XL2 limiting my audio

[Vence Vida]

I have had my XL2 for a few months now, but belive it or not, I just used the XLR inputs for the first time last night. (I had done a large project that required no audio and recorded audio on other devices for other jobs)

This is tough to describe, so bear with me.

Here's the set-up: I was running two mics through a Mackie 1202 mixer using the channel inserts to utilize a DBX 266 compressor and then out of the Mackie into the XLR inputs on the camera. I was using an outboard LCD monitor to watch the levels on the camera (I had a camera op handling the shooting while I watched the audio)

Here's the problem: The XL2 seemed to be limiting the audio. There seemed to be a threshold, directly related to the level set with the manual audio pots on the camera, and the audio would not go above that threshold.

In other words, no matter how much gain I put out of the mixer, the audio meters on the camera would stop at, let's say -12. I could turn the mixer output down below that and the levels would drop, but anything above that would just stop at -12, like a hard limit setting. If I turned the camera audio input pots up, that threshold would raise. I could make that threshold any level I wanted by setting the camera knobs, but it would always act like a limit. I could not peak the meters, regardles of how much sound I pounded out of the mixer, unless I turned up the pots on the XL2

The limit was very harsh. When sound would hit that limit, it would distort as if I was peaking, even if the camera meters only read -6 or -12 or whatever the limit was at any particular time. The meters on my console were operating normally and the sound level in headphones was good at the mixer.

Any ideas?

[Jonathan Jones]

I haven't tried your setup in any of my situations, but I do know this...the XLR inputs on the XL2 are 'mic level' inputs only - as opposed to 'line-level' switchable, which seems like what you are trying to output from your Mackie. You should be able to connect them and get sound, but if you are using XLR line level output from a board into the mic level only input of the XL2, it should pretty much sound like crap...I am pretty sure that is what you are hearing.

Try to find a way to get the line level output from the board into the RCA connections of the XL2, which should have no problem with the signal.

The lack of mic/line switching on the XL2 has been a much debated topic.

Hope this helps.
-Jon

[Don Palomaki]

Try setting the Mackie Main Ouput to MIC level (if the 1202 has that option) if you need to use the XLR connection, otherwise try connecting the tape output from the Mackie to the XLs RCA audio input and set it to line level.

Note that the MA-100/200, and likely the XL2, mic inputs are not designed to accept line-level signals, only MIC level. They will start to distort and then clip if the input signal gets too high, which turns out to be around consumer line level (-10 dBV).

This clipping in the front-end preamps (before the level controls) is likely the source of the "hard limiting" you are seeing.

[Vence Vida]

Jon & Don,

Due to the symptoms, it does make sense that the clip is occuring before the level controls, such as at the mic pre-amp of the XL2, but I had the mixer set to mic level output (it is switchable on the 1202). I will try running into the rca inputs of the camera.

The frustrating thing about that is that I want to be able to use a low-z balanced XLR signal so I can run longer lines and easily lift ground if I detect 60hz interference. I would much rather run xlr mic cables around the room than RCA cables.

I'll repost after I've experimented with the switch between line level and mic level set-ups later this afternoon.

[Miguel Lombana]

Originally Posted by Vence Vida

I have had my XL2 for a few months now, but belive it or not, I just used the XLR inputs for the first time last night. (I had done a large project that required no audio and recorded audio on other devices for other jobs)

This is tough to describe, so bear with me.

Here's the set-up: I was running two mics through a Mackie 1202 mixer using the channel inserts to utilize a DBX 266 compressor and then out of the Mackie into the XLR inputs on the camera. I was using an outboard LCD monitor to watch the levels on the camera (I had a camera op handling the shooting while I watched the audio)

Here's the problem: The XL2 seemed to be limiting the audio. There seemed to be a threshold, directly related to the level set with the manual audio pots on the camera, and the audio would not go above that threshold.

In other words, no matter how much gain I put out of the mixer, the audio meters on the camera would stop at, let's say -12. I could turn the mixer output down below that and the levels would drop, but anything above that would just stop at -12, like a hard limit setting. If I turned the camera audio input pots up, that threshold would raise. I could make that threshold any level I wanted by setting the camera knobs, but it would always act like a limit. I could not peak the meters, regardles of how much sound I pounded out of the mixer, unless I turned up the pots on the XL2

The limit was very harsh. When sound would hit that limit, it would distort as if I was peaking, even if the camera meters only read -6 or -12 or whatever the limit was at any particular time. The meters on my console were operating normally and the sound level in headphones was good at the mixer.

Any ideas?

You sure you were not in auto mode with limiting on that cam? There are a couple of other things that you might want to check in the setups.

1. In the menu for audio there is a setting for a 12db bump in the xlr in, see if you had that enabled, you might want to set it back to non.

2. See if you had the MIC ATT buttons on the back of the cam enabled, this will also cause a limited to engage.

BTW, I just had a huge issue during a wedding I shot this weekend and found that all the ambienet audio from my Azden on channel 2 was shot and distorted due to the 12db bump enabled and the ATT also enabled. I really basically blew it.

Miguel

[Vence Vida]

I have now had the opportunity to do some investigating and I believe I have solved the issue.

I took the camera into my studio and hooked it up every different way I could think of and experiemented with various audio feeds. I believe the problem did not occur in the camera, per se, but with the discrepency between standard audio metering and audio for video metering.

Unity on audio devices is indicated as 0db, whereas unity on video devices is indicated as -12db with 0db being the threshold for clipping on digital video devices. Even though I never hit 0db on the camera when the signal distorted, I was peaking at +10 and hotter on the meters of the console. I figured (erroneously, it now appears) that as long as I did not clip the console (which clips at +28, by the way), the stronger the signal the better and I would just dampen it with the audio controls on the XL2. What I found (and this makes perfect sense, now that I really think about it) was that extra hot levels on the audio console would overload the pre-amps of the camera. Even though I had the output of the console set to mic level, I was, effectively, creating a line level signal by boosting the output so far above unity.

I re-shot the same project that originally gave me the limiting, only this time I kept the console around 0db, peaking around +4db and everything worked great.

A couple of notes: Miguel, I did not realize the XL2 had a 12 db bump in the menu. I will look for that tomorrow when I get back to work and see where that is set. I'm sure that could have an impact. I did make sure I was in manual audio mode. When I heard limiting - that was the first thing I though of.

Also, as far as the mic attenuator goes, I believe I had it engaged to give myself a bit more headroom for the input pots, but it would not cause limiting. The attenuator is simply a set reduction in signal prior to certain audio circuitry. It would not limit the signal, and it would probably be the last device in the signal flow of the camera to cause distortion, since it's job is to handle signal that is too hot for the pre-amps, input potentiometers, and other more sensitive devices in the chain.

[Steve House]

If you can, send a tone into the mixer and adjust the mixer output so it registers 0dB on the mixer's output meters. Set the XL2's audio controls to manual, and adjust the recording levels so that the tone reads -12 dbFS on the camera's level meters. Ideally the levels controls will be about 2/3 to 3/4 full up at that point. If you have to turn them way down to get the meters down to -12dbfs, turn on the camera's input attenuator to avoid clipping in the camera's preamps. Also when dealing with line levels remember that pro equipment references +4dBU as 0 dB on the meter while consumer equipment, such as the XL2 officially is, references a signal level of -10 dBV as 0db on the meter, so "zero" on the meter of consumer gear is about 12 db lower in actual voltage than "zero" on the meter of pro gear such as the Mackie mixer (however I think that mixer actually has switch to select between a +4 or a -10 output). Zero ain't necessarily zero <grin>.