Stacking audio levels in ch 1 and 2

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christermolander

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Stacking audio levels in ch 1 and 2

PostMon Dec 02, 2019 10:02 pm

On ENG-camcorders it’s been practice to use one microphone and attach it to one input to your camera, then use different audio levels on the two channels. Most helpful when trying to ”save it in post”.
Can we have that in BM cameras?


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rick.lang

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 6:30 am

Generally, yes. Which BMD camera? What mic?
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Denny Smith

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 6:51 am

To add to Rick’s comment, Which mic input? More info is needed. ;)
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Tim Lota

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 10:01 am

You can do that for input 1 & 2 on most cameras. Just don't select the left or right channel, but put them both into mono and set different volume levels for them. At least on the Pocket4K that works with the 3.5, the XLR and even the camera's mics (when on mic, not on line setting).
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christermolander

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 10:21 am

It’s on an UMP4,6 and Pocket4K. XLR input/s.
I’ll try to set on mono. Thanks for the tip Tim.


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Robert Niessner

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 11:44 am

christermolander wrote:It’s on an UMP4,6 and Pocket4K. XLR input/s.
I’ll try to set on mono. Thanks for the tip Tim.


On the UMP you can set the audio inputs to:

a) CH1 -> XLR 1 Mic | CH2 -> XLR 1 Mic Backup <- does a 20dB lower recording than the main channel
b) CH1 -> XLR 1 Mic | CH2 -> XLR 1 <- you can set individual audio levels manually

This is a quote from BMD support which a user got as an answer about a):

Regarding the XLR Mic Backup feature; when properly set, the second channel will bring in the original mic input signal at 20dB lower than the standard Mic input giving you extra headroom in case loud noises occur. The mic backup level is a fixed "line" level and does not follow the adjustments to gain levels on the standard mic input. Levels on the mic backup channel will be detected on the onscreen audio meters when the standard mic input channel exceeds 0dB.

Source

And I found the audio specs:

Available audio gain in dB (decibels) from XLR inputs:
  • LINE input has fixed gain to support maximum +24 dBu.
  • MIC Preamp Gain Range = +10 to +65 dB.
  • MIC Preamp PAD = -20 dB.
  • MIC Preamp Input Signal Range (for 0dBFS) without 20dB PAD = -50 to +5 dBu.
  • MIC Preamp Input Signal Range (for 0dBFS) with 20dB PAD on = -30 to +25 dBu.

Audio signal to noise specification from XLR inputs
  • XLR MIC Preamp has E.I.N. (Equivalent Input Noise) = -128 dBV(A) or better.
  • XLR LINE input has a typical Noise Floor = -118 dBFS(A) or better.
  • XLR MIC Back Up has a typical Noise Floor = -117 dBFS(A).
Source
Robert Niessner
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christermolander

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 12:18 pm

Thank you Robert for the deepdive.
I feel like a slacker for not checking better before asking.
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Robert Niessner

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Re: Stacking audio levels in ch 1 and 2

PostTue Dec 03, 2019 12:33 pm

No worries. I occasionally expand my own knowledge by diving into those topics :)
Robert Niessner
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christermolander

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Re: Stacking audio levels in ch 1 and 2

PostWed Dec 04, 2019 11:54 am

Hi,
I can’t find the Mic Backup feature. This UM 4,6 is on firmware 4.8. Have this feature been added later?
Sorry I called it UMP. This is not the Pro. This is the UM4,6. And that does not have a later FW has it?



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Robert Niessner

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Re: Stacking audio levels in ch 1 and 2

PostWed Dec 04, 2019 1:50 pm

Yeah, that is right. The UM46k doesn't have this feature. Last FW is 4.8
BMD changed the audio hardware in the UMP so you can route the channels around, which isn't possible with the UM46k.

But you can do this with the PCC4k/6k - just set the same input on both channels and trim the gain.
Robert Niessner
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christermolander

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Re: Stacking audio levels in ch 1 and 2

PostWed Dec 04, 2019 2:49 pm

Thank you. Question answered.


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