Mic or Line Level?

M

mhood

Veteran
It seems I've been assuming mic level feeds from boards at conventions and I've been getting line level feeds. I also just read that wireless lav's receivers output line level (not mic level). I'm really confused. Has the whole world gone line level on me? What happened to the good old days when main ballroom boards output 0db mic level?

Recording at -12db instead of 0db? Line level feeds at -12db instead of mic level feeds at 0db? Wireless receivers that output line level? What's this world coming to?
 
For starters, 0dB is not generally a level cited in terms of mic-level vs. line-level. You have your terms very confused.

Mic-level and line-level refer to the strength of the electrical signal (voltage). Line-level has two basic measures: +4dB for balanced (XLR, 1/4" TRS), and -10dB for unbalanced (RCA, 1/4" TS, and any 3-conductor wired for stereo). Mic-level is typically in the range around -50dB and -60dB.

-12dB vs. 0dB has to do with digital vs. analog reference levels. These are the levels you're watching on your mixer's or recorder's or camera's meters. In the analog world, 0dB is the ideal mark to hit for the balance between cleanest signal saturation and lowest noise floor. There is headroom above 0dB, but much above can start to result in distortion, though analog distortion is sometimes desired in small amounts. In the digital world, however, 0dB is the absolute top and the signal cannot go above (trying to pass 0dB causes clipping which has a very nasty sound to it). So -12dB is the target for dialog, allowing for a bit of headroom before clipping.

Now, as for what feeds what and at which levels...

Most sound consoles output line-level, but some can output mic-level. You need to do your research based on the make/model of mixer to see which you'll be receiving. If there's a house engineer running the board and you've arranged for a feed, it's as simple as asking if the signal is mic or line.

Your mixer, recorder, or camera should be set to accept whichever signal you're being sent. And if you have a device that can only accept mic-level, and the only signal you can get is line-level, you need to get some inline padding to drop the signal level down between the mixer and the recorder.

And wireless receivers? It depends on the make and model, but most systems that are even modestly reputable have selectable line- and mic-level output.
 
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Alex H. said:
And wireless receivers? It depends on the make and model, but most systems that are even modestly reputable have selectable line- and mic-level output.
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Mine are Lectrosonics...and there is no line/mic level output switch that I can find.
 
mhood said:
Mine are Lectrosonics...and there is no line/mic level output switch that I can find.
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That's why I said most instead of all. Sennheiser G2/G3 systems can send out both. And many Lectro systems that I've worked with can. Which model of Lectro are you using? If I recall correctly, some models have a hidden switch inside the 9V battery compartment that selects between mic and line.
 
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Alex H. said:
That's why I said most instead of all. Sennheiser G2/G3 systems can send out both. And many Lecteo systems that I've worked with can. Which model of Lectro are you using? If I recall correctly, some models have a hidden switch inside the 9V battery compartment that selects between mic and line.
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Mine are old ones (VHF) and don't seem to have mic/line switches hidden inside the 9V battery compartment. CR187s...any idea which they are?
 
The CR187 is one of the models with dedicated mic-level output.

This shouldn't be an issue, though, as long as you set the input on your recording device to receive mic-level.
 
Gr8. TYVM Alex. I'm recording with a Canon EOS C100 BTW and there is a mic/line input switch on each channel. I just got burned recently recording a line level board send at mic level...pretty stoopid and pretty horrible audio.
 
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mhood said:
Gr8. TYVM Alex. I'm recording with a Canon EOS C100 BTW and there is a mic/line input switch on each channel. I just got burned recently recording a line level board send at mic level...pretty stoopid and pretty horrible audio.
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And you didn't pick this up when monitoring the output of the camera with headphones during setup and testing?
 
The Lectro 185/7 series receivers operated at mic level... via the XLR, as did the 195 I recall, however in a pinch, it was possible to get (unbalanced) -10dB (or there abouts) out of the HP circuit.
The Lectro 211 and 411 receivers can output +4dB.
The Sennheiser G2/3 EK100 portable receiver can output -10dB.. but adequate gain could be an issue with some +4 inputs.
 
