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Old December 8th, 2007, 09:50 AM   #1
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Sony HVR-A1U and external microphones

Hi, I haven't been on the forum for awhile and I'm not finding the right place to post a question I have about my Sony HVR-A1U and the use of external microphones. Forgive me if you see this question posted on different lists, because I'm not sure where it will be "found"!

I want to mic the interviewer and the interviewee in an upcoming video shoot. The interviewee will be on a wireless lav and the interviewer will be on a wired lav. I assume that if I connect the wireless in input 1, channel one, and the wired in input 2, that the wired lav in input 2 will automatically go to channel 2.

The question is, I'm not sure if both mics should be set at "mic", or if the wireless should be set to "line" and the wired to "mic". I heard somewhere that the wireless works better on "line".

Thanks.
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Old December 8th, 2007, 10:51 AM   #2
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Quote:
Originally Posted by Cindy Konits View Post
...The question is, I'm not sure if both mics should be set at "mic", or if the wireless should be set to "line" and the wired to "mic". I heard somewhere that the wireless works better on "line".

Thanks.
In a better scenario, you would send both mic inputs into a mixer (something like a Sound Devices MixPre) and then send "line" level via a breakaway cable to both camera inputs. And hire a good sound person.

But, to answer your question...you need to go "MIC" level with both inputs. Turn "off" phantom power and make sure a good battery is in the "wired" lav.

I believe that camera also has a switch to send channel 1 to both channels. You need to test that out and make sure that channel 1 is set to channel 1 ONLY.

Setting your levels is critical when you are not going through a mixer (well, it's always critical) without a good limiter. You want your average peaks to be around -16 in order to stay away from digital distortion.
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Old December 8th, 2007, 11:26 AM   #3
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Jim,
Thank you so much for your reply. Input 1 is set to channel 1. I don't see another switch which would ensure that Input 1 is sending to channel 1 only. I turned off phantom power for both mics. Is that correct?

The problem is, sound is coming in at a lower level on the wireless in Input 1 than the wired on Input 2. Neither are peaking in capture, though. Maybe this is simply the nature of wireless?

I experimented by putting the wireless in Input 2 and the wired in Input 1 and it sounds like the levels might be more equal. I haven't captured this in FCP yet, where I'd get a better idea if this is true. Would this make sense to you?
Cindy
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Old December 8th, 2007, 02:35 PM   #4
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Quote:
Originally Posted by Cindy Konits View Post
Jim,
....Input 1 is set to channel 1. I don't see another switch which would ensure that Input 1 is sending to channel 1 only.
That's probably the correct switch. If you were using just one mic, you could switch that selection to both channel 1 & channel 2...and could send a slightly lower signal to one of the tracks to help ensure the louder peaks don't get crunched.

Quote:
I turned off phantom power for both mics. Is that correct?
That is correct. Both the wireless and wired lav should get power from their own power supply (batteries).

Quote:
The problem is, sound is coming in at a lower level on the wireless in Input 1 than the wired on Input 2. Neither are peaking in capture, though. Maybe this is simply the nature of wireless?
Most wireless systems allow you to dial in both the transmitter and receiver for optimum levels. What wireless system are you using?

Quote:
I experimented by putting the wireless in Input 2 and the wired in Input 1 and it sounds like the levels might be more equal. I haven't captured this in FCP yet, where I'd get a better idea if this is true. Would this make sense to you?
Cindy
That's where using an external mixer really helps. You send a reference tone from the mixer and set your levels (on the camera) at -20 or -12 depending on the dynamic range of the source material.

Some wireless systems have a reference tone.

Trust your ears and trust your meter levels.
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Old December 9th, 2007, 06:41 AM   #5
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Settings for HVR-A1u

We really need to know what mics you plan to use to give more detailed advice. Maybe I can help by explaining what each setting does. But first, a quick primer:
Generally wired mics put out MIC level.
Wireless mics can output mic or line level, I think most have a switchable output, but can't recall.
Most other electronics, [tape decks, vcrs, ipods etc] all use line output via RCA jack [ipod via headphone adapter]. Because they have two conductors and no shield to speak of, we call them unbalanced cables as they can pick up hum or injected noise. Since they run at much higher voltage than mic level, it's usually not a problem.

Mic level is a really tiny voltage. Line is much larger voltage. The reason this exists is because adding line level to a mic increases cost/weight/size and each amplification induces noise/distortion. It's hard enough to make a mike which does not inject some self noise due to the electronics, since the voltages are so tiny. Also most mics simply don't have the power supply to provide line level, again line level adds bulk, weight and complexity.

