MixPre-D and Windows 7?

[Ty Ford]

Hello David and welcome to the Cow Audio Forum.

-12? I’m pretty sure the MixPre’s 0 should be -20 on your computer’s “meters.” Where are you seeing that it should be -12?

There may be a technical note about Windows 7 on the Sound Devices web site. I suggest you give them a call this morning and let them help you get back on track. They’re very good at that.

Regards,

Ty Ford
Cow Audio Forum Leader

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[David Veeneman]

Thanks, Ty!

I went for -12, because that’s what I use on cameras–it’s what I was taught in a class. It hadn’t occured to me that a different setting would work better when interfacing directly with Windows. Time to do some testing.

I checked SD’s tech notes, and didn’t find anything on the proper setting.

If anyone can point me to an article on using a 1K tone to set levels on a recording device, I’d appreciate it. Thanks for your help.

[David Veeneman]

A quick Google search uncovered this thread:

“Using the camera’s input level adjustments the recording level is set so the camera’s audio meters read either -18 dBFS (EBU standard level) or -20 dBFS (SMPTE standard practice).”

And Safari Books Online a section from Voice and Vision (2d Ed) that explains calibrating to reference tones.

And both agree that -20 dBFS to -18 dBFS is the standard. Can’t argue with SMPTE!

[Ty Ford]

David,

I explain that in my book. You push tone from the mixpre-D. It shows as 0 on the MixPreD meter. Notice that the meter on the MixPreD goes to +20. So when you adjust tone on your camera to -20, you can now run audio on your mixer to +20 on it’s meters and that will be up to 0 on your camera.

Make sense?

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford’s Blog

[David Veeneman]

Thanks Ty! I am finally starting to understand a bit.

[Craig Alan]

Yes that is correct. However, on small consumer level cams -12 is marked and -20 is not and I find it depends on what you are recording. Sometimes more headroom is needed and sometimes you need to use more of the cam’s preamp to end up above -12. on better cams with better audio -20 is marked and is correct. Since the mix-pre D is designed to mount under the cam, I just find that eyeballing at what level on the mix-pre the proper level is achieved on the cam is the way to go. If you can’t get a high enough level when calibrated below -12 (and its a guess where -20 is) then make the adjustment.

Mac Pro, macbook pro, Imacs (i7); Camcorders: Panasonic AG-HPX170/AG-HPX250P, Canon HV30/40, Sony Z7U, VX2000, PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.

[David Veeneman]

Since I’m at about -18 on the PC, I should be fine.

As to the -12 setting, it goes up past consumer goods–Panny P2 and AVCCAM units calibrate to -12, which now strikes me as kind of odd.

Am I missing something? Why the different levels? I would have expected all devices to calibrate to the SMPTE standard.

[Ty Ford]

David,

You’re not missing anything and I’m not in agreement with Craig’s response. Sending you’re 0 dB tome to a camera and setting the record level to -12 on the camera means you have 8 dB more signal on the mixer than the camera can take. You will clip the audio if you use the full scale of the mixer.

I have had versions of this conversation with several camera ops and they just don’t get it. One even said, “I don’t need your tone, my camera generates its own tone.” And as I recall it was at -12. I told him that his camera’s tone was not the point. The point is I’m calibrating my mixer to the camera so I don’t have to look at the camera meters during the shoot. I have 20 dB of headroom above 0. If you count down from 0 on your camera, you’re at -20 dB. Some get it some still don’t

In many of today’s professional cameras, there are no marks at all! It’s pretty stupid not to do provide calibration help, but there you are. The only response I can give is that camera mfgrs don’t care as much about sound as they do picture.

In addition, some mfgrs set their line level electronics to Consumer Line Level, which is not 0, but -10. You can calibrate with -20 tone, but in operation the camera input will clip at about -10 because the voltage from the mixer is overdriving the front end of the camera.

My Sound Devices 442 mixer has selectable outputs of mic, -10 or line. When I encounter one of these cameras, it’s because I’m trying to send it line level at 0. When I hear the clipping in the headphones from the camera return during my initial setup and the camera meters are nowhere near peaking. I switch to -10 output on my mixer and set tone again on the camera at -20. If you don’t have a -10 output on your mixer, the best thing to do is switch to mic level output on the mixer and mic level input on the camera and recalibrate to -20.

Regards,

Ty Ford
Cow Audio Forum Leader

Want better production audio?: Ty Ford’s Audio Bootcamp Field Guide
Ty Ford Blog: Ty Ford’s Blog

[David Veeneman]

Very helpful–thanks!

[Craig Alan]

[Ty Ford] “You’re not missing anything and I’m not in agreement with Craig’s response. Sending you’re 0 dB tome to a camera and setting the record level to -12 on the camera means you have 8 dB more signal on the mixer than the camera can take. You will clip the audio if you use the full scale of the mixer. “

Yes you will and that is a concern and does defeat some of the beauty of the Mix-PRE-D’s LED meter.

The manual for these cams does say to have the sound peak to the right of the -12 only occasionally. This implies from -12 to just below 0 is headroom not your desired levels.

But with some talent using a dynamic mike and the mix pre-D they are consistently recording under -12 (on the cam). Even with the gain control on the mix-pre D set to 4-5-6 o’clock. Now that would not be a big deal if say -14/-18 on the camera was actually +2/+6 on a pro meter. But when I playback footage from these small cams, I find I really want to be a touch over -12. There does not seem to a lot of wiggle room in terms of decent sound levels. During class we are playing the footage back using the AV out port on the cam into a professional monitor. We use the AV only for sound and component out for visual. We can also use HDMI out for both. Either way if the sound levels are below -12 we need to increase the volume on the monitor all the way up to hear dialog. When levels are at or above -12 but not into the 0 they do not sound distorted.

So if I recalibrate to the -12 on the cam using 0 tone then I tell students to aim for 0/+4/+6 on the mixer and this will translate to over the -12 but not into the 0 on the cam.

Further the camera does not have a -20 mark so how do you know where to set it?

Let me ask you this Ty, is this simply a playback issue and I’m in a good range as long as I’m above -20 on the camera meter even though there is no mark for -20? We can barely hear -about14 playing back on a pro panasonic monitor. My experience in post seems to confirm my ballpark though. If I want to get the sound at decent settings in FC I do better starting with the cam meters at or above -12. Below and I’m adding noise to the signal.

On our P2 cams and our Sony cams there is a -20 mark as well as a -12 mark and we use the -20 to calibrate and it’s a lot nicer with better results.

[Ty Ford] “In many of today’s professional cameras, there are no marks at all! It’s pretty stupid not to do provide calibration help, but there you are.”

Some of the pro cams that have no marks have a way to magnify the audio meters which now gives you the marks. The design idea is blow it up when you are calibrating or just spot checking but then minimize them to save real estate so the cam op can concentrate on exposure and focus. My Panasonic AG-HPX250PJ-s work this way. You can assign a button to display “MAG A. LVL” Isn’t that intuitive? (magnify audio level meters, I think).

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Mac Pro, macbook pro, Imacs (i7); Camcorders: Panasonic AG-HPX170/AG-HPX250P, Canon HV30/40, Sony Z7U, VX2000, PD170; FCP 6 certified; write professionally for a variety of media; teach video production in L.A.