I would like some advice on setting gains. I have a Q-3433/MKII mixer.
To set gains, should I aim for the LED's to average around 0 or +4?

At what point will this mixer start clipping? My intention is to play
prerecorded soundtracks, should I set the gains to match the loudest
peak instead of the average? If so, what is the loudest peak I should
allow (ie, +4, +7, +10)?

I doubt they are pertinent, but here are the system specifications just
in case. The input will be a CD Player. Output is via XLR to two
Mackie SA-1532z (1300w/ea, 3 way, with two 15" woofers). Venue is
outdoors open field.

The mixers manual is available at:
http://www.americanaudio.us/manual.asp

Thanks,
Daniel Clark

wrote:

I would like some advice on setting gains. I have a Q-3433/MKII mixer.
To set gains, should I aim for the LED's to average around 0 or +4?

At what point will this mixer start clipping? My intention is to play
prerecorded soundtracks, should I set the gains to match the loudest
peak instead of the average? If so, what is the loudest peak I should
allow (ie, +4, +7, +10)?


This would be a good place to start your education on the
topic:

http://www.rane.com/note135.html

After you have absorbed and practiced what is discussed,
feel free to do whatever you want. The principles are the
same regardless of the pretty silkscreening on the
equipment.




TM

On 23 Sep 2005 22:16:46 -0700, wrote:

I would like some advice on setting gains. I have a Q-3433/MKII mixer.
To set gains, should I aim for the LED's to average around 0 or +4?

At what point will this mixer start clipping? My intention is to play
prerecorded soundtracks, should I set the gains to match the loudest
peak instead of the average? If so, what is the loudest peak I should
allow (ie, +4, +7, +10)?

I doubt they are pertinent, but here are the system specifications just
in case. The input will be a CD Player. Output is via XLR to two
Mackie SA-1532z (1300w/ea, 3 way, with two 15" woofers). Venue is
outdoors open field.

The mixers manual is available at:
http://www.americanaudio.us/manual.asp

Thanks,
Daniel Clark

Danny,

You haven't posted here often, and your questions make it clear that
you are new to live sound, but I want to say that you have an
excellent command of newsgroup etiquette and clear descriptive
writing. Your post includes all the information I would need to answer
your question. This is rare. Thank you!

I've never seen an American Audio mixer, but I don't do much work with
DJ equipment. However, the physics remains the same, so I'll try to
answer your questions based on the mixer's specification and my
experience with PA and radio station equipment.

Q: At what point will this mixer start clipping?
If the CD player is a regular consumer unit (signal on unbalanced
phono plugs) it is unlikely that you will clip at the inputs. The
mixer's meters will show the output level.

from the manual:
Maximum Output: (LOAD = 47K, THD = 1%)
MASTER/ZONE: MORE THAN +18 dBV (8.0V)

This means that the mixer's outputs clip at +18 dBV (or more?).
That means that you have 8 dB of headroom to handle peaks when the
meters read +10. The meters may not show very short peaks (or they
might, it's not specified in the manual). However, you should be OK as
long as the meters only show a +10 indication on short peaks.

note: Most commercial CDs will have a peak-to-average ratio of 3 to 12
dB. In other words, peaks could be 3 to 12 dB above the average
reading on the meters.

I think the Mackie SA1532z includes a limiter. If it has a switch,
make sure it's enabled. It also has an LED indicator. Put on a CD,
turn it up, and see what meters read when the limit LED starts
blinking. Don't go any louder than that.

Mike T.

Mike and TM,

Thanks for taking the time to reply. Mike, you are correct, I am a
beginner at pro audio. But I have been using USENET since 1989. I
typically lurk in the pyrotechnics forums. In fact, this sound system
is for fireworks shows.

If you dont mind, I would like to confirm that I am understanding you
correctly.

To keep a low S/N ratio I should use the highest output possible.
The upper end of which is determined by the clipping factor. But in my
case, clipping happens at 18, but my highest LED is at +10. So that I
can set gains correctly, I assume that I need my top end to be at +10.

Since I know the soundtrack in advance, I can match it's highest peak
to just under the +10. (Thus still leaving me +8 headroom that is
unused on my mixer). Then I can set the sensitivity of the speakers to
start clipping at +10, which should never be obtained with the
soundtrack.

If I understand the article and the message correctly, this should
give me the best signal/noise ratio, while still being able to use the
LED's on the mixer effectively. Since the soundtrack is not live, I
should be using the peak and not the average to determine the output
level of the mixer.

I know this sounds a bit like a teenager asking silly questions that
you have already answered, but I really want to learn how to do this
properly.

One piece of info that I left out of the original message, is that
the CD player is the Gemini MPX-3.

Thanks again for all your help.

Danny