View Full Version : What the heck is the attenuator?


Marco Leavitt
July 24th, 2002, 07:22 AM
Can anyone tell me what the attenuator does? The GL1 manual tells me sometimes it should be on and sometimes it should be off when using an external mike, but it doesn't say why. We're running a Sennheiser shotgun mike (sorry, don't know model) with a K6 power module through a studio 1 XLR adapter. No matter what volume level is selected on the Studio 1, the sound comes out very low with lots of background hiss. It's almost as if there is some kind of override inside the camera that keeps the audio set to the same low level. So far, we've kept the attenuator off. Should it be on? Since we're renting the microphone, we haven't had as much time to experiment with the settings as I would have liked. When played back through a television, the sound does sound pretty crisp, except for all that noise. Is the noise actually on the recording, or is it a product of having to turn the volume all the way up on the television? Our sound engineer seems to think we're going to be able to boost the volume digitally without all that noise. I'm hoping he's right, but I wouldn't mind a second opinion about this.

Bill Ravens
July 24th, 2002, 08:03 AM
the attenuator is used to select between line level and mic level input voltage. with att on, you get line level, with it off you get mic level.

Marco Leavitt
July 24th, 2002, 09:25 AM
Thanks. Since going through the Studio 1, does that mean I want line level? I don't think it boosts the sound any. It doesn't have an internal power supply.

Bill Ravens
July 24th, 2002, 09:33 AM
not sure which model you have. The PRO version allows you to select either line level or mic level output.

Marco Leavitt
July 24th, 2002, 09:48 AM
I've got the pro version. With the mike going directly into the Studio 1, would it be better to select line and turn the attenuator on or select mike and turn it off?

Bill Ravens
July 24th, 2002, 10:03 AM
I don't really know, but, I'd be inclined to select line level at the Studio 1. That way, the Studio 1 provides the amplification and noise level is lower out of the Studio 1.

Marco Leavitt
July 24th, 2002, 10:49 AM
Thanks again.

normbaits
July 24th, 2002, 11:31 AM
Do not set the Studio to line level. That box acts as a balanced wiring adapter for camcorders. It does not do anything else. You are right, there is no internal power to it, it is strickly passive. The Line Level on the Studio 1 is strickly for when the signal that comes to the box is LINE level, a mixer, your mic is certainly not line level so if you switch the Studio 1 to line level you will not be able to hear anything. Keep the Studio 1 to mic. As for the GL1, there is no need to keep the attenuation on in the camera. The signal coming from the Studio 1 is mic, and when attenuated should be pretty quiet if not completely muted. Again since no line levels are being delt with here, keep your camera's Attenuation off always. If you ever need to feed a mixer's out to your camera, use the Line Level pad that is in the Studio 1, you dont have to touch the camera's audio ever. Hope this helps.

Don Palomaki
July 24th, 2002, 03:58 PM
Some points to ponder:

The MIC ATT setting is used in loud venues and with hot mics. It reduces the mic input jack sensitivity by 20 dB from -55 dBV to -35 dBV. It does NOT allow line level. Consumer line level is -10 dB, about 0.32 volts while -35 dBV is 0.018 volts, a big difference. If feeding the GL1 in camcorder mode from a mixer, be sure the ouput is set to mic level, or use an attenuating adapter.

The MIC ATT setting also reduces the efffective noise floor of the GL1 mic input preamps by about 20 dB. So if you can, it is usually better to use MIC ATT setting and a hotter input form the mic, e.g., running the Beachtek or Studio One adapter at a higher setting.

The basic Studio One and Beachtek XLR adapters do NOT provide gain. They can only reduce the signal level.

Using the LINE setting reduces the signal to roughly mic level for use with a mic input on a camcorder.

Note that for audio dub purposes the GL1 has a LINE and LINE ATT setting. The LINE ATT setting provides 10 dB of attenuation. (From what I read, not many folks use that capability.)

Marco Leavitt
July 25th, 2002, 06:51 AM
Thanks much everyone. I must confess though, I'm more confused than ever on what settings I should be using on the Studio 1 and inside the camera. :)

Don Palomaki
July 25th, 2002, 07:17 AM
In summary, try MIC ATT, with the Studio One set to mic input and the level control at or near max. Adjust the Studio One level down if the recorded auido is too hot or show evidence of clipping/distortion or the noise level increases during quiet portions of the recording.