OzGizmo said:
And you didn't pick this up when monitoring the output of the camera with headphones during setup and testing?
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Yes, I heard it but it sounded fine at sound check when they were feeding me a main out set to mic level. Just before the show began, my send was switched to an AUX send at line level. I didn't have a chance to deal with it until the first break. My deafness (lots of years shooting concerts) didn't help matters either. Oh well, sorry performance on my part and lesson learned...
 
I've not come across a theatre, or live sound mixer for years that has mic level output. If people ask for mic level on XLR, the generally get given a line output with the fader very low. If you absolutely need mic level, then carry a DI box and give that to the sound op. The thing that bothers me the most is that very often, we start with decent audio at +4dB, then drop it down by the proper method, or the fudge (as above) to feed into the mic socket of a camera which then adds back extra gain to get it back up to line level. This isn't good for s/n ratio. Most cameras, at least proper cameras with real audio controls have mic/line switches, keeping the gain structure at optimum - line out from the mixer, line in to the camera. Dropping to mic level at the mixer is just bad practice and to be avoided if you have real aims of maintaining sonic quality. Exactly the same problem happens with radio mic receivers that have switchable levels - switching in attenuator is only sensible when your camera ONLY has mic level inputs.

The previous post maintains that the level was mic in rehearsal then switched to aux at line level. This assumes a mixer with a dedicated mic level out (unlikely) and then somebody physically pulling out a plug and sticking it back into an aux output, then doing some routing. I'd bet that what really happened was they used an aux output, did the low fader trick and you said yep - great. Then the show started and when it got a bit lively, they did the very usual thing, lifted the overall levels, and as often happens, they probably ran out of fader travel - it was up full, and still not enough, so they backed the fader off at the same time as turning up the input gain, forgetting that your level would ramp up - as it was probably a pre-fade send (so their fader twiddling didn't mess up your audio). I've done the very same thing myself. The rehearsal level with no screaming teens in the audience seemed adequate, but when the show started I needed more, so a quick tweak of the mic and track preamp levels sorted it for me - the meters on the video output were previously hardly tickling as the psuedo mic level was so low, yet after the input gain tweaks, the video output had a respectable level on it. No red lights to jog my memory - BUT the out to the camera is far too hot. Sound ops use their ears and won't think about a listen to the video out, it's not their role - they may notice when things are running, but usually it's only discovered when the video person runs up and waves at them!
 
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paulears said:
The previous post maintains that the level was mic in rehearsal then switched to aux at line level. This assumes a mixer with a dedicated mic level out (unlikely) and then somebody physically pulling out a plug and sticking it back into an aux output, then doing some routing. I'd bet that what really happened was they used an aux output, did the low fader trick and you said yep - great. Then the show started and when it got a bit lively, they did the very usual thing, lifted the overall levels, and as often happens, they probably ran out of fader travel - it was up full, and still not enough, so they backed the fader off at the same time as turning up the input gain, forgetting that your level would ramp up - as it was probably a pre-fade send (so their fader twiddling didn't mess up your audio). I've done the very same thing myself. The rehearsal level with no screaming teens in the audience seemed adequate, but when the show started I needed more, so a quick tweak of the mic and track preamp levels sorted it for me - the meters on the video output were previously hardly tickling as the psuedo mic level was so low, yet after the input gain tweaks, the video output had a respectable level on it. No red lights to jog my memory - BUT the out to the camera is far too hot. Sound ops use their ears and won't think about a listen to the video out, it's not their role - they may notice when things are running, but usually it's only discovered when the video person runs up and waves at them!
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It was a Mackie board with switchable mains but what you just described sounds totally plausible. I was that vidiot running up and waving at them at the break. I think you nailed it...thanks.
 
mhood said:
It seems I've been assuming mic level feeds from boards at conventions and I've been getting line level feeds. I also just read that wireless lav's receivers output line level (not mic level). I'm really confused. Has the whole world gone line level on me? What happened to the good old days when main ballroom boards output 0db mic level?

Recording at -12db instead of 0db? Line level feeds at -12db instead of mic level feeds at 0db? Wireless receivers that output line level? What's this world coming to?
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I believe there's a confusion here between 0 dBVU and -12 dBFS.

