# SMPTE Level Problems



## cbrandt (Dec 27, 2012)

I'm having some problems with my new test rig for pre-programming with timecode. I just got my M-Sync module (an add on module for the M1 and other Martin consoles to add SMPTE), and would love to loop an audio track out of my laptop into the module. The problem I seem to be running into is that the module would really like the timecode to come in at around -18db (according to Martin) and my laptop seems to be outputting at far too high of a volume. I don't seem to be able to achieve that level of control when playing around with levels running sound files out of windows media player. Any thoughts on what would be a reliable way to play back some smpte timecode files for testing purposes? For performances I'll be receiving timecode from the audio desk.


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## ruinexplorer (Dec 27, 2012)

Is the timecode being passed through the sound card on your laptop? I would assume that you could adjust it properly through that. If not, can you edit your sound file attached to the timecode using something like audacity?


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## museav (Dec 28, 2012)

cbrandt said:


> I'm having some problems with my new test rig for pre-programming with timecode. I just got my M-Sync module (an add on module for the M1 and other Martin consoles to add SMPTE), and would love to loop an audio track out of my laptop into the module. The problem I seem to be running into is that the module would really like the timecode to come in at around -18db (according to Martin) and my laptop seems to be outputting at far too high of a volume. I don't seem to be able to achieve that level of control when playing around with levels running sound files out of windows media player. Any thoughts on what would be a reliable way to play back some smpte timecode files for testing purposes? For performances I'll be receiving timecode from the audio desk.


Is the laptop output a line level output or a headphone output? How are you wired from the laptop to the M-Sync? Martin seems to say only that the M-Sync has a "3-pin XLR" input but that seems likely to be for a single channel balanced signal while the laptop output is probably a stereo TRS 3.5mm with two unbalanced channels. In that case you'd probably want tip to Pin 2 (Hot/+), Sleeve to Pin 3 (Cold/-) and the cable shield to Pin 1 (Ground) with no connection to the ring on the 3.5mm TRS.

If you are going to be using timecode from the mixer then would it make sense to take the test feed from a mixer, if not that same mixer? Something that provides a similar signal level and connectivity to what you will be using. Note that most mixing consoles have a nominal analog output level of around +4dBu, so if a -18dBu level (assuming it is dBu being referenced) is desired that might be around 22dB below the nominal mixer output.


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## themuzicman (Dec 28, 2012)

No idea what the bigger picture is and why the choice to go with LTC, but the M1 does have a MIDI in. You could just use MTC which might make things easier.


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## cbrandt (Dec 28, 2012)

Yeah, outputting from the laptop's soundcard, from a headphone jack, as I don't have a line level output on the laptop. Another company will be supplying the mixer and audio system for this particular production. My company only supplies lighting equipment, so I don't have access to any real audio equipment short of renting it, and that would be a bit silly for a long range pre-production scenario like this one. We will have tech on site to adjust any small timing requirements, but have to be able to hammer in the basic timecode before hand. I was hoping to not have to add on a lot of hardware to my laptop.

I did wire up the xlr connector to only use the the pin and have the ring not wired in.

The M1 does support midi, with an add on card that I don't have. When I consulted with my audio guys, they highly recommended SMPTE for reliability.


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## themuzicman (Dec 29, 2012)

cbrandt said:


> The M1 does support midi, with an add on card that I don't have. When I consulted with my audio guys, they highly recommended SMPTE for reliability.



Midi Time Code (MTC) is SMPTE just packaged in quick MIDI messages. LTC is SMPTE as well, but packaged in an audio signal. I find MTC is easier to work with just because you're not having the type of issue you are currently running in to with LTC, plus there are many more tools to help troubleshoot a system should the sync not be working. You can output from a computer running QLab, or any of a dozen freeware midi utilities (I use MIDI-Ox on PC) or get a SMPTE/MTC master clock and shoot signal around a system that way.


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## wakkoroti (Dec 29, 2012)

When you turn down the volume from your laptop, are you able to make it work at all?


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## ruinexplorer (Dec 29, 2012)

Even though you only have a headphone jack, you may want to check the settings on your sound card. My laptop has two different settings for headphones or speakers (mimicking line level).


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## cbrandt (Jan 2, 2013)

Thanks to ruinexplorer for the thought about switching the headphone jack to a line out. That and playing my files through audacity seems to have done the trick! Turning up Audacity's sample rate seems to smooth out the timecode as well.


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## ruinexplorer (Jan 2, 2013)

Awesome, I'm glad that it worked for you.


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## cbrandt (Jan 2, 2013)

I still need to play around with levels a little bit to get a consistent frame rate, still seems like I'm only gettting around 90% of the frames, but that's a heck of a lot better than I was getting before.


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## museav (Jan 4, 2013)

cbrandt said:


> I still need to play around with levels a little bit to get a consistent frame rate, still seems like I'm only gettting around 90% of the frames, but that's a heck of a lot better than I was getting before.


May or may not be relevant but the -18dB (assuming that is dBu) level the M-Sync apparently wants is around 10-20dB below what many master sync generators output for LTC, 18-22dB below the nominal "0" output of most mixing consoles and about 10dB below nominal consumer audio level, so it apparently wants a lower than typical signal level.


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## cbrandt (Jan 4, 2013)

Now that I have it working, I've been back checking all the steps I took to get it working. The major problem seems to have been the sample rate/bit depth setting for windows. Adjusting that to the highest quality settings available made the most difference, and made the device far more tolerant of other volumes in the audio track. I think that was likely the root of the problem.


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