Mic connectors are called XLR jacks. Most have three conductors, one conductor is soldered to the metal casing {shield], providing a good ground. These three wires are shielded in braided wire or an aluminum foil sort of wrapper. This allows them to be run a long way and not pickup hum or injected noise. These are called "balanced" cables. With properly shielded mic cable, you can run mic level over 50 feet, we ran them over 200 feet in TV without significant issues.

Mic attenuation "pads" (lowers) the input level to prevent distortion from too high an input level coming from the mic. Some mics naturally run "hot" and some are positioned next to the kick drum in a rock band, hence this switch's existence.

In digital audio exceeding 0vu [zero volume units] is the "brick wall" of audio. Like overblown white in the video, it is not correctable, so err on side of not over driving the audio. But too low, you will hear Hisss -- the mics self noise or possibly artifacts, like injected noise or hum will be annoyingly noticable. Between -25 and 0 are good levels. It's normal for it to instantaneously go slightly over 0vu, "into the red" but not sustained.

+48vDc Phantom: Mics have to have a bit of voltage to make them work, same as an ipod. You can use a battery or phantom power to provide DC [direct current]. It's REALLY important to RTFM [read the friggin' manual] on this!! While most will work just fine with the battery in-place and phantom off, I've found phantom power generally gives a much better sound due to the higher bias voltage applied. But some mics require the battery to be in with phantom to operate and I've encountered a few that will be DAMAGED if you do this. RTFM! Manufacturer website, if no manual.

Above are generalities, we could go into permutations like wiring an XLR to carry 18volts for a light, but that's offtopic. Ok, I am looking at my beloved a1u... here's the controls and what they do.

First, lets assume the:
wired is Input 1;
Wireless Input 2.
Wired is typically MIC level, Wireless, probably LINE level. PLEASE be aware, it's possible to have a wireless with MIC level output as many are switchable.

Going across the switches from left to right:
REC CH SELECT: CH1
INPUT LEVEL: MIC or Mic Atten*
+48V: depends on mic

INPUT LEVEL: MIC or Mic Atten* or Line
+48: off

To ATTEN or not: Go to P-MEUN. Bring up Status Check - have the subject read something.
Look at the first page: AUDIO.
The channels should move independently of each other in terms of levels. Each mic will likely pick up the other person's voice to a small degree, hopefully not too much. See above for proper levels. Use headphones to confirm sound is ok, there is no hollow sound or excessive room ambiance, air conditioner rumble, etc.
The INPUT should say XLR. If not, your audio's module's camera connector is loose.
Audio CH1 and CH2 levels should say auto. You can do them manually, if you wish, but I'd recommend separate mixer if you do.

Finally, the back of the audio has lo-cut. This rolls off the lower frequency sounds at the price of bass. Great to reduce air conditionaer rumble, not so good if you are micing Barry White (ok, I know that has it's own set of challenges!) Your ears arebest guide, but I found the headphone out of the Au1 to be lacking without closed ear headphones.

Last edited by James Harring; December 9th, 2007 at 07:28 AM. Reason: reread post
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Old December 9th, 2007, 01:09 PM   #6
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James and Jim,
You both are incredibly generous to share such detailed knowledge of the equipment with me.

First of all, I'm using the Shure wireless mic Model T1-CV. Shameful I know, but I don't believe I have the manual anymore so I will look it up online. The wired lav is Sony ECM-77B, same regarding the manual.

What are closed ear headphones? The headphones I am using are Sony Dynamic Stereo Headphones MDR-7506.

I understand that batteries is better than 48v phantom power, but I'm not sure if you're suggesting that it's best to use both. I could test both mics with both, but it's sounding pretty good with just battery.

For clarity, this is what I understand so far, and please correct me if I'm wrong:
I only use mic atten if the channels don't move independently in status check, OR if I need to get rid of air conditioner-type noise.
If I still have trouble with noise using mic atten, then I should use low cut as well? (I try mic atten first to get rid of noise, then low cut, then both?)
Even though it is suggested to use wireless with Line, I've gotten better results with mic, so I'll assume that's fine!

Thank you so much again, for your help.
Cindy
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Old January 2nd, 2009, 03:57 PM   #7
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i just got a sony HVR-A1U and i was curious if there was a way to have the Ch1 and Ch2 audio levels displayed on the LCD Screen because i would like to see that on my screen when recording.
thanks
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Old January 2nd, 2009, 04:13 PM   #8
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ok, so i figured that out, nevermind.
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Old January 3rd, 2009, 06:05 AM   #9
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Hello Cindy,

I see you have a new camera. I'm having a workshop here in February that sounds like it might be right up your alley.

Ty Ford?s Audio Bootcamp Workshop Saturday February 21, 2009 1-5PM

Regards,

Ty Ford
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