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Bob K

Alexa Mini audio menu

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I worked with an Alexa Mini for the first time recently, sending two discreet channels of audio to the A-box.  I had the ARRI operating manual and the audio menu seemed simple.  But, I allowed the AC to read the menu while I told her what the settings should be.  I was overconfident.  I later heard from the editor that we recorded the two discreet channels summed together on the camera's track 1, and the same two channels summed together on track 2.  My independently-recorded backup files had each mic recorded on its own track, so problem solved.

But, I would still like to know what was set wrong in the camera's menu.  I've never heard of such a thing before, and wouldn't know how to obtain that result if I wanted it.  Does anyone know?

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Whatever Sound goes to the mini should be considered scratch/guide track.

 

I have noticed when sending tone to ch1, that ch2 shows signal - even when only plugged into ch1, with level pulled all the way down on ch2.

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That would be the same thing I experienced.  There must be a menu setting that prevents   that.  As to audio quality, it does record 24 bit, 48 kHz audio.

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Some cameras have the option of sending 1 signal to 2 channels, often at independent levels. Does the Alexa mini have an engineer's menu allowing for set-ups like this (and others) that can't be overridden in the normal menu? I worked with few over the years but only had problems on 1 shoot where both bodies were fresh from the box (new) and it didn't matter what AC and I tried, we couldn't get sound or TC into either of the cameras from my recorder or Lockit.

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I work with Minis quite frequently and I'm not aware of a menu setting that could do this (unless it's been added in. recent firmware update). The audio options in an Alexa Mini are quite basic, to say the least. I'm wondering if they were recording on the in-camera cfast card, or using an external recorder which might be the issue? Otherwise, was it a basic passive A-Box, or one of the little 2-channel active preamp boxes now available for the mini and quite popular with the Documentary folks? They might have track selection / mixing depending on the brand - pretty sure the Beachtek one does.

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nickreich,

 

When you say you're "not aware of a menu setting that could do this," by "this" do you mean sum two channels to mono?

 

The camera had a passive Wooden Camera A-box, most definitely.  There was no external recorder, so it must have been recording to an in-camera card.  I couldn't tell you what type.  The only external device was a video monitor connected by HD-SDI. 

I tried and failed to upload a pic of the camera's relevant menu page in this reply.  That menu page shows that for each channel there is a choice of manual, manual+Limiter, or Auto.  "Auto" meaning automatic leveling I assume. We set each channel to manual, and I sent line level and set a good level (-10) on the camera.  I don't know what we could have missed.  

 

Daniel, I don't know if the Mini has an engineer's menu, and I don't know how old or new this particular camera was.  It was a one-day shoot for me. 

 

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To clarify what I said above, I don't think it's a function, like on the Canon C300, where you can set channel 1 to go to both tracks. Rather it's the two channels bleeding across to each other. I mean, we are pushing two channels of line level signal into a single tiny little Lemo connector....

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OK, thanks for clarifying.  I doubt that's the explanation though.  I know it's a small Lemo connector, but I'd be surprised if that kind of a problem got past Arri's engineers.

 

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5 hours ago, Bob K said:

nickreich,

 

When you say you're "not aware of a menu setting that could do this," by "this" do you mean sum two channels to mono?

 

The camera had a passive Wooden Camera A-box, most definitely. 

 

yes, that's what I meant - I don't believe there is a function in the Alexa Mini to merge or sum Left and Right inputs. There is no problem with pushing two channels of line level audio into the lemo connector - my usual music video-style workflow has guide audio on one channel and playback timecode on the other. Never had any complaints of crosstalk. Assuming the channels were separate going into the Alexa, I'm wondering if the issue has happened in Post or in transcoding before it got to Editorial? 

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10 hours ago, Johnny Karlsson said:

I have noticed when sending tone to ch1, that ch2 shows signal - even when only plugged into ch1, with level pulled all the way down on ch2.


I noticed a similar oddity last weekend as well on a two day shoot with an Arri Alexa Mini. That both channels were showing audio even though I only was feeding audio to one of them! Was using an Aputure Deity shotgun into a Sound Devices MP1 into the Arri Alexa Mini:
 


Anyway, there was audio! Even if acting a little odd by being in both audio channels, so I didn't stress too much over it as it was a busy day for me and I had other fires to fight instead. 

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nickreich,

Yes, I'm starting to wonder if it happened in post production as well.  I'm working with another Mini (with A-box) tomorrow, so I'll do some tests to be sure it's recording discreet channels.

