Gennip" wrote in message
...
On Sun, 20 Aug 2006 14:21:22 +0200, peter wrote:

Is there any portable mixer/pre-amp for microphone with an AGC that
works almost as well as a human operator?

....

This would be useful for shooting video when I already have too many
other things to adjust. The built-in AGC of camcorder usually increases
the background noise to an annoying level.

Yes: an AGC switched OFF. The dynamic range of even a 16 bit recording is
sufficient to record without gain adjustments during recording.


The dynamic range of "even 16 bit recording", in theory, has little to do
with the signal to noise capabilities of many pro-sumer cameras in common
use. In cameras such as the VX2000/PD150 and their successors the
microphone pre-amps are sufficiently noisy that audio recorded without
compression and with sufficient head-room to avoid clipping are often too
noisy to use. Remember, the OP wants to set it and forget it. The AGC in
the VX2000 is a peak limiter. It does not ride up the gain on quiet
passages. It does maximize the recording levels. It doesn't clip. It
isn't a great solution, but it is better than noisy tracks.

Steve King

[Julian]

On Sun, 20 Aug 2006 12:21:22 GMT, "peter" wrote:

Is there any portable mixer/pre-amp for microphone with an AGC that works
almost as well as a human operator?

It should allow the operator to set the maximum gain limit so that
background noise does not become noticeable when nobody is talking. But if
the input is too strong, it should reduce the gain automatically, and
gradually increase it (perhaps this rate of increase is also adjustable).

Audio Technica makes automatic mixers:

http://www.audio-technica.com/cms/mi...a45/index.html

also:

http://www.lectrosonics.com/lecnet/am8.htm

Shure has discontinued this model:

http://www.shure.com/ProAudio/Produc...MS8100_content

Julian

[Julian]

On 20 Aug 2006 06:14:44 -0700, "Mike Rivers"
wrote:

That's when you need an audio engineer to help you out (or a cameraman,
if your primary interest is with the audio). There's no such thing as
an ideal automatic level control. One thing that a human can do that a
circuit can't is see what's happening and anticipate what adjustments
will be necessary.

In a perfect world given certain applications and budget. We don't
anything about his application or budget. An automatic mixer might be
just what he needs.

I have mixed audio for video shoots in situations where there is a
panel discussion for example and it is difficult to anticipate who is
going to jump on mic next. To make this sound smooth without gates,
you have to leave everything up higher than you'd like and more get
background noise as well. An automated gate / AGC mixer can actually
do a better job than a live person in certain situations.

The built-in AGC of camcorder usually increases the
background noise to an annoying level.

Best to just turn it off, record at a level that doesn't overload, and
make volume adjustments in production.

In some situations yes, others no.

But of course when you have to
turn something up, expect the background noise to come up along with
it.

Not if he gates only the mic that is being used.

Julian

[Mike Rivers]

Julian wrote:

In a perfect world given certain applications and budget. We don't
anything about his application or budget. An automatic mixer might be
just what he needs.

But that's not what he asked for. An automatic mixer doesn't do what he
needs anyway. An automatic mixer is to keep the gain of several mics
below the feedbak level, and mix with some intelligence if two people
are talking at once. They also have priority features so that one
designated speaker can always talk louder than anyone else. And if he
had a budget, the best way to spend it would be with an assitant rather
than a piece of hardware. It's peope who have limited budgets who try
to do too many things themself - and he said specifically that was his
problem.

Surely you have something better to contribute than to comment on my
assumption about his budget and needs. I'll bet you a quarter that I'm
right about this.

I have mixed audio for video shoots in situations where there is a
panel discussion for example and it is difficult to anticipate who is
going to jump on mic next.

Did he say anything about panel discussions or multiple mics? Perhaps
multiple mics and an automatic mixer would be the best solution, but I
don't think you have any reason to assume that this is what he's doing.
And, sure, it's "difficult" to anticipate who is going to jump on mic
next, but that's why you pay attention, keep a finger on each fader,
and watch who's moving toward a mic. This is a skill that you develop
when you work with this sort of thing. Automatic mixers are for
unattended sound reinforcement, not mixing for recording.

To make this sound smooth without gates,
you have to leave everything up higher than you'd like and more get
background noise as well. An automated gate / AGC mixer can actually
do a better job than a live person in certain situations.

Shure used to make a gated mixer that allowed you to set the "gated
off" gain so that you didn't hear a large change in background level
when the gate opens. But the gain with the gate open is set by the
channel volume control. If you have the same speakers, usually you only
need to set the gain once for each speaker (unless they get into a
shouting match) and then you can leave things alone.


