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-   -   Wirless LTC solution (http://www.dvinfo.net/forum/all-things-audio/490999-wirless-ltc-solution.html)

Jan Klier January 31st, 2011 10:40 AM

Wirless LTC solution
 
I working on refining my dual audio setup with LTC sync. Searched previous posts here, and while there is lots of good info on the topic, the particular combination I'm looking for isn't covered.

My setup is a Sony EX-3 and a Tascam HD-P2. I've synced them successfully using a wired connection from the camera LTC out to the recorder LTC in. Works really well for what I'm doing. Except for the long cable (sometimes the soundboard is up to 100' from the camera) and in other cases I'm shooting with a steadicam and the wired connection is getting in the way of mobility and camera balance.

So the ideal solution would be a wireless link for the LTC from camera to recorder. I understand that LTC is mostly an audio link. Any good suggestions? Has to connect to camera BNC and recorder XLR. Prefer OTS but can rig cables if needed. Could a standard wireless mic system be used for that?

PS: dvinfo.net is a great resource, appreciate everyone's knowledge sharing here!

Rick Reineke January 31st, 2011 12:23 PM

I have run camera LTC links via a Sennheiser G2 to TC-in for jam-sync re-generation. I have never actually recorded the LTC's signal to an audio track, which is normally not recommended.
That being said, for the G2 transmitter, I made a BNC to 1/8" TRS plug adapter cable using the G2's 'line-in' plug wiring scheme. Hot (+) to the plug's 'Ring' connector. Shield (-) and plug's Tip shunted to Sleeve/ground.

Jan Klier January 31st, 2011 12:50 PM

Thanks Rick. I will give that a try.

For clarification: The Tascam P2 recorder has a LTC sync input. So it's not recording the LTC as audio but using it to chase & lock. I just need a good way of getting it there w/o the wire.

Rick Reineke January 31st, 2011 01:27 PM

That's good.
If the recorder's TC input has any difficulty 'reading' the LTC from the wireless receiver, increase the 'AF' receiver output level, since it is normally mic level.

Addendum: The same wiring applies to the G3 as well.

Garrett Low January 31st, 2011 01:46 PM

Jan, I've got pretty much the same set up, Tascam HD-P2 and EX3 and would be really interested to know if this works. If so I may be in the market for a used G2 or G3 just for the purpose of sending LTC as I do a lot of shows were I place my HD-P2 in the control room away from my camera.

Please keep me posted.

Thanks,
Garrett

Jay Massengill February 1st, 2011 08:01 AM

Just a side question? If you aren't syncing the two devices by video connection and will therefore get some potential drift in the recordings, if you simply used Free Run TC on both devices and jammed them in the morning and again at lunch, etc. Wouldn't that be satisfactory as far as timecode, which is much more coarse of a measurement than sample rate? Perhaps you are syncing both devices with a house sync generator since you mentioned a "control room".

Jan Klier February 1st, 2011 08:46 AM

Agreed that there is risk of drift in this setup (although the documentation does say that the audio clock is locked on the LTC rather than just an initial sync, albeit there seems to be some debate around that - not 100% what the answer is)

However, the other advantage of this setup is that the Tascam P2 starts/stops based on LTC signal. As I control the camera I get a separate audio recording per take and don't run out of card space. That makes the post workflow really efficient as all I have to do is locate the audio file with the corresponding LTC and sync it in Premiere.

Jan Klier February 4th, 2011 03:32 PM

Got together with our audio guy earlier today to give this a shot. Worked great.

Now the details: The LTC signal is 1Vpp, when we plugged it into the wireless mic as is, it peaked the channel horribly, but worked out of the box. The Tascam would follow the camera w/o any problems. Now that's a bit ugly to have the signal peak that way.

So we rigged a 30db attenuator to be between the Sony camera and the wireless transmitter, setting the transmitter to line level input (0db). That gave us a nice clean signal. However, the recorder wouldn't follow until we boosted the signal on the receiver end back to line level as well. With that, it worked smoothly again.

So the wireless path is definitely viable, just have to find a system that can be adjusted correctly on both ends. Now off to specing that. In this test we used a Shure wireless system.

Jan Klier April 10th, 2011 06:45 PM

Re: Wirless LTC solution
 
A quick update on this. I did end up buying a Sennheiser G3 setup and it works nicely. I chose this one since it has level adjustments both on the transmitter and receiver. The camera is connected via an attenuator to an EW100 transmitter. The EK100 receiver connects to the Tascam recorder. I had to further limit the signal on the transmitter via the menu, and I had to boost the signal on the receiver via the menu.

Greg Miller April 10th, 2011 10:46 PM

Re: Wirless LTC solution
 
Quote:

Originally Posted by Jan Klier (Post 1613477)
the Tascam P2 starts/stops based on LTC signal.

So what happens if the wireless link happens to drop out, or die altogether, in the middle of a take? I think I'd feel much safer with a system that switches over to internal crystal and keeps running. (Well, OK, I have been accused of being a pessimist.)

However, congratulations for getting the thing set up and working, getting all the levels adjusted, etc. That does sound like success.

Jan Klier April 24th, 2011 07:12 PM

Re: Wirless LTC solution
 
Greg - fair concern.

There is a project setting on the LTC to 'freewheel' which can be set to up to 30 frames or infinite. If the LTC drops out, the recorder will use it's internal clock to keep running. If you have just minor drop-outs, 30 frames will get you through that. If you need to be absolutely safe, set it to 'infinite'. Of course, you will have to stop the recorder manually.

Depends on the situation. If you use wireless because you're on a steadicam, no big issue. If you use wireless because the camera is far away from the audio board, then you may need a second set of hands.


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