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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Recording line level audio

Mike Burke

Mike Burke

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I've just received our camera back from Red with the audio upgrade.
Using release Build 17, upgraded audio board, with new cables.
Audio menu settings are as follows: Line level, 0db.

What I am finding regarding line level audio levels is totally confusing.
With a mixer supplying zero level tone, at line level,
the LED display shows levels well into the orange quadrant of the display.
This is to the right of the solid line.
Having lowered the output of the mixer to the solid line of the
camera LED display, my mixer now displays an output of -10db.
Clearly something is out of cal.

Exactly what levels are these hash marks on the LED display representing?
There is no information in the manual.
What is the proper procedure for establishing a -20db input level
when using a 0db reference tone from a mixer.
Any one from Red?

This camera begins a commercial job Friday, utilizing dual audio recordings.
Thanks much.
 
Audio Levels.

Audio Levels.

Process is just this-

Feed the camera - 20dB FS with Line Input gain set to 0dB. The -20dB FS point should line up to the right hand hash mark.

Make a recording and verify in FCP or other software application that you are at -20 dB.
 
Stuart English said:
Process is just this-

Feed the camera - 20dB FS with Line Input gain set to 0dB. The -20dB FS point should line up to the right hand hash mark.

Make a recording and verify in FCP or other software application that you are at -20 dB.
Click to expand...

Stuart, thanks for the response.

My quandry is this: In order to achieve -20db FS at the camera,
I must set my mixer output to somewhere around -10 VU, with tone as a reference.
Something must be wrong that I'm overlooking.
 
Audio Levels.

Audio Levels.

My quandry is this: In order to achieve -20db FS at the camera,
I must set my mixer output to somewhere around -10 VU, with tone as a reference. Something must be wrong that I'm overlooking.
Click to expand...

Two questions -

How are you measuring that?

Are you using the mini-XLR to XLR cable or the cable with mini-XLR to mini-XLR plus mini-XLR to XLR adaptor?

As to the Build 18 question: its the same as 17.
 
Joel Kaye said:
Is this any different on build 18?
Click to expand...

I can't say as I haven't tested Beta 18 yet. I probably won't get
the opportunity to test 18 by the time this job starts.
What I can say is this has changed as a result of the board upgrade, or
the change to Build 17. I had been on Build 16 up until that point.

I'm really curious as to what others with the new board have experienced.
 
Stuart English said:
Two questions -

How are you measuring that? Are you using the mini-XLR to XLR cable or the cable with mini-XLR to mini-XLR plus mini-XLR to XLR adaptor?
Click to expand...

1. I'm referring to the VU display on the mixer. Actually, I used a second mixer
to confirm that the mixer wasn't the problem.

2. I've used both: mini-XLR to XLR cable as well as the cable with mini-XLR to mini-XLR plus mini-XLR to XLR adaptor.
 
Audio Levels.

Audio Levels.

O.K. The VU on the mixer will tell you the output level of the mixer itself, so lets assume that is fine at 0dB / - 20 dBFS. The reason I ask about the type of XLR input cable you are using is that the mini-XLR to XLR version has a -10dB pad in it to help the older style audio board accept higher input voltage levels than it otherwise could. In the new audio board, those pads are designed into the audio pre-amp so those cables shouldn't be used, else you will over attenuate.

If you were using -20dBFS out of your mixer, and mini-XLR to mini-XLR cable with mini-XLR to XLR adaptor, I'd expect the level being recorded to be fine.
 
Stuart English said:
O.K. The VU on the mixer will tell you the output level of the mixer itself, so lets assume that is fine at 0dB / - 20 dBFS. The reason I ask about the type of XLR input cable you are using is that the mini-XLR to XLR version has a -10dB pad in it to help the older style audio board accept higher input voltage levels than it otherwise could. In the new audio board, those pads are designed into the audio pre-amp so those cables shouldn't be used, else you will over attenuate.

If you were using -20dBFS out of your mixer, and mini-XLR to mini-XLR cable with mini-XLR to XLR adaptor, I'd expect the level being recorded to be fine.
Click to expand...

I should have specified better.
The mini XLR to XLR cables are custom made at our studio.
They have no pads whatsoever. The input level at the camera is identical
to that of the mini-XLR to mini-XLR cable with mini-XLR to XLR adaptor provided by Red.

It's odd. At this point, I wish I still had one of the padded cables to compare with.
My level seems to be about 10db too hot.
 
Audio levels.

Audio levels.

re "10 dB too hot .. "

You mean the level you need to send it / the level that gets recorded / or the level the camera sends back?
 
