Panasonic GH4 Audio Buzz Fix

The Good, the Bad, & the Strange
By Sol March in Resources

After the GH4 returned from Panasonic’s service center, I ran it through a battery of tests to confirm whether the audio buzz was truly gone for good.

The tests yielded a wide range of results– some good, some bad, and some just downright strange.

Note: I am not an audio engineer (nor any other mythical creature). If you are an audio engineer/unicorn, please let me know how I can make these tests better if necessary.

The Good: The Buzz is Gone

The good news is that the fluttering buzz that previously plagued the GH4– especially at high gain levels– has been reduced to the point that it is a non-issue in most situations.

While the buzz is still detectable if you pump up the GH4’s audio gain with an unpowered mic attached, it’s so far below the camera’s noise floor (which is another story– more on this in a bit) that the buzz will be the least of your problems by the time you can actually hear it.

In any real-world production situation, maxing any camera’s audio gain is definitely not recommended. The best practice to set the camera’s gain as low as possible and feed it a strong audio signal. With the GH4’s audio levels set to the minimum -12dB setting, the buzz is inaudible even if you increase volume in post more than you should ever need to.

Bottom line: The GH4’s audio is effectively buzz-free after the repair.

The Bad: The GH4 is Noisier

Ridding the GH4 of the buzz was not without it’s share of side-effects. One of these side-effects is that the GH4 is now noisier than it was before the fix.

In fact, as a result of the buzz fix, the GH4’s noise floor has increased by as much as 10dB in some cases.

Can you say “noisy”?

Noise Floor Test Setup

Here is the setup used to evaluate the GH4’s noise floor before and after Panasonic’s repairs:

Noise Floor Testing Setup

  • Mic: Rode VideoMic Pro (turned off)
  • Headphones: None
  • Recording Mode: 1080/24P/100mbps/MOV
  • Shutter Speed: 1/160
  • Aperture: f/1.4
  • Lens: Panasonic 25mm f/1.4

Note: Any unpowered device for the GH4’s mic input will suffice as the goal is to activate the GH4’s external mic input in order to isolate the camera’s self-noise from the room tone, etc.

Noise Floor @ +6dB Audio Gain

As previously noted, you ideally would not use the GH4 with the audio gain set to +6dB. This test demonstrates worst-case scenario.

  • Pre-Repair: -46dB
  • Post-Repair: -36dB
  • Result: The GH4 is 10dB noisier after Panasonic’s repairs.

This audio sample gives you an idea of the relative difference between the GH4’s noise floor before and after Panasonic’s repairs. The volumes of both samples have been increased by the same amount to make it easier to compare (raw samples can be downloaded at the end of this post).

Bottom line: A -46dB noise floor was already quite noisy, but at -36dB after Panasonic’s repairs, the GH4’s +6dB audio setting should now be considered unusable.

Noise Floor @ -9dB Audio Gain

Maxing out the GH4’s audio gain may not be recommended, but adding a bit of in-camera gain can be helpful if you have a slightly quiet audio signal. Here are the GH4’s noise floor results with audio gain set to -9dB:

  • Pre-Repair: -55dB
  • Post-Repair: -51dB
  • Result: The GH4 is 4dB noisier after Panasonic’s repairs.

Thankfully, the increase in noise is not the same across all gain levels. At lower gain settings, the noise floor has not increased as dramatically as it does at the +6dB setting.

This audio sample demonstrates the relative difference between the GH4’s noise floor before and after Panasonic’s repairs. As before, the volumes of both samples have been increased by the same amount to make it easier to compare (raw samples can be downloaded at the end of this post).

Bottom line: A -51dB noise floor is not great, but it can be usable.

Noise Floor @ -12dB Audio Gain

The best audio performance from the GH4 is achieved by setting the audio gain as low as possible. Here are the results of the GH4’s noise floor when audio gain is set to -12dB:

  • Pre-Repair: -57dB
  • Post-Repair: -52dB
  • Result: The GH4 is 5dB noisier after the repair

Interestingly, the difference in pre-repair/post-repair noise levels actually increased when the GH4’s audio gain was dropped to it’s minimum. In fact, the GH4 was actually quieter when set to -9dB before the repair, than it is when set to -12dB after the repair.

That is a bit sad.

This audio sample demonstrates the relative difference between the GH4’s noise floor before and after Panasonic’s repairs. As before, the volumes of both samples have been increased by the same amount to make it easier to compare (raw samples can be downloaded at the end of this post).

Bottom line: The GH4 is only slightly quieter at -12dB than it is at -9dB.

As you may have noticed from the audio samples, the GH4’s noise also features more hiss than it did before Panasonic’s repairs. Prior to sending the GH4 in, the buzz was quite prominent, but now it’s mostly white noise.

Bottom line: The buzz has been greatly reduced after Panasonic’s repairs, but this comes at the cost of a noisier camera.

The Strange: Mismatched Audio Levels

While shooting with the GH4 after it returned from Panasonic’s service center, I noticed that the on-screen audio meters often did not match, despite the fact that both channels were receiving the exact same signal.

GH4 Levels Mismatch

Further testing confirmed that the GH4’s 2 audio channels record the same signal at different levels.

Test Setup

Audio Levels Testing Setup

  • GH4 Audio Gain: -12dB
  • Audio Source: -12dB tone generated by Tascam DR-60D
  • Audio Output: Camera Out
  • Audio Level: Tascam DR-60D is calibrated to roughly -12dB on the GH4 when audio gain is set to -12dB. Once set, the DR-60D’s level dial was covered with tape to prevent adjustment.

Calibrating audio level Taping over level dial

GH4 Audio Levels

  • Channel 1 (L) Level: -12.2dB
  • Channel 2 (R) Level: -14.9dB
  • Variance: 2.7dB

Audio channel level mismatch on meters

This sample demonstrates the difference in levels between the GH4 audio channels (raw samples can be downloaded at the end of this post).

Note: Tests were performed multiple times with different cables to confirm that the variance in levels was not being caused by another link in the audio chain.

This variance between the GH4 audio channels obviously adds a wrinkle to your post-production workflow. Depending on the NLE you use, accounting for this variance (e.g. by using just one channel of audio) for every single clip on the timeline can range from a minor annoyance to an exercise in frustration.

Regardless of how you deal with the mismatched levels in post, this issue is not ideal, especially when you are shooting with a single mic.

Bottom line: The variance between the GH4’s audio channels puts an unnecessary stress on your post-production workflow.

Back to the Service Center

The buzz is thankfully no longer an issue, and while the increased noise floor is unfortunate, the mismatched audio levels is untenable.

As a result, my GH4 is heading back to Panasonic for another round of repairs that will hopefully resolve the issues that were uncovered through these tests.

As Panasonic’s buzz repair was a manual one-off process, there is hope that not all GH4’s are affected in the same way as my GH4 is. To find out how widespread these issues are, I invite you to download the audio test kit below and send me your results so that we see whether Panasonic’s buzz fix actually did more harm than good.

Download the GH4 Audio Test Kit

Make sure your GH4 is working properly and providing usable in-camera audio.

The GH4 Audio Test Kit includes audio samples and instructions to test and evaluate your GH4’s audio performance. (The test kit also includes raw samples from the tests in this post)

Send me your test results so that we can see how widespread the new audio issues are.

Pay $0 or more for this resource. How much? You decide!

Download Audio Test Kit

Related

  • Panasonic DMC-GH4 — A very capable camera despite the current audio issues.
  • Tascam DR-60D — A compact 4-track audio mixer with high-quality preamps that attaches to the bottom of your camera.

Panasonic GH4 Audio Resources

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