Sorting through the definitions of mic and line level can be confusing because there are varied definitions of the terms among audio engineers and manufacturers.
Line level refers to the typical level (strength or amplitude) of the audio signal from tape decks, CD players, VCR's, mixers, signal processing equipment and other consumer and professional audio gear. There are two types of line level: consumer and professional. Consumer level line level is generally thought of as a signal whose level is at -10 dBV (0.316). CD players and VCR's are examples of consumer line level equipment. Professional line level is generally thought of as a signal whose level is at +4 dBu (1.23 volts or significantly higher). Signal-processing equipment and professional mixing consoles are examples of professional line level equipment
Mic level is the typical level (strength) of a microphone signal. Mic level is generally significantly lower than line level, although that is not always the case. Depending upon the microphone and the sound pressure level (SPL) injected into the microphone, the level may range from a few microvolts for a whisper, up to several volts for a microphone in front of a guitar cabinet.
The Open Circuit Sensitivity specification tells how much electrical output a microphone produces in response to certain sound pressure input. If two microphones are subject to the same sound pressure level and one puts out a stronger signal (higher voltage), that microphone is said to have higher sensitivity. However, keep in mind that a higher sensitivity rating does not necessarily make one microphone better than another microphone with a lower sensitivity rating.
At Audio-Technica, we test Open Circuit Sensitivity by placing the microphone in a sound field with a frequency of 1 kHz at a sound pressure level of 1 Pascal (1 Pa, which is equivalent to 94 dB SPL); then we measure the voltage at the microphone's output terminals.
A note about decibels: In the audio world, a decibel (dB) is a mathematical shorthand that is used to represent how two different audio levels compare to each other. It is a logarithmic ratio (logarithms use powers of 10 to make large numbers smaller and easier to work with). Since decibels are about comparisons (comparing volts with volts, or watts with watts, for instance), a reference number is included with the decibel (often in the suffix). For example, dBV = dB referenced to 1 Volt. One decibel (1 dB) is generally thought of as the smallest change human hearing can perceive.
Back to Open Circuit Sensitivity. Our AE3000 cardioid condenser microphone has an Open Circuit Sensitivity of -43 dB (7.0 mV) re 1V at 1Pa. This specification means that a 1 kHz tone played at a sound pressure level of 1 Pascal produces a voltage of 7.0 milivolts. Please note we state the output voltage in decibels referenced to 1 volt (dB re 1V) by using the following formula 20Log(0.007)= -43.098 dBV.
Feedback occurs when the amplified sound from any loudspeaker reenters the sound system through a microphone and is amplified again and again, causing a loop. To avoid or lessen the likelihood of feedback, try some of these steps:
- Keep the microphone behind the loudspeakers to minimize the sound that can reenter the microphone. If the microphone is in front of the speakers, then feedback is nearly guaranteed.
- Use a microphone with a unidirectional (cardioid) polar pattern. A cardioid microphone has its maximum rejection at the rear of the mic. Keep monitors or loudspeakers in this area of maximum rejection.
- Place the microphone close to the sound source. When you reduce the distance between the sound source and the microphone by half, you double the sound pressure level at the microphone. This increases your gain before feedback (i.e., it allows your sound system to produce more SPL before reaching a level that would induce feedback).
- Use an equalizer or feedback eliminator to dampen the frequencies where feedback is occuring.
A restring kit is available through Audio-Technica U.S. (email firstname.lastname@example.org
). For instructions on how to restring the AT8410a shock mount, click here
. For instructions on how to restring the AT8441 and AT8449 shock mounts, click here
The very first thing to check is your USB cable to make sure it is working properly. You may try swapping the cable with a known working cable to see if this resolves the problem.
If the cable is in proper working condition, there may be an issue with your computer's USB Audio Codec driver. Computer systems communicate with the turntable (and other USB audio devices) by using the USB Audio Codec driver. If your computer does not recognize the turntable, one of three possible conditions may exist:
1) Your computer is missing the USB Audio Codec driver.
2) Your USB Audio Codec driver is corrupted.
3) Your computer does not support a USB Audio Codec driver.
If your computer's USB Audio Codec driver is missing or corrupted, you will need to contact Microsoft Technical Support at: http://support.microsoft.com/
You will need to contact the manufacturer or place of purchase to determine if your computer system supports a USB Audio Codec driver.
