Topic: Tascam DR-70D 4-channel audio recorder (Part 4)

[voltronic]

So excuse my ignorance but I see the slate button on my DR-70D and really have no clue what it's for if one DID want to use it. Anyone care to explain?

Reference tone for level matching external cameras and recorders.  Also marking takes if doing video work.

how would one go about using it for level matching?

Check the FAQ.

[2manyrocks]

So excuse my ignorance but I see the slate button on my DR-70D and really have no clue what it's for if one DID want to use it. Anyone care to explain?

As I recall, someone mentioned earlier in the thread(s), the camera out gain is set in the 70d menu instead of a physical gain control like on the 60d.  Once you start recording, the camera gain can't be changed since there is no physical gain control for this on the 70d.  The slate can be used to more carefully match the gain between the camera and the 70d.  If you set your camera gain too high and then adjust the channel gains on the 70d, you can brickwall your camera audio.  This is why you want to be careful about how you set the camera gain using the slate.  Others can probably give a better explanation than mine. 

This is partly why I use the 60d for video.

[ButchAlmberg]

Thanks for the explanations. Based on that, I'm wondering what percentage of the DR-70D market goes to us in the strictly audio taper market vs. folks who use the recorder incorporated with video (as it is seemingly intended).

[voltronic]

So excuse my ignorance but I see the slate button on my DR-70D and really have no clue what it's for if one DID want to use it. Anyone care to explain?

As I recall, someone mentioned earlier in the thread(s), the camera out gain is set in the 70d menu instead of a physical gain control like on the 60d.  Once you start recording, the camera gain can't be changed since there is no physical gain control for this on the 70d.  The slate can be used to more carefully match the gain between the camera and the 70d.  If you set your camera gain too high and then adjust the channel gains on the 70d, you can brickwall your camera audio.  This is why you want to be careful about how you set the camera gain using the slate.  Others can probably give a better explanation than mine. 

This is partly why I use the 60d for video.

Great explanation of why the SLATE is useful.  There's absolutely no reason not to use it when sending a signal to any external device.

Yeah, the locked level adjustment is one of the biggest problems with the 70D when using it with an external device.  The only levels that can be adjusted while recording are the 4 input gain levels; everything else is fixed.  So use the slate at an appropriately high level beforehand so you're sure you're not going to blast the inputs of whatever you're connecting to once the show starts.

If you change the setting to CAM out, that lowers the level by 30dB.  From the manual:

When set to CAMERA OUT
  Nominal output level: -40 dBV
  Maximum output level: -24 dBV
When set to LINE OUT
  Nominal output level: -10 dBV
  Maximum output level: +6 dBV

[Life In Rewind]

I'd like to hear an Film/AVs guys explanation of the uses of slate tones or otherwise.

The biggest flaw in the DR-70D is the gain controls that don't pass any signal at their lowest setting.

This is a big defect IMO...hopefully the new MID gain setting will lessen this circumstance.

The gain should just stop being reduced when the knobs hit minimum. Isn't that the whole point of the 4 gain ranges!?

That feeling that the knob has stopped is a valuable physical index - we need that!

TASCAM please fix this!!!

[willndmb]

I still don't see how the slate is good for matching levels but I use the 60 which has much better control over everything as well as multi outs active at once.
I really don't see how the slate is even useful in lining up audio/video since you need your camera hooked up in order for it to "hear" the slate. So why not just use the feed to the camera and be done with it?
Only reason I can think of is because the tascam might have better sound over the camera but fcp has synch features built in and lines everything up for you anyway.


It is dumb to have the knob all the way down cut off the signal though

[2manyrocks]

As I recall, we both had to figure out the right gain settings on the 60d for our Canon camcorders in the 60d thread.  It's that same thing except someone was smart enough to figure out how to use the slate as a reference tone on the 70d. 

The slate gets you a fixed reference point on the 70d that you can match to your camera gain settings before you start recording for real so you don't have the camera running say 15db hot relative to the 70d.  If you were low setting gain on the 70d XLRs and then corrected it with the camera gain get too high, you'd have a good chance of brickwalling the audio recording on your camera during the actual recording.  Adding the slate tone to a recording you're going to use for real without matching gain on the camera wouldn't help you avoid running the risk of brickwalling or having levels set too low, either, on the camera. 

In one sense, there are three variable gains:  the XLR gain, the camera out gain, and the camera's own gain.  By matching the camera out and camera's own gain, hopefully, you have reduced the variables that might mess you up to only the XLR gain when it comes to actual recording.   

Setting aside the matter of gain matching for a second, if you're just going to use the audio recorded in the camera and be done, the slate tone is in the way if you actually use it as a slate during the actual recording in my experience because I have to go in and edit it out. 

I sometimes run multiple cameras and there's no slate on the ones not connected to the 60d.  An old fashioned clapper board would give a better reference on all of them simultaneously for sync purposes.  I have yet to use the 70d for an actual video recording.   