 

edward chick,

Do you know if the Mini has "unity" mode, and where to set it?

 

Johnny Karlsson and IronFilm,

You both have the same issue, and I can only think it may be in your Lemo connector.  What brand of adapter cable are you using?  I know those tiny Lemos are difficult to solder, and if two wires are touching inside the connector that would explain some things.  I'm not sure, however, why you would see audio on a track where the level is pulled all the way down.

 

I'm confident in the Wooden Camera A-box's quality, but then it comes with the camera package, so who knows if it's been damaged or modified?

 

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There's certainly a thing with old vs new versions of the Audio hardware board within an Arri Amira behaving differently, no matter what the firmware. Various menu items are greyed out on an Amira with the old board. I've never seen it mentioned, but maybe there are some differently-spec'd early-issue Minis out there, perhaps with different Lemo wiring. I DID see something recently on the Arri user forum about the Mini always recording 5 tracks of audio, with only two having program on them, presumed to be a hangover in shared firmware from the Amira, which can record 4 inputs plus 'voice notes' from a Bluetooth headset. I'd never heard of that before.

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Well I'm working with a different Arri Alexa Mini this Saturday on another shoot, so if I get a moment I'll take a look to see if this is behaving differently or not (as I'll probably be using my same gear again).

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I encountered a breakout cable that came with the camera that was wired wrong. I plugged in to the XLR’s, channel 1 only out of my 633, showed up on both of the minis channels. I used my cable and it worked correctly. Something to consider. 

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I did two days with another Mini (with A-box) this week, and was careful to test whether I was recording discrete tracks on the camera.  No problems.  So, perhaps the summed-to-mono issue with the first Mini was due an older board in the camera (as nichreich mentions), or perhaps there was some still-unknown or unnoticed feature in the camera's menu that was set incorrectly, or perhaps it happened in post. 

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On 8/17/2018 at 11:20 AM, Bob K said:

I did two days with another Mini (with A-box) this week, and was careful to test whether I was recording discrete tracks on the camera.  No problems.  So, perhaps the summed-to-mono issue with the first Mini was due an older board in the camera (as nichreich mentions), or perhaps there was some still-unknown or unnoticed feature in the camera's menu that was set incorrectly, or perhaps it happened in post. 

Hi Bob,

I just looked at the manual for the mini and as you mentioned there is no mention of summing channel one to both channels.  I'm guessing something was mis wired especially if your experience was different with the next mini.  I've seen other cameras that do have that feature.  Its usually when they just have one source for audio and want it on both channels.  The second channel can then be set lower for safety.  As part of my camera set up routine I always confirm that one is going to one and two is going to two discretely.  If I skip that step then Murphey's law will surely be invoked.

BB

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I ultimately discovered what happened with the audio recorded on the Alexa Mini, so thought I should share with everyone who joined the discussion here.  In summary, we recorded several interviews using a body mic and a boom mic on separate channels, and after the shoot I got a call from the editor in L.A. telling me that the discreet audio channels I'd sent to the camera were mixed together.  How that might have happened was a mystery, and we tried on various explanations here.

 

The answer came when I reviewed the recording of the phone call from the editor.  (I should have done that sooner.)  He mentioned he'd found just two tracks of audio on the camera cards, "A1 and A2, and that's it.  And, there's five tracks of audio, but only two are recorded.  I brought it in mono, so it's like AR (?) stereo left and right, but it's my mix left and my mix right."

 

"I brought it in mono."  That statement somehow didn't register at the time.  Apparently, he summed the two discreet audio tracks together when transferring the files from the camera cards to the NLE.  Then, I suppose, wiped the camera cards?

 

So, it wasn't the camera menu, or the A-Box, or a malfunctioning mini-Lemo on the camera.  It was post-production.

 

  

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On 3/31/2019 at 6:26 AM, Bob K said:

"I brought it in mono." 

Wow, what a screw up

 

On 3/31/2019 at 6:26 AM, Bob K said:

And, there's five tracks of audio

Five tracks?? Huh?

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Yet another reason for only sending the Boom channel to the camera. If they don't like the sound of the Boom (rarely if ever), send them the Lav track afterwords.

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On 3/30/2019 at 2:26 PM, Bob K said:

 

So, it wasn't the camera menu, or the A-Box, or a malfunctioning mini-Lemo on the camera.  It was post-production.

 

  

Usually is in my experience.

 

 

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