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Canon XL and GL Series DV Camcorders
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Old November 6th, 2004, 08:58 AM   #1
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XL2 Audio Level Indicator

A beginner's question:

I'm attempting to record an interview using two mics connected directly into the rear XLR connections of the XL2. For 'INPUT SELECT' I've selected "Rear" and for 'REC CH SELECT' I've selected "CH1-CH2". Under those circumstances the audio level indicators for channel 1 and channel 2 display audio input identically, whether in auto or manual. When I switch 'REC CH SELECT' to "CH1" I appear to get differentiated indicators for channels 1 and 2. This seems counterintuitive to me, but I presume I'm doing something wrong here.

Can anyone provide me with an assist on this?
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Old November 6th, 2004, 10:58 AM   #2
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Hi Andrew,

This is sort of explained at the bottom of page 51 of the manual but it's confusing. The deal is, under REC CH SELECT when you choose CH1 - CH2 what you're doing is porting the input from one XLR jack onto both channels. In other words this option duplicates one mic input onto two channels. So effectively it disregards whatever mic is plugged into the other XLR jack. As long as you have it set to CH1 then you should see separate levels for separate mics.

We just had a thread related to this, see http://www.dvinfo.net/conf/showthrea...threadid=34453.
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Old November 6th, 2004, 11:00 AM   #3
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Hi Andrew,

I'll definitely agree the labeling isn't very clear, but all is well as you've described it.

The REC CHANNEL SELECT button allows you to record either:

- Channel 1 alone on one magnetic stripe on the tape and the Channel 2 onto the next stripe (that's the CH1 setting normally used for 16-bit stereo recordings as you were doing), or

- Channels 1 and 2 co-existing on a single stripe at 12-bit resolution, leaving room on the next stripe for channels 3 and 4.

If you wanted to record in 12-bit with four mics, or wanted to dub a second stereo signal to the tape later (that is, add 3rd and 4th channels), you'd place the button to CH1-CH2 so the signal will be laid down on the tape in a way that allows room for 4 channels (at 12-bit resolution) -- 1 and 2 would be recorded on the same stripe on the tape together, and channels 3 and 4 would live together on the next magnetic stripe.

A picture's worth a thousand words. If you have access to the owner's manual, this setup is described, with diagrams and tables, on pages 50-51. There are also block diagrams of the whole audio system in the appendix on pages 122-123...too much info for me right now!

This does raise follow-on questions, though, that perhaps someone smart in electronics can answer. If we have 16-bit selected in the menus but then set the the button to CH1-CH2, we see that identical signals are sent to channels 1 and 2 in our viewfinder. I wonder if they are averaged to mono, or only one is selected and output to both channels. Presumably the signal is 16-bit and sent to every stripe, since we see signal in both channels in the viewfinder...or not?

If the family allows me any free time this weekend (not holding my breath), I might try a test of this with two mics recording very different sounds.

The short answer for what you're doing is that you want the REC CH SELECT button set on CH1 for what you're doing. That'll send the channel 1 mic to a magnetic stripe that'll be read as the 16-bit left channel, and the channel 2 mic to the next stripe, and repeat!

Cheers,
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Old November 6th, 2004, 11:03 AM   #4
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Chris & Pete,

Thanks so much for that clarification. I had reviewed the manual, obviously without sufficient scrutiny and also handicapped by my inexperience. You've made it crystal clear, and as I suspected, my equipment is functioning properly. As usual, operator error.

Cheers,
Andrew
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Old November 6th, 2004, 01:00 PM   #5
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<<<-- Originally posted by Pete Bauer :

This does raise follow-on questions, though, that perhaps someone smart in electronics can answer. If we have 16-bit selected in the menus but then set the the button to CH1-CH2, we see that identical signals are sent to channels 1 and 2 in our viewfinder. I wonder if they are averaged to mono, or only one is selected and output to both channels. Presumably the signal is 16-bit and sent to every stripe, since we see signal in both channels in the viewfinder...or not?-->>>

Logically, when selecting CH1-CH2 for recording, the signal is outputed to both channels. I don't see the point of this option if it isn't. Basically, you plug your mono mic with an XLR cable to the CH1/3 connection and it sends the signal to both channels. This might be a good way to avoid sound drop-outs on very important sound recordings where you don't need the 2nd channel for an other track of sound. It's also a way to hear the CH1 feed in both left and right speakers of your monitoring earphones at the same time.
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Old November 6th, 2004, 02:48 PM   #6
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David is right. I did a quick check in 16-bit mode using the XLR jacks:

Set on CH1: The mic in the Ch1/3 XLR jack went to the L audio channel in the viewfinder, and the mic in the Ch2/4 XLR jack went to the R, as expected.

Set on CH1-CH2: The Ch1/3 XLR jack went to both channels equally in the viewfinder. The Ch2/4 XLR jack was dead. They do not mix. As best I could tell doing just a quick check, the levels on the Ch1/3 jack are not diminished by "splitting" the signal to both viewfinder channels; it appears that the left channel is just "copied" to the right.

What I take away from this is that I'll be leaving the REC CHANNEL SELECT button in CH1 unless I'm using only one mono mic and don't want to center the sound field in post, or invent the need to do some 4 channel, 12-bit recording.

I guess once I expend the brain bytes to figure this out, the labeling makes some abstract sort of sense. It is saying, "In CH1, the left jack goes to the left channel only; the right jack and channel are still there for you to use. In CH1-CH2, the left (mono) jack goes to both channels. You've got dual mono and you're done. No room left for second mic input in 16-bit mode."
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