Audio on 5D Mark III - noisy in-camera pre-amp?

[JasonATL]

It seems that the 5D3's pre-amp can be quite noisy, at least when combined with my Beachtek DSA-XLR pre-amp. So, I sat down to try to see how to get the best results.

Here's a video I made of my tests. https://vimeo.com/47819373

The solution seems to be to set the 5D3's pre-amp as low as possible using the manual audio (microphone) controls. At zero, the audio is off. So, I set it to +1 click above off. To get a signal, though, I had to use the headphone out on my Beachtek, rather than the line out. The apparent (I don't know how to test this technically) signal-to-noise ratio defintely seems good, or at least better, in this configuration.

To get the same signal using the line out (rather than headphone out) on the Beachtek, I had to have the 5D3 set to about +1 or +2 clicks above center (50%). As you see (or hear) in the video, the pre-amp noise is really high at that setting.

Oddly, the pre-amp noise gets WORSE as you lower the manual control from +2 to +1 clicks above center.

My takeaway is to use as low a 5D3 audio setting as possible. However, I wonder if the unconventional headphone out from the Beachtek could cause problems that I haven't thought of or that don't show up (or sound off) in this test.

Any thoughts? Experiences? Suggestions for a better configuration?

 

[Axilrod]

Yes noise was an issue in the 5DII that I thought they surely would have fixed in the 5D Mark III, but I noticed the same things you did. Turn it almost all the way down and the noise goes away. Sescom (http://www.sescom.com/sescom-product-index.asp) makes cables that have a built-in attenuator that drops the level by -25db. I got it for my Zoom H4n and 5D3 and it seems like you still have to turn the camera levels low, so I can't really say how effective it is. But I have heard of people having good results with it, so I dont know.

I don't know much about audio, hopefully PaulieWalnut5 will respond to this, I'm sure he'll know.

 

[jcs]

Hey Jason- I've gotten excellent results with manual +1 and a very high quality preamp (Sound Devices USB Pre2, same hardware topology as the 722):

5D Mark III - Pro Audio Test

An older test using the 5D2: Lilliput 5D-II-O-P Peaking, Audio Technica 4029 Audio

G3 and lav mic into 5D2: http://www.youtube.com/watch?v=qh1HRjtihwc#ws[/url

 

[JasonATL]

Axilrod - thanks for the helpful reply and information. I agree that setting the levels low seems to reduce the noise significantly and result in very nice quality sound. At this point, I don't need to attenuate the signal from the line out of the Beachtek. Rather, I need the boost in it that I get from the headphone out so that I can keep the 5D3's levels set low.

John - as always, thanks for the information. Question: are you using the aux out or the headphone out from the Sound Devices?

The thing I'm still unsure of is whether there are any "gotchas" that I might be missing by resorting to using the headphone out from the Beachtek rather than its line out. Using the line out just requires too high a setting in the 5D3, which brings the 5D3's pre-amp noise in. So, I'm hoping that someone can say to me, "It is okay to use a headphone signal into the 5D3." Again, it sounds on my tests like it is fine, but I wonder if I'm missing something.

If that's kosher, then I'm thrilled, because the tests in the video really sound great to me at this configuration.

 

[LetTheRightLensIn]

yeah it's noisy, 5D2 was noisy, 7D was noisy, all very noisy even for consumer goods so the solution has long been to either use 100% external recording or to use a pre-amp, i'm using a JuicedLink DT414 and trying to dial down the internal gain as much as possible.

 

[jcs]

John - as always, thanks for the information. Question: are you using the aux out or the headphone out from the Sound Devices?

I'm using the Mic/Line out from the Sound Devices. If you can hit -12dB with camera mic level set to +1 and it sounds good, you are good to go.

 

[paul13walnut5]

What mic are you using?
Where is it positioned?
How is it powered?

The DXA-SLR has a pre-amp and also has AGC over-ride.

I'm using the DXA-5Da (without pre-amp) and found that my cabled lavs (Sony ECM-55's and ECM-77's) were too cold for practical use with the beachtek, my wireless lavs (Senn EW112's) were fine (but they have their own pre-amp output control from the reciever - distinct from level control) and my Sennheiser K6/ME66 and Rode NT2 work great with their internal power supply.

