Audio Levels from External Recorder ???

[Andy Roberts]

I have a Sound Devices 702 Digital Audio Recorder. When I send a -12dB test tone into my Epic, I have to attenuate the line out signal to -32dB for the signal to be -12dB on my Epic. I verify this by looking at the meters in Premiere, comparing the recorded signal from the 702 WAV file and the audio file in the .R3D.

When I look at my audio set up on my Epic, the preamp level is set at the LOWEST it can go which is +30dB.

If my -32dB attenuation on my 702 matched the +30dB on my Epic, then my mind would feel resolved. (Why the 2dB difference?) But for now I feel a bit confused as to why there is such a strong signal coming into my Epic from the 702 that I need to attenuate it 32dB.

Any audio guys out there that can help me understand the numbers and signal chain here?

Is this just a line level / mic level issue ? BTW, I do not have Phantom Power on.

P.S. My intention is to record to the 702 and pass the signal on to the Epic with identical signal strength. I want to KNOW that all is well on both devices when I’m only looking at the meters on the 702.

 

[ericyoung]

Epic only takes MIC level inputs. If you are sending LINE level output from the 702, it will need a lot of attenuation not to overdrive the Epic inputs as you have found.

The Epic input preamps are pretty noisy and not well isolated, so sending a loud MIC level from the 702 and keeping the Epic preamps turned to default or lower level will ensure the best signal to noise going into the camera.

Audio guys will be better able to tell you exact numbers than I, but do read the Epic manual regarding the Epic audio metering and default settings.

 

[Andy Roberts]

I find it very odd that the pre amps start at +30dB. I've scoured the Epic manual but don't see any way to set it any lower. Apparently the Pro IO is capable of line level inputs (as well as the old Red One).

 

[Marc Wielage]

I have a Sound Devices 702 Digital Audio Recorder. When I send a -12dB test tone into my Epic, I have to attenuate the line out signal to -32dB for the signal to be -12dB on my Epic. I verify this by looking at the meters in Premiere, comparing the recorded signal from the 702 WAV file and the audio file in the .R3D. When I look at my audio set up on my Epic, the preamp level is set at the LOWEST it can go which is +30dB.

Knock the level down -40dB and it might be better. Given that a line-level signal could easily be 30 or 40 dB higher than a mic level signal, it figures that you have to attenuate it quite a bit.

Don't worry about where the knobs are -- worry about whether the input chain is getting overloaded before the knobs. Once that happens, no amount of adjustment can fix it.

My advice is to hire a pro location sound mixer who knows what he or she is doing and has the right equipment and experience for the job, and not to record in the camera at all. Any pro will understand the importance of gain staging:

http://www.alesis.com/tipsdec08

 

[scott william]

+30 is too high for my zoom h6 which is a little dissopointing. I wish the epic would be +10.

 

[Marc Wielage]

+30 is too high for my zoom h6 which is a little dissopointing. I wish the epic would be +10.

 

[Andy Roberts]

Thanks Marc. Like I said, the difference is exactly 32dB. So I have the internal attenuation of the SD 702 set to -32dB and the recorded signal is identical on both the 702 and the Epic.

I just wish now I had paid the extra money to get the 702T with timecode.

 

[scott william]

Thanks Marc, I will order tomorrow for my 416 shotgun.

 

[Marc Wielage]

The MKH416 has a standard mic-level output, so no attenuator would be necessary to use it with the phantom-powered mic input on a camera.