Understanding my 1khz tone at DVinfo.net

Peter Manojlovic · May 9th, 2011, 07:35 PM

I had a bit of a nightmare (baptizm by fire). I use a Canon XHA1, and attempted to capture board feed on channel 2, and a Rode NTG2 mic on channel 1..

I got to a wedding reception, and the only thing i knew for sure, was the four man band had everything coming through a mixer, and out to powered speakers. From my little bit of knowledge, it's not a fancy setup.

Here's where my long winded question comes.
I had confusion with my levels..

I had a Sennheiser G2 transmitter, outputting with sensitivity of -30db to make up for the Line/Mic drop, since i didn't have a proper in line attenuator.
My signal was coming in so hot, that i thought something was faulty with my equipment.
Finally, after lots of sweat and swear, i realized that i had to attenuate the XLR input on the camera (channel 2). Therefore a double attenuation.
I didn't have to attenuate my Rode. That was a simple level adjustment with audio dials.

Now what is the proper sequence for sending a signal out to my camera, so i've got something to measure a correct signal?
I know i have a 1khz tone, that registers at -12db. But that's it.

In layman's terms, what are the correct steps of sending out the correct level for my situation..

BTW, i finally got my audio to work, and it sounds gorgeous. I'm so happy.
I just feel that i'm short changing myself by not understanding my situation correctly..
TIA

Bill Davis · May 10th, 2011, 12:09 AM

A good place to start is to Google "gain structure."

That should point you to plenty of the basics of thinking of level setting as a step by step process that starts at whatever is making the sounds, and outlines the process of following sound generated signals - stage by stage - to where you're recording.

As a recordist, you need to understand ALL the various signal stages between the mic and your camera, and learn how to either control, collaborate with house, or separate and split off signals so that YOU can control the levels and consistency of the signals hitting your camera inputs.

That is the ONLY path that eventually leads you to consistent quality audio recordings in ANY circumstance.

Good luck.

Paul R Johnson · May 10th, 2011, 02:13 AM

The sensitivity on the transmitter is for setting it's mic gain - so a really close in head mic on a singer might need the -30dB setting, but for a quietly spoken speaker with a mic at lapel level, 0dB might be more suitable. The idea being to get the best signal to noise. Using the sensitivity to drop the level means that any noise on the link, and there always is some - is at a much higher level compared to the wanted signal. Using this to adjust the input level at the XLR of the camera is just asking for trouble - and flutters or noise bursts will be FULL level and painful!

I assume you have the on-camera receiver? I don't have problems feeding this into my cameras - it will either be on the mic setting with gain low, or more commonly for me, on line, with the receiver level up around three quarters or so. Even if the transmitter is vastly overloaded, the level from the receiver, although distorted badly will still be at a level the camera should be able to cope with. The transmitter gain is then adjusted to give distortion free output, the receiver will then be at the right level. The worst thing for gain structure is to lower levels early in the chain, and then have to use amplification to restore them later - this always produces noise.

Steve House · May 10th, 2011, 03:06 AM

Quote:

Originally Posted by Peter Manojlovic

...Now what is the proper sequence for sending a signal out to my camera, so i've got something to measure a correct signal?
I know i have a 1khz tone, that registers at -12db. But that's it.
...

Just what is it in your equipment that is generating that tone? I don't see where you are using a mixer and that is usually the tone source. The tone the camera can generate and record is used to provide a standard reference level for post and is not for setting up the recording inputs.

The 1kHz tone is used to align the INPUT of a camera or recorder to the OUTPUT of a mixer. The mixer generates the tone and sends it to the camera at a 0VU level. 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). The camera recording level controls are locked off and all level adjustments during the actual shooting are done at the mixer. With this procedure, when the person manning the mixer see's signal levels on its meters hovering at or a touch above 0VU s/he knows the camera is recording at the optimum level.

Rick Reineke · May 10th, 2011, 10:50 AM

Yes, Steve is absolutely correct, the camera's internal test tone level has nothing to do with your incoming audio's level adjustment.
Regarding line level with the G2: I'm surprised you got away with 'distortion free' audio, by just lowering the software sensitivity adj. alone. Normally one should use a physical attenuator... or better yet, make (or buy) a line-level input cable for the G2/3 transmitter.
3.5mm TRS wired: (+ signal) to the 'Ring'; (- ground) to 'Shield'; jumper the unused 'Tip' to ground/shield.

Tracy Foust · May 12th, 2011, 06:45 AM

I carry 2 Shure A15AS in line pads with me. I have actually used the 2 ganged together with the addition of a direct box to take a signal from a speaker to get audio. Aside from a little bit of "amp hiss" (cleaned up in post) it worked reasonably well.