The built-in AGC of camcorder usually increases the
background noise to an annoying level.

Best to just turn it off, record at a level that doesn't overload, and
make volume adjustments in production.

In some situations yes, others no.

If increased background noise is a problem, then it should be turned
off. If there's always something coming into the mic, you can use it,
but you're still better off without it. It's a crutch and it never
works as well as a real operator. However, some cameras (mea culpa - it
tends to be a low budget "feature") don't allow you to turn it off -
which would also largely defeat an automated mixer.

But of course when you have to
turn something up, expect the background noise to come up along with
it.

Not if he gates only the mic that is being used.

And if there's only one mic, you can't gate it and turn it up at the
same time.

Why are you confusing the issue with your arguments of my completely
valid points, based on the question and the way it was asked? Do you
know something that I don't?

[David Satz]

peter wrote:

Is there any portable mixer/pre-amp for microphone with an AGC that works
almost as well as a human operator?

The practical benefit of an AGC--preventing both overload and signals
getting "buried" in the background noise of a recording--is based the
fact that it adjusts its gain (amplification factor) dynamically. But
the more it has to do so, the worse the recording will sound, simply
because such gain changes are disorienting to the ear.

Thus by the nature of the task, there's a limit to how much benefit you
can ever obtain from any AGC without grossly audible side effects. It's
not so much a matter of a good or a bad AGC; there's no AGC in the
world that can sound good if it continually has to adjust the recording
gain by substantial amounts.

If you can anticipate the loudest sounds and set your gains
accordingly, the AGC won't need to do very much. The less an AGC has to
vary its signal gain during a recording, the less offensive those gain
changes will ultimately sound.


I heard of a feature called a "soft limiter". I'm guessing this reduces the
gain to avoid clipping, but the moment the strong signal is gone, it
instantly returns to its previous gain. I want the gain to return
*gradually*.

Right--as you seem to have realized, a "soft limiter" is exactly what
you _don't_ want for this application.


This would be useful for shooting video when I already have too many other
things to adjust. The built-in AGC of camcorder usually increases the
background noise to an annoying level.

That's symptomatic of an AGC in which the nominal gain has been set too
high for the sound levels and the sensitivity of the microphone(s) that
you're using. If your circuit has any user-adjustable settings (which
it may well not), try turning down its gain control. Conceivably the
circuit could still be of use that way--or you could create a similar
effect by padding down (attenuating) the signal(s) from the
microphone(s), though that carries a risk of raising the effective
noise level of the microphone preamp(s) in the camcorder. It's worth at
least a bit of experimentation.

--best regards

[Scott Dorsey]

In article 6tYFg.2732$hP6.1109@trnddc04, peter wrote:
Is there any portable mixer/pre-amp for microphone with an AGC that works
almost as well as a human operator?

For what? For voice use?

It should allow the operator to set the maximum gain limit so that
background noise does not become noticeable when nobody is talking. But if
the input is too strong, it should reduce the gain automatically, and
gradually increase it (perhaps this rate of increase is also adjustable).

And it shouldn't pump it up between words either.

I heard of a feature called a "soft limiter". I'm guessing this reduces the
gain to avoid clipping, but the moment the strong signal is gone, it
instantly returns to its previous gain. I want the gain to return
*gradually*.

You might want something like an Audimax. The Audimax has all sorts of
stuff in it to prevent pumping. It will still pump like hell given a lot
of signal sources, though.

This would be useful for shooting video when I already have too many other
things to adjust. The built-in AGC of camcorder usually increases the
background noise to an annoying level.

It's too late, then. If you can't defeat the camcorder AGC, you're screwed.
If you CAN defeat the camcorder AGC, just leave the levels way down and bring
them up in post. If you don't have a low enough noise floor to be able to do
that, go double-system.

Or hire a mixer.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Steve King]

"Chel van Gennip" wrote in message
...
On Sun, 20 Aug 2006 16:21:41 +0200, Steve King wrote:

The dynamic range of "even 16 bit recording", in theory, has little to
do with the signal to noise capabilities of many pro-sumer cameras in
common use.

SNIP
Therfore I only use the audio from the camera for synchronisation. I use a
seperate 24 bit recorder for audio. Then you are able to record at a fixed
level, and adjust levels later in your DAW without noise penalties.

That's nice, when you can do it. The video production jobs that we do often
don't allow that for either logistical or budget reasons. Last week we were
videotaping an unusually demanding crane lift. I had three cameras with an
'expert' commenting on the operation at each camera. Three mixers (human
beings) with double system kit simply wasn't a possibility. I have fought
for double-system recording, when videotaping music; sometimes one wins
those fights; sometimes one doesn't.

