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Old March 2nd, 2006, 07:00 AM   #1
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Mic attenuation

When I use the Countryman B6 lav. on my PD150, I use the Mic. Attenuator switch on the camera to keep it from clipping. The HD100 doesn't have that option as far as I can tell. Does the -60, -50db mic. reference setting or the Audio reference setting factor in? What's the best way to handle the signal from the B6?

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Old March 2nd, 2006, 09:11 AM   #2
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Bill,

I'm moving this to the "Now Hear This" forum so the audio experts over there can have a stab at answering your question. The question probably also applies to the DVX/HVX and XL2/XLH1.
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Old March 2nd, 2006, 09:44 AM   #3
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The -50db setting is less sensitive and the -60db setting is more sensitive. However this 10db difference isn't as large a swing as the 20db change the PD-150 attenuation setting gives. You may need an additional attenuator.
AudioTechnica makes one that is switchable 10/20/30 db and Shure makes one that is switchable 15/25/35 db. If you get the Shure version and use it in combination with the camera's menu settings, you can get either 5 or 10 db changes which will allow finer tuning than just a 10db change.
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Old March 2nd, 2006, 09:49 AM   #4
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Thanks. I'll look into it.
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Old March 7th, 2006, 03:45 PM   #5
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I tried the Shure attenuator and got too much hiss. -15 db was the only one I could possibly use and that created way too much hiss. I actually find that I''m getting hiss no matter what I do. Even when I use the Sony ECM-44B, I'm getting some hiss. I've been using the PD150 before this, so I'm used to some hiss, but I shouldn't be having this poblem with the HD100, no?

I'm sure there's something I'm doing wrong. Has anyone used a lav w/ this camera and if so, what were your settings?

Thanks.
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Old March 8th, 2006, 09:47 PM   #6
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Did you use the -15db setting on the Shure in combination with the more sensitive -60db setting on the camera? In essence that should give you 5db of attenuation. Have you tried using no attenuation with this new camera? If you're getting clipping with no attenuation but adding only 5db of attenuation gives too much hiss, then the mic preamps of the camera are probably performing poorly.
Also the headphone amp, the level settings and the auto versus manual controls can make a big difference in hiss while monitoring. Are you actually capturing footage and testing it on your editing system?
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Old March 9th, 2006, 08:32 AM   #7
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OK, I figured it out. I've been recording using -12db reference for peaking - which was appropriate for DV, but HDV uses -18db for reference. I never needed the attenuator, I just needed to record at a lower level. The HD100 has an audio meter, but there are no numbers - the same is true of the HD50.
I'm assuming the white dot (which moves when you set the reference to -12db or -18db - on the camera) is my reference point for peaking audio. It's so far to the left of the meter, it seems weird setting my peaking level there. The deck doesn't even have that, just five LEDs.

Now that I know this, do you see the need to use manual control in an interview? I read in Steve Mullens guide that "gain riding" is typically not necessary. Unless the subject is all over the place, do you see the need to ride levels?

If it isn't obvious yet that audio is not my strong suit, it should be. Thanks for your patience.
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Old March 9th, 2006, 09:28 AM   #8
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Just to follow up. I ran some more tests and discovered that the B6 when it comes in to the HD100 w/ out attenuation in the Auto mode will peak at -12db and higher. When I bring it down manually, I can get it to the right range. I'd rather go with the Auto mode, but I don't think I have a choice. Thanks again.
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Old March 9th, 2006, 09:59 AM   #9
 
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Quote:
Originally Posted by Bill Parker
OK, I figured it out. I've been recording using -12db reference for peaking - which was appropriate for DV, but HDV uses -18db for reference. I never needed the attenuator, I just needed to record at a lower level. The HD100 has an audio meter, but there are no numbers - the same is true of the HD50.
I'm assuming the white dot (which moves when you set the reference to -12db or -18db - on the camera) is my reference point for peaking audio. It's so far to the left of the meter, it seems weird setting my peaking level there. The deck doesn't even have that, just five LEDs.