Connecting a wireless system directly to your home stereo system is not recommended, because the voltage provided by the wireless system may not be strong enough to drive the input on your home stereo system. Most home stereo systems' line level RCA inputs require a minimum voltage of 300 mV, while the balanced and unbalanced outputs on all Audio-Technica wireless systems are providing much less. We recommend that you connect the wireless system to an external mixer and then connect the mixer to the stereo. There are many mixers, including DJ mixers, that work well for this application; some microphone pre-amps are also effective.
In some home stereo systems, voltage provided by the wireless system may be enough to drive the input. However, you may not be satisfied with the output level; you will probably want to connect the wireless system to an external mixer and then connect the mixer to the stereo to boost the output.
If you decide to connect your wireless system directly to your home stereo system, there are many things to consider:
- The first thing to consider is the output connector from the wireless system.
- This is usually a 1/4 inch unbalanced output, an XLR balanced mic level output, 1/4 inch balanced output or 1/8 inch unbalanced output. Some receivers have a combination of output connectors.
- Generally the mic level output is not strong enough to drive the input of a home stereo system.
- You will probably need an adapter from 1/4 inch or 1/8 inch to whatever type input connector is on your stereo system, usually 2 RCA connectors.
- You will need a "Y" adapter to send the mono signal from the wireless receiver to both the left and right inputs of your home stereo system. Otherwise the sound will only be present on either the right or left channels of your home stereo system.
- The second thing to consider is where to connect the wireless system. Most systems have auxiliary inputs that you may use. Just make sure that the input is a line level input. Consult your home stereo system users manual for instructions on how to connect external devices
- Also, you must determine if you want to use other devices connected to the home stereo at the same time as the wireless system. For example, singing through the wireless microphone while playing a CD or tape as accompaniment. Most home stereo systems will allow only one device to be played at a time. If this is a requirement you will need to connect both devices to an external mixer and then connect the mixer to the stereo. Again there are many mixers, including DJ mixers that will work well for this application.
Because of the many advantages of wireless microphones, simultaneous use of four, six or even more systems at a location is quite common. Often, one or two wireless microphones are used initially, but as the benefits of wireless operation become more apparent, the need for additional systems develops. The freedom, flexibility and enhanced presentation made possible by wireless microphones are almost irresistible, and it is natural for their use to increase over time.
However, as the number of wireless systems in operation at a location increases, so does the potential for problems. Unless some simple preventative measures are taken, it may eventually become difficult to achieve reliable and trouble-free operation. In particular, interference is a common problem when several systems are used unless the wireless frequencies are carefully chosen. Other problems such as reduced range, unexpected signal losses and erratic squelch operation can also occur.
The most common problem with using multiple wireless systems is interference, and the most common cause of interference is the use of wireless frequencies that are not compatible with each other. Wireless frequencies must be selected to work with local TV stations and with all other wireless systems in the area. Otherwise, serious interference problems are highly likely, especially when several wireless systems are used simultaneously.
Other types of interference can also occur when using multiple wireless systems. Interference can result from using too many wireless systems in a particular frequency range, or from using wireless frequencies that are too close to each other. Another interference problem can occur when the antennas for two receivers touch or are parallel and close together. In these situations, a small amount of radio energy can leak from one receiver to the next, causing harmful interference under certain conditions. A similar problem can occur when receivers are stacked directly on top of each other. As a practical matter, the need to keep receiver antennas well separated makes it very difficult to use more than a few units on a tabletop. Audio cables and power cords also tend to compound the problem, especially if more than one row of receivers is needed.
As the number of wireless systems at a location increases, so does the amount of effort required to ensure reliable and trouble-free operation. It is also necessary to begin taking into account the arrangement and mounting of equipment, the positioning of antennas and other factors that can safely be ignored when only one or two systems are being used. Although there is no hard and fast dividing line, once more than four or five wireless systems are involved a new approach is probably appropriate.
Frequency selection is the critical first step in achieving success with multiple wireless systems. Unless all the frequencies used are compatible, the chances of satisfactory operation are very low. The TV channels in the area of use must also be considered when selecting frequencies. It is common for a system to work well in one city and perform very poorly in another city because the local TV channels are different. For this reason, it is essential that TV channel data be available for all locations where the system will be used.
