GH2 Managing (loud) Audio input and levels

Shooter

Shooter

Veteran
I will do some more searching elsewhere on this topic but..

How does one Manage (High) Audio input and levels on a GH2?

I wish to use my GH2 to record some guitar practice sessions.

Amp/Speakers are close micc'd up and into an AZDEN field mixer that has an output Mini Stereo to Mini Stereo. -36dBu (fixed)

Thats fine...but the Lowest input level on the GH2 camera is really restrictive and only just avoiding "red"...if I playback amp at relatively low level.

THis is rock and roll and I need to playback at r&r level without overdriving the camera audio.

Thoughts please.
 
Shooter, is there any reason why you don't want to record the electric guitar directly? ( i.e. Do you want the "live" sound of the room? )

If your recording system is set up to take LINE level input you should be just fine with INSTUMENT input. ( which is usually between -20 to -40 dB )

For music recording I bought a couple of Mackie 402 VLZ3 mixers ( about $100 each ) that have an INSTRUMENT level push-button right below each GAIN pot. Your recording system still has to be able to take LINE level input from the Mackie, which can be any portable recorder with a LINE input, or a passive BeachTek adapter that will provide you with LINE/MIC switches and trim pots for each channel and can feed your camera directly.

If you want something more portable then a JuicedLink Riggy RA222 would do the job all by itself, and still be useful for regular XLR mics. ( i.e. LINE / MIC switches, Phanom Power, 30 dB of clean gain )
 
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@Shooter Are you shooting with the stock settings or the Pasadena Pulse Audio ones?

Assuming that you are shooting with the Pasadena Pulse Audio ones (the ones included in the new Driftwood, LPowell, bkmwcd, ones, etc.) then there isn't anything you can do in the camera settings to get extra dynamic range. However, you can attenuate the signal coming into the camera.

Assuming that you don't want to reduce the output level on the mixer for some reason, the trick would be to attenuate the signal between the time it leaves the mixer and the time it reaches the input on the GH2 - essentially, you just want a pad. There are various cables that let you do this but I haven't experimented with them.

Here are a couple posts about it.

http://www.dvxuser.com/V6/showthrea...ew-amp-video&p=2166077&viewfull=1#post2166077

http://www.dvxuser.com/V6/showthrea...tion-for-GH2&p=2148683&viewfull=1#post2148683
 
Shooter, is there any reason why you don't want to record the electric guitar directly? ( i.e. Do you want the "live" sound of the room? )
Click to expand...

Yes. I do like the live sound in this case ( the amp is a modelling amp with FX)

My GH2 is in stock mode.

Pad is a great idea but I need to do it on the output of the Field Mixer....so...

Will have to construct one. Its a curse that the GH2 uses the 2.5 mini-mini stereo jack.

Thing is ..I have perfect signal set up into the field mixer and no real control coming out to the GH2 .... because at lowest Audio In level (GH2) ..its still kind of high.

My only option is to drop my Master Level on the Field Mixer..which just maybe the same as padding it ???? (I dont know?)

Note: My Master Level is set at 1kHz which does look good on the GH2 meter.

EDIT - will add. This would be so easy on my AF102. Its just I thought the GH2 would be less camera set up hassle.
 
Per Lichtman said:
@shooter I would try dropping the Master Level before you do anything else - it might get the job done.
Click to expand...


I will test that but effectively what that is doing ...is dropping the output level via dropping the input level.


If I can pad the output..that will be ideal me thinks.
 
Definitely drop your input level on the AZDEN. At the input knobs.
That is almost always a good practice. Generally you want to use as little microphone amplifying as possible. Mic pre-amps lose what linearity they have as you push their gain higher. I don't know what the gain range is on those Azden inputs - but if your output is fixed, and the GH2 input is "basically" fixed, then hopefully the Azden's minimum input gain level won't still be so high as to max out the GH2.
If you turn the input knob on the Azden all the way down and it's still too loud - then a separate pad is really the only thing left.
 
Turning the Inputs down enough...results in the VU meters barely moving and right at the bottom end of the scale...so that makes recording all just a big guess!

BTW: They are analogue VU meters.

I am having a -40db pad connector cable made. Will post back if it works or otherwise.

As a non audio guy...I would have thought it desireable to have the best input signal / level possible and dont understand why one would not be driving good quality microphones towards peaking at 0db on the meters.
 
@Shooter I look forward to hearing how it works for you. I would have thought that 40dB would be quite excessive unless the quietest parts of the recording were also clipping.

I understand your frustration with proper gain-staging. The truth is that it's a bit too complicated to give a quick summary of it in a forum post, but here are the basics.

