[[email protected]]

I am having a brain blockage on channel summing, and if someone could
help that would be great.

I have heard that if you are going to mix several channels, then do
not set gain to zero on main meters for each individual channel.
Instead for each doubling of channels (1 to 2 to 4...) you ned to -3DB
for each double. So if you are mixing 1 channel only set it at zero ,
or unity gain, on main level meters. But, if you are mixing 2 channels
then each individual channel should be at -3Db, on main level meters,
then by raising both channels to unity the main level meter should now
be at unity also. Other wise if you set each channel to unity,
seperately, then when you bring all channels up the overall level in
the mains will start to approach clipping.

Does any of this sound right? Am I close and is this a standard on all
boards? Is it a lawm and if so what is the law?

Thanks.

[Mike Rivers]

On Feb 25, 2:30 pm, " wrote:

I have heard that if you are going to mix several channels, then do
not set gain to zero on main meters for each individual channel.
Instead for each doubling of channels (1 to 2 to 4...) you ned to -3DB
for each double. So if you are mixing 1 channel only set it at zero ,
or unity gain, on main level meters. But, if you are mixing 2 channels
then each individual channel should be at -3Db, on main level meters,
then by raising both channels to unity the main level meter should now
be at unity also.

You can only mix by the numbers if you're mixing identical, constant,
in-phase signals. Your theory would work for sine waves of the same
frequency, but there isn't much point to mixing four sine waves all of
the same frequency and in phase. You might as well just listen to
one.

But, yes, as you add music or voice channels into the mix, you can't
have them all at the same level and expect to get that same level out.
1+1+1+1 does not equal 1.

And don't confuse zero dBFS (an acutal digital level) with 0 dB (unity
gain).

[Scott Dorsey]

Mike Rivers wrote:
On Feb 25, 2:30 pm, " wrote:

I have heard that if you are going to mix several channels, then do
not set gain to zero on main meters for each individual channel.
Instead for each doubling of channels (1 to 2 to 4...) you ned to -3DB
for each double. So if you are mixing 1 channel only set it at zero ,
or unity gain, on main level meters. But, if you are mixing 2 channels
then each individual channel should be at -3Db, on main level meters,
then by raising both channels to unity the main level meter should now
be at unity also.

You can only mix by the numbers if you're mixing identical, constant,
in-phase signals. Your theory would work for sine waves of the same
frequency, but there isn't much point to mixing four sine waves all of
the same frequency and in phase. You might as well just listen to
one.

But, yes, as you add music or voice channels into the mix, you can't
have them all at the same level and expect to get that same level out.
1+1+1+1 does not equal 1.

However, professional consoles are designed with huge amounts of headroom
on the summing amplifiers, so you can keep adding stuff and adding stuff
without clipping the mix buss amps.

Many inexpensive consoles are not this way, and you have to be very
careful about the total mix buss level on them. But, most of those
consoles don't have trustworthy metering anyway. So you have to
use your ears.

And don't confuse zero dBFS (an acutal digital level) with 0 dB (unity
gain).

I like to think of internal signal levels in terms of millivolts, when
talking about clipping issues. But that's just me.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On Feb 25, 2:56 pm, (Scott Dorsey) wrote:

However, professional consoles are designed with huge amounts of headroom
on the summing amplifiers, so you can keep adding stuff and adding stuff
without clipping the mix buss amps.

I think the original poster was talking about digital mixing. Some
DAWs have trickery that makes it look like they have headroom for
summing so they work like analog consoles, but still, you can't end up
with more bits than you can turn on at once.

[Romeo Rondeau]

Mike Rivers wrote:
On Feb 25, 2:56 pm, (Scott Dorsey) wrote:

However, professional consoles are designed with huge amounts of headroom
on the summing amplifiers, so you can keep adding stuff and adding stuff
without clipping the mix buss amps.

I think the original poster was talking about digital mixing. Some
DAWs have trickery that makes it look like they have headroom for
summing so they work like analog consoles, but still, you can't end up
with more bits than you can turn on at once.


Yeah, but there's plenty of those bits in a modern DAW :-)

[[email protected]]

On Feb 25, 3:49 pm, Romeo Rondeau wrote:
Mike Rivers wrote:
On Feb 25, 2:56 pm, (Scott Dorsey) wrote:

However, professional consoles are designed with huge amounts of headroom
on the summing amplifiers, so you can keep adding stuff and adding stuff
without clipping the mix buss amps.