Stuart English said:
re "10 dB too hot .. "

You mean the level you need to send it / the level that gets recorded / or the level the camera sends back?
Click to expand...

With a mixer supplying tone at zero VU, line level,
the LED display shows levels well into the orange quadrant of the display.
This is to the right of the solid line.
In order to achieve a level at the camera of -20db FS, (at the solid line),
I must attenuate the output of the mixer -10db.
The camera audio inputs are set at line level, 0db.
I am using cables that have no pad, supplied by Red.
 
seacliffe301 said:
With a mixer supplying tone at zero VU, line level,
the camera LED display shows levels well into the orange quadrant of the display.
This is to the right of the solid line.
In order to achieve an input level at the camera of -20db FS, (at the solid line),
I must attenuate the output of the mixer -10db.
The camera audio inputs are set at line level, 0db.
I am using cables that have no pad, supplied by Red.
Click to expand...

Has anyone seen anything like this, or have all line level audio
records with the audio board upgrade been successful?
We're pretty baffled here...
 
seacliffe301 said:
With a mixer supplying tone at zero VU, line level,
the LED display shows levels well into the orange quadrant of the display.
This is to the right of the solid line.
In order to achieve a level at the camera of -20db FS, (at the solid line),
I must attenuate the output of the mixer -10db.
The camera audio inputs are set at line level, 0db.
I am using cables that have no pad, supplied by Red.
Click to expand...

Yes I understand that. My question then is if you ignore the PPM meter of the camera and record the -20dB FS signal to the camera with 0dB Gain applied, what is the level of the recorded signal? i.e is - 20dB FS also?

The way I check that is to bring the recording into Final Cut Pro and observe the level in the audio adjust panel.
 
I think your problem lies in your audio input level settings on the RED. By setting to Line at 0dB, you are saying that full scale or 0dBFs would be 0dBU. Your mixer has a headroom of somewhere in the range of +15dBU to +18dBU. Try setting the line input to +18dBU and then see if that allows your meters to match up correctly. If not, just adjust your line settings until it matches. Make sure you remember to set the outputs on the FP33 back to full range.
 
Audio Levels.

Audio Levels.

I think your problem lies in your audio input level settings on the RED. By setting to Line at 0dB, you are saying that full scale or 0dBFs would be 0dBU..
Click to expand...

With respect, that is not true, so don't attempt to do that. Please do the test I described first ?

Thanks,
 
Stuart English said:
Yes I understand that. My question then is if you ignore the PPM meter of the camera and record the -20dB FS signal to the camera with 0dB Gain applied, what is the level of the recorded signal? i.e is - 20dB FS also?

The way I check that is to bring the recording into Final Cut Pro and observe the level in the audio adjust panel.
Click to expand...


Alright, I've done as you've described regarding the input level to the camera,
disregarding the PPM meter. I've made a recording applying -20db with the camera input set to line level, 0db.

While I don't have access to a Final Cut system at the moment, I was able to perform another test.
I've played out of the Red Cam at 1080P, with audio embedded on the SDI to an HD-D5.
With the VTR audio input in the unity or fixed mode, calibrated for line level, -20dbFS,
the recorded level on the camera hits the VTR at -8db.
This appears to 12db hotter than it should be.
While I will try the FCP test,
this seems to support everthing I have found up until now.
And also, the recording is mildly overmodulated.
 
Tom Visser said:
I think your problem lies in your audio input level settings on the RED. By setting to Line at 0dB, you are saying that full scale or 0dBFs would be 0dBU. Your mixer has a headroom of somewhere in the range of +15dBU to +18dBU. Try setting the line input to +18dBU and then see if that allows your meters to match up correctly. If not, just adjust your line settings until it matches. Make sure you remember to set the outputs on the FP33 back to full range.
Click to expand...

ah, looking at the manual on page 10 build 16, it led me to believe that the line input was adjustable, but then on page 11 it mentions that it is not. my bad.
 
Audio Levels

Audio Levels

seacliffe301 said:
Alright, I've done as you've described regarding the input level to the camera,
disregarding the PPM meter. I've made a recording applying -20db with the camera input set to line level, 0db.

While I don't have access to a Final Cut system at the moment, I was able to perform another test.
I've played out of the Red Cam at 1080P, with audio embedded on the SDI to an HD-D5.
With the VTR audio input in the unity or fixed mode, calibrated for line level, -20dbFS,
the recorded level on the camera hits the VTR at -8db.
This appears to 12db hotter than it should be.
While I will try the FCP test,
this seems to support everthing I have found up until now.
And also, the recording is mildly overmodulated.
Click to expand...


Build 17 added an option for + 10dB gain on line inputs, can you verify that that is not enabled.....
 
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