The power module attached to some condenser microphones provides several important functions. First, it converts the 11 – 52 VDC phantom power into a smaller DC bias voltage used to power the FET impedance matching circuit inside the microphone. Also, it provides low frequency roll off, supplies battery power if phantom power is not available, converts the signal to the proper impedance and balances the output. The power module is a necessary component.
This is referred to as a low-cut filter, bass roll off, low-requency roll off or a high-pass filter. This switch enables internal circuitry that filters frequencies from the audio signal below the specified frequency. Enabling this switch can help filter out sounds in the low frequency range such as HVAC rumbles and certain wind sounds (in an outdoor application). Please note this filter does not completely cut all low frequencies. The straight line means that nothing is being filtered; the bent line means the filters are enabled.
There are many factors to consider when connecting a professional microphone to a computer. The two most important are:
- What type of interface will be used to connect the microphone to the computer?
- What type of microphone will be used and what are the specifications for that mic?
Interfaces will generally fall into one of two categories, internal (sound card) or external. The external interfaces are specifically designed for connecting professional microphones and / or instruments to a computer system and are by far the easiest to use. These external devices will connect to the computer via a USB port, Firewire or an internal card on the PC designed for this purpose. The external interfaces usually provide other features such as pre-amps and phantom power. Audio-Technica does not manufacture an external interface. For this discussion external interfaces will not be discussed in detail.
The most common type of interface found on the computer is the internal sound card. Although there are many brands and configurations of sound cards, most will have a 3.5 mm (1/8 inch) mic input and possibly a 3.5 mm line input. The line input is designed for use with CD players, tape decks and other consumer audio devices; it is not suitable for connecting a microphone. The 3.5 mm mic input is usually a "TRS" (Tip, Ring and Sleeve) sometimes called a stereo connector, although sometimes this may be a "mono" connector that has only the "Tip and "Sleeve". In both configurations the "Tip" will carry the audio signal and the "Sleeve" is the ground connection. On the "TRS" connection the "Ring" portion is often used to carry a low DC voltage (bias voltage) for powering a computer microphone. Consult your sound card documentation or computer manufacturer to determine the types and configuration of connector and the bias voltage that is provided.
Most microphones can be placed in to one of two categories: dynamic and condenser. See our Brief Guide to Microphones for a detailed description of these two microphone types; for our discussion here, it is enough to remember that a condenser microphone needs power and a dynamic does not. Because of the power requirements, connecting a condenser microphone to a sound card is much more difficult than connecting a dynamic microphone. Some condenser microphones need phantom power to provide power for a small internal pre-amplifier; other condenser mics offer the option of using either an internal battery or phantom power. Phantom power is in the range of 9V DC to 52V DC and is not available on a typical sound card. Other microphones need bias voltage -- usually between 3V DC and 9V DC-- to power internal circuitry. Some internal sound cards are capable of providing bias voltage; to learn more about this option, consult your sound card owner's manual or contact the manufacturer for instructions.
- Signal level
Professional microphones produce a very weak electrical signal, usually much less than is needed by the audio input of most sound cards. This will manifest itself in a very low level when recording the microphone or low volume when outputting the microphone to a speaker. In order to compensate for discrepancy in signal, either the signal for the microphone must be boosted with an external device such as a pre-amplifier, or the sensitivity of the sound card can be increased. This is accomplished by adjusting the gain via the computer's software programs. Again, consult your computer or sound card owner's manual or contact the manufacturer for instructions.
- Impedance - Impedance is the total passive opposition offered to the flow of electric current and is measured in "ohms". Professional microphones usually have an output impedance of 600 ohms or less; most sound card have a higher input impedance (up to 2000 ohms). The amount of signal transferred from the microphone to the sound card can be greatly reduced if the output impedance of the microphone is greater than input impedance of the sound card. This is usually not the case, but consult your sound card documentation and the microphone specifications to make sure that the output impedance of the microphone is less than the input impedance of the sound card.
- Cable length - The microphone cable should be as short as possible (15 feet or less). The reason for this is that most professional microphones have balanced outputs while sound card inputs are unbalanced. The unbalanced input could allow electromagnetic interference to be introduced into the signal if a longer cable is used.
