Line/Mic level

[mofo22]

What's the difference between mic level and line level?
Someone asked me if my microphone is Mic or Line level when i plug it into the external MIC connector on my camcorder. I don't know!

[Cornucopia]

There are more particulars and exceptions to the general rule, but to make it short and sweet:

1. Line Level--There are 2 kinds, Pro and Consumer. Pro is +4dBV (~ 1 Volt) and Consumer is -10dBu. Difference of 11-14dB. The way to tell the difference (physically) is that Consumer connectors are almost always RCA phono jacks, Pro connectors are mostly Canon XLR jacks.

2. Mic Level--There is no 1 mic level! All models vary in terms of sensitivity and output. The majority of them, however, hover in the range of -40...-60 dB. This means that they're ~50dB quieter than Line level signals. Big difference. Mic connectors also come in Pro versions--XLR or 1/4" phone jacks, or Consumer versions--1/4" or 1/8" phone jacks. These have less to do with level than to do with impedance and whether the signal is electrically balanced or not (balanced=hum and noise cancelling). As you can probably guess, Pro is balanced, Consumer isn't.

How to tell if Mics actually are at mic level?
Usually, they are mic level unless they come with a built-in preamp. This would, of course, require a power supply like a battery.

Good rule of thumb: If a mic requires phantom power (12 or 48 volts), it's balanced and mic level.

*Just to gum up the works for you, there is an additional level--"Guitar" or "Instrument" level. This is ~ -20...-30dB and usually is connected via 1/4" unbalanced phone jacks. Some mics do fall into this range.

Always try to match the mic and level with the recording device.
If you have it too hot: Distortion
If you have it too quiet: Extra Noise (Hiss & Hum & Interference)
Me, I'd rather it be too quiet than be distorted so I tend to set up equipment conservatively (when I don't know the levels or have the needed adapters).

HTH,
Scott

[ktton]

I have a Creative usb sound that has a stereo rca line in connector(red and white rca connector) and a small mic connector as you would see in most sound cards. I am trying to convert my old cassete tapes to mp3 and I am wondering if I should use mic connector since it is more quiet and less noise.

[dphirschler]

Use the line-in. Chances are the mic-in is mono. Also, the line-in can handle a heavier load.


Darryl

[ktton]

Use the line-in. Chances are the mic-in is mono. Also, the line-in can handle a heavier load.


Darryl

Thanks Darry.

[mofo22]

Cornucopia -- thanks for the explanation. So basically the way i understand it, the difference is in the -db rating, and depending on your application one type of microphone (mic or line level) works better than the other.
Is it safe to assume (rule of thumb?) that if you need to record in a low-noise environment, you'd want to use a Line-level microphone because they are more sensible, and in a noisy stadium during a ball game you'd use the Mic-level microphone to minimize overall noise?

[Cornucopia]

Sorry, I'm gonna have to "get technical on your buttocks":

Mics differ by a number of factors--
1. Frequency response (fairly obvious)
2. Phase and/or amplitude linearity (we'll skip that one for now)
3. Self-noise (how much internal noise does the mike itself generate)
4. Sensitivity (how quiet can the source be and still get a signal)
5. Gain (how much is that internal signal amplified to "mic" or "line" level)
6. Maximum sound power level (how loud can a sound be before it cruds the signal)
7. More practical concerns, like pickup pattern (all directions, some, or one)
8. Type of powering needed (dynamic--needs no power, condenser or ribbon--needs phantom power, electret condenser--needs battery).


The level is really a combination of factors 3,4,and 5. Balanced or not is more about the connection & cabling.

Sorry, your rule of thumb is flawed...
In a "low noise/studio" environment, I'd want a mic that has very low self-noise, and was fairly "sensitive", even if the gain (and subsequent output level) wasn't the highest.
In a sporting event, I wouldn't even worry about either one of these factors. What I would focus on would be "pickup pattern" (#7) and max SPL (#6).
In all events, when I work, I vastly prefer a balanced condenser mic, with mic level output, with switch-selectable pickup pattern and wide frequency response, but with switch-selectable filtering. Of course, I almost always carry a portable/field mixer that includes mic preamps (which do the gain converting from mic-to-line level) and then I output line level to wherever it's supposed to go (usually a vidcam or recorder deck). This way I get lots of control over the quality of the final signal.

Best thing to do is read the specs on your camera and find out what mics that others (successfully) using the same camera are incorporating.

