AX100 audio blown out, why?

[Jeff Harper]

My audio, when using my Rode shotgun on my primary AX100, is distorted from my wedding yesterday, it's really bad.

Never had this issue before. The cam is set to auto gain, which normally works perfectly, and the mic setting is on 0 gain.

Lower levels of sound were find but anything loud is distorted.

[Charles W. Hull]

When using an external microphone use the Manual mode, and adjust the level so it doesn't clip. I have not used a Rode, but with a Sennheiser ew 100 I turn the level about halfway down.

[Robert Young]

Originally Posted by Jeff Harper

The cam is set to auto gain, which normally works perfectly...

You might check to see that the Automatic Gain Control Limiter (AGC Limit) is turned on and set to an appropriate level.
This should prevent clipping when using Auto Gain.

[Jeff Harper]

Thanks for your replies. Robert, the Auto Gain limiter is for video, not audio, unless I'm misunderstanding you.

The problem is now clear, and David Johns has shared it with me via a video. The Sony has a built in limiter that can really create havoc.

If you own the AX100 or CX900 you should watch this video. Even in Manual mode you must calibrate each time or you risk blown out audio when using an external mic.

Audio tests and tips: Sony HDR-CX900 camcorder - YouTube

[Robert Young]

Jeff
You are absolutely correct- the AGC Limit on the AX100/X70 is for video gain, it is not an AGL for audio as I was thinking.
David's excellent video illustrates that there is indeed an AGL feature. However, it is always on- no matter if recording manual or auto, and is not adjustable.
Even though this limiter can cause unintended swings in volume, as he shows, shouldn't it still prevent actual clipping?

[David Johns]

It should yes (at least that's what I'd expect). You can hear in my tests though that when you go from very quiet (and when the limiter has turned off or at least minimised, enabling the gain to raise) to very loud, there is "some" distortion albeit briefly whilst it struggles to cap the volume and reduce the input, which is does gently over a couple of seconds.

I don't, I must confess, understand why Jeff's levels on Auto should be overblown except insofar as I found the camera always overcranks the auto gain and compresses the audio too much. I'm pondering whether the mic is somehow overblowing the mic input (need to know what mic was used and what if any settings)

Regards
David

[Jeff Harper]

David, Rode Videomic used at 0 gain. Used it at countless weddings on a variety of camcorders always on auto, always perfectly fine. Loud bands, DJs, it has made no difference, it's always been great.

The reception music for the last wedding was totally distorted, it's unusable. Interestingly enough the 2nd AX100 ran in auto also but without external mic and it was fine.

So the issue seems to be, for me, when using an external mic.

I dread working on all of the weddings before this one, I have no idea what awaits.

[Charles W. Hull]

Originally Posted by Jeff Harper

If you own the AX100 or CX900 you should watch this video. Even in Manual mode you must calibrate each time or you risk blown out audio when using an external mic.

Jeff, in my case I adjusted the manual setting for the Sennheiser mic and that was it - I didn't need to adjust it after that. If you mean it needs to be adjusted for each different external microphone, isn't this the same as every other video camera? You should be able to manually adjust for the Rode mic one time and be good.

[David Johns]

Originally Posted by Jeff Harper

Rode Videomic used at 0 gain. The reception music for the last wedding was totally distorted, it's unusable.

Peculiar. I can only image that:-

a) the mic has become damaged somehow? (does it sound OK now?)
b) the mic was closer to the band / loud speakers than prior filming - overloaded?
c) The gain was accidentally switched to +20 and overcooked the camcorder input?
d) the music actually was distorted and it has recorded perfectly ;-)

Much testing required, methinks... have fun.

Dave

[Mark Fry]

Originally Posted by Jeff Harper

David, Rode Videomic used at 0 gain. Used it at countless weddings on a variety of camcorders always on auto, always perfectly fine. Loud bands, DJs, it has made no difference, it's always been great.

The reception music for the last wedding was totally distorted, it's unusable. Interestingly enough the 2nd AX100 ran in auto also but without external mic and it was fine.

So the issue seems to be, for me, when using an external mic.

I dread working on all of the weddings before this one, I have no idea what awaits.

The original Rode VideoMic is a particularly "hot" microphone, possibly because it uses a 9v PP3 battery, rather than a 1.5v AA or watch-cell battery. Is that the model you are using? I have had a few problems because of this in the past. Does the AX100 have a mic att (attenuation) setting? That can sometimes help.

[Jeff Harper]

Thanks for your comments.

This issue has occurred for me with a Sennheiser mic as well as my Videomic Pro. A the time of the incident with the Sennheiser I had no idea what the issue was and had other audio sources (other cams) so I forgot about it.

Incidentially I've also used the original Videomic on a number of cameras and never had issues with it, as long as it was correctly set.

I have used shotguns of various types on a variety of cameras for 10 years and this is the first time I've had issues with autogain allowing distortion. I've recorded live bands, VERY loud bands, with camera next to a speaker (out of necessity not by choice) and aside from only getting half the stereo, the audio was very good, no distortion.