HMC 80 XLR Inputs and Single Mono Microphones?

[canavp]

Hi,
I have now had a HMC 81e for a few months and am quite happy with the results I'm getting from it! I have one thing that bugs me about the camera though. Prior to purchasing this camera I was using a Sony PD170 and as with all good sound recording practices used external phantom powered balanced XLR mono microphones. The Sony PD170 had switching on it so that when using a single mono microphone, one could switch that single XLR input to also put the sound on the second audio channel. Job Done! But, the HMC 81e does not appear to have theses switches (or menu settings) to allow this function, or have I missed something? Subsequently all audio is only on one of the audio channels depending on which of the two XLR inputs is used. This is a pain in the editing suite as I then have to play around and get the sound onto the second channel!.

I'm just wondering if I have missed something in the set-up of the camera, or if there is an external way of getting the sound from a single phantom powered microphone on to both audio channels at the time of shooting rather than in the editing stage of the workflow. When shooting I monitor on headphone and quite frankly having audio in one ear only is disconcerting to say the least.

Can any one help with ideas on how to overcome this problem please.

Vince.

 

[Alex H.]

Looks like Panasonic left that feature off the camera, which is annoying.

However:

This is a pain in the editing suite as I then have to play around and get the sound onto the second channel!.

Standard practice in production is 1 mic = 1 channel. Even if recording one mic to both channels in-camera, only one of those record tracks should be used in post. Generally, when recording a single mic to two record channels, the second channel is set at least -6dB lower as a safety channel, just in case a sudden and drastic peak happens to overmodulate (distort) the primary recording channel. In editing, the two tracks will be split apart and the primary track used unless distortion requires the use of the -6dB safety track.

An external mixer will allow you to send one mic to both XLR inputs.

 

[canavp]

Thanks for your reply Alex. I must say I like the idea of recording the second channel -6dB. In Première CS5 its easy to say Fill Left or Right channel in the sound mixer I know. I was sort of hoping that someone might come up with an inexpensive way of achieving sound on both channels at the time of recording. The mixer is of course one way of doing it, but what with a blimped microphone and light on the camera, plus a mixer, it all becomes a bit of an untidy lump to lug around. Hi Hi.

 

[Greg Smith]

Thanks for your reply Alex. I must say I like the idea of recording the second channel -6dB. In Première CS5 its easy to say Fill Left or Right channel in the sound mixer I know. I was sort of hoping that someone might come up with an inexpensive way of achieving sound on both channels at the time of recording. The mixer is of course one way of doing it, but what with a blimped microphone and light on the camera, plus a mixer, it all becomes a bit of an untidy lump to lug around. Hi Hi.

The only way I know of to record on both channels with one mic (whether at the same level, or different) is to use some kind of splitter between the microphone and the two XLR inputs. A simple Y cable wouldn't, technically, be recommended for this, as it would present the microphone with a different impedance load than it is designed to operate into. Some mics probably wouldn't care, but the noise level and frequency response of others might be affected. It's also problematic exactly how you should handle phantom power in that situation. It would be best NOT to have the +48V from one jack feed back into the other one. So ideally, you'd want a splitter with transformers (or equivalent active balanced circuitry) on both its input and two outputs, and only feeding phantom power to the mic from one of the input jacks, but blocking it to the other. Unfortunately, once you get up to this level of complexity in the interface, it's probably just about as practical, and would cost about the same, to use a "real" external mixer to begin with.

So I regard the native audio circuitry of the HMC80 as adequate for handling one mic going into one channel, or two separate mics going into two channels. Anything more complicated really calls for a separate mixer. In practice, it's not so bad for me, actually -- the bare setup is adequate for about 90% of what I do with the HMC80 (I also have an AF100 for use in more controlled settings), and I have a variety of mixers to use if necessary. Mixing and/or filling the tracks in post is a fairly trivial step compared to all the other stuff I usually do to the audio. But I do understand that it's a limitation, and kind of an artificial one, at that, since the circuitry probably exists inside the camera to do what you want and it's only a matter of adding some settings to the firmware to enable it.

- Greg

 

[canavp]

Thanks Greg for your thoughts. They were much along the lines I was thinking. At the end of the day I can copy it on to the blank audio track in the NLE. Regrading sound in the headphones while shooting, I think I can get round that using an existing battery powered headphone amplifier and making up an adaptor on the output of it to feed audio to both sides of the headphones. Your last comment re the limitaion is so right. All it needs is to be some where in the setting menu as it not a function one would be continually wanting to change. Sony on the PD170 actually gave external switches on the body of the camera to do this!

Thanks all for your comments and help.

Vince

 

[Greg Smith]

I had my first chance since this thread started to fool around with my HMC80 today, and confirmed that there is a solution to the audio monitoring problem with only one mic plugged in. On the "Other Functions" menu, use the "Audio Out" setting (last item on page 3 of the menu, at least with my firmware) to select only the input channel you want to listen to -- not the default "Ch1/Ch2" mode that gives you "stereo" audio with channel 1 in the left ear and channel 2 in the right. For example, with a microphone plugged into channel 1 and the menu setting also on "Ch1," you'll hear the single mic in both ears. The manual only mentioned that this controls the audio line outputs on the back of the camera, but it didn't say whether the headphone jack was also affected. I can confirm now that it works for the headphones as well.

You'll still need to "fill right" or "fill left" in post to duplicate the audio on both channels, but at least this gives you a better sense of what you're recording out in the field.

- Greg