GH4 Panasonic discovered a fix for the audio buzz!

Gweilo66 said:
Thanks Dingo. So you had to send it in? How long of a turnaround?
Click to expand...

No, I specifically bought one with the audio fix applied during manufacturing. Pretty much any GH4 made since last August is going to have the same audio fix. ( check the serial number if you are unsure )
 
Does the serial # have identifiable date? Or is there a specific "Post __" serial # that identifies? I wonder if those released with "fix" fare better than those sent in.
 
I know this is an old thread, but I just sent my GH4 off for the audio buzz fix (I hadn't used an on-camera shotgun previously, but have just bought one and it's not that far from the end of the two year warranty period). Anyway it just came back from Panasonic's only UK repairers with the job description of "replaced main PCB" and the firmware has dropped from v2.3 to 2.1 - all of which is most odd as the repair was described to me as "solder a couple of components onto the PCB". Also it's going to be a real pain to set up the camera the way I had it again, I'd tweaked so many things. (BTW I don't use VLog-L, but am surprised it didn't come back with firmware 2.4 in it.)

(Update) I'm not sure the buzz had changed at all??? The channels look about balanced (although maybe a mono mic should do better than I see, but they are close enough). The noise floor is similar to before... Very odd.
 
Last edited:
Dr_Jon said:
The noise floor is similar to before... Very odd.
Click to expand...

When tested with the 1 kHz test-tone from a good mixer ( I am using a Sound Devices mixer ) you should see a noise-floor around -70 dB RMS, where the old un-fixed GH4 showed a noise-floor of about -55 dB RMS. ( the "motor-boat" sound on the un-fixed GH4 was pretty obvious when ever you boosted a very quiet LPCM recording. )
 
Dr_Jon said:
Maybe it's just me, but it seems the same as it was before they "repaired" it. You tell me (please), these are with the mic turned off and +6dB on the camera
Click to expand...

With a real -50 dB MIC level signal I set my GH4 to it's lowest gain level which is -12 dB, so +6 dB would be way too much gain for any of my audio gear. ( checking your recordings the BEFORE and AFTER do appear to have the same -50 dB RMS noise-floor )

If you lowered the GH4 gain level to -12 dB you would see a noise-floor around -68 dB RMS ( the samples you linked to are metering around -50 dB RMS ) but you will need mics/preamps that can deliver at least a -50 dB MIC level signal to get a good recording with your GH4 set to -12 dB gain.
 
Here's all I can come up with easily, does that explain what they did as I'm not convinced they changed anything? I should say I'm in no way an expert on GH4 audio and can't do any side-by-side testing. Also any idea why the post-fix ones all have an audio blip at the start, it's the same firmware version sa before?
https://dl.dropboxusercontent.com/u/11275485/BeforeFix_MicOff_CameraGain=0.wav
https://dl.dropboxusercontent.com/u/11275485/PostFix_MicOff_CameraGain=0.wav
https://dl.dropboxusercontent.com/u/11275485/PostFix_MicOff_CameraGain-12.wav
 
Last edited:
Ok, I finally had a chance to re-test my GH4 tonight and will post a download link for the WAV file...

My GH4 was bought in August 2014, and was one of the first GH4 cameras with the factory installed audio fix. I waited to buy my camera until I was certain I could buy one with the factory installed audio fix.

For this test I used my Sound Devices MixPre-D mixer and connected the -50 dB MIC level XLR output to an XLR-to-3.5mm mini-plug HOSA adapter which I plugged into my GH4's MIC input socket. My GH4 was set to record 100 Mbit MP4 video with LPCM audio. ( make sure you have your audio set to LPCM if you want to get the best audio performance from this camera ) My GH4 MIC level input was set to -12 dB and the MIC level limiter was set to OFF. I am currently running firmware ver 2.4 on my GH4.

To test the audio level I switched ON the 1 kHz test-tone generator built-in to the SD MixPre-D mixer and saw that the GH4 audio level was indicating what I consider "normal" on my GH4, which was 5 white segments lit. I then started to record the test-tone for 10 seconds, then switched off the test-tone and continued to record "silence" for another 20 seconds. Checking the levels of the recording with my Sony Vegas Pro editor, the test tone shows at -12 dB RMS like I expected, and the "silence" is bouncing around -72 dB RMS. So I'm getting about 72 dB of dynamic range being recorded, which is better than I've ever had with a ZOOM H4n recorder, and a little worse than my Tascam DR-40 recorder.

Here's the download link to the WAV file : GH4 Factory Fixed 48 kHz 16-bit Audio Test
 
Sorry for the delay, life intervened. It does seem a bit night and day to mine, but I think I need a different input to a switched-off mic, which I was never completely happy with. Alas with the demise of my previous employer my access to kit isn't what it used to be.
Many thanks for that!
It would be most interesting to see what you get with a switched-off mic attached, and 0 and +6 dB selected in camera, if you get a sec?
 
Dr_Jon said:
It would be most interesting to see what you get with a switched-off mic attached, and 0 and +6 dB selected in camera, if you get a sec?
Click to expand...

My Sound Devices mixer has a dynamic range of 110+ dB, so adding 30 dB of gain would still mean it's noise-floor is going to be at least -80 dB. With the GH4 the maximum dynamic range is probably 72 dB, so adding 18 dB of gain ( the maximum gain the camera can produce ) leaves you with a noise-floor of -54 dB RMS.

So raising the MIC level to 0 dB and +6 dB is going to produce a noise-floor of : -72 dB + 12 = -60 dB RMS, -72 dB + 18 = -54 dB RMS

I don't know if I own a 3.5mm mic that can be switched off, but I do own a BeachTek adapter that I can record without a mic plugged in. ( or even just a HOSA 3.5mm to XLR adapter with no mic attached ) My guess is that you will see the same -72 dB RMS noise-floor with the GH4 mic level set to -12 dB.
 
Last edited:
I was really after something that's produced the same way as I can test, to make sure I wasn't giving Panasonic any grief unintentionally. I mentioned 0 and +6 and I have before and after samples for that and only an after for -12. I suspect just having a cable plugged in is very similar to a Mic, as it presumably will disable the internal Mics..
 
You must log in or register to reply here.
Back
Top