Jump to content

ERX hard wire timecode jam


fieldmixer

Recommended Posts

Here are more detailed ERX time code drift findings. 

 

My test setup utilized time code generated by a Denecke Master Clock feeding a Deva V which, in turn, fed an IFB100.  At the start point of the test, power was removed from the IFB100 and the offset of each ERX unit -- compared to the Denecke Master Clock -- was noted.  The offset ranged from -.06 to -.07.

 

The testing methodology is as follows:

- Comparisons were made in reference to a Denecke Master Clock. 
- All units had the same settings.
- Time code was set to 23.976 fps.
- Tests were done in a controlled space at room temperature.
- No attempts were made to see how much affect temperature changes would have on the units. 
- Even though the devices were set to output both audio & time code, no audio was being transmitted to the units. 
- Units remained static and weren't moved around between tests.
- Findings are in hundredths of a frame. 

- Their beginning offset was noted and results referenced to that (typically about -.06 frame)
- The test results listed were obtained at fifteen minute intervals, and span a two hour period.

 

MIN.:          15      30      45      60      75      90    105    120

ERX-#1   +.11   +.23   +.36   +.48   +.62   +.74   +.87   +.99
ERX-#2   +.07   +.14   +.23   +.32   +.39   +.48   +.57   +.64
ERX-#3   +.07   +.08   +.13   +.18   +.23   +.28   +.33   +.38
ERX-#4   +.10   +.08   +.08   +.12   +.14   +.17   +.20   +.23
ERX-#5   +.18   +.23   -.13    -.18    -.21    -.26    -.30    -.35

By comparison, my Deva (which I calibrated maybe a couple of years ago) was -.06 at the end of the two hours.

The first four units were purchased new, two at one time, and another two at a later date.  Unit five was purchased used and upgraded to time code operation.

Under these conditions (I remind you, definitely not field conditions) all stayed within a quarter of a frame for at least a half hour.

Among ERX one through four, it appears that the units that have experienced the fewest hours of use, show the least deviation, and it seems to be relative to their amount of use.

I make no claim to this being any kind of definitive test and the comments above are not intended as conclusions, but simply my musings.
 

Link to comment
Share on other sites

  • Replies 94
  • Created
  • Last Reply

Top Posters In This Topic

I archived the old Zaxcom web site prior to its renovation.  Here is what the original ERX page states about accuracy:

 

"The ERX2TCD has a built-in timecode reader/generator and output to continuously jam digital slates ensuring no timecode drift between Deva/Fusion and the slate.  The timecode will stay accurate even in the case of an extended RF dropout."

 

The unit seems to meet its intended goal with flying colors -- fifteen to thirty minutes is some pretty extended RF dropout.

Link to comment
Share on other sites

John, how did you measure the TC? Did you feed it into something?

 

A Denecke Master Clock will compare incoming time code to its internal generator and display any offset to the nearest 1/100th of a frame. 

 

I meant to include the following (which I'll add to above):

 

My test setup utilized time code generated by a Denecke Master Clock feeding a Deva V which, in turn, fed an IFB100.  At the start point of the test, power was removed from the IFB100 and the offset of each unit -- compared to the Denecke Master Clock -- was noted.  The offset ranged from -.06 to -.07.

Link to comment
Share on other sites

Thanks John for posting your results. Very interesting.

The only testing I did was run it for a couple hours in a driving scene where my zaxnet couldn't reach, and it didn't hold sync, so I just decided I have to stay within range most the time.

I have been extremely happy with the performance of my erx system, and haven't used my lockit box once since switching over.

Link to comment
Share on other sites

A Denecke Master Clock will compare incoming time code to its internal generator and display any offset to the nearest 1/100th of a frame. 

 

I meant to include that following (which I'll add to the above):

 

My test setup utilized time code generated by a Denecke Master Clock feeding a Deva V which, in turn, fed an IFB100.  At the start point of the test, power was removed from the IFB100 and the offset of each unit -- compared to the Denecke Master Clock -- was noted.  The offset ranged from -.06 to -.07.

great info, john. thanks for your tests and posting your findings.

 

Ken

Link to comment
Share on other sites

Thanks John for posting your results. Very interesting.

The only testing I did was run it for a couple hours in a driving scene where my zaxnet couldn't reach, and it didn't hold sync, so I just decided I have to stay within range most the time.

I have been extremely happy with the performance of my erx system, and haven't used my lockit box once since switching over.

same here, i keep my denecke's in my kit just in case but have not used them since i first purchased erx's. they seem to do the job for the type of work i do, but i always keep other options handy.

 

Ken

Link to comment
Share on other sites

I think a camera specific version of the ERX would be ideal, with a sturdy locking connection for TC & Audio.

 

Audio Dept does a mod to the ERXs where they remove the volume button and replace it with a BNC connector, and rout the TC to it, leaving the 1/8" jack for the audio. Volume is adjusted via the menu. 

 

Far from ideal for use as an IFB, but perfectly suited for cameras.

Link to comment
Share on other sites

Audio Dept does a mod to the ERXs where they remove the volume button and replace it with a BNC connector, and rout the TC to it, leaving the 1/8" jack for the audio. Volume is adjusted via the menu.

