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Auto Gain Control
Brandon W.
Posts: 12
The AGC is used to keep the average level of a signal at a constant level. This is done by
selecting a desired Target output level and Window. The AGC keeps the signal within the
Window about the selected Target by slowly adjusting the gain. The maximum gain that can
be applied to the signal is selected by the Gain parameter. When the input signal falls below
the Low Threshold the AGC releases the gain and returns to unity. This prevents the AGC from
adding gain when there is no signal present and raising the system noise floor. High level sig-
nals are reduced by a fast limiter to prevent distortion by clipping. The AGC Threshold meters
show what region of the AGC the input signal is in. The T (yellow) indicates the signal is with-
in the Window. A + (red) indicates the signal is going into the Limiter. A – (green) indicates
the AGC is adding maximum Gain and is at or below the Window. When the Threshold meter
is off the signal is below the Low Threshold.
AGC:On/Off
Turns the AGC module On and Off.
Target:(Targ) -20 to 20 dB
The Target parameter defines where you would like the average level of the AGC output to be.
If the average level of the signal rises above the Target the gain will be reduced. For signals
with an average level below the Target the gain will be increased.
Gain:1 to 20dB
This adjusts the maximum amount of gain that can be added by the AGC.
Window:1 to 10dB
This adjusts the amount of variation in the output
Low Threshold:-60 to -30dB
The Low Threshold sets a lower limit to the AGC. This prevents the AGC from adding gain to
low level signals or noise.
Attack:0.20 to 5 Seconds
This adjusts how fast the AGC will increase gain.
Release:30.0 to 1 dB/Second
This adjusts how fast the AGC will reduce ga4.5 Automatic Gain Control (AGC)
Equipment...
Mainly a small mobil DJ club setup for House/techno/dance/dnb/trance music set up in two stereo stacks
2x Mackie Sr1522z tops (built in amps set at -15db) 500w total biamped each
2x Mackie Sw1801z subs (built in amps set at 0bd) 800w
1 Pioneer 600dj mixer
1 Driverack 260
XLR into Driverack
2x4 Biamp setup with crossover betwen 90 and 100 hrz with the sub rolled off at 45 hrz
Peak Stop limiters are set for tops and subs but I change settings nightly because im still new and trying to find what works best.
My main goal is to set up the system so the built in limiters in the speaker amps will never be hit. This problem is really only in the subs at this point.
My tops overpower the subs so setting the limiter on the sub correctly may be my biggest problem?
Also I would prefer that the tops never overpower the subs even though they can handle it no problem. I love bass and hate ear piercing highs so I would rather call my system maxed out when the subs run out of power then be louder with not enough bass. I'm usually in smaller rooms anyway.
I have my subs amps and the tops amps set so in the driverack crossover section they can both stay at 0db.
{(SIDE QUESTION):: is anything over 0db going into the speaker amps going to cause the limit light to go on?}
Now the main question
With several djs playing over the night and even after I tell them how hot to run the mixer to sound good, loud, and not damage the system it seems some dont understand what the gain nob is for. Will auto gain control be able to compensate for the changing levels (to loude and too quiet) over the entire night?
From my understanding it's a limiter with an extremely long release time.
so im thinking (if anything over 0db will cause the built in amp limiters to turn on) my settings should be...
Target (average level output... is this peak or rms?) should be something like -3db to -5db?... or maybe 0db and let the sub limiter kick in a bit to keep if from clipping
Im not really sure what the gain does. Is this how much gain will be added if the target is not reached? Does this kick in at the low threshold?
Im not sure what the window does either. What does it mean by adjusting the amount of variation in the input?
0
Comments
Give it a shot. Set your mixer channel 1 hotter than channel 2 and crossfade bach and forth and see what happens.
DRA
All you can hope for is to be able to LIMIT the damage those IDIOTS will inflict...You are sub shy... and you need to set a brick wall limiter to thwart those nefarious usurpers...
1. put the subs together (a sussed from your post that you have 2?) you will get 3db free from the coupling...
2. Limit the amount of super low end you feed the subs... that stuff is power robbing FLUFF in an under powered system...Try a 45 hz hipass..BW18...
3. Depending on where your gain structure ends up... set the limiter to brick wall,set the \"Auto\" to OFF! and let them sound like shit as they squash the sound against the limiter...
Hey, you want to make them tow the line... the ONLY way is to protect your system...optimize it so that you can make yourself and those that listen sound \"fabulous\"...but when the limiters start protecting the system the mixer is usually already in distress...so they morons :roll: are so desperate for more volume (you HAVE TO BE THE LOUDEST ... you know...) they will ram the mains till they bleed RED!
My stuff.. MY rules! My way or the hi-way...simple as that...
\"G\" too stubborn, and too old to care...Gadget
So for my need in this situation its useless. I had a feeling it would mess with the dynamics as they weren't intended?
Before owning a drive rack I wanted a mixer after the dj mixer to control levels but after some advise and my low cashfund I bought the driverack260. After owning it the solution to djs level unnormality seems to be to change the DR input AB level but so far with my preset this is difficult because you have a separate master level for input 1 and 2. Is there an easy way to link them or is it even possable?
I haven't had a place to try this out yet. The places im at I need the sub to elevate the tops.
I am sub shy, the Mackies are known to go out without even having the limiter lite on. Im trying to save them long enough that I can sell them and upgrade. Not much for sell used around here in that price range unless I get JBL.
I did this after reading why here and at psw.
If your familiar with a pioneer 600 I set the levels on the master channel at three redlights to sound the best and use the gain/trim nob on the back of the 600 mixer to set the best volume for the room. By the end of the night if djs are pushing 4 to 5 redlights the input on the Driverack is reading +6db a max.
Usually the sub limiter are the only ones kicking in but it doesnt seem like much limiting is done (I dont want to squash it just protect it)
Sounds like maybe I need to set the sub limiter better for protection. I think I have auto turned on also so Ill change that since I don't even know what it does.
Thanks
Brandon
Ya it's unfortunate that the darn DJ's get so carried away... but the unfortunaly fact is they WILL NOT LISTEN! The brick wall limiter is the only way, the thing about the 'auto\" on the limiter and compressor is it makes the affect more audible...
With those big speakers you can't put them on a tripod... but you can build a light weight frame to get them up...
G
BTW all this info is in the \"training\" modules...
http://www.dbxpro.com/techsupport.php
I watched the gui training video but at this point I have no available comm port that I can get working with driveware but thats a whole nother issue im working.
Although it seems I won't be using auto gain function anyways can you help with what these two functions actual do?
Function... "Gain:1 to 20dB. This adjusts the maximum amount of gain that can be added by the AGC."
At What point does this kick it? Im guessing the low threshold?
Window:1 to 10dB. This adjusts the amount of variation in the output.
Does this mean the AGC won't kick in (add gain) unless it's outside of the target range by a number defined by "Window"?
And I have no room in my truck (s10) to take extra stands nor am I getting paid enough. Shi# I still need to get a rack to put the driverack in.
I'll have to check the manual on how to link input AB without the gui but thanks for letting me know its possible. Changing them one at a time was very noticeable and a pain.
Thanks.
Brandon
I don't have driveware working yet so I have been searching the manual for a way to adjust/link the I/O Master level for input A and B at the same time but didn't see it in the manual. Is this even possible? Mainly I just want an easy master level control at the input before the pre crossover compressor.