GH3 Audio Issue - Zoom H4N linked directly into GH3?

M

Mike Lorushe

Active member
Hey guys,

I recently acquired a GH3 and I'm trying to get to grips with the GH3 audio's AGC. On my old T2I I used magic lantern to disable it's AGC and would feed my Zoom H4N's audio output directly into it. I had great results with this and it saved me the hassle of recording separately and syncing up in post. I want to do the same with my GH3 but I cant seem to stop it's AGC kicking in. I've tried setting the GH3's level to 1 and increasing the volume output on the H4N but I'm not having any luck.

Any tips? Thank's in advance.
 
The GH3 AGC has a maximum gain of 3 dB when the camera audio is set to 1, which is how I set my GH3 when I use an external audio source. With the camera audio level set to 1 the noise-floor varies between -66 dB to -63 dB, which is quite good for a DSLR camera. ( equivalent to the noise-floor of a Zoom H4n recorder )

When the GH3 audio level is set to 1 you need to supply a very strong audio signal ( between -20 to -10 dB ) to obtain a proper recording level, which means you will need to use an external pre-amp to achieve a strong enough signal. ( i.e. external mixer, JuicedLink Riggy, etc... )

Also, the Rode Video Mic Pro has a +20 dB setting, which works quite well with the GH3 when the camera level is set to 1.
 
Thanks TheDingo. Looks like I'll go back to syncing in post then; not interested in acquiring new gear at the moment.
 
Fresno Bob said:
Surely you would be compromising the sound quality if recorded into the GH2 / 3?
Click to expand...

The GH2 records audio using AC3 compression, which might be audible with higher quality recordings.

With the GH3 if you shoot using the 50 Mbits/sec MOV mode the audio is stored as uncompressed PCM tracks, so the audio fidelity will be better.

Both of these cameras have a good noise-floor ( -63 dB RMS for the GH2 and -66 dB RMS for the GH3 ), which makes it possible to achieve a "noise-free" recording provided you get everything else right.

A good $300-$500 portable recorder will have a noise floor 15 to 20 dB RMS quieter and allow you to record audio as 24-bit WAV files, which gives you a lot more room to make corrections in post. With the GH2 / GH3 you pretty much have to get everything right when you shoot to get similar results. ( i.e. no room for errors )

For most of my corporate training work, I record directly to my GH3 to simplify the workflow and my results are almost always very good. Where I occasionally get nailed is when I don't have time to properly prep the room for audio, and then have to fix things in post. ( see sample audio below )

Here's a sample from one of my training videos where I had to film in a big boardroom that had strong central AC going the whole time. If I had an extra 15 minutes I could have blocked off all of the AC vents, which would have made for a much quieter recording environment, but I was under the gun so I had to just wing it.

This ZIP download contains my original GH3 recording using a Sennheiser G3 UHF system and a TRAM TR50 lav mic that I positioned under the presenter's shirt ( so it was not visible ), you can clearly hear the noise of the AC in the background. In the 2nd "fixed" audio file, I have used EQ to improve the sound of the presenters voice, and I used the Sony Sound Forge Noise Reduction plug-in to remove most of the AC noise. It may not be perfect audio, but it good enough for me and my client.

Sample GH3 audio in noisy room and my "fixed" version
 
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Thanks for the post. I think they both sound fine for the examples you uploaded. The uncorrected one does have a slight hiss and the corrected one is deeper.
Overall i think they both sound fine.
 
Tascam DR-40 headphone OUT to GH3 mic input?

Tascam DR-40 headphone OUT to GH3 mic input?

I have had good luck recording dual sound with my Tascam DR-40 and DR-680 recorders and syncing with PluralEyes. I have an event where I want to try recording audio on the DR-40 and also send the DR-40 audio to the mic input on the GH3. I will be using a Sennheiser wireless lav mic, plus a wired hand held mic and both will be connected to the DR-40.

My questions are:
1. Do I need a special cable to adjust the level coming from the DR-40 into the GH3, or...
2. ...can I use a generic 3.5mm male to male shielded audio cable and adjust the DR-40 headphone output level?
3. I want to monitor levels as I am recording, so I presume I will monitor off the GH3's headphone output.

Although I expect to sync audio in post, I'm interested in trying to get better audio directly into the GH3. The GH3 mics are poor quality and badly placed, so having better audio directly into the camera would allow more accurate sync'ing, and provide backup audio. Any advice would be appreciated.
 
I just did a quick test where I ran the LINE out from my Sound Devices MixPre-D into the XLR input of the DR-40, and then connected the LINE/Headphone out to the MIC input of the GH3.

Turning on the MixPre's 1 kHz test-tone, the DR-40 showed a recording level of -20 dB, and the LINE OUT from the DR-40 into the GH3 was recording without distortion.

The DR-40's LINE OUT level was set to 0

The GH-3's MIC input level was set to 1

So yes, this looks like you won't have any problems recording with this set-up, and you can have audio recorded on both your DR-40 and your GH3. The only catch is that you need a good INPUT signal into your DR-40, in this case it will be full LINE level signal. ( I don't think you can adjust the LINE INPUT level on the DR-40 if you are using the same control to set the LINE OUTPUT level )
 
I need some clarification

I need some clarification

RE: TheDingo - Thanks for taking time to do this test.

I suspect there is a flaw in my plan to use the Sennheiser wireless lav mic and a wired hand held mic, both connected to the DR-40. To be clear, I am not using an external mixer that is sending line level signal to the DR-40. As the Sennheiser receiver outputs line level, I probably won't be able to adjust it to work with the hand held mic's mic level signal.

So now I am thinking about just using the hand held mic with the wireless SK 100 wireless plug. As the Sennheiser receiver outputs a line level signal, will I need one of those Sescom attenuation cables between the DR-40 and the GH3's mic input, or will a generic, shielded 3.5mm stereo cable work? Does it have to be a 4 conductor cable? What kind of cable did you use?
 
GH3 with JuicedLink and various mics

GH3 with JuicedLink and various mics

We have been very happy using the JuicedLink preamp feeding audio into the GH3. We turn down the audio amps in the GH3 to lowest level 1 and then use the amp in the JuicedLink. We made a test with direct vs via JuicedLink with various microphones including Sennheiser EW100 G3, Audio Technica ATR 897 shotgun and a cheap wired lavalier (ATR35S).

Panasonic GH3 audio and microphone tests

And here's some auditions to final production scenes that demonstrate the sound quality we got with the Juicedlink and the very reasonable Audio Technica ATR 897 shotgun (and Sennheiser EW100 G3 system). First you'll hear the audition clips - very raw - poor sound vs the final production which was boomed and wireless lav going into GH3 via the JuicedLink. We've tried the H4N and found it to be quite a bit noisier than the JuiceLink.

Panasonic GH3 sound comparisons from audition to final production
 
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