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1 kHz vs pink noise
luiss
Posts: 35
When I was in college I was taught to use 1k to align equipment. The recommendations on this forum suggest pink noise. I'm still wrapping around crest factor, so maybe when the penny drops I'll get it....
For the mean time..
Why won't 1 kHz give as good a result when setting gain structure.
For the mean time..
Why won't 1 kHz give as good a result when setting gain structure.
0
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When checking the level for the main outs on the desk, what advantage does an AFL give you? Don't the main meters show the post fader level by default? I suppose this goes to the heart of why do AFL functions exist when the main mix bus defaults to the meters and the headphone monitor source?
Why do we set the input level on the mic pre to -6dB, while we set the mix bus level to just clip? It is then recommended that the level in the DR be set to 3dB below clipping. What makes each of these levels of headroom optimal for each gain stage? I can see that there is a difference between the desk and the DR in that the DR is using dBFS.
When I undertake this I will not have access to the GUI (no PC laptop) so how do I monitor levels and adjust settings via the unit itself (260). I can't get my hands on the gear until the day...
When you look at a speaker specs you will note an Ohm rating. This is either a nominal, or minimum resistance, meaning that at different frequencies the speaker offers different resistance, often as high as 2k ohms and more. This will then mean a difference in how the speaker loads the amps as well.
So try and get as many pieces of the system into the gain structure as possible.
That after fader listen is for monitoring signal...I have a monitor set up so that when I want to listen to what ever is on that channel I can isolate it and evaluate it... this is typically PFL, so AFL allows you to eval after the fader as well. You can also use it to set up the individual channels (again usually PFL) and you can then use the output meters for input channel setup.
Well, I'm not exactly sure what you mean here.. I like to get the input signal on any analog console into the -0- vu average or a little higher to maybe +6 dB - +8 to allow for some headroom on the individual channel. I like to maintain 10-12 dB if possible...on each channel. Now remember also that on analog mixers (I'm almost exclusively digital right now) that signal to noise is the critical factor on the individual channels.
Remember too that there are far more inputs than outputs so there is also a much better chance of introducing noise at the outputs if you have a strong output from the main faders and a weak signal from the channels.
Further we DO NOT WANT ANY CLIPPING in the driverack! NONE so 3dB would be the MINIMUM headroom you would want there.
Gadget
Hope that helps..
G
Ran into an annoying problem along the way. When pumping pink noise through the desk at the required level (as per link above) the input of the DR showed clipping regardless of the input gain settings (via > i/o > input mixer). After some exploration we determined that the clip indication (blinking up on the LCD) was indicating clipping at the very input of the unit, prior to input gain adjustment. This was confirmed with a call to the dbx distributor. How odd.
DR 260 signal flow:
The LED input meters were not clipping, neither were any of the output meters....
It occurs to me now that it would be impossible to have clipping occurring between the XLR and the input gain....
So where did this clipping actually occur? At the DSP Input? Can this happen before the input meter registers clipping in the analogue input stage?
What an absolute pain in the arse to have clip indication without any refference to where the signal is actuall clipping. Ridiculous..
Bring on mac compatibility dbx, so we can all use the GUI.
Now, your telling me that with NO output from the mixer (which mixer?) the 260 is clipping? Are you sure your mixer doesn't have a hot chassis? (as in a power supply that has a leaky capacitor or something that is causing DC on the outputs...)
Check that the mixer attached DIRECTLY to the amps (no speakers attached) doesn't cause the same problem...
Check the input mixer on the 260 to see where the gain is set...(input 1 should be 1 @ unity -0- and the other @ infinity down fully) ( input 2 should be channel 2 @ unity and one @ infinity)
Perhaps you need to detail exactly what your doing here...
G
I'll re-write this in more detail when I get the time... Remember this is all happening while setting the gain structure.
When I say "Input Gains" I am talking about the DR, not the desk.
When Bouncing the pink noise at the clip point on the main L/R bus on the desk, the clip indicator on the DR was flashing on the LCD. When I turned the input gains down on the DR the front panel input meters appropriately showed no level, but the LCD still had a clip indicator blinking on the screen.
Pulling the main bus level back on the desk stopped the clipping. What I don't understand (and this relates to my lack of understanding about the electronic in the signal flow) is how can the DR be clipping prior to the input gains?
DR signal flow:
ie XLR in > input gain >summing amplifier > Master Level > input meter > DSP input
So how I have interpreted it, the DR was sensing clipping between the XLR in and the input gain. What component exists there?
Is this a new problem?
Just trying to figure out whats going on here, but it's VERY unclear whats happening...
If the 260 IS clipping the sound would be BAD... Digital clipping AIN'T pretty...so if your not actually HEARING clipping the display could be acting up...and then you would need to contact tech support.
G
System:
A&H MixWizard 16:12. Max output gain = +26dBu
New DR 260. Manual tells me that default input gain setting is +22dBu
Procedure: (as per forum instructions)
Pink noise into channel, fader at unity, input gain so that level meters at approx' -6dB
Master faders pushed so that LR level is bouncing in the red.
This is where I had to depart from the given instructions as I am currently unable to use the GUI.
So off to the DR... Looking at the LED input meters there is no clipping.
On the LCD screen a clip indicator is showing.
I eventually figure out that the clip on the SCREEN is indicating clipping earlier in the signal flow than the LED meters.
DR260 Input signal flow:
So looking at the signal flow, if the clipping is occurring before the input gains, where is the signal clipping? What physically exists between the XLR and the input gain?
Pulling the input gains back down to infinity did not solve the problem, so I took this to mean that the signal was clipping before it reached the input gain point. Does this show a misunderstanding of what happens when clipping occurs? If the desk is pumping out +26dBu and the DR is set to receive 22dBu max, then is this clipping actually occurring at the input gain stage? As I write this, I'm thinking that it is and that it's also embarrassingly obvious.... @#$%! Even with full attenuation, if the input gain stage is receiving +26dBu, the signal is too hot!
I'm happy that the gain structure was set correctly, as I pulled the desks master fader back until the clip indicator stopped blinking.
Geez.. This took way too much thinking to figure out, for something so simple. I'm a bit ashamed.
Let me know if I've got it wrong..
As I said I like to set the channel input this way:
1. Set the input channel PFL button to on.. this makes the left channel output meter into a channel strip meter(greater resolution than a tri color LED)
2. Place the channel fader @ unity gain/-0-
3. Using the input gain control, adjust the pink noise input level so that the average is -0- VU and the crest factor carries the peaks to +6/+12 (depending on the crest factor of the pink noise)
now the optimum signal to noise ratio has been reached for this channel....What I think DRA was getting at is when roughing in a mix with live instruments you may need to set the level lower for dynamics (like drum hits) to insure they don't clip...but pink noise has a given crest factor that makes it pretty safe to assume that a 12dB crest will in fact be a 12 dB crest..
G