- There is a gap between expensive and inexpensive gear in terms of the noisefloor and quality of the gain provided during amplification. The more gain you are applying, the wider that gap becomes.

- The "character" of a given pre-amp is more evident in the input gain than the output gain (and for simplicity we are assuming a fully analog path here). To get a less colored sound, you want to use as little input gain as you need to in order to get sufficient level and use output gain to compensate. Conversely, if you really like the way the pre-amp is changing the sound, you would use more input gain and less output gain.

- At every stage of the process you are trying to balance two competing concerns: making sure that your peaks don't clip and that your quiet parts don't get lost. As you increase gain you also increase the noisefloor (much like increasing ISO/Visual Gain on your camera).

- Almost every piece of gear you are using has different dynamic range and behavior that you want to be aware: the microphones distort above a certain SPL, the pre-amp gets really noisy and introduces distortion at higher gain (and that depends on the unit), the analog cables introduce noise (often more so when they are longer), each input may potentially have different expectations/requirements about the signal level coming in, etc.

So what's the basic point of all this? The GH2 was not originally designed to interface with studio audio equipment - just small shotgun mics and the like. So you often have to change the signal before it gets to the GH2 because it is pretty lacking in flexibility.
 
Rather than have a custom padded cable made, you might want to pick up a few inline-XLR pads. Whirlwind In-Line XLR 40 dB Pad : $14

As long as your mics are not being over-driven and your audio peaks are not clipping, you should be recording at a normal level where the peaks are safely below 0 dB and everything else will fall below this, then you'll probably have to apply compression in post to reduce the dynamic range of your recording.

At it's lowest audio setting the GH2 has a noise floor of -63 dB RMS, so it's a fairly limited dynamic range compared to a Sound Devices recorder that has 100+ dB of dynamic range.

i.e. Record too loud and the GH2 clips, record too low and you've got a noise issue.
 
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This is the thrust of the issue exactly.

The GH2 was not originally designed to interface with studio audio equipment - just small shotgun mics and the like. So you often have to change the signal before it gets to the GH2 because it is pretty lacking in flexibility.
Click to expand...

I really admire people who manage to shoot video and audio on DSLRS. ( its real messy and audio is messy anyway)

Thanx both for excellent advice and input.

The -40db was suggested by the technician.

I will test it next week.

Custom cable was decided on because already you start with an adapter into a GH2 ( stoopid 2.5 stereo jack. wtf were they thinking!). I have rigged that adapter in a way that takes stress off the little socket and pin.
 
I am an audio guy and I'd want to see the following: How does it sound when I set the gain knobs so it hits the RECORDER (The GH2) at a decent level.
Since the Azden you have has a fixed output that stage becomes a non-issue. I would set the GH2 to its lowest mic gain setting first. Then I would watch the GH2's meters and raise the input pots on the Azden until you have a good strong, but not clipping, level. That's all there is to it.
As for gain staging concerns - there are almost none because this path has so FEW gain stages at all.
It does not matter that the Azden meters are barely moving - look at the GH2 meters to see your activity. The only real concern to check for is this: Is there noise being generated by the Azden that is audible and/or problematic when I play back the video in post. My guess is there is not going to be much AT ALL. That Azden stuff is pretty clean. When you lower the input gain of the mic channels you might make the machine's noise floor more evident in playback..."MIGHT". But the lower your input gain on the mic channels the more linear (accurate) the signal will be.
If the Azden has too much of a noise floor to allow for low input levels through the knobs into the GH2 then you have your answer and you'll need the Pads. I don't know Azden stuff intimately - but I would be surprised if their noise floor is that audible.
 
Thanx for that advice and I understand what you are saying.

I will try that option as well as the new pad option and see what I am comfortable with and what "works".

To me as a D.P..I guess I trust my eyes and "seeing" that I have levels is comforting.

Those tiny bar VU meters on digital cameras are disconcerting to me.
 
Just reporting back.

The cable I had professionally built with -40db padding ...works like a dream! (L&R XLR to 3.5mm stereo)

Reiterating: Issue was uncontrolleable level control at GH2 (using the lowest available audio input setting)

Situation: Recording (live from loud guitar speaker cabinets) with mics to a Field Mixer then out to a GH2.

Now with pad on the output from the Mixer....Input levels displaying and peaking perfectly on the Mixer VU and running into GH2 using setting 3.
That gives me room to go down to 1 and 2 if the source get really loud. (and it does) or 4 if it gets quiet ( and it doesnt).

Thanx for all advice given.
 
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