Blasted Time Code Again

[porkchop]

Hey everyone, sorry about the hiatus but the combination of tour and refurb will demand that sometimes. I have a question about time code, but I'll give a little background first. My company has been using time code for about two years now, it worked fairly efficiently for the first two year with minimal hiccups. Now that show has closed and some of it's equipment has been transfered to my show. That equipment being redundant audio racks both running the show in pro tools, the time code stripe is sent up our snake, split at a DMX switcher and goes into two Martin Maxxyz consoles, one main one spare.

Of course when it works it works wonderfully and being that we have almost 1000 Q's in a two hour show it's nice to have. But we've only been out for two weeks and we're already having problems with it. There are a few of us with a little bit of time code experience, but our training was largely here's a toy, run it this way exactly, it will always work, don't break it. Well not unsurprisingly it's not working all the time. So now we're on the lookout for trouble shooting materials. I did a search and "Control Systems for Live Entertainment" came up a few times as a book to get about time code, my question before making the show buy the book is, is this book the best one for us to get for trouble shooting an existing SMPTE time code system or are there other materials that arre more pointed at trouble shooting problems in an existing system?

[derekleffew]

Specifically, what problems are you experiencing?

Originally Posted by porkchop

... split at a DMX switcher ...

This cannot be correct, as SMPTE TC is a analog audio signal. It shouldn't pass through a "DMX switcher" like a pasive switchbox and won't work at all with a more advanced DataLynx-type device. It's possible to just split the TC signal, with a passive Y-cable or audio distribution amplifier, and run a line to the main and back-up lighting consoles. A Brainstorm Distripalyzer is the ultimate method of distributing and reclocking timecode.

I believe we've discussed this before, but I can't remember the conclusion. Does the Maxxyz take SMPTE TC directly or must it first be converted to MTC? The latter adds another layer of complexity, and sometimes introduces issues with sending MIDI long distances.

John Huntington's book, Control Systems for Live Entertainment, is, without a doubt, THE best source for information for this application. The next best thing is the resources at Richmond Sound Design, although a quick glance finds nothing on target. Google doesn't reveal much useful information either, except this. [Edit: The article linked to LTC in our glossary is a good one for a general explanation.]

Hope this helps. Short answer: buy the book. Las Vegas pirates, volcanoes, and fountains couldn't be synchronized without it.

[porkchop]

Originally Posted by derekleffew

Specifically, what problems are you experiencing?

Most recently found problems where: an accidentally copied cue out of order in the cuelist that caused one clue to be skipped over, and problems getting the stripe to the board correctly that was fixed by bypassing the Y.

Originally Posted by derekleffew

This cannot be correct, as SMPTE TC is a analog audio signal. It shouldn't pass through a "DMX switcher".....

It must be a passive switcher then, because it has worked for two years with no real problems coming from that part of the system.

Originally Posted by derekleffew

I believe we've discussed this before, but I can't remember the conclusion. Does the Maxxyz take SMPTE TC directly or must it first be converted to MTC? The latter adds another layer of complexity, and sometimes introduces issues with sending MIDI long distances.

I have no idea really, again I have to rely on the company telling me it will work and the fact that it has thus far. I wish I knew more, but that's the whole purpose of this post. I do intend on getting the show to buy John Huntington's book so we can all educate ourselves and bring trouble shooting down to our local level so we don't have to call corporate show support every time a new problem comes up.

[jxgriffi]

I'm with Derek on this one...

I've done more SMPTE shows that I can count and you should NEVER put it through a DMX splitter. An AUDIO split would be one thing, but not a DMX split.

Now, some of your problems could be as simple as the SMPTE feed is being OVER driven to you. If the signal is too hot, you'll get hiccups, missed cues,, etc. If the signal is too low, you'll get hiccups, missed cues, etc.

I would suggest looking into a Brainstorm unit to split the SMPTE feed and get away from the DMX splitter.
SR-15+

And the Maxxyz can take in either MTC or SMPTE (it likes both). XLR3 for the SMPTE and, of course, MIDI for MTC.

[mstaylor]

I know nothing about time code, no experience, so I find this thread very interesting. The book that was recommended is one that has been on my list for a while.

[TimmyP1955]

The snake could be part of the problem, just as it can be a problem when used to transmit DMX. You likely need to change to an impedance-appropriate cable, or at least one with lower capacitance so that the leading edges of the signal pulses are not rounded off.

[Axislights]

I'm currently in the same situation with a Luis Miguel Tour rig we ended up using an F-22 from Fast Forward (around$1200msrp) to solve our issues. It has a smtpe pass through that has a rotary pot for dialing up/down the output signal if you have issues with volume.
It also has a seperate MTC port as well so you could feed 1 console smpte and 1 MTC from the same source without a splitter
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