I think the original poster was talking about digital mixing. Some
DAWs have trickery that makes it look like they have headroom for
summing so they work like analog consoles, but still, you can't end up
with more bits than you can turn on at once.

Yeah, but there's plenty of those bits in a modern DAW :-)

Thanks to both of you, but I am talking about anaolg, although we are
going to the M7CL real soon. Does the rules apply to analog as well as
digital? Also is there a mathmatical law or rule that states this or
just an industry standard?

Thanks again.

[Scott Dorsey]

wrote:

Thanks to both of you, but I am talking about anaolg, although we are
going to the M7CL real soon. Does the rules apply to analog as well as
digital? Also is there a mathmatical law or rule that states this or
just an industry standard?

The summing buss on most older consoles is just a bunch of resistors.
The channel strips put current into each resistor, and the current
that comes out and goes into the buss amp is the sum of all the output
currents. So, the buss amplifier needs to be designed to handle a very
wide variety of levels, and on a good console it will be. On a cheap
console, it might not be.

The Mackies, for example, use active summing networks which have headroom
problems... it's a bad idea to go into the yellow on the meters with the
VLZ and VLZ-Pro consoles because they don't sound good at high levels.

But take an old Neve... one of the reasons people like them is that you
can be very sloppy about gain staging and they still sound good.

There's no substitute for using your ears and knowing the console you're
working on.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Romeo Rondeau]

wrote:
On Feb 25, 3:49 pm, Romeo Rondeau wrote:
Mike Rivers wrote:
On Feb 25, 2:56 pm, (Scott Dorsey) wrote:
However, professional consoles are designed with huge amounts of headroom
on the summing amplifiers, so you can keep adding stuff and adding stuff
without clipping the mix buss amps.
I think the original poster was talking about digital mixing. Some
DAWs have trickery that makes it look like they have headroom for
summing so they work like analog consoles, but still, you can't end up
with more bits than you can turn on at once.
Yeah, but there's plenty of those bits in a modern DAW :-)

Thanks to both of you, but I am talking about anaolg, although we are
going to the M7CL real soon. Does the rules apply to analog as well as
digital? Also is there a mathmatical law or rule that states this or
just an industry standard?

Thanks again.


There's really no hard and fast rule. If you employ proper gain staging,
it's usually not a problem. It's kinda hard to **** up a system that's
been setup properly anyway. After a while you get a feel for where
things need to go in the L-R buss when you start a mix. I used to do a
little trick on one of my old analog boards (It was a D&R), mixing into
a DAT machine. I would put the master fader up to 0dB , then I would
reference everything around 0 in the master (where the meters were most
accurate, they were peak meters), then I did the following, soloing each
one, one at a time channel faders at +10, gain coming from the trim pot:

Kick at 0
Snare at +2
Toms at -6
OH at -8
Hat at -12
Bass guitar at -8
Piano at -6, etc.

Then I pulled the channel faders back down to 0, cut the last solo and
viola! A good starting point for a rough mix. This left plenty of
headroom for vocals which came in to taste. This was for rock, blues etc
where it's usually mixed from the "drums up." For jazz, synth pop,
country and so forth, I started the mix from the "vocals up" in a
similar fashion and brought instruments up to fill the space. All of
these things will be different on your music recorded the way that you
record, they worked for me... Anyway, most good consoles have enough
headroom to hit either your power amps or your mixdown deck (whatever
the case may be) as hard as you need to hit them (provided that their
gains are set reasonably), but you can still work this way with cheap
consoles, you just have to know where distortion starts to set in (just
because there's meter left doesn't mean that the board isn't clipping
(Behringer and Mackie come to mind here :-) Anyway, the above scenario
worked for me on my board, your mileage may vary. It really pays to know
your board and in the end your ears are the final judge. Keep in mind
that the main reason why there is no hard and fast rule is that the
types of signals that you are mixing are varied, some have high peak
levels and some have high average levels, and in the case of mixing to
analog tape... varied frequency spectrum. If you tried to reduce gain by
50% everytime you added a channel, chances are you wouldn't have very
much level at the L-R buss by the time you got everything into the mix.
Unless of course your music was all sine waves or something like that :-)

[Mike Rivers]

On Feb 25, 7:54 pm, " wrote:

I am talking about anaolg, although we are
going to the M7CL real soon. Does the rules apply to analog as well as
digital? Also is there a mathmatical law or rule that states this or
just an industry standard?

