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Getting back to meters...


Bob Marts
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My Cooper 208 mixer has the meters as pictured below.

For many years, I used a Sonosax SX8 (and various Nagras) and I was very comfortable with it's meters sending to both analog and digital recorders.

With the Cooper, I still get a little disoriented when I'm sending to my SD recorders and to various digital cameras. I'm never quite sure that I'm getting the best out of the Cooper's S/N and limiters -- I tend to be conservative with the trim and output. These meters kind of freak me out. I'm not exactly sure how to cross reference them

Any 208 users care to describe their levels and experience with these meters?

Thanks, Bob

post-52-0-98861900-1323050938.jpg

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Bob, I am glad that you posted this concern.

I too have felt some kind of strange meter mismatch between 208 meters and SD 788t. I came to the conclusion that I should feed tone from 208 (-8db on meter scale) to the 788t at just about -12db. Two LEDs above -20db indicator.

If feeding video at same time, I line up to -20db on video camera.

I do not know why this works but so far it does. I'd like to hear how you've been making it work. This is still a work in progress for me, I'd love some feedback.

Thanks,

John.

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Bob, I am glad that you posted this concern.

I too have felt some kind of strange meter mismatch between 208 meters and SD 788t. I came to the conclusion that I should feed tone from 208 (-8db on meter scale) to the 788t at just about -12db. Two LEDs above -20db indicator.

If feeding video at same time, I line up to -20db on video camera.

I do not know why this works but so far it does. I'd like to hear how you've been making it work. This is still a work in progress for me, I'd love some feedback.

Thanks,

John.

John,

One other thing you could do to get some confidence in how your meters interact with other equipment would be to do a full scale tone test. Feed tone into the 208 with an external generator and bring the input trim up to the clipping point and back off just a hair. Now feed that to the 788 and set the 788 input trim so that same signal hits just below -1 dBFS -- the 788T Zoom mode or a custom mode meter would work really well here.

Now that you have both devices set to match at their respective absolute maximum headroom, use the 208 tone gen to see where everything lands on your meters.

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I would second Matt's advice. This is my method as well for mystery meters. Usually I use this method when calibrating to a camera that I'm not familiar with.

It will also inform you where the device actually starts clipping. Which is sometimes sooner than the meter would have you believe.

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The meters of the Cooper mixers were chosen to mimmick the modulometers of the analog Nagra tape recorders, where the 0VU reference was at "-8", with an additional 4dB above the "0" to indicate maximum level of the Nagra recorder. This results in 12dB of headroom above the 0VU reference of -8. Therefore, it makes sense that the Cooper meters seem to track more closely to a digital device's full-scale meters if the 0VU reference tone from the Cooper is lined up at -12dBfs on the Sound Devices meter.

However, if I recall correctly, the Cooper 208 has 20dB of headroom above it's 0VU reference (-8 on the Cooper's meter). So, you could align the Cooper's tone to the -20dBfs mark on the Sound Devices recorders and achieve 0dBfs (max) without clipping the output of the Cooper. Aligning the Cooper's tone at -12dBfs would be safer with regards to clipping the output of the Cooper, especially if an input compressor is also used on the recorder, but the additional 8dB of headroom capability of the Cooper mixer would be excessive and never fully used.

It's going to take a book.

gt

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http://www.thesoundmanifesto.co.uk/TSM_LineLevels_Nagra_v1.pdf

This website, The Sound Manifesto, has a useful equivalency chart I use for the times when I drag out my Nagra mixer. When shooting for tape versus digital, I find that I back down my calibration levels so that 0 on the Modulometer equals 0dBfs, with the limiter kicking in quite a bit earlier at around -16dBfs (if used at all on the Mixer as I can also use the limiters on the recorder instead). I find this calibration scheme quite convenient as I've basically made the modulometer readings equal to dBfs scale, +/- a few dB here and there as the ballistics don't quite match up in real world terms. I know that this is quite a bit more conservative than the 0 Mod = -12dBfs proposed, and is what would seem appropriate, especially in the context of limited dynamic range of tape, but I've tried more aggressive alignment in the past and haven't had much success with my particular mixer and headroom. My mixer's modulometer has a nice green bar between -15 and -6, and I find that if I hover around -20 to -15 that I get appropriate -22 to -12 levels on my recorder. (also having set the mixer output to +12dBU and adjusted the input trim on my recorder to match)

At the end of the day, I've come up with a scheme that works basically having used the recorder's dBfs scale as a reference and having worked backwards from there to come up with an analog meter range that works.

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