Hum with phantom power and EVF off on A1 at DVinfo.net

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Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


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Old February 7th, 2009, 04:39 PM   #1
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Hum with phantom power and EVF off on A1

Hi -

I have been searching for some info on a problem I am having, but I have not had much luck. Basically, when using XLR and phantom power, I have a low level but very noticeable hum when the EVF is off. If I set the EVF to always be on, I don't get the hiss. Same if I close the LCD, or turn it facing forward so the EVF comes on. I don't notice this noise with the internal mic or with my Rode Videomic, and I have not tested without phantom power, but I suspect it is related to phantom power.

Has anyone else experienced this? I just plugged in an XLR mic today for the first time, and my camcorder is only about 2 - 3 weeks old. Any chance I am just doing something wrong here?
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Old February 7th, 2009, 05:41 PM   #2
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I'm new to the xha1 but did you make sure that the switch is selected to mic and not Line?
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Old February 7th, 2009, 07:27 PM   #3
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I just double checked - yes, set to mic...
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Old February 7th, 2009, 08:31 PM   #4
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Quote:
Originally Posted by Jay Bratcher View Post
... Basically, when using XLR and phantom power, I have a low level but very noticeable hum when the EVF is off. If I set the EVF to always be on, I don't get the hiss.
Is it hum or hiss? I'm confused.

Also, what mic are you using for the xlr connection?
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Old February 7th, 2009, 08:36 PM   #5
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Hi jay,

I haven't used phantom powered mic yet with my xha1. I have a couple of questions for you to clarify:

The mic does require phantom power, right?

Where is the phantom powered mic located?

How long is the xlr cable?

Have you tried another xlr cable?

Is the hum present if the xlr cable removed? or changed to another channel?

I have my evf set to always on......at least you have a remedy....but it sure would be nice to "treat the cause" and not "treat the symptom."

I may have the opportunity to record with phantom next weekend and if so I will do some testing. Hopefully someone who runs phantom power now will be able to test and get you some feedback sooner. I used to run sound for a theatre co, and a constant hum was normally caused by a ground loop or bad cable.
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Old February 7th, 2009, 09:31 PM   #6
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Quote:
Originally Posted by Bill Busby View Post
Is it hum or hiss? I'm confused.

Also, what mic are you using for the xlr connection?

Hi Bill -

I knew someone would catch that :D - I realized I said hiss right after I hit submit. It is a hum, actually....

The mic in question is a Sennheiser ME66...

Quote:
Originally Posted by Michael Hutson View Post
Hi jay,

I haven't used phantom powered mic yet with my xha1. I have a couple of questions for you to clarify:

The mic does require phantom power, right?

Where is the phantom powered mic located?

How long is the xlr cable?

Have you tried another xlr cable?

Is the hum present if the xlr cable removed? or changed to another channel?

I have my evf set to always on......at least you have a remedy....but it sure would be nice to "treat the cause" and not "treat the symptom."

I may have the opportunity to record with phantom next weekend and if so I will do some testing. Hopefully someone who runs phantom power now will be able to test and get you some feedback sooner. I used to run sound for a theatre co, and a constant hum was normally caused by a ground loop or bad cable.
Hi Michael -

The mic can run on phantom or from a single AA battery. I haven't tried powering from battery yet though, as the one in the mic was dead, and the last AA battery I had in the house seems to be dead as well.

Location doesn't seem to matter - I have tried both a 30 ft. and a 3 ft. cable, and I pick up the hum with the mic on camera and also on a mic stand. I feel confident in saying that the hum does not come from the mic, but rather from the camera's electronics. Incidentally, getting the mic out of the on-board mic holder does miracles for sound - but does nothing to eliminate the hum...

The hum is present on both channels (I can only test one at a time though). I suspect your ground loop diagnosis is correct, but it seems to me that it would have to be internal, since the EVF affects it.
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Old February 7th, 2009, 09:40 PM   #7
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How is the A1 being powered? A/C or battery....
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Old February 7th, 2009, 11:22 PM   #8
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a ground loop though is normally when componants are plugged into 2 different ground circuits.....you are only plugged into one. so i don't think that is it.

