Getting a sound feed for Sony PXW-X70 camcorder from SD 744T

[Richard Crowley]

The Sound Devices 744T has several outputs that could be used for this purpose. But all of them are line-level or headphone-level (which is very similar to line-level).

The Sony ECM-W1M Wireless Microphone has a microphone input jack on the top (the one with red band). You would need a special attenuating cable to take the line-level out of the 744T and create a mic-level signal suitable to input into the ECM-W1M. I don’t know that a suitable cable is available to purchase ready-made. You would need to make a custom cable for this application. It is not a complex or difficult thing, but not available commercially that I am aware of.

Note that the BlueTooth system introduces some transmission delay which may prevent PluralEyes from properly synchronizing the sound and picture. Is the camera so far away from the sound source that using the camera’s internal mic (or external camera-mounted mic) is unable to get a track that PluralEyes can use? Can you help it by using a slate/clap stick (or even a hand-clap) to establish a clear sync point?

[Anna Wong]

Thanks Richard for your answer!

Since we mostly make documentaries, we try to make ourselves as invisible as possible during filming. Therefore we avoid using hand claps. I am not sure if it is a good practice. Maybe you can share your experience with us.

The problem we are facing now is, we used to check sync with camera audio during post production. But some people challenge us that the camera audio may not be accurate to use as a guide track, particularly for the distant subjects. Therefore, we are designing some solutions to have a prefect guide track. Do you have any suggestion for this? Yes, the bluetooth transmission isn’t reliable enough.

Thousands thanks,
Anna

[Brian Reynolds]

If there is a delay in the system it will be in the Sony ‘Bluetooth’ link between the SD744 and the camera…. BUT the good thing it will be a constant regardless of what or where you are shooting. As a suggestion do some VERY critical testing at the office / studio prior to a shoot.
When you have determined any delay note it down, or keep the number in your brain as you will use it on every edit session.

I once had a system that had a (-2 frame) difference on a particular analogue play out machine, so every time that machine was used in a production it was xx-xx-xx time code then minus 2 frames.

[Richard Crowley]

Yes, I agree that if the wireless signal is reliable enough (considering that you are competing with WiFi and all the other BlueTooth gadgets in the room), then it would be a potential solution to establish the offset factor by careful experiment.

The only remaining issue would be to get a properly-wired attenuating cable to take the line-level output from the SoundDevices 744 and knock it down to mic-level for the Sony Bluetooth transmitter. It isn’t rocket surgery, but it isn’t trivial, either.

[Anna Wong]

Thank Brian for your experience! Richard mentioned about the attenuating cable connecting the SD744T and Sony ECM-W1M transmitter. Which cable did you use? Any ready-made option? Besides, about the time delay, is it constant? Or it varies with locations? Many thanks for both of you!

[Craig Alan]

From the 744T manual:

Analog Line Out L, R
The analog line outputs are active-balanced line-level signals on Switchcraft TA3M locking connec- tors. The output level is a nominally 0 dBu at -20 dBFS. The level of the line output can be attenuated in the setup menu by up to 40 dB in 1 dB increments. Attenuation is done as an output pair.

Richard, doesn’t this imply that the signal could be set to mike level?

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