Marco Leavitt
July 25th, 2002, 07:27 AM
Will give it a try.

Michael Westphal
July 26th, 2002, 02:47 PM
If you are using only one mic into the Studio 1, and in fact have the Studio 1 set to Mono, then it's important to set the volume on BOTH channels! i.e. do not turn the empty channel to ZERO. It will affect the volume of the hot channel. This is documented in the Studio 1 "Manual" but it's non-intuitive and easy to forget.

Marco Leavitt
July 26th, 2002, 03:00 PM
Yeah, this one had us tearing out our hair for a while. It's unrelated to our current problem, however.

Lee Sharp
October 30th, 2009, 09:44 PM
Hey again,

Did a shoot once more levels were fine but I thought Id run this by the group

when reference level is -20 and peak is -12

I assume you want to be as close to the -12 end most of the time for a good strong signal, is there any level which it should not go below or aslong as the peaks are at -12 does th rest not matter so much covering the full dynamic range of the actors delivery?

Reason I ask I thought to myself, if one scene has talk then shouting, the shouting is gonna be the peak point and the talking is then gonna fall closer to the -20 area maybe less....

But then in another sequence where its all average talking you can whack up the levels so average talking is close to the peak area.... which can then be lowered in post to fit the general levels of all scenes (is this right?)

Any advice on this? Any point the signal should not drop below keeping in mind of shouting scenes where theres loud and quiet, also with PPM shouting peaking around 6ppm talking then averages around 4ppm or less.


Any opinion/advice welcomed :D!

S

Don Palomaki
October 31st, 2009, 07:02 AM
You woke a long slumbering thread.

Where you want the average and peak levels depends in large part on what you are recording and you intended end use of the video..

For highest digital dynamic range you want the peaks to be as close to "0" as you can without clipping. This also provides the highest signal to noise potential. I say potential because it depends on factors both within and external to the camcorder. Occasionally exceeding "0" (clipping) might not be a bad thing, depending on the program material (e.g., clipping on a random door slam or hand clapping and coughing of the oaf sitting in front of you).

Similarly, where you want the average signal level depends on that signal. Around -12 is OK for most typical home video purposes, but may not be appropriate for serious acoustic music in a concert environment. Profession gear, which usually has a better sound system, often records average audio at more like -18, thanks to having a wider usable dynamic range (lower noise floor).

And for some, perhaps many things, such as speaking voices, AGC is fine, maybe even better than trying to ride manual gain while shooting.

I usually try keep the wanted portion of the audio peaks slightly below "0," do not worry about audio I intend to edit out anyway, and let the average levels fall where they may, which usually is around -12 or so. And I tend to use AGC for things that are not musical in nature (i.e., where it is not important to preserve the original dynamic range ).

Lee Sharp
October 31st, 2009, 11:42 AM
im talking for professional broadcast and TV where the peaks spcifically have to be no more than -10dbfs/8dbu, 0dbfs is the peak for dbfs in studio recording.

Don Palomaki
November 1st, 2009, 06:35 AM
If shooting video for a specific market/client, then do what they want you to do. The soudl will no doubt be subject to a lot of sweetening while being edited.

The golder rule applies; that is, the person supplying the gold makes the rules.

Marco Leavitt
November 10th, 2009, 04:15 PM
Yeah, what Don says. You generally want the hottest signal you can get without clipping.

On a side note ... sheesh, was that really me way back in 2002 wondering what an attenuator was? I hope none of my current clients see that ;)

Paul Bestwick
July 31st, 2011, 07:17 AM
Ok... I am a complete novice and struggling with the basics. I have a Canon XA10 with a Rode NTG 3 mic connected via XLR input (CH 1). The volume level was extremely low and I have turned attenuation off. The manual advises that the level indicator should be around -18 but that seems to low on playback. To get an acceptable level of voliume it seems I have to turn the input dial to Max..... Really confused here.

Graham Bernard
August 1st, 2011, 08:27 AM
. . . . To get an acceptable level of voliume it seems I have to turn the input dial to Max..... Really confused here.

Do you use Headphones to check your mic/line IN?

Grazie