Far from ideal for use as an IFB, but perfectly suited for cameras.

It's a pretty cool mod. I've been considering doing my own mod this winter when I have time.

Link to comment
Share on other sites

Gene Martin from Audio Dept in the Zaxcom FB group:
"This is the ERX modification we've done for anyone that primarily uses an ERX on camera for TC and scratch track. The volume pot becomes the BNC for TC and we change out the 1/8 jack to a mono jack dedicated just for audio. Camera dept likes it almost as much as I do."

1013232_207890329399848_1559677618_n.jpg

 

Gene had also stated that "It's $120 if you have ERX2 cases if not the case is an additional $65 which is the cost of the case."

Link to comment
Share on other sites

JA: " I'm going to ask Zax about what they consider to be the likely drift on the ERX over several hours and if this is common to each and every unit or different on each one. "

great idea...

I believe JB's test covered the questions pretty well, and I agree: " The unit seems to meet its intended (and stated!) goal with flying colors -- fifteen to thirty minutes is some pretty extended RF dropout. "

Link to comment
Share on other sites

"The timecode will stay accurate even in the case of an extended RF dropout."

 

This is subjective by what one believes is an "extended" period of time.... :unsure:

 

It sounds like playing with semantics to me.  Dropout is a temporary, and normally brief, loss of signal -- typically, a second or two at most. 

 

Trying to construe "extended dropout" to mean several hours is quite a reach, IMO.

 

If you recorded for several hours and your client came back and told you there was no audio in the file, would you, with a straight face, tell your client, "It was extended dropout."

Link to comment
Share on other sites

It sounds like playing with semantics to me.

Yes it does, and it's Zaxcom playing the game.

Of course, I'm only a guest here, language-wise, but when I first got interested in the IFB2 and read about it on Zax's page, I read EXTENDED droput. To me that sounds like a longer period than a couple of seconds. And that's what I wanted it to sound like, too, so I may have mis-read out of excitement, but I also think that this was what Zaxcom was bargaining on. They could've just published actual measurements.

Then again, no one really does that anymore.

Link to comment
Share on other sites

"The timecode will stay accurate even in the case of an extended RF dropout."

This is subjective by what one believes is an "extended" period of time.... :unsure:

Agreed. And I think John is being very fair with his tests and dissection of that particular quote. However I think this has caught me and a few others on the hop. I've already spoken to a few recordists who were also under the impression that the sync held over a much more extended period.

Because the range on Zaxnet is often quite short and easily beaten by the range on wireless mics there are many many scenarios with my work that would allow ERX sync to go south (and then abruptly be corrected when back in range).

It would be interesting to see if in any future 'ERX3' Zaxcom could employ a crystal sync in the receivers that could work like the Lockits and TCBuddies. It seems a shame not to keep it all Zaxcom with the many advantages that Zaxnet brings (instant sync of timecode without needing to set and jam boxes for starters). There was a proposal a while back to include a scratch track in the TCBuddies. If that does ever happen then the ERX will look a lot less useful.

I guess I will have to purchase some Ambients. Dammit! I wanted to maintain the Zaxnet thing!

Link to comment
Share on other sites

Yes it does, and it's Zaxcom playing the game.

Of course, I'm only a guest here, language-wise, but when I first got interested in the IFB2 and read about it on Zax's page, I read EXTENDED droput. To me that sounds like a longer period than a couple of seconds. And that's what I wanted it to sound like, too, so I may have mis-read out of excitement, but I also think that this was what Zaxcom was bargaining on. They could've just published actual measurements.

Then again, no one really does that anymore.

 

Have you checked out the results of my tests above?  The average deviation was about a quarter frame after one hour and a half frame at the two hour mark.  That's well over "a couple of seconds" and pretty darn good "extended dropout" protection.

Link to comment
Share on other sites

The ZaxNet signal that is updating the TC is being sent from the sound bag/cart. The sound bag/cart is also where your audio is being recorded and being sent to camera from. 

So if the ERX goes that far out of range of the sound bag/cart for an "extended" period of time your audio will NOT be getting to the camera either and you will not have talent audio at the sound bag/cart either. So there is no real sync issue here.

And as John has pointed out several times - even if the ERX is out of range for an "extended" period of time (1.5 hours) the ERX will still keep very accurate code. That code will be way more than accurate enough considering that there will be no sync audio coming from the sound bag/cart. 

And when that camera comes back into the range of the sound bag/cart the code on the ERX will automatically re-jam and once again be frame accurate. So I'm sorry I don't understand what the issue is here.

The bottom line is if you need to sync a camera that will be going off and shooting for hours then there is no substitute for a dedicated sync box. The ERX was not intended for that purpose. The ERX was designed to keep accurate sync when it can update its TC via ZaxNet. And if the ERX does not get ZaxNet code updated for an "extended" time it will still keep very good sync. 

How many people have ever had a sync issue with an ERX? I haven't.

Link to comment
Share on other sites

The ZaxNet signal that is updating the TC is being sent from the sound bag/cart. The sound bag/cart is also where your audio is being recorded and being sent to camera from. 