Fran
 
Fran Guidry said:
I believe there's a confusion here between 0 dBVU and -12 dBFS.

Fran
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That would be a good bet, Fran. :-)

I have a VU meter on my C100 and am now confused to the point that I have no idea what to set my levels to. The last thing I recorded, I looked at the VUs on the board that was feeding me my (line level for sure) signal and one green light was flashing at peaks. Nothing anywhere near 0 on the board. And when I'm compressing finals for internet delivery, I've been normalizing to -0.1 in Audition but am now hearing folks say I should be no more than -6 and some folks have told me -12. I can't turn a -12 master up loud enough to hear it via my PC's headphone feed with my abused old ears. Yea, I'm confused about a lot of things.
 
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Fran Guidry said:
I believe there's a confusion here between 0 dBVU and -12 dBFS.
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That's basically what I addressed earlier, though I didn't include the scales.

So, to recap/clarify:

Line-level and mic-level refer to dBu (or dBv), which are +4dBu for balanced line, -10dBu for unbalanced line, and approx. -50dBu for mic. These are the measures of the voltage for the electrical signal passing through the cables and have nothing to do with the meters on your camera or recorder.

With analog mixing and recording, 0dBVU is the central reference point on the meters, and there is headroom above it. It is also the level at which is found the optimal signal-to-noise ratio.

With digital audio, 0dB is the absolute top on the meter, thus being named Full Scale (dBFS). -12dBFS is one target for dialog average during recording, though really -10dB is much more common. -12dB is often the marked reference point for pro-sumer cameras, especially those that don't actually have any numbers on the meter scales.
 
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Alex H. said:
With digital audio, 0dB is the absolute top on the meter, thus being named Full Scale (dBFS). -12dBFS is one target for dialog average during recording, though really -10dB is much more common. -12dB is often the marked reference point for pro-sumer cameras, especially those that don't actually have any numbers on the meter scales.
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Thanks again Alex for the gr8 information. Any tips about making a master for internet? Is my tired old procedure of hard limiting (with no boost) the few tall peaks, then normalizing to -0.1dB(FS I guess) appropriate or should I be normalizing to -3 or -6? I do want to keep up with CD loudness on the internet.
 
This is terrible when the people at the sound board change the signal at the last minute.

Entirely defeats the purpose of doing a sound check. I often do recordings of stage performances where the sound people change from one night to the next at a particular venue.

I find it convenient to take a photo of where they plug me in so that I can get the same port the next night.

I ask what the settings are and write these down in a book.
 
kwkeirstead said:
This is terrible when the people at the sound board change the signal at the last minute.

Entirely defeats the purpose of doing a sound check. I often do recordings of stage performances where the sound people change from one night to the next at a particular venue.

I find it convenient to take a photo of where they plug me in so that I can get the same port the next night.

I ask what the settings are and write these down in a book.
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But everyone needs to remember, the front-of-house sound engineer's job is to be completely focused on providing a mix for the audience and any feeds they might provide you are done purely as a courtesy. IMHO, one needs to plan the shoot assuming you won't get any sort of usable feed at all from the house sound system and arrive on site with the necessary gear and skills to mic and mix the show yourself for a proper professional recording.
 
Steve House said:
But everyone needs to remember, the front-of-house sound engineer's job is to be completely focused on providing a mix for the audience and any feeds they might provide you are done purely as a courtesy. IMHO, one needs to plan the shoot assuming you won't get any sort of usable feed at all from the house sound system and arrive on site with the necessary gear and skills to mic and mix the show yourself for a proper professional recording.
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My company has already paid for the house sound...the feed to my camera is not a courtesy...it is a paid service just like the many wireless lavs and hand helds. It makes no sense at all for me to show up with a duplicate audio system and a sound engineer just to provide a feed to my C100 in the back of the ballroom. It's hard enough to mic GMs and VPs with one lav...I don't want to think about trying to get two on them.

But you did mention the reason I try to get a main feed...if they just keep the sliders the same on the mains, what they are hearing on house PA is what is being fed to my camera. I really don't trust AUX sends for the very reason you gave.
 
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