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Mobilemike

Zaxcom IFB200 timecode with Sound Devices MixPre

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Hey all,

 

I was on a shoot today using a Zaxcom IFB-200 as timecode generator, feeding a Sound Devices MixPre-6. 

 

Timecode seemed stable on the IFB200, and was fine on a couple of ERX’s feeding cameras. However the MixPre kept losing timecode sync for brief moments. It would be receiving timecode fine and then all of a sudden seem to lose signal and flash “- - - - - -“ briefly before resuming timecode as if nothing happened. This would happen at random intervals but on a pretty regular basis. 

 

Tried several different cable configurations from the IFB200 to the MixPre, and tried both Aux 1 and Aux 2 on the MixPre and nothing helped. 

 

Eventually I fed the MixPre from a spare ERX instead of directly from the BNC jack of the IFB200 and that seemed to work fine. Of course that’s another thing in the bag and another set of batteries to monitor though, so that’s not an ideal long term solution. 

 

Has anyone had this issue before, or can offer any tips? 

 

Thanks!

-Mike

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2 hours ago, Bouke said:

Pure speculation, were all framerates on all devices set to the same FPS?

 

Hmm, the MP6 autodetects FPS.

 

Are you using the same cable? The MP6 can stop recording if it doesn't detect TC for a few seconds. 

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I’ve tried with several different cables, all do the same thing. 

 

New update for today: it’s doing the same thing with timecode from the ERX as well (new cable there too). 

 

Everything is is set to 23.98. 

 

The MP6 has not come out of record yet (fingers crossed, knocking on wood), so it’s only really an issue if it happens right as I am pressing record, because then the file does not get stamped with timecode. That happened to one file yesterday, and a few files a few days ago. Those files just have a timecode of 00:00:00:00 and no frame rate when viewed in WaveAgent. 

 

The dropouts are are very short, less than a second long. 

 

Still definitely something id love to solve though. 

 

I was wondering if it might be somehow related to the timecode level, but I don’t see a way to adjust the level in the IFB-200?

 

-Mike

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The whole thing about LTC is that it is NOT related to level for qualty, that is only for the tape to carry it. (And there should be a rise time to lower the power needed, but no-one seems to care anymore. So, whatever you investigate, level 'should' be the least of your worries. DC offset is something else, but it'll be a cold day in hell if you manage to screw that.

 

 

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I know that’s not usually the case here but in a lot of remote ADR sessions I do, the level of LTC does matter. Over Source Connect or ISDN, if the LTC is too soft or too loud the receiving end experiences lots of dropouts just like I’m experiencing here. 

 

Those are Pro Tools based computer systems though, so a little different from this world, but I couldn’t think of anything else that might be the issue. 

 

The issue seems worse later in the day too, despite a fresh battery change on all machines and a rest over lunch. 

 

-Mike

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For testing purposes run the tc through a mixer and play with the level. If you can reproduce/eliminate the problem you know it is that...

 

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It's possible this is related to the jitter in Zaxcom's tc stream fooling the mixpre's auto frame rate detection similar to the way it fools denecke slates.  If you don't have another generator to try, try different frame rates and see if you find the same behavior.

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16 minutes ago, Wandering Ear said:

It's possible this is related to the jitter in Zaxcom's tc stream fooling the mixpre's auto frame rate detection similar to the way it fools denecke slates.  If you don't have another generator to try, try different frame rates and see if you find the same behavior.

Interesting! I vaguely remember hearing about that - was there a solution to that that you remember?

 

I have used a tentacle as a TC generator for the MixPre before I had the Zaxcom and had zero issues. 

 

-Mike

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I don't actually know this is what's happening, it's just a thing to check and possibly rule out.  With the slates the solution is to set the TC rate manually.

I don't think i've tried my mixpre getting TC from the ifb200, but I have had problems with the tentacles not taking a jam from Zaxcom at certain frame rates. 

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On 4/25/2019 at 8:01 PM, Mobilemike said:

Interesting! I vaguely remember hearing about that - was there a solution to that that you remember?

 

I have used a tentacle as a TC generator for the MixPre before I had the Zaxcom and had zero issues. 