Peter Manojlovic · May 12th, 2011, 09:42 PM

Thanks everybody for your patience and explanations...

I'm getting a better grasp on mixer terminology..The "Gain structure" search string is invaluable...
Thank you.

Part of my problem with being too hot on the sennheiser receiver, was the fact that i had the mic/line set to mic. Unfortunately, this switch sets for both Channel 1 and 2. This makes sense as to the signal being hot on channel 2, but fine on the Rode mic for channel 1.

On page 48 of the XHA1 manual, it states that there's a XLR MIC ATT. switch to attenuate the microphone by 20 dB. Therefore the sennheiser played back fine once this was set.

I guess this would lead me to the next question....
Knowing now that i can record line level to the camera:

Should i get my Rode to output for line level to match the Sennheiser

or

Should i stick to mic level, and attenuate the Sennheiser, to match the mic level.

Thanx..

Steve House · May 13th, 2011, 03:12 AM

Quote:

Originally Posted by Peter Manojlovic

...I guess this would lead me to the next question....
Knowing now that i can record line level to the camera:

Should i get my Rode to output for line level to match the Sennheiser

or

Should i stick to mic level, and attenuate the Sennheiser, to match the mic level.

Thanx..

Mics, such as your Rode NTG-2, can't be set to 'output line level' - they're mic level output by definition. You could get a proper field mixer, feed your sources such as the wireless, the shotgun, etc, into it, and then feed the mixer output to the camera. Thats the way it's usually done.

Les Wilson · May 14th, 2011, 06:39 AM

As a former A1 owner who's done what you are doing (mix Line level and mic level), I just want to re-affirm what's been recommended: Get a field mixer.

The A1 audio block is not as flexible as some others where you can set one input to be at line level and the other at mic level. A good field mixer like a used Shure FP33 will let you set each channel's input impedance separately and it will output two channels at the same impedance for your A1.

Basically, you set tone by generating the tone from your field mixer, set it's master output volume to 0 on it's VU meter, then adjust the A1 channel volumes till the A1 meter is -12 to -18.

From this point on, you monitor audio thru the mixer and adjust the channel input volumes on the individual input controls as needed.

If you are hooking up to a live event's sound board, set tone by having the FOH op send a 1KHz tone and adjust that input channel so your field mixer VU meter reads 0. As long as your feed is post fader, that channel is fire and forget as you will get the Op's adjustments on the output volume for free. If it's pre-fader, then you have to ride the volume yourself.

For important and complex events, having someone do this for you frees you up to be creative on the camera side. Welcome to production.

May 9th, 2011, 07:35 PM	#1
Peter Manojlovic Major Player Join Date: Jun 2007 Location: Hamilton Ontario Posts: 769	Understanding my 1khz tone I had a bit of a nightmare (baptizm by fire). I use a Canon XHA1, and attempted to capture board feed on channel 2, and a Rode NTG2 mic on channel 1.. I got to a wedding reception, and the only thing i knew for sure, was the four man band had everything coming through a mixer, and out to powered speakers. From my little bit of knowledge, it's not a fancy setup. Here's where my long winded question comes. I had confusion with my levels.. I had a Sennheiser G2 transmitter, outputting with sensitivity of -30db to make up for the Line/Mic drop, since i didn't have a proper in line attenuator. My signal was coming in so hot, that i thought something was faulty with my equipment. Finally, after lots of sweat and swear, i realized that i had to attenuate the XLR input on the camera (channel 2). Therefore a double attenuation. I didn't have to attenuate my Rode. That was a simple level adjustment with audio dials. Now what is the proper sequence for sending a signal out to my camera, so i've got something to measure a correct signal? I know i have a 1khz tone, that registers at -12db. But that's it. In layman's terms, what are the correct steps of sending out the correct level for my situation.. BTW, i finally got my audio to work, and it sounds gorgeous. I'm so happy. I just feel that i'm short changing myself by not understanding my situation correctly.. TIA

May 10th, 2011, 12:09 AM	#2
Bill Davis Trustee Join Date: Jan 2004 Location: Scottsdale, AZ 85260 Posts: 1,538	Re: Understanding my 1khz tone A good place to start is to Google "gain structure." That should point you to plenty of the basics of thinking of level setting as a step by step process that starts at whatever is making the sounds, and outlines the process of following sound generated signals - stage by stage - to where you're recording. As a recordist, you need to understand ALL the various signal stages between the mic and your camera, and learn how to either control, collaborate with house, or separate and split off signals so that YOU can control the levels and consistency of the signals hitting your camera inputs. That is the ONLY path that eventually leads you to consistent quality audio recordings in ANY circumstance. Good luck. __________________ Classroom editing instructor? Check out www.starteditingnow.com Turnkey editor training content including licensed training footage for classroom use.

