Topic: Soundboard Audience Matrix and Time Clock Issues

[Scooter123]

This one has me stumped.

I have a stereo soundboard file from the 1st Set.  I have an audience file from the 1st Set.

I mono'ed the audience file and loaded it into a two channel stereo wave file as the other side.  The second side is the L. soundboard file.

I aligned the start, snipping off bits and pieces of the audience file to exactly start the two together.  So far so good.

I then went to the end, and using the Time Stretcher, I shortened the audience file so the last few notes are in perfect alignment with soundboard. 

I go the middle section of the file and it off by as much as a second.  WTF?  Sounds impossible. 

The start is still in perfect alignment as is the end. 

[mattmiller]

Sounds like what has been speculated to be the case with these clocks -- not only do they differ from device to device, but they differ over time within the same recording.  I haven't noticed this happening with any of the mixes I've done using an HD-P2 and M10, but one (or both) of your recorders looks to vary over the length of the recording.

[Scooter123]

OK

So I aligned them every three tracks which seems to work now. 

What a pain in the ass.

Time to get a SD 744 I think

[page]

Time to get a SD 744 I think

at least something clockable (the 7 series, usbpre2, hdp2 all come to mind).

[achalsey]

I had the exact same thing happen a week ago.  As far as I could tell (thanks to members here) it was an ADC clock issue.  I ran two sources (same stand, even same mounts (taped my Church -14s onto the C4 mounts)) both into separate iRiver H120s, except one was running analog in and the other was digital in.  Started at the same point and were very close at the end but close to a second off in the middle.  Might be a huge difference but the ADC clocks were on a Pmod UA5 (optical into an iRiver) as opposed to just analog into the other iRiver, definitely weren't working smoothly together.

Basically just reiterating the point but here's what I asked on another thread about the same issue:

http://taperssection.com/index.php?topic=147988.msg1896625#msg1896625

[Scooter123]

Got It.

So what I need for multiple sources is an External Clock and plug the spdif connectors from the clock to the two different recorders, Yes? 

This assumes the recorder has such spdif connectors. 

That way multiple sources, even started and ending at different times would have identical clocking.

Did I get that right? 

[hi and lo]

Why did you mono the audience source? When mixing sbd+aud, it's generally the sbd source that would be mixed to mono. The aud source is what fills out the stereo imaging which sbd feeds generally lack; very few FOH engineers will pan R and L significantly.

[Scooter123]

There was a wide separation in the Soundboard. 

Very little separation in the stealth source. 

Seemed logical to keep the separation in the final product

I'm actually re-doing later this week and may keep the L-R files intact, so Left would be L Soundboard and L Audience and Right would be R Soundboard and R Audience.

I've got about 20 hours in the project and getting dirty with the work has taught me a lot. 

I need a SD 744 and Pro Tools is what I need........

[page]

Got It.

So what I need for multiple sources is an External Clock and plug the spdif connectors from the clock to the two different recorders, Yes? 

This assumes the recorder has such spdif connectors. 

That way multiple sources, even started and ending at different times would have identical clocking.

Did I get that right?

Getting there.

You need a recorder or ADC that can accept a clock signal from elsewhere. This can be accomplished a couple of ways but is generally via either a word clock connection (typically BNC) or getting that word clock signal from a valid SPDIF connection. It could be as simple as the 7 series recorders which have a "word clock" plug or the usbpre2 which get's it's external clock signal from the incoming spdif. Alternatively you could pick up an R-44 which does all 4 channels in one box.

You'll still have to timeshift stuff (because the sbd will be off from the audience tape), but at least you won't have to re-clock it (cause it will be off consistently, just slide it back or forth in time).

[Scooter123]

Won't the SD 744 also have an internal clock which would snych all sources coming into the SD 744 making an external clock redundant? 

And what you are saying is, like the SD 744, the Edirol Rolland R-44 has an internal clock as well.  It is a third of the price.  The difference would be in preamps, I surmise?  But I digress.  I shouldn't be asking to compare the SD  744 with the R-44 Here. 

[page]

Won't the SD 744 also have an internal clock which would snych all sources coming into the SD 744 making an external clock redundant? 

Correct. You don't need an external clock (ala Apogee's Big Ben) so much as you need an ADC that will accept a clock signal and use it without resampling. While I think a 744 is a great piece of hardware, I think for 90% of what we do, there are cheaper options that are probably acceptable. Even 2 usbpre2s which have the same ADC/preamps when linked together is cheaper than a used 744.

[morst]

Something sounds dramatically wrong, even with your "kludged" time alignment (which I do frequently). Unless this is a very very long recording, you should not see a difference of one second anywhere in the source, especially with start & end aligned!? Are you sure there is not an edit somewhere, or that a small part of one track didn't get deleted?

I align sources from separately-clocked decks a lot, and modern digital recorders are usually pretty close to each other. My current pair of Sony PCM-M10's run about 0.0006% different. That's about 2000 samples over nearly 2 hours.

This one has me stumped.

I go the middle section of the file and it off by as much as a second.  WTF?  Sounds impossible. 

The start is still in perfect alignment as is the end.

[achalsey]

Something sounds dramatically wrong, even with your "kludged" time alignment (which I do frequently). Unless this is a very very long recording, you should not see a difference of one second anywhere in the source, especially with start & end aligned!? Are you sure there is not an edit somewhere, or that a small part of one track didn't get deleted?

I align sources from separately-clocked decks a lot, and modern digital recorders are usually pretty close to each other. My current pair of Sony PCM-M10's run about 0.0006% different. That's about 2000 samples over nearly 2 hours.

Oops, pressed post so here's the 'edit':

Not sure what the OP was recording with, but from what I found was that it was the ADC clock that proved to be a problem for me.  I recorded with two iRiver H120s running one analog in and the other digital in and had the same problem as the OP.  A few days later I ran the same two recorders doing a SBD + onstage mix both analog in and did not have any middle drift issues.  So like you said, if you're running very similar, if not identical devices (two M10s or like me H120s) with the same inputs, drift probably shouldn't be too much of an issue that you can't fix in post, but if you're running two separate ADCs there seems like there can be some significant time issues.