HPX250 - Audio issue when using external shotgun mic.

[Chris Dumont]

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.


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.
Turned phantom power off and ran just on mic battery, removed battery and powered just from camera.


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 also on the HPX250 that they have in the showroom (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. 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.


This is my first post on a forum like this so I hope this is all clear and explains the issue, look forward to your replies.

Audio Sample


I couldn't work out how to post audio on the forum so here is a link to the audio on youtube.

[Greg Smith]

Sounds like RF from a local radio transmitter getting in there somehow -- there is just a hint of modulation on the signal that could be some kind of program content. That, in turn, could be the result of a bad ground, cold solder connection, missing or insecure shielding around a component or circuit board. I take it you didn't try a second 250 -- that would probably give a definitive answer. Have you tested in a variety of different locations that might have varying RF environments (closer or farther from broadcast transmitters, cell phone towers, etc.)? It may sound silly, but make sure your own cell phone is turned off (or left in the car) when you're testing.

One thing you might try is connecting the shell of the XLR cable at the camera end to the shield in the cable -- or conversely, disconnecting it if it's wired that way now. (The standard is supposed to be NOT to ground the shell, but there are cables out there made both ways.) Just changing cables might not demonstrate this if they were both wired the same way.

You don't say whether you're using phantom power or the internal battery with the ME66, although I presume you were using phantom when you tested with the NTG-3. Try it both ways.

My bet is that you have a defective camera, but it's worth trying a few more simple things before sending it in.

- Greg

[Chris Dumont]

Thanks for replying Greg.

I have tested it in numerous locations so I'm sure its nothing to do with radio signals. That signal sample is only created by making a loud noise into the mic. I have used numerous XLR cables which were fine on other cameras including the 160. the cables I'm am using have Neutric connectors but I'm not sure how they are wired as regards to grounding. I tested it with and without phantom power. I have also used phantom power with the battery removed from the ME66.

I have ran the same tests on another HPX250 which was exactly the same. Thats why I'm now thinking it is a design fault in the camera rather than my one being defective. When making a loud noise into a mic on the HPX250 competitors such as Canons XF305, the electronic distortion is not preset at all which further more suggests it is a fault with the camera.

[rzr219]

Hum,

I am going to try the same test this week and see what I get. If you tried it on different 250's and the same issue, then it tells me its the camera. I will let you know what I get later this week or weekend.

[Chris Dumont]

Amazing.

What I did to create the issue outside of operating in a loud environment is position the shotgun mic 10/15cm ffrom my mouth and make a relatively loud ahh. This is done with the levels set to manual and completely at zero so you shouldn't hear anything technically. You will be able to see the "electronic distortion" on the audio metre and monitor it with headphones. As I say, this happens normally when operating in a loud environment. This is the method I used to replicate the issue however my dealership had replicated it by playing loud music from a radio.

The main reason this is such a big problem is that is uncontrollable and records onto the audio channel ruining your audio.

Thanks for the replies so far, anyone have any further ideas as to what is causing it or is willing to test it, please let me know.

[JohnnyD]

If you're good at soldering, try switching the wired pins on ONE of the XLR cable connectors from pin 3 to pin 2, etc. If it's the same problem, go back to he original wiring, and switch Pins 1 and 2. I'm also an electronic tech, and have seen mis-wired circuit boards and internal connectors on equipment.

[mmaller]

Chris,

I did a test with my HPX250 just as you described and here is what I discovered.
I happen to have the same Sennheiser ME66 microphone as you do and when I used it for the test, I got the same result as you did,
a distortion in the channel even though the level was completely turned down. A crackling distortion coinciding with the loud level.

But when I repeated the test using a different microphone, this time a Sennheiser MD421U which is a dynamic mic, The crackling distortion
did not occur. I wonder if it is somehow related to only condenser mics or maybe just the ME66?

[Jim Simon]

Has anyone tested this using the built-in mics? I'm planning on buying a 250, and will often be within 5 feet of some very loud music (wedding reception).

I can't have this kind of issue with the internal mics. I'd have to find another camera if that was affected as well.

[Chris Dumont]

Hi mmaller,

Thank you for taking the time to do that test. It seems that this is definitely a fault in the camera design across all HPX250's. It's definitely not the ME66 that is causing it as I have tested it with a Rode NT1/NT3? which gave the same result. What you say regarding whether it is a condenser mic or dynamic is very interesting. Panasonic's microphone, The AG-MC200G I believe is a dynamic mic. This would indicate why people haven't experienced it if they are using that. For me, I want to be able to use any mic I choose on the camera, especially Sennheiser ENG microphones. For a professional camera, this just doesn't seem right. As I have said before, the biggest problem for me is that it is uncontrollable and releases that signal randomly with no way (as yet) of preventing it.

Again, thank you for taking the time to check.

Jim, I have tested the internal mic for you and I'm happy to say it does NOT suffer from the same issue. This probably to do with the fact that its either a dynamic mic, has different circuitry or both.

Anyone else experiencing the "electronic distortion" with a condenser mic (or something else) please let me know.

[mmaller]

It seems as Chris noted that this is a problem across all HPX250's.
Like Chris said, I didn't buy this camera to only use a certain type of microphone. My ME66 is my camera mounted shotgun of choice.
If this is a problem across the board, what are all the owners of HPX250's going to do now?
Or what is Panasonic going to do?
My camera is a little over a month old at this point, and I don't think my retailer will take it back.
What is the course of action now?