.
-18 is close to the ATSC spec of -20dB, which is likely what you're referring to. Audio for the average speaker should peak around -6dB. If you record audio too low, your resolution is lost, and this is even more critical with HDV as opposed to DV, since it's a compressed format. Where did you get information that HDV is "-18dB reference?" That doesn't compute.
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Old March 9th, 2006, 10:44 AM   #10
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Sorry - I meant -20dBFS. (How is dBFS different than db?) I'm using Steve Mullen's guide as a reference. He has -12dBFS as the default Nominal reference Level for DV and -20dBFS as the NRL for HD. He also offered -18dBFS as a reference level for audio that has a moderate dynamic range - such as on-location voice recording which applies to my typical situation.

Just to put it into my analog mind, would -20db represent for me hitting 0 on an analog meter and going up to -6db hitting about +2 in the red area of an anolog meter?

I promise you, that is my last question. Thanks yet again.
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Old March 9th, 2006, 11:18 AM   #11
 
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I guess you'll have to ask Mullen. There is no difference in audio levels via ATSC or SMPTE for HD vs SD, or HDV vs DV. Period.
-20dBfs is the digital equivalent of 0dBVU. For many years, this level was debated and confused by every manufacturer of digital audio gear, until ATSC set the spec. Panasonic was -14dB, Tascam was -18dB, Alesis was -16dB, and video was trying to come in at -15dB, with other DATs like Casio and a few others in a wider range all the way up to -9dB. This was settled by the ATSC when they generated the HD spec a number of years ago.
There is no audio past 0dB in full scale. It truncates, blows away, shatters, whatever you want to call it.
http://www.vasst.com/search.aspx?text=deadly

There is no nominal reference level in the form you're mentioning it as a spec, but various recordists try to get as much resolution as possible by finding the average, which could/should be in the -16/-12dB range, depending on the subject. I'm more interested in peaks, as I want the hottest audio I can get without truncation. I'm looking more at -6 than I am at -20.
You're also potentially confusing recording levels with output levels?
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Old March 9th, 2006, 01:21 PM   #12
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Quote:
Originally Posted by Douglas Spotted Eagle
I guess you'll have to ask Mullen. There is no difference in audio levels via ATSC or SMPTE for HD vs SD, or HDV vs DV. Period.
-20dBfs is the digital equivalent of 0dBVU. For many years, this level was debated and confused by every manufacturer of digital audio gear, until ATSC set the spec. Panasonic was -14dB, Tascam was -18dB, Alesis was -16dB, and video was trying to come in at -15dB, with other DATs like Casio and a few others in a wider range all the way up to -9dB. This was settled by the ATSC when they generated the HD spec a number of years ago.
There is no audio past 0dB in full scale. It truncates, blows away, shatters, whatever you want to call it.
http://www.vasst.com/search.aspx?text=deadly

There is no nominal reference level in the form you're mentioning it as a spec, but various recordists try to get as much resolution as possible by finding the average, which could/should be in the -16/-12dB range, depending on the subject. I'm more interested in peaks, as I want the hottest audio I can get without truncation. I'm looking more at -6 than I am at -20.
You're also potentially confusing recording levels with output levels?
Good point ... am I correct, that -20dbfs might be the average levels for the distribution medium but for the original master you'd record as hot as you can without the peaks clipping. The digitization process represents levels as numbers and for the best S/N ratio and dynamic range you want as wide a range of values as you can without hitting the ceiling. Recording at a reduced level means there's a lot of numbers you could be using that you aren't <grin>.

The -20dbfs comes in as the recording level to set for the 1kHz tone in the "bars & tone" leader on material destined for broadcast or duplication and the average program material should be set at the same level, right?
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Last edited by Steve House; March 9th, 2006 at 01:53 PM.
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Old March 9th, 2006, 08:53 PM   #13
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Some networks require tone at -20 and no peaks over -10, not over -12 for satellite uplinks.

Going right into the camera without a good limiter is a bad idea. Going into a mixer with a good limiter is a sane way to record high and keep your peaks in check.

Regards,

Ty Ford
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