- Making the Connection
The professional microphone usually has a 3-pin XLR-type output connecter to allow for microphone cables of varying lengths, although some microphones have a cable hard-wired to the mic. In either case, the connection at the end of the cable will probably not match the input of the sound card—most commonly a 3.5 mm input. The microphone cable's output connector will be either an XLR-type, 1/4" or 1/8" (3.5 mm) connecter. To connect the XLR and 1/4" connectors to the sound card, a special cable will need to be purchased or made; adapters are also available commercially.
- Connecting a professional microphone to a Macintosh computer
Most Macintosh computers have one audio input which is a stereo 3.5 mm input. This input requires a 100 millivolt input that no standard microphone can provide. In this case an external pre-amp is required.
Some Macintosh computers have a special four-conductor input that will allow the computer to determine if the connected device is mono or stereo. Please note this is a non-standard jack and is longer than the standard 3.5 mm connector, although a standard 3.5 mm connector will work. Again, an external pre-amp is required.
Other Macintosh computers do not have an audio interface. In this case, an external USB audio interface device is necessary to make the microphone connection.
Connecting an Audio-Technical microphone to a camcorder can greatly enhance the audio quality of the recording. When connecting an Audio-Technica microphone to a camcorder, there are many variables to consider in both the camcorder and the microphone. Please be prepared to read the users manual for the camcorder and / or to contact the camcorder manufacturer for configuration and accessories. Below are listed several things to consider.
- Does the camcorder allow for an external microphone connection? Not all camcorders do; consult the users manual for the camcorder and / or contact the camcorder manufacturer for this information.
- What type of input connector(s) does the camcorder have? Camcorders are available with a variety of different connectors, including 3 pin XLR, 1/4" mono, 1/4" stereo, 1/8" mono or 1/8" stereo.
- What type of output connector(s) does the microphone have? Microphones are available with a variety of connectors, including 3 pin XLR, 1/4"mono, or 1/8" mono. Also, if the microphone is stereo it may have 2-3 pin XLR, 2- 1/8" mono or a 1/8" stereo connector.
- Does the camcorder accept a mono or stereo connection? Connecting a single mono microphone to a camera with stereo inputs could be a bit complicated. Some camcorders allow you to assign one of its inputs to both left and right cannels; consult the user's manual for the camcorder and / or contact the camcorder manufacturer for this information. If the camcorder does not provide this function, then an adapter that splits the signal will be necessary.
- Is an adapter necessary ? If the input of the camcorder and the output of the microphone are different, then some type of adapter is necessary. Consult the users manual for the camcorder and / or contact the camcorder manufacturer for this information.
Alkaline batteries are the preferred choice for powering wireless transmitters. They are convenient, offer an excellent balance between cost and operating life, and are reliable. In addition, they are widely available, hold their capacity well in storage and usually do not begin to leak for several years. The market for alkaline batteries is also quite large, and competition is likely to keep prices low.
Zinc-carbon batteries are not recommended for wireless transmitters except in an emergency. Only better quality zinc-carbon batteries from well-known companies should even be considered. Cheaply made "toy" batteries sometimes last only a few minutes because of poor construction and low storage capacity. This type of battery also starts losing capacity as soon as it is made, and packaged units in local stores might have already lost more than 50 percent of their original capacity. Zinc-carbon batteries perform poorly when cold and, at best, have only about 25 to 35 percent of the useful life of an alkaline battery. Perhaps worst of all, they often leak badly and if not removed, they can ruin a transmitter in only a few weeks.
Audio-Technica does not recommend the use of rechargeable ni-cad batteries. Readily available "9-volt" ni-cad batteries are usually really only 7.2 volts when fully charged and have only 15 to 20 percent of the capacity of good alkaline batteries. The lower voltage will result in significantly reduced transmitter power within a short period of time, and audio distortion usually starts to increase after only 20 or 30 minutes of use. The usable operating life of these batteries is usually less that an hour, sometimes quite a bit less. Charging time is typically 14 to 16 hours.
Premium "7-cell" ni-cad batteries are available, but may be difficult to find. These units have approximately 25 percent of the capacity of an alkaline battery, and tend to be very costly. Even when new, their useful operating life is rarely much more than about 3 hours. This will drop slightly with each new charge and the life is likely to fall below 2 hours after 200 or so charge cycles. Another serious problem is that ni-cads exhibit a "memory effect," such that their capacity declines rapidly if they are not fully discharged each time they are used. This can be a particular problem with wireless equipment, since the fully discharged voltage is below that required for satisfactory operation of the transmitter.
