LINE LEVEL VS MIC LEVEL (Impedance issues!!!!!) Mic Level = (2 millivolts) Line Level (pro) = +4db (1.23 volts) Line Level (consumer) = -10db. (.316 volts) Audio in the field usually comes in one of two flavors - MIC LEVEL OR - LINE LEVEL (pro)
If you deal with them incorrectly audio will be very distorted or barely audible. Mic level audio is exactly what it sounds like... it's audio directly from the microphone with no amplifiers in between the microphone and your camera. When you plug a microphone into your camera's mic jack this is the flavor of audio you're getting. So normally there's no problem with this type of audio. Line level audio is audio that has been AMPLIFIED. Typical sources of this kind of audio are feeds from public address systems or microphone mixers. You'll run into line level audio if you are plugged into an audio feed at an event.
- LINE LEVEL into MIC JACK = DISTORTION If you feed line level audio directly into your camera's mic jack you'll end up with distortion and your audio will sound like it was recorded next to a jet engine. If you have an audio meter on your camera, very often (but not always) the audio level will be pushed all the way to the right. After audio is recorded like this, there is NO WAY to fix it. Many cameras and Microphone adapter boxes like the Beachteks have a mic/line switch. Line level feed flip the switch to "line, if microphone directly switch to "mic". - MIC LEVEL into LINE INPUT = QUIET If you leave switch in the wrong positionv(plug a microphone directly into the adaptor box and the switch is set to "line" you ll get barely audible audio. You can boost the level of this audio when I edit if you like lots of hiss or other noise. Always monitor at end of audio chain/signal path! LINE LEVEL Line level is a term used to denote the strength of an audio signal used to transmit analog sound between audio components such as CD and DVD players, TVs, audio amplifiers, and mixing consoles, and sometimes MP3 players. In contrast to line level, there are weaker audio signals, such as those from microphones and instrument pickups, and stronger signals, such as those used to drive headphones and loudspeakers. The strength of the various signals does
not necessarily correlate with the output voltage of a device; it also depends on the source's output impedance, or the amount of current available to drive different loads. MIC LEVEL The level (or voltage) of signal generated by a microphone. Typically around 2 millivolts. Compare this with the two normal line levels (1.23 volts and.316 volts), and it becomes apparent just how much amplification is going on in a microphone preamp, and why it is essential that preamps be of as high quality as possible! WHY USE A MIXER in PRODUCTION AUDIO? 1) SIMPLE ANSWER CONTROL!!!! high level of desired signal while minimizing the noise floor, which is commonly referred to as a good signal-tonoise ratio.
2) PREAMPS ON MIXERS ARE BETTER!!! quality that those on a camera. The preamps take the signal from microphone-level to linelevel. 3) PREAMPS TAKE THE SIGNAL FROM MICROPHONE- LEVEL TO LINE-LEVEL. We would prefer to stay at line level; again because the signal-to-noise ratio of line-level is substantially better than mic-level There are two basic levels of impedance and variations within each that we need to know. They are Mic Level and Line Level. Mic Level When an input is at Microphone level, it is often said to be either High Impedance (HiZ) or Low Impedance (LoZ). Typically, high impedance Mics are those that are connected to cables with a 1/4" unbalanced output, though keep in mind I said typically. Usually these are cheap mics designed to work with guitar amplifiers, pocket recorders and toys. Most electric guitars and basses are also outputting at high impedance. Sometimes a high impedance input is called "instrument level". If you plug one of these hi impedance sources into a line level input what happens? The source is very weak, and as you add gain to bring it up to useable level, you find you are adding a lot of noise.
Low impedance microphones would be even more faint plugged into a line level device. They require a preamplifier designed to work at extremely low signal levels and be able to boost these weak signal cleanly. What happens when you take a line level synth and plug it into a low impedance mic preamp? It overdrives the signal past the breaking point of the circuit and extreme distortion can be heard. Line Level Much of our gear is said to be at Line level. Audio interfaces, mixers, effects boxes, synths, keyboard workstations, preamp outputs are generally all at line level. However, there are 2 standards, often referred to as +4 and -10. It used to be, over a decade ago, that "professional" gear was set to +4 and "consumer" gear was set to -10. This does not hold up as well as it did. Many pieces of consumer and professional gear today can be switched from -10 to +4 via a switch in the piece's firmware. But it is not always the case. And this is why you need to be careful. When you plug a +4 output into a -10 input its very easy to overload the input and bring in noise. Likewise a -10 output into a +4 input seems a little faint, which makes one want to boost the volume and add noise that way. Often, you can make a mismatch work, but you will know its not ideal and that the integrity of the signal was blemished. The practical application of this knowledge is as follows; if you know you have consumer -10 gear you want to use, but
you also want to use better +4 gear, make sure your audio interface or mixer can handle both +4 and -10. A lot of DJ mixers and DJ audio interfaces will only take -10 impedance at line level. Unfortunately for the industry, DJ rigs tend to fall back on a standard of RCA cables at -10 impedance and unbalanced gear, which can be a problem rejecting ground loops, using long cables and driving a loud and clean signal to the amp and speakers. Common Impedance Issues and their solutions Perhaps the most common mismatch is when someone plugs a guitar or other instrument level device direct into a mixer. Mixers typically only have LoZ and line level inputs, so plugging in the HiZ guitar output is a bad recipe. In this case the direct box is often used. The Direct box or DI box as it is sometimes called changes the unbalanced HiZ signal to a balanced LoZ signal. This allows 3 things to happen. 1) the impedance is matched and gain can be applied cleanly to the signal. 2) longer cable lengths can be used. 3) the circuit resists ground loops (hum). There may even be a "ground lift" on some DI boxes that will kill any ground loop that has formed. The audio result using a DI box is often clearly superior. Some indications you may have an impedance mismatch are when you say: "I turned the channel up all the way but I can barely hear the track" "When I plugged in the outboard gear, it was way louder than any other piece and had hums and buzzes and radio stations leaking in"