 

-Mike

I have a Mixpre 6 with an IFB100, but instead of using the IFB100 as the master clock I use a tentacle as the master and then had Gotham Sound build me a Y cable that feeds both the 100 and the Mixpre from the tentacle. Haven’t had any issues with the Mixpre losing code and the cable was pretty cheap. 

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2 hours ago, Robert Bluemke said:

I have a Mixpre 6 with an IFB100, but instead of using the IFB100 as the master clock I use a tentacle as the master and then had Gotham Sound build me a Y cable that feeds both the 100 and the Mixpre from the tentacle. Haven’t had any issues with the Mixpre losing code and the cable was pretty cheap. 

I would recommend working like this.  I don't know that the Zax IFB stuff was meant to be used as a master clock.

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Have you turned up the TC output level on the ERX - I jam my mozegear boxes from ERX but it needs to be at the highest level for them to register input.

ive recently had issues jamming Alexa minis with ERXs and after some research including reading how someone did some testing recently and found the Zax tc output to be a bit lo fi and thus falling below Alexa tc spec - Perhaps similar situation with the mixpre requiring cleaner tc

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On 5/7/2019 at 3:01 PM, jozzafunk said:

Have you turned up the TC output level on the ERX - I jam my mozegear boxes from ERX but it needs to be at the highest level for them to register input.

ive recently had issues jamming Alexa minis with ERXs and after some research including reading how someone did some testing recently and found the Zax tc output to be a bit lo fi and thus falling below Alexa tc spec - Perhaps similar situation with the mixpre requiring cleaner tc

Yeh I always have the. "!" come up on TC on Mini's when I leave the ERX on the camera all day....   makes sense because the ERX is lo fi, maybe like you said, the Mini sees it as an error.  I've always ignored the "!" and never had a problem with sync in post.  

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what firmware are you running on the mixpre? on the ifb200 etc? dont follow the firmware history too closely since i don't use those units but might be worth checking out

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Thanks guys - I appreciate all the thoughts and input. 

 

Updating here for posterity...

 

I am running the latest firmware on all devices, that was definitely something I checked too. 

 

I spoke with both Zaxcom and Sound Devices about this and neither one could offer much insight. Matt at Sound Devices said that jitter or auto frame rate detect shouldn't affect anything on the MixPre - it simply picks up whatever timecode is put into it and isn't too fussy about changes. He said it will pretty much follow along with anything. He did suggest that I record the incoming timecode onto an audio track to check and see if the timecode stream was dropping out completely at those moments where it loses connection. I did that and recorded quite a few hours of timecode and did not see any physical drops of the TC stream. 

 

Glenn at Zax simply said that it definitely couldn't be the IFB200, but didn't elaborate. He did offhandedly mention that he didn't even remember that teh IFB200 had a timecode generator though, which was a little disconcerting.  

 

I also have an older Denecke TS-2 slate (with the 23.98 mod) that I have been using with this rig. I've noticed however, that when I jam the Denecke from the IFB200 that I have to rejam it every 20-30 minutes because it starts drifting. I assumed that was because of an old crystal so I sent the slate back to Denecke for service. They checked it out and said the crystal was totally fine and not experiencing any drift. 

 

So... at this point I'm forced to conclude that the timecode generator in the IFB200 is just no good; that it is just not very reliable. Like several people suggested above I am going to try clocking everything (including the IFB200) from another TC generator and see how that works out. I have a couple UltraSync One's which have dual LTC outputs, so I can send one into the MixPre and the other into the IFB200. I was hoping to avoid this solution just to keep the rig simple - this just adds one more thing in the bag and one more battery to keep track of - but if its the only way for reliable TC then I guess its worth it. 

 

I'll update after I've run with this configuration a few times.

 

-Mike

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I asked SD about the LTC input level on the mixpre 6 the other day in relation to the signal level feeds from my Ultrasync One. 

 

Dennis at SD told me that they did not have any specs on the matter but he measured the LTC Lemo output from the 688 - which always had worked great for them - and it was about 112mV. 

 

He recommended me to begin with then Mic level output on the USO which is 70mV and see if the Mixpre 6 was happy with that. 

The Low setting from the USO is 600mV. 

 

Unfortunately I’ve not been able to set it up yet as I have been away on travel. 

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