GENERAL MICROPHONE QUESTIONS
Question: What Is Phantom Power:
Answer: Phantom power is a method of powering a condenser microphone from the connected audio component. If a component provides phantom power, it should be listed in the features section of the manual.
Question: What is impedance and why is impedance matching for microphones necessary?
Answer: Impedance is the electronic measurement of a device's resistance to the flow of an AC signal, such as audio. It is similar to resistance, which indicates a device's resistance to the flow of a DC signal. Both impedance and resistance are measured in ohms.
When referring to microphones, low impedance is less than 600 ohms, medium impedance is 600 ohms to 10,000 ohms, and high impedance is greater than 10,000 ohms."Low impedance" inputs on audio mixers usually have an impedance between 1000 and 2000 ohms, and can be used with both low and medium impedance microphones. A low impedance microphone may always be connected to an input with a higher impedance. However, the microphone may not always be able to provide enough signal strength to properly drive the mixer's audio input. For the best signal strength, you should always compare the microphone's output level (or sensitivity) to the required mixer input level.
High impedance microphones should be connected to high impedance inputs for the best performance. When a high impedance microphone is connected to a low impedance input, there will be some loss of the microphone signal.
Question: What is the difference between a balanced and an unbalanced line?
Answer: A balanced (or directionally balanced) line is a circuit that uses two conductors and a shield for connection, in which first conductor carries the standard audio signal and the second conductor carriers an inverted signal, which is re-inverted and added to the first signal at the destination. This inversion also inverts any line noise which is picked up by the cable, so that the line noise is cancelled out. Compare to the illustration of an unbalanced line, such as a mono microphone cable, shown below.
Question: Can I use a telephone headset as a microphone headset with my computer?
Answer: Yes. You will need to use an 1/8" (3.5mm) Stereo Jack to Two 1/8" Plugs and adapter to convert the 1/8" stereo plug for microphone and earphone to two 1/8" mono plugs. One 1/8" mono plug will connect to the speaker output of the computer and the other 1/8" mono plug will connect to the microphone input on the computer.
For those headsets that use 3/32" (2.5 mm), you would also need to use a 3/32" Stereo Jack to 1/8" Stereo Plug and adapter to convert the 3/32" plug to a 1/8" stereo plug; then you would use the adapter above.
Question: Why does one wireless microphone cut out when two microphones are used close to each other?
Answer: They will do this if the microphones are on the same channel or adjacent channels (such as channels A and B). We recommend that microphones that are to be used at the same time be at least 2 channels away from each other.
Question: What is the maximum distance between the microphone and the receiver?
Answer: We do not test the distance as there are too many variables involved.
Question: Do 170 MHz wireless microphone and PA systems require an FCC license?
Answer: Yes. You will need to contact the FCC directly for information on license applications and fees.
Question: Do 49 MHz wireless microphone and PA systems require an FCC license?
Answer: No, they do not.
Question: When I record using my microphone I hear "pops" and 'hissing" when listening to the playback. What can I do to prevent this?
Answer: Popping noises that are heard on the playback after recording using a microphone are usually vocally induced distortions due to hard consonants like "b" or "t". The hissing noise known as sibilance is also usually vocally induced and caused by "s" sounds. The use of a microphone windscreen will reduce or prevent this.
Question: What is the difference between dynamic and condenser microphones? The terms dynamic and condenser refer to the two most common forms of professional microphones. They refer to the method in which the microphone generates an electrical signal.
Answer: The dynamic (moving-coil) microphone operates by electromagnetic induction to generate an output signal voltage. It is like a miniature loudspeaker working in reverse. The diaphragm is attached to a coil of fine wire. The coil is mounted in the air gap of the magnet such that it is free to move back and forth within the gap. When the sound wave strikes the diaphragm, the diaphragm vibrates in response. The coil attached to the diaphragm moves back and forth in the field of the magnet. As the coil moves through the lines of magnetic force in the gap, a small electrical current is induced in the wire. The magnitude and direction of that current is directly related to the motion of the coil, and the current then is an electrical representation of the sound wave. One of the major drawbacks of the dynamic microphone relates to the mass of its moving coil. Due to this mass, the dynamic mic has a relatively poor transient response, and is less sensitive on the average than the condenser mic. The other major microphone type is the condenser. The diaphragm of a condenser microphone is a very thin plastic film, coated on one side with gold or nickel, and mounted very close to a conductive stationary back plate. A polarizing voltage is applied to the diaphragm by an external power supply (battery or phantom power) or by the charge on an electret material in the diaphragm or on the backplate charging it with a fixed static voltage. The diaphragm and back plate, separated by a small volume of air, form an electrical component called a capacitor (or condenser). The capacitance between these two plates varies as the freely suspended diaphragm is displaced by the sound wave. When the diaphragm vibrates in response to a sound, it moves closer to and farther away from the back plate. As it does so, the electrical charge that it induces in the back plate changes proportionally. The fluctuating voltage on the back plate is therefore an electrical representation of the diaphragm motion.
Because the diaphragm of the condenser is not loaded down with the mass of a coil, it can respond very quickly to transients. Also, the condenser capsule can be made very small. Condensers generally have excellent sonic characteristics, and are widely used in high-quality professional microphones in sound reinforcement, measurement and recording.
Question: Why Can't I Get Enough Volume From My Mic?
Answer: Some users have reported problems getting enough level into their minidisc recorders or small DAT recorders. Make sure you are manually setting the record level, the automatic gain control rarely sounds good. Many of the little Sony minidiscs have the irritating feature of only allowing level adjustments while the deck is in pause, so you have to pick a level and stick with it. If you have the record input level turned up all the way (this adjustment may be a few levels down in menus, it is NOT the volume + and - on the top of the deck: that's the headphone volume) and you still aren't getting enough level, you have a few options. Make sure you have a good quality cable, not a pieced-together series of adapters and mis-matched connectors. If you're using a dynamic mic, you may want to try a condenser instead, they almost always have a louder output. Condenser mics require phantom power, so be sure to pick one that can use an internal battery, unless you have an external source. A consumer minidisc recorder's "plug-in power " will not power a pro mic. Another volume-increasing tactic is to use an impedance transformer. The 1/8 " connectors on small minidisc machines are high impedance, while pro mics with XLR connectors are almost always low impedance. You actually don't want the impedances to match exactly, but raising the impedance a bit can give you a few more dB of volume. A cable like the A96F from Shure will do both things: convert your XLR to a mini and raise the impedance enough to give a bit more volume.
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