The trick is to get the mic as close as possible without being in shot, for lavs this can mean using a corn plaster under an open collar for a rifle mic it usually means boomed or on a stand.

This is the same for any camera.

I've not used the manual audio on my 7D in anger yet, but on the T3i the beachtek works fine at -18db to -12db.

Handbook says -12db, I'm used to the -18db from old ENG cameras (plenty of headroom in case of a spike)

Make sure that your beachtek is set to stereo (this keeps the audio from each channel seperate) and with the level set on camera open the attenuators fully (the level control on the beachtek attenuates, not amplifies, more level on the dial does not mean more amplification, just less clipped, to make the most of what you've got open them right up.

If you have a very strong source or a very hot mic or the sound changes dramatically during your recording you can trim as you go, but set your cam up with them wide open and this gives the pre-amps less work and less noise.

Don't be afraid to keep the levels low in camera, -18db or -12db is absolutely fine and should be nice and clean.
You can add gain more cleanly in post than on camera, as well as adding (to make an L channel into linear stereo) panning etc

With the 5D3 you can headphone monitor straight from the camera, keep the headphone level pretty high.
If need be check the impedence of your headphones and buy a more sensitive set (I alternate between HD-25'lls and Akg k450's depending on what kit bag I lift)

I haven't used the 5D3, so cannot comment on the qualities of that camera, but in my experience you can get good audio from a DSLR with the right kit and approach.

I'm not a fan of the seperate audio recorder approach for a few reasons, but there are plenty who are.
I don't think you should need to resort to that, but I'm one voice on a busy thread!

Good luck.

If problems persist please update us.

 

[JasonATL]

Paul, et al. Thanks again for the comments and tips. Keep 'em coming. Very helpful as I continue to learn.

We were using a Sony ECM-673 (shotgun) on a boom and, as suggested, getting as close to the talent as shots permitted. The problems we had were with the settings on and between the 5D3 and the Beachtek. The tips here will undoubtedly help fix those issues.

Since the 5D3 has manual audio control, I'm not going to address AGC in the below.

Not disregarding the suggestions for mic placement, etc... Just focusing on settings, here is my understanding of the suggestions for settings so far (I'm even listing the rather simple ones, just to make sure - I know, this all looks like common sense to many here).
- Connect the Beachtek to the 5D3 via the Beachtek's line out (not the headphone out)
- Monitor using good headphones from the 5D3 headphone output, with headphone level set high
- Set the Beachtek to stereo mode (as channels can be isolated in post to be made mono or panned, if desired)
- Set the Beachtek mic levels as hot as possible (unless there is clipping) (if there were just an "11"! )
- Set the 5D3 pre-amp audio levels as low as possible to get a good signal at about -12db (or perhaps even -18db with gain added in post)
- If 5D3 is at its lowest setting and the signal is still too hot (i.e., clipping is likely), back off on the Beachtek mic levels

I agree that the internal recording sounds very good with the proper signal and settings... Good enough not to need to bother with an external recorder. I'm getting there!

Would the NTG-2 be a worthwhile step up from the Sony? The Sony uses phantom power (supplied by the Beachtek, of course). Does the use of phantom power usually result in less signal? In other words, is it better to have a mic that has its own power supply, as a general rule?

 

[paul13walnut5]

I've porbably used a Sony ECM-673 or very similar on my old z1, or ENG cameras, my take on it is that is fine for front micing, for ambient. I wouldn't use it for critical close audio.

It's cardiod but something like a rode NT1 or 2 (either works with phantom, 2 also works with internal AA) or if you can stretch to it a Sennheiser K6 module with ME66 or ME67 capsule would be even more cardiod, hypercardiod, making for a better directional pick up. Both the NTG-2 and K6-ME66 run plenty hot for my purposes.

You seem to have everything else sussed, just got to get out and practise.

Phantom or internal is fine, just keep a few spare PP3's/9v batteries in your kit bag.

 

[JasonATL]

Thanks again, Paul!

 

[paul13walnut5]

N.B. Should have also said, if you are only using one of the beachtek channels then turn the other down to zero, even switched to stereo.. noise from the empty channel will come through the monitors causing a distraction.