Nickel metal hydride (also called NiMH or NH) batteries are a more acceptable choice for a rechargeable battery. Premium models are true 9-volt designs and have about 60-70 percent greater capacity than most premium ni-cad batteries. Because of the extra capacity, operating life is typically about 5 hours, which may be adequate for some applications. The most important advantage of nickel metal hydride batteries, however, is that they are essentially free of the "memory effect" that is so troublesome in ni-cad batteries. Unfortunately, these advantages come at a price; premium NiMH batteries generally cost $20 or more.
There are two other potential problems with using either ni-cad or NiMH batteries in wireless transmitters. One is that even "discharged" batteries will work acceptably for a minute or two, and it is very easy to mix up charged and discharged batteries. In addition, it is very easy to forget to charge the batteries after each use. These problems often result in embarrassing transmitter failures.
Lithium batteries provide approximately three times the life of an alkaline at six to eight times the cost. There are a few situations where the extra life is worth the added cost, but the 9 to 15 hours of life provided by alkaline batteries is more than adequate for most purposes. The low temperature performance of lithium batteries is also considerably better than for alkaline batteries, an advantage in certain situations. For economy, Audio-Technica recommends using lithium batteries only in special situations where the extra time between battery changes is necessary or where use at very low temperatures is required.
Actual battery life estimates may be found on the spec sheet for each product in the users manual or via this web site. Sometimes it appears that batteries are providing less than the expected operating life. When this happens there is a tendency to blame the wireless transmitter for the apparent problem. However, only very rarely does a transmitter's power consumption actually increase. The vast majority of transmitter failures result in less power being drawn from the battery, not more. While a sudden jump in transmitter power drain is not completely unknown, in most cases the actual problem is related to the batteries themselves.
There are several reasons why battery life may appear to be short. Because used batteries don't look different from new ones, it is very easy to mix used or partially used batteries with brand new ones. Often, partially used batteries are kept for other purposes, such as for use in small electronic devices or toys. To avoid problems, it is suggested that batteries removed from wireless transmitters be immediately set aside for recycling or discarded if they are of no further use.
If used batteries are to be kept for another purpose, they should immediately be permanently marked to indicate that they are not new, and placed in a separate location. An inexpensive battery tester is a worthwhile investment, both to verify that new batteries are really new and to estimate the remaining life of used batteries. Careful handling of batteries is absolutely essential to trouble-free wireless operation. On any particular occasion, the difference between success and failure with wireless can be as simple as mixing up the old battery and the new battery during a change.
Sometimes wireless users forget to turn off wireless transmitters when they are not actively being used. When use resumes after a delay or break, the battery life may appear short because the idle time is not being considered. The drain on a wireless battery is essentially the same whether or not audio is being transmitted. Similarly, if a transmitter is only used an hour or so per day or per week, it is very easy to lose track of the total operating time on the battery.
Batteries that are purchased as new might not have the expected operating life if they have been in storage a long time, or have been stored in a hot, humid location. Even when batteries are date coded, it is possible that a significant percentage of their capacity has been lost well before the expiration date. The expiration date is based upon some percentage of the original capacity, such as 75 percent. If the batteries have been stored for one or two summers in a warehouse without air conditioning, the actual remaining capacity could be less than 50 percent of original. High humidity also shortens battery life significantly.
If, after the above considerations, you believe that new, fresh alkaline batteries are providing less than the expected operating life, please contact Audio-Technica or your dealer for further assistance.
It is not necessary to remove the battery when using phantom power. When phantom power is present, the batteries are not used. Keeping the batteries in installed while using phantom power, although not necessary, is a good practice. If for some reason phantom power is dropped during operation, the batteries will take over and provide the needed power.
Pin 1 - Ground
Pin 2 - High Z (instrument)
Pin 3 - Low Z (mic)
Pin 4 - Bias voltage
**Please note **
When wiring a microphone connect both Pin 1 and Pin 2 to shield.