For the 70d not to pass any signal at the lowest setting is a huge defect, IMO too. 

[Life In Rewind]

Is "SLATE" really about levels?

The AUTO slate setting - makes maybe a 1 second pulse at the beginning (or beginning and end) of each take.

Not terribly useful for level calibration...

Something tells me we don't really know what the heck slate is...

[2manyrocks]

In my case, that's absolutely true. 

[Life In Rewind]

I thought SLATE had to do with syncing audio and video together in post...

Even if you route your DR-70 Audio to your camera - isn't always better to replace it in post?

And since they are different recorders - not clock synced - the audio would drift...

I figured the tone was a way of tuning one source to the correct pitch and speed...somehow.

[2manyrocks]

Presumably, the audio recording quality inside the 70d is better than my camcorder, but since there is a bit of drift over an hour or more recording, I'd rather just live with the audio in my camcorder than sync in post in most cases.   

The slate tone is there primarily to make a spike in the audio waveform on the tascam and on the camera so you can more easily align spikes for syncing the "better" Tascam audio  with the camera video.   Because the slate is silent to the audience, it's not like you run down front to the stage and slap a clapperboard, either.   

[voltronic]

I thought SLATE had to do with syncing audio and video together in post...

Even if you route your DR-70 Audio to your camera - isn't always better to replace it in post?

And since they are different recorders - not clock synced - the audio would drift...

I figured the tone was a way of tuning one source to the correct pitch and speed...somehow.

Yes they're different clocks, but as long as you set both to the same sample rate (48kHz) you should be fine.  I do this all the time and it's pretty easy to line up the camera audio with the high-quality recorded audio and delete the camera audio track.  Drift hasn't been a problem for me, but I don't record anything longer than about 2 hours at a time.  I don't use slate tones for this - I use percussive transients at various points throughout the concert.

I think the speed / pitch issue you're referring to is what you'd use with analog audio recording on tape and video on film.  Today there's timecode with digital recording that does this better.  You still have to make sure all of your audio is recorded at the sample rate, or you will get drift or potentially pitch changes if one track is stretched or shrunk to match the length of the other.

For audio only, slate tones are very useful to help set levels, as 2manyrocks laid out.  Here's a great tutorial from DigiGal on setting the level between a MixPre-D and a PCM-M10:
http://taperssection.com/index.php?topic=165688.msg2069471#msg2069471

There's a similar procedure on how to do this with the 70D in the FAQ thread.

The dead zone of the gain pots is weird, and I put it in the Issues / Requests section of the FAQ.  We need to be prepared for the fact that this may not be a software issue where it's set to not pick up anything until 8:00.  It could be that the switches themselves have this dead zone, although why you'd use parts like that is beyond me.

[voltronic]

Presumably, the audio recording quality inside the 70d is better than my camcorder, but since there is a bit of drift over an hour or more recording, I'd rather just live with the audio in my camcorder than sync in post in most cases.

If you are absolutely sure you have synced up the beginning of your recordings and you're getting drift in that amount of time, that's a strong indication you have a sample rate mismatch.  You can't record your audio at 44.1 kHz and have it match up with the camera, which is going to be running at 48 kHz.  You need to set your audio recording to 48 kHz or 96 kHz.

[Life In Rewind]

Presumably, the audio recording quality inside the 70d is better than my camcorder, but since there is a bit of drift over an hour or more recording, I'd rather just live with the audio in my camcorder than sync in post in most cases.   

The slate tone is there primarily to make a spike in the audio waveform on the tascam and on the camera so you can more easily align spikes for syncing the "better" Tascam audio  with the camera video.   Because the slate is silent to the audience, it's not like you run down front to the stage and slap a clapperboard, either.

That makes sense to me...the AUTO feature has a setting to make a SLATE tone at the beginning and end of each take...seems ideal for post-sync work.

But I do get the sense that guys are using the mixer feature live - and just being happy with that level of improvement...and not bothering with the post audio sync.

Depending on your camera and available settings - that's probably ok.

The level calibration might be more a sidecar - "can also be used for" feature...

[Life In Rewind]

Presumably, the audio recording quality inside the 70d is better than my camcorder, but since there is a bit of drift over an hour or more recording, I'd rather just live with the audio in my camcorder than sync in post in most cases.

If you are absolutely sure you have synced up the beginning of your recordings and you're getting drift in that amount of time, that's a strong indication you have a sample rate mismatch.  You can't record your audio at 44.1 kHz and have it match up with the camera, which is going to be running at 48 kHz.  You need to set your audio recording to 48 kHz or 96 kHz.

I doubt that - sample rate drift between non clocked synced sources is a long existing problem when combining audio tracks in post. Even with two exact same devices set to the same rate - you will likely see some drift...that's the whole beauty of these new 4 channel recorders - its all the same clock...but the camera is a separate audio recorder/system.