HTH (and didn't confuse you further)
Scott

[mofo22]

Ok, let's look at this particular microphone that i have here. I got the specs from the manufacturer:

Microphone Type:
Uni-Directional Condenser

Frequency Response:
200-20KHz

Impedance:
Low Impedance

Sensitivity:
-62dB±3dB at 1KHz

Output Connection:
Ø3.5mm Stereo Plug

So, if i understood correctly, the fact that this mic is rated at -62dB would mean it's at Mic level. When i plug this mic into a portable .wav recording device that i have, it works. That must mean the .wav recorder is Mic level. When i plug it into a camcorder's MIC connector, it doesn't work. SO... i take it the external MIC connector requires the use of a line-level microphone, or the use of a pre-amp and mic-level microphone combo.

Sorry for repeating myself over, but i need to dumb it down a shade so i can keep track.
I have more questions but please correct me before i get too far off!

[Cornucopia]

You're almost there...


The specs state that it is low impedance and of condenser (capacitor) construction. Therefore, it's probably NOT an electret condenser which uses its own battery for power (remember-condensers require power). Therefore, my guess is that your wav recording device, in addition to accepting the (correctly guessed) mic level, is also supplying phantom power to the mic. The camcorder device, evidently, doesn't.

Of course, you could be right that the camcorder accepts only line level, but I find that extremely unlikely. Most camcorders ONLY accept mic level, unless they either come with their own custom "line-level" configured mic, or they are pro camcorders that are switchable.

As a general rule, computer sound cards don't provide phantom power to microphones via the usual microphone input jack on their sound cards, so you could test the mic to see if it works at all with your computer sound card...

HTH,
Scott

[mofo22]

I tested the mic with my pc sound card but it doesn't seem to work either. I'm trying to understand what this microphone is good for? Being a condenser type, it requires power, but it doesn't have a battery compartment. So whoever buys such a microphone is just going to have to hope that it works with the recording device that they have in mind? Sorry i'm not this type of consumer. No big deal anyways, as this is a very low quality unit made-in-china and didn't cost much to try.

[mofo22]

One last thing: How do you match the mic level with your recording device? Like for example, say i wanted to use a microphone in the MIC jack of my camcorder. What would be the steps involved?

[Cornucopia]

Here is the path the signal takes:

Sound --> Microphone Capsule --> PreAmp --> Line Level Device

(Unless they're already Line Level)

If your Device isn't set up to receive Mic Level input (that is--it includes its own preamp), then you need to add a preamp between the mic and the device.

As I said before, the great majority of camcorders accept mic level input. This means that they have their own built-in preamps attached to that connection.

You can buy external portable preamp boxes (which may also supply the phantom power needed by condenser mics) at a number of places. I usually get such things at Markertek.

Otherwise, get a dynamic (Moving magnet/coil) microphone. It doesn't need power. Most people prefer the flat, extended frequency response of condenser mics for recording, using dynamic mics for live stuff and sound re-inforcement, but this isn't a rule set in stone. There is a lot of overlap.

BTW, Macintosh has used in the past a style of microphone that needs power (and also provides more of a line level), and their connector supplies it, but their connector was a kind of non-standard 1/8", IIRC. Maybe this mic is meant for that type of system.

HTH,
Scott

[mofo22]

Ok thanks for the clarification. Does the pre-amp thing work both ways? Meaning you could also have a line-level mic and would need a pre-amp to make it work down to mic-level, as well as having a mic-level microphone and using a pre-amp to make it work with line-level devices?

[Cornucopia]

Usually, no.

You can, of course, buy or make a device that is just a glorified volume control (includes impedance matching, etc) to lower the output from line-to-mic level. That's mainly all it needs to do.

BTW--As an example of price, I have a couple of boxes: all they do are convert from Pro Line level XLR jacks to Consumer Line level RCA, and vice versa (2 pairs). The boxes cost $189 each. They're quite high quality and can be tweaked to get the levels exactly right, but would still be a chunk of change for the average consumer--just for a converter box.
Making your own, if that's possible for you, is the cheaper way to go.

Good luck,

Scott

[mofo22]

Well, now that i am a little more up-to-date on the various types of mics and the terminology, feel free to respond to my latest thread in the Audio forum, about choosing the right microphone for my application.
I appreciate all your help.

[mofo22]

One last thing. I just managed to make this mic work in the mic jack of the camcorder. It seems that when you try to record off the AV/IN connection, in VCR mode on the camcorder, the MIC jack becomes obsolete. I can only make the mic work when the camcorder is in camera mode. So i guess the only way to do it is to get an adapter 1/8" to connect the mic and RCA on the other end to connect to the AV/IN connection instead of using the mic connection.