Pin Transmitter Condenser Mic Dynamic Mic Hi-Z Line
1 Shield (Ground) Shield/Bias – Shield/Audio "–" Shield/Audio "–"
2 Bias + Out Bias + In Open Open
3 Lo-Z Mic In Mic Audio Mic Audio "+" Jumper to Pin 1
4 Source Load(2.2 kV) Jumper to Pin 1 Open Jumper to Pin 1
5 Hi-Z Line In Open Open Line Audio "+"
Pin 1 - Ground - Shield
Pin 2 - Audio - 2 twisted yellow wires
Pin 3 - Bias voltage - 2 twisted red wires
Balanced connectors are usually 3-pin XLR connectors in which Pin 1 is ground, Pin 2 is audio positive (also called Hot), and Pin 3 is audio negative (also called Cold). Balanced connectors may also be a 3 conductor TRS (Tip Ring Sleeve) connector where Tip is audio positive, Ring is audio negative and Sleeve is ground. Unbalanced connectors are usually TS (Tip Sleeve) connectors;Tip is the audio signal and Sleeve is ground.
Whenever possible use a balanced line to protect against electromagnetic interference. If the balanced line must be converted to unbalanced an adapter or cable should be purchased or made. This adapter (or cable) connects audio positive of the balanced signal to the "hot" pin (Tip) of the unbalanced signal connector and connects audio negative of the balanced signal to the "ground" pin (Sleeve) of the unbalanced connector. The shield of the balanced signal is connected to the "ground" pin (Sleeve) of the unbalanced connector. Unbalanced cables can pick up electromagnetic interference particularly at distances. To preserve sound quality, use the shortest cable possible. If a long cable is necessary an isolation transformer should be used.
Phantom power is DC voltage sent down the microphone cable to power the preamplifier of a condenser mic capsule - sometimes through a power module. The power module attached to the mic unit converts the 9 - 52VDC into a small bias voltage that the mic capsule's FET needs for the microphone to operate.
A balanced mic cable has three conductors; Pin 1 is ground, Pin 2 is audio positive, and Pin 3 is audio negative. Most microphones produce a positive voltage on Pin 2 when sound pressure is applied to the diaphragm.
Phantom power is 9 - 52VDC applied across Pin 1 and Pin 2 - and at the same time applied across Pin 1 and Pin 3. The term 'phantom power' was assigned because if you take a measurement across the two audio lines - Pin 2 and Pin 3 - you find 0 Volts DC. The voltage does not affect the mic signal.
If the mixing console does not provide phantom power and the microphone itself does not provide power via a battery, then phantom power must be provided by an external source. Audio-Technica manufactures two external phantom power supplies, the CP8506 and the AT8801. The Audio-Technica CP8506 provides 48V phantom power for up to four microphones, while the AT8801 provides 48V phantom power for a single microphone. They allow the use of remote-powered microphones with systems that do not supply phantom power. They are line-powered devices. The CP8506 includes an attached 6' grounded line cord and a power switch with an associated LED indicator. The AT8801 includes a plug-in power module that attaches to the electronics module with a 6' cable. Each unit features a highly-regulated power supply that provides a constant voltage source, even with a heavily loaded input. The regulator IC is internally protected to prevent overheating or damage even if shorted. The rugged steel case is finished in enamel and provides shielding from electrostatic interference. The CP8506 and AT8801 will adequately supply phantom power to the microphones connected to them via XLR-type connectors; additional phantom power (from a mixer or other source) is unnecessary, and is not recommended. For optimum phantom powering, an uninterrupted line must exist between the phantom supply and the microphone; no filters or transformers should be present.
A balanced mic cable has three conductors; Pin 1 is ground, Pin 2 is audio positive (also called Hot), and Pin 3 is audio negative (also called Cold). Most microphones produce a positive voltage on Pin 2 when sound pressure is applied to the diaphragm.
Phantom power is 9 - 52VDC applied across Pin1 and Pin 2 - and at the same time applied across Pin 1 and Pin 3. The term 'phantom power' was assigned because if you take a measurement across the two audio lines - Pin 2 and Pin 3 - you find 0 Volts DC. The voltage does not affect the mic signal.
Keep in mind that all three balanced microphone cable conductors are needed for phantom power to reach the microphone. If one or more conductors in the cable (or at the XLR plugs) are broken or intermittent, phantom power will be compromised and the mic will not work.