Hissing on audio with external mics?

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Richard Peters

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I had a Rode Stereo Mic a while ago, but using it always resulted in a hiss on the audio track. I read somewhere that it was to do with the auto gain control in the camera on Canons, but on the D3s you can turn that off. I've heard of two other Nikon shooters with the same issue and also the guy I sold my mic on to has a 7D and it has the same issue.

There seems to be generally very little mention of it though when I read reviews for mics for DSLRs :shrug:
 
thankfully you can now turn off the auto gain on the 5d mark 2 due to a firmware upgrade
 
Thanks for the replies and suggestions. I'm more interested in finding out why it does this to start with and if there are any microphones out there that do not produce this hiss? Just seems odd that nobody ever seems to point it out, so I'm wondering if other mics are better?
 
A change of mic won't help, it's the cam's mic amp that is ramping up the gain. Most video cams and a few dslrs can knock auto gain off and control the input manually. Hope this helps :)
 
The gain for a mic on camera is always going to need to be pretty high since you're fairly far from the subject. Do you have an opportunity to use a boom mic instead?
 
You can turn auto gain off on the D3s but whatever settings I have on camera or mic this hiss was always there, even when standing 1 foot from the camera in my living room. The hiss is just constant regardless of how load or close any sound source is. Frustrating :(
 
Richard Peters said:
You can turn auto gain off on the D3s but whatever settings I have on camera or mic this hiss was always there, even when standing 1 foot from the camera in my living room. The hiss is just constant regardless of how load or close any sound source is. Frustrating :(
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Hi - Did you try with manual audio with a range of mics?
The only shure (sic) way of getting great audio is a separate recorder and syncing in the edit :)
 
You basically need to set the record level lower on the camera and boost the mic input.

I don't know about the Rode Stereo Videomic, but the Rode Videomic Pro has this feature built in to boost the output.

This hiss is basically down to the signal to noise ratio. If you record at a high level on the camera but have a low audio input signal, there will be more noise relative to actual desired sound. Boosting the mic's output level, and recording at a lower setting on the camera (which will give you the same ultimate volume) will increase the signal to noise ratio and help eliminate the hiss (which you can further tweak in post - to a degree).

But, most DSLRs only record 44Khz 16Bit sound, so as soon as you try to do anything to it in post, it degrades very very quickly. I think there are a couple out there that record 48Khz, but as it's still 16Bit it degrades quickly if you try to do anything to it in post.

I'd consider looking into an external recorder like the Zoom H4n or Tascam DR-100. I use the DR-100 myself, which has 48v phantom power to power condenser mics through XLR inputs, recording at 96Khz 24Bit audio, then you can take the line out from the recorder through an appropriate cable to the mic input on the camera for syncing up in post.

In-camera audio will never be perfect, no matter what you do (although it can get "good enough", depending on your needs). It was just never designed as a recording device for master quality audio really.
 
incapete said:
Another vote for the Zoom or Tascam... Great recorders.
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They are. I had a good play with both of them at the Broadcast Video Expo at Earls Court a couple of months ago and ultimately decided to go for the Tascam (I'd listened to many sample recordings from both online beforehand too).

I just felt that the Tascam had a slightly better sound than the Zoom that I liked more - of course, like Nikon vs. Canon, at the end of the day it's down to personal preference. Both are excellent.
 
incapete said:
I know the guys at Tascam more than Zoom so I'd probably support that choice too! They were demo'ing some at PLASA last week as well.
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If you know guys at Tascam, tell 'em to make a dedicated charger for the DR-100 LiIon battery. That's the ONLY drawback. It can only be charged inside the DR-100 (which means even if you switch out to a second battery on the job, you can't charge the dead one til you're done and you need a crapload of spares to help ensure you last all day).
 
Hopefully anyone who uses a dslr for video will now realise that the audio is a big part, some will say superior, of that world. It can get very serious, but at the bare minimum get rid of the hiss. It'll (eventually) drive you crazy :)
 
mercedes said:
Hopefully anyone who uses a dslr for video will now realise that the audio is a big part, some will say superior, of that world.
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Aye. Many will watch something that has good audio and give the video a chance no matter how bad the quality may be, but if the sound's crap most will turn it off in a few seconds no matter how beautiful the imagery.
 
I have a Rode Videomic - NO hiss because I turned off Auto Gain Control (AGC) using Magic Lantern. It works.
 
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