So if the ERX goes that far out of range of the sound bag/cart for an "extended" period of time your audio will NOT be getting to the camera either and you will not have talent audio at the sound bag/cart either. So there is no real sync issue here.

And as John has pointed out several times - even if the ERX is out of range for an "extended" period of time (1.5 hours) the ERX will still keep very accurate code. That code will be way more than accurate enough considering that there will be no sync audio coming from the sound bag/cart. 

And when that camera comes back into the range of the sound bag/cart the code on the ERX will automatically re-jam and once again be frame accurate. So I'm sorry I don't understand what the issue is here.

The bottom line is if you need to sync a camera that will be going off and shooting for hours then there is no substitute for a dedicated sync box. The ERX was not intended for that purpose. The ERX was designed to keep accurate sync when it can update its TC via ZaxNet. And if the ERX does not get ZaxNet code updated for an "extended" time it will still keep very good sync. 

How many people have ever had a sync issue with an ERX? I haven't.

 

Jack, I'm happy to learn that in most cases the sync from the ERX will only drift marginally, and also to admit I may have been using the devices 'not for purpose'.

However, I would like to point out that are plenty of times on TV shoots where wireless range is far, far greater than anything that Zaxnet can achieve. I'm often recording straight to my Nomad in such circumstances rather than sending to camera, although I suspect my hops have greater range than the ERX anyway. Most of these times are thankfully shortlived, but I've certainly had cause to be separated from the ERX for longer on multicam shoots. One can argue that in those cases I should be using Lockits of some description, but not that this isn't a regular occurence. So your confusion confuses me.

Link to comment
Share on other sites

+1000 for Jack's response above (and relevant parts quoted below):

 

"The bottom line is if you need to sync a camera that will be going off and shooting for hours then there is no substitute for a dedicated sync box. The ERX was not intended for that purpose."

 

"The ERX was designed to keep accurate sync when it can update its TC via ZaxNet. And if the ERX does not get ZaxNet code updated for an "extended" time it will still keep very good sync."

 

"So if the ERX goes that far out of range of the sound bag/cart for an "extended" period of time your audio will NOT be getting to the camera either and you will not have talent audio at the sound bag/cart either. So there is no real sync issue here."

 

There can be a sync issue for those people, and I believe it is a very small number of people, who have chosen to use the ERX as a sync box, placed on a camera that is likely to be off shooting far away from where the sound mixer is working. I can imagine as well that they may not even be concerned about audio feed or wireless range --- just the expectation (incorrectly) that the ERX receiver is identical to the ubiquitous sync boxes from Denecke and Ambient.

Link to comment
Share on other sites

"I'm often recording straight to my Nomad in such circumstances rather than sending to camera, although I suspect my hops have greater range than the ERX anyway."  Now I'm confused. Are you running a conventional wireless hop for your audio feed to camera? That means you have both a wireless receiver (Lectro, Senn., etc.) on the camera AND the ERX? 

 

"I've certainly had cause to be separated from the ERX for longer on multicam shoots. One can argue that in those cases I should be using Lockits of some description"  That's right. You should be using regular sync boxes if you plan on being out of wireless range.

Link to comment
Share on other sites

"I'm often recording straight to my Nomad in such circumstances rather than sending to camera, although I suspect my hops have greater range than the ERX anyway."  Now I'm confused. Are you running a conventional wireless hop for your audio feed to camera? That means you have both a wireless receiver (Lectro, Senn., etc.) on the camera AND the ERX? 

 

"I've certainly had cause to be separated from the ERX for longer on multicam shoots. One can argue that in those cases I should be using Lockits of some description"  That's right. You should be using regular sync boxes if you plan on being out of wireless range.

 

Yes. Why is this strange? A wireless link to camera is commonly backed up with a recording at the mixer end in case of drop out. The ERX is being used to maintain timecode sync with the recorder in case of this recording being required. In my experience wireless range is usually much greater than that of Zaxnet so any risk of drift on the ERX in this situation concerns me. Thankfully this looks to be minimal although I for one wouldn't mind some kind of figures for a more prolonged period.

I'm happy to put up my hand and admit that my thinking re the ERX may have been wrong, although as other mixers have commented on this elsewhere I submit that I'm not the only one - even if we are in the minority. There are two mixers on this very thread who were under the same impression, although they seem to have worked this out previous to myself.

I note that we are also discussing a historic quote from the old Zaxcom website. There is nothing in the current manual or product information from which to establish the ERX sync abilities when out of Zaxnet range.

Link to comment
Share on other sites

Has anyone heard the saying that "assume" makes an "ass" out of "u" and "me".

 

Ultimately, the end user is responsible for understanding the limitations of his/her equipment. If you don't know or are uncertain, the manufacturer is only a phone call or email away. And Zaxcom is one of the easiest companies to get a hold of.

 

Personally, I find the range of the ZaxNet system to be its biggest demerit.

 

Mark O.

 

PS - another fine saying goes something like this, "Complaining about a piece of equipment on JWSoundGroup is like peeing in a dark suit. It makes you feel warm inside, but no one else notices."

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...