Hi all,

Any help with this would be much appreciated.

The issue -

I am experiencing an issue with my recently purchased HPX 250, that when I am using the camera in a relatively loud environment with a shotgun mic attached via XLR, I am getting a strange electronic distortion through the camera (please listen to audio sample attached). I am controlling the levels on the camera manually with the level around-18/-12db. This "electronic distortion" then peaks over that level. In trying to identify what was causing this to happen I turned the level completely to zero. The "electronic distortion" still gets through and records to the card. This is how I have a clean recording of the distortion in the audio sample with no ambient noise.

Equipment -

HPX250
Sennheiser ME66 with K6 power module.
Rycote Softie
XLR Cable (tried multiple cables)

Troubleshooting -

This is everything I have done to try and find the cause of the issue but nothing has resolved it.

*Changed XLR cables
*Changed Channel on camera (different XLR port)
*Turned the camera limiter on and off
*Turned the levels down to zero (this is how audio sample was recorded)
*Changed the internal (menu) mic gain option from default -50db to other two options -40db and -60db
*Replicated the issue at home in a quiet environment by making a loud noise into the microphone from around 10/15cm from mic.
*Turned phantom power off and ran just on mic battery, removed battery and powered just from camera (phantom power).

Not getting anywhere, I then took the camera to the dealership I bought it from and we replicated the issue not only on my camera but the same issue also occured on the HPX250 that they have in the showroom, SO THAT IS TWO SEPARATE HPX250 CAMERAS THAT THIS HAPPENS ON! (leading me to believe this might be a design fault in the camera).

At the dealership we also -

Used a different mic on the camera (Rode NT3?) and ran the same test (making a loud noise into the mic) which gave us the same result of the "electronic distortion". We then ran the same test on the Canon XF305 and another Sony camera of a similar level with both mics and these did not allow the signal through giving a completely silent channel as you would expect when the level/pre amp is at zero. This unfortunately indicates to us that the fault is with the camera(s) not the microphone.

Verdict -

I am not an audio expert nor a sound man, however, my theory is that the loud noise is causing the mic to create an electrical signal that the camera is not resisting??

I have spoken to a sound recordist that I know and played the audio sample to him, he feels that its a problem with the pre amps on the camera.

My dealership are currently doing their best to resolve this issue for me, but at the moment it is still on going. Has anyone had this issue with this camera yet? Does anyone know what this might be?

If you do own the camera, could you try the test and make a loud noise into your mic and see if that signal breaks through with the level on zero (as in no gain at all), I can hear the "electronic distortion", record it and see it on the level metre.

I hope this is all clear and explains the issue well. Some feedback about rewiring XLR cables but this doesn't make sense to me if the cables are brand new XLR cables from the dealership specially for video cameras and the cables work fine on other cameras including the Panasonic 160. I look forward to your replies.

Audio sample link (had to post on youtube as I couldn't work out how to post it on a forum) - Electronic distortion - YouTube

Thanks!

Does the same problem occur using a mixer in between the mic and the camera? Try Line level out of the mixer as well. I might have time later in the week to check my HPX-250. You should also include a sample where the sound is being recorded with a regular signal with it as the lack of any other signal may not tell us as much as you think. Haven't used my HPX 250 in enough situations to determine if this problem is showing up in my usage or not.

That sounds like a digital encoding problem to me similar to pixelation on the video side, you can hear the digital bleeping at the end and its unlikely that mic would be making such noises, I would get in touch with panasonic under your warranty registration as it sounds like a faulty component or something is not working right on the camera to encode the audio.

I have HPX301 and 371 camera's which are similar in design to the 250 and they have never made such noises.

Note the HPX255 update has now been released so it may be that a firmware update may cure this, more here: http://news.doddleme.com/equipment/nab-2012-panasonic-introduces-ag-hpx255-handheld-ag-hpx600-shoulder-mount-hd-cameras/

Hi guys, Thanks for your posts on this.

Daniel - I don't own a mixer so haven't had chance to try that as yet. I have taken a couple of samples from when I was filming, at this point I had given up on this particular audio due to the interference on the "electronic distortion" and just left the level around -18db to -12db. I have posted it below.

Gary - Thanks for the post, will download that update and see what that does.

Audio clip posted to youtube, levels untouched from when recorded.

Audio distortion with background music. - YouTube

Yup that sure sounds like a digital audio encode/decode problem as you can hear the samples glitching when the distortion happens.

This sometimes happens when the digital audio is out of sync with the picture frame rate so I would contact panasonic as it is a camera fault and needs to be highlighted with them.

I presume you are working at PAL rates and that the camera is set to 50i or 25p, I also assume that you are not gen-locking or feeding the camera from an external timecode source as that could possibly cause sync issues, a variable frame rate could also be a problem but should mute the audio altogether if it is being used.

I would also check the firmware version (in the menu) and see if panasonic are aware of it as it could be that the camera's you have tried have been shipped with incorrect firmware or beta versions.

I'll cross post my reply to this issue:

For the purpose of my remarks, I'm going to call the distorted sound, "clipping". Depending on the audio circuit design, it is possible to clip at the input stage before the signal gets to the gain control.

I had a similar experience with a HMC150 when 1) the menu audio setting was -60db (should have been -50), 2) the external audio recorder decided it didn't like it's CF card, and 3) we were shooting a rock guitar amp commercial (think loud) ... also using a neumann U87 and Shure sm57. The audio gain controls were set low, ie between 1 and 2 on a scale of 11. The meters were normal, but some clipping distortion was found in post.

I'm thinking the audio design is similar in the HPX250, and is just a little too "fragile" in the input stage. The easy fix it just to attenuate a strong signal with a 10 or 20 db pad. Also the audio menu setting should be -40db. If I needed perfect audio from a HPX250, I would only run with the gain controls around 5, (12 o'clock on the camera)... or higher to setup correct metering levels. Turning the gain down close to 0 reduces the output (metered) but the input can still clip. Also, FYI, this clipping can be subtle, and hard to detect with headphone monitoring in a loud room.

I have not seen this on my HPX250 because I only record sound from the internal mikes to use for multi cam syncing. All project audio is recorded on a Sound Devices 788T or PIX240 because I specialize in musical events.

Hello

Chris or anyone else - did you ever resolve this problem? I have the same issue with my HPX250 and ME66. I have been able to continue using the mic by using it through a radio mic transmitter and adjusting the sensitivity -10db there, but it's still vulnerable to loud noises and obviously not an ideal solution.

I have the latest firmware on the camera, it's also still under warranty.

Any advice much appreciated.