May 10th, 2011, 02:13 AM	#3
Paul R Johnson Inner Circle Join Date: Nov 2005 Location: Lowestoft - UK Posts: 4,045	Re: Understanding my 1khz tone The sensitivity on the transmitter is for setting it's mic gain - so a really close in head mic on a singer might need the -30dB setting, but for a quietly spoken speaker with a mic at lapel level, 0dB might be more suitable. The idea being to get the best signal to noise. Using the sensitivity to drop the level means that any noise on the link, and there always is some - is at a much higher level compared to the wanted signal. Using this to adjust the input level at the XLR of the camera is just asking for trouble - and flutters or noise bursts will be FULL level and painful! I assume you have the on-camera receiver? I don't have problems feeding this into my cameras - it will either be on the mic setting with gain low, or more commonly for me, on line, with the receiver level up around three quarters or so. Even if the transmitter is vastly overloaded, the level from the receiver, although distorted badly will still be at a level the camera should be able to cope with. The transmitter gain is then adjusted to give distortion free output, the receiver will then be at the right level. The worst thing for gain structure is to lower levels early in the chain, and then have to use amplification to restore them later - this always produces noise.

May 10th, 2011, 10:50 AM	#5
Rick Reineke Inner Circle Join Date: Aug 2008 Location: New York Posts: 2,039	Re: Understanding my 1khz tone Yes, Steve is absolutely correct, the camera's internal test tone level has nothing to do with your incoming audio's level adjustment. Regarding line level with the G2: I'm surprised you got away with 'distortion free' audio, by just lowering the software sensitivity adj. alone. Normally one should use a physical attenuator... or better yet, make (or buy) a line-level input cable for the G2/3 transmitter. 3.5mm TRS wired: (+ signal) to the 'Ring'; (- ground) to 'Shield'; jumper the unused 'Tip' to ground/shield.

May 12th, 2011, 06:45 AM	#6
Tracy Foust Regular Crew Join Date: Jun 2009 Location: Annapolis, MD Posts: 58	*Addition to the "Oh, SHT" gadget box.** I carry 2 Shure A15AS in line pads with me. I have actually used the 2 ganged together with the addition of a direct box to take a signal from a speaker to get audio. Aside from a little bit of "amp hiss" (cleaned up in post) it worked reasonably well.

May 12th, 2011, 09:42 PM	#7
Peter Manojlovic Major Player Join Date: Jun 2007 Location: Hamilton Ontario Posts: 769	Re: Understanding my 1khz tone Thanks everybody for your patience and explanations... I'm getting a better grasp on mixer terminology..The "Gain structure" search string is invaluable... Thank you. Part of my problem with being too hot on the sennheiser receiver, was the fact that i had the mic/line set to mic. Unfortunately, this switch sets for both Channel 1 and 2. This makes sense as to the signal being hot on channel 2, but fine on the Rode mic for channel 1. On page 48 of the XHA1 manual, it states that there's a XLR MIC ATT. switch to attenuate the microphone by 20 dB. Therefore the sennheiser played back fine once this was set. I guess this would lead me to the next question.... Knowing now that i can record line level to the camera: Should i get my Rode to output for line level to match the Sennheiser or Should i stick to mic level, and attenuate the Sennheiser, to match the mic level. Thanx..

May 14th, 2011, 06:39 AM	#9
Les Wilson Inner Circle Join Date: Jan 2004 Location: Boca Raton, FL Posts: 3,014	Re: Understanding my 1khz tone As a former A1 owner who's done what you are doing (mix Line level and mic level), I just want to re-affirm what's been recommended: Get a field mixer. The A1 audio block is not as flexible as some others where you can set one input to be at line level and the other at mic level. A good field mixer like a used Shure FP33 will let you set each channel's input impedance separately and it will output two channels at the same impedance for your A1. Basically, you set tone by generating the tone from your field mixer, set it's master output volume to 0 on it's VU meter, then adjust the A1 channel volumes till the A1 meter is -12 to -18. From this point on, you monitor audio thru the mixer and adjust the channel input volumes on the individual input controls as needed. If you are hooking up to a live event's sound board, set tone by having the FOH op send a 1KHz tone and adjust that input channel so your field mixer VU meter reads 0. As long as your feed is post fader, that channel is fire and forget as you will get the Op's adjustments on the output volume for free. If it's pre-fader, then you have to ride the volume yourself. For important and complex events, having someone do this for you frees you up to be creative on the camera side. Welcome to production.