Hopefully someone can do some testing for you and see if they have the same issue. I'm kinda leaning towards an internal circuit issue on the camera.
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Old February 8th, 2009, 03:41 AM   #9
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the mic could be picking up camera noise. mine does and the only solution is not using the onboard mic holder.
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Old February 8th, 2009, 09:57 AM   #10
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I was on a shoot yesterday and experienced what I think is the same problem. Setup was the A1 with a Rode NTG-1 channel 1 and a Countryman B6 lav on channel 2. Both connected via XLR. Both mics require phantom power and it was turned on. The hum appeared to be 60Hz on the Countryman but the Rode was clear. The camera was plugged into 110v.

If the interviewee put his hand on Countryman's connection to the cable connecting it to the camera, the hum disappeared. We doused all the lights in the building and hum remained. However, when I unplugged the camera from the wall and ran it on battery the hum disappeared so I did the entire shoot on battery power without further problem. I have not tested the EVF setting.

I don't know for certain if this is related to the OP's issue but it seems to be. I'm going to play with this a bit more in the next few days and will report what I find.
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Old February 8th, 2009, 10:42 AM   #11
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thanks tripp,

I am very curious.
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Old February 8th, 2009, 01:14 PM   #12
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Hi all -

Actually, the camera is on battery power. I will try A/C later today to see if that changes anything.

I get the hum with the mic both on and off the camera, and I am quite sure it is not camera noise - this hum is distinguishable from the various motor noises that come from the camera itself.

It is a very quiet hum, and the volume seems to vary, although that is somewhat subjective. For example, I was trying to see if headphone volume or mic gain had any bearing last night, and I could not hear it over the various sounds that the mic was picking up (like my very noisy PC, or even the refrigerator in the next room). I ended up going to the garage, and it was just audible in there - it seemed louder earlier in the day. The difference could just be me too though, I suppose...

Incidentally, the volume of the hum changes with both headphone volume (expected), and mic gain. Not sure if that has any significance or not.

I think at this point, I may call Canon tomorrow, but I don't think I will be returning it for repair any time soon - I have a couple of things I will be working on over the next couple of months, and don't think I could go without the camera for say, 3 weeks...
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Old February 8th, 2009, 02:46 PM   #13
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Quote:
Originally Posted by Jay Bratcher View Post
It is a very quiet hum, and the volume seems to vary, although that is somewhat subjective.
This is a different symptom than mine. My hum is not very quiet. It's not loud either but it's reasonably pronounced. So much so that you could not bury under music. The hum would render any audio useless.

I'm going to post my results in a new thread so that I don't hijack this thread or confuse people with two problems.
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Old February 8th, 2009, 04:47 PM   #14
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Can you post a small sample of the hum?

Does it happen with other microphones?

Is it there is the mic is not connected but all other settings are the same?

Are you using manual or auto for audio level control.
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Old February 8th, 2009, 11:10 PM   #15
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OK. I finally got around to doing another test - four tests, actually...

First test was with AC power, both with and without EVF. This was very interesting, because in both tests, I had no hum. Honestly, I expected the result to be the same, especially after reading Tripp's comments. However, I agree that Tripp and I are experiencing different issues, so my results kind of make sense.

The second test was again on battery power. As expected, with the LVF off, the hum was back. I am baffled as to why AC vs. battery would be different, and I would actually expect more noise when running off of AC than off of battery. From the camera's perspective, I just don't see that there could be much of a difference. I mean, the camera is getting a specific DC voltage, right? BTW, I tried with two different batteries - I get hum with both of them. I don't believe my batteries could be weak, as both are new.

Quote:
Originally Posted by Don Palomaki View Post
Can you post a small sample of the hum?

Does it happen with other microphones?

Is it there is the mic is not connected but all other settings are the same?

Are you using manual or auto for audio level control.

Hi Don -

I do have audio from my tests, but I want to re-record it so it is obvious what I am testing. I should be able to get that done in the morning.

I do not have another microphone to test with, unfortunately - in fact, this one is a rental...

I apologize, but I do not quite follow your third question. The mic is connected when I hear the hum - if I disconnect the mic, the hum goes away. I also do not get the hum using the internal mic, nor do I get it using a Rode Videomic attached to the 1/8" mini-pliug, if that helps.

As for the audio level control, I have been setting the gain manually. I can certainly throw in another test to see if auto mode gives the same results.

I should have some samples up some time tomorrow...
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