Steve King

[Scott Dorsey]

Steve King wrote:

That's nice, when you can do it. The video production jobs that we do often
don't allow that for either logistical or budget reasons. Last week we were
videotaping an unusually demanding crane lift. I had three cameras with an
'expert' commenting on the operation at each camera. Three mixers (human
beings) with double system kit simply wasn't a possibility. I have fought
for double-system recording, when videotaping music; sometimes one wins
those fights; sometimes one doesn't.

So treat that as MOS... keep some of the location sound for an effects
track but redub the "expert" in again after the fact. That's how it
would be done shooting film, anyway.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Julian]

On 20 Aug 2006 08:22:49 -0700, "Mike Rivers"
wrote:

An automatic mixer doesn't do what he
needs anyway. An automatic mixer is to keep the gain of several mics
below the feedbak level, and mix with some intelligence if two people
are talking at once.

And gates off mics that aren't being used. That will certainly help
keep the noise floor down.

the best way to spend it would be with an assitant rather
than a piece of hardware. It's peope who have limited budgets who try
to do too many things themself - and he said specifically that was his
problem.

Sometimes, no matter how good a live person is a gate is better.

Surely you have something better to contribute than to comment on my
assumption about his budget and needs. I'll bet you a quarter that I'm
right about this.

I see it happen over and over where everyone gets off a an tangent
that may make perfect technical sense in a theoretical manner but is
totally irrelevant to the OP's actual situation. You might be right
but the way but he asked for advice on an automatic device. I think
he would probably have already thought of hiring someone first if that
fit his need.

You're on for that quarter.

And, sure, it's "difficult" to anticipate who is going to jump on mic
next, but that's why you pay attention, keep a finger on each fader,
and watch who's moving toward a mic. This is a skill that you develop
when you work with this sort of thing.

I have some skill and have done jobs where I wished I had gates.
Others where I did have gates and it went much better.

Automatic mixers are for
unattended sound reinforcement, not mixing for recording.

I think that is not necessarily true. The AT mixer I linked to
mentions using it for camera audio.

Shure used to make a gated mixer that allowed you to set the "gated
off" gain so that you didn't hear a large change in background level
when the gate opens.

I think that is the Shure product I gave a link to.

Why are you confusing the issue with your arguments of my completely
valid points, based on the question and the way it was asked? Do you
know something that I don't?

I'd have to ask you the exactly the same. there are a lot of
situations where a gated mixer or automatic mixer of some sort is
perfect legit. The OP specifically asked for such a device.

Julian

[Steve King]

"Scott Dorsey" wrote in message
...
Steve King wrote:

That's nice, when you can do it. The video production jobs that we do
often
don't allow that for either logistical or budget reasons. Last week we
were
videotaping an unusually demanding crane lift. I had three cameras with
an
'expert' commenting on the operation at each camera. Three mixers (human
beings) with double system kit simply wasn't a possibility. I have fought
for double-system recording, when videotaping music; sometimes one wins
those fights; sometimes one doesn't.

So treat that as MOS... keep some of the location sound for an effects
track but redub the "expert" in again after the fact. That's how it
would be done shooting film, anyway.
--scott

Been there done that; in the right circumstance I'll do that again. For the
situation I cited I like my solution better: three angles to select from,
three expert's commentary to select from, perfectly good audio for the
purpose, minimum post time, a happy client at the 7 AM debriefing the day
after, and a very nice profit margin.

Steve King

[Steve King]

"Chel van Gennip" wrote in message
...
On Sun, 20 Aug 2006 19:51:07 +0200, Steve King wrote:

Therfore I only use the audio from the camera for synchronisation. I
use a seperate 24 bit recorder for audio. Then you are able to record
at a fixed level, and adjust levels later in your DAW without noise
penalties.

That's nice, when you can do it. The video production jobs that we do
often don't allow that for either logistical or budget reasons. Last
week we were videotaping an unusually demanding crane lift. I had three
cameras with an 'expert' commenting on the operation at each camera.
Three mixers (human beings) with double system kit simply wasn't a
possibility.

There are small inexpensive flash audio recorders. I use the M-Audio
Microtrack 2496 ($350) with an external USB batterypack. You need a flash
card, e.g. $150 for a 4GB flash card. There is no synchronisation
mechanism, but I see no drift between the digital audio and digital video,
so synchonisation on the camera audio is not dificult. I think that is a
better solution than adding an external microphone preamp with an extra
AGC to overcome camera audio problems.


Maybe for you. For the situation I cited the Auto function in two PD150s
and a VX2000 resulted in audio, speech and ambient, that worked very well.
Horses for courses.

Steve King