The rule (and there is only one rule) is the same for analog and
digital mixing. The instantaneous sum cannot be larger than the
maximum output level of the summing bus (or what passes for a 'bus" in
a digital mixer).

We accomplish this by mixing at a "nominal" level and allowing what we
think will be ample headroom, but there's no industry standard for
headroom. About as close as we can come (in the analog world anyway)
is an industry standard for nominal level. With most modern equipment,
this is +4 dBu, and most analog level meters are calibrated so that
the meter reads 0 dB when the level is +4 dBu. If the device clips (or
reaches an unacceptable level of distortion) at +18 dBu, then you have
14 dB of headroom. If it's capable of putting out +24 dBu before
clipping, then you have 20 dB of headroom. It makes no difference to
the device whether it's handling a mix or a single channel - it only
knows that when the sum gets to be larger than it can handle, it clips
or distorts.

You can use that headroom as headroom - a safety zone where you can
get unexpected peaks and still not have distortion. Or you can raise
the "nominal" level to make the mix louder, and either take the risk
of distorted peaks or make your own brand of distortion that you deem
acceptable by using limiting or compression somewhere along the chain
so those peaks won't be as large as without processing.

But you also have to be cognizant of the capability of the next link
of the chain. If you have a mic preamp that can put out +28 dBu
without clipping and that's going into a sound card with an input
stage that clips at +18 dBu, you can't use that preamp to its maximum
output level.

Digital works the same way except that instead of 0 on the meter being
located 20 dB or so below the maximum level, it's located at the
maximum level. So if you want to leave some headroom, you must choose
your own, lower, nominal operating level. Many people get confused
over this, trying to make 0 on an analog meter coincide with 0 on a
digital meter and wonder why either they can't (the source doesn't
have a high enough maximum output level) or they get distortion
because they're letting peaks go through that would exceed the maximum
digital level if they only could.

[Arny Krueger]

wrote in message
oups.com
On Feb 25, 3:49 pm, Romeo Rondeau
wrote:
Mike Rivers wrote:
On Feb 25, 2:56 pm, (Scott Dorsey)
wrote:

However, professional consoles are designed with huge
amounts of headroom on the summing amplifiers, so you
can keep adding stuff and adding stuff without
clipping the mix buss amps.

I think the original poster was talking about digital
mixing. Some DAWs have trickery that makes it look like
they have headroom for summing so they work like analog
consoles, but still, you can't end up with more bits
than you can turn on at once.

Yeah, but there's plenty of those bits in a modern DAW
:-)

Thanks to both of you, but I am talking about anaolg,
although we are going to the M7CL real soon. Does the
rules apply to analog as well as digital? Also is there a
mathmatical law or rule that states this or just an
industry standard?

I think you have to presume some common sense on the part of the audio
industry, There just isn't a big market for $7,000-14,000 mixing consoles,
digital or analog, that don't work well. ;-)

I don't know exactly how many generations of digital consoles there were
before the M7CL, but I know of at least 4, and have an example of the
previous generation - the 02R96. Long story short - it works.

In the real world, the business of summing audio signals is surprisingly
complex and unpredictable. For example, during a morning service I may have
anywhere from 1 microphone to 30+ mixed analog and digital sources active
and being mixed. I expect and can obtain a full-scale analog output from the
console at all times. I have put no little effort into adjusting analog
input trims and digital channel gain adjustments in order to obtain this
result. At no point did the digital nature of the console intrude on the
process, except to facilitate it.

[NRen2k5]

Mike Rivers wrote:
On Feb 25, 2:56 pm, (Scott Dorsey) wrote:

However, professional consoles are designed with huge amounts of headroom
on the summing amplifiers, so you can keep adding stuff and adding stuff
without clipping the mix buss amps.

I think the original poster was talking about digital mixing. Some
DAWs have trickery that makes it look like they have headroom for
summing so they work like analog consoles, but still, you can't end up
with more bits than you can turn on at once.

Of course if you're working in digital you could just do a downmix.