Before you can store a digital signal onto a hard disk, the analogue sound signal needs to be converted into a digital signal. In this chapter you will find various ways to connect a microphone to a computer.
Microphone
- Balanced: In general, microphones provide an analogue audio signal. Professional microphones feature an XLR-output with three pins that transfer a balanced signal. One pin is ground, and the other two carry the audio signal. Pin 2 is the so called hot signal and pin 3 the cold. This method reduces the susceptibility of external noise while allowing the usage of longer cables.
- Unbalanced: Entry level microphones often feature an attached cable with an unbalanced 6.3 mm or 3.5 mm connector. An unbalanced output carries the signal on a single conductor and is more susceptible to external noise. For that reason only balanced connections are used in professional miking applications.
USB
More and more professional USB microphones are available. A USB microphone is essentially a mic with a built-in USB audio interface that converts the analogue signal into a digital signal. It can be directly plugged into a computer without requiring an external audio interface. USB microphones, such as the Shure PG27USB and the PG42USB with plug and play functionality, are an easy start into home recording and podcasting. But how can microphones without a digital output be connected to a computer?
Sound Card
To be able to record analogue audio onto a computer hard drive, you need a sound card. In general, all laptops and most computers are equipped with one. Many internal sound cards are not shielded from electrical noise that is often caused by fans, hard drives, and the computer’s own circuitry, which means noise and hum can be introduced into your audio.
Also, most internal sound cards are not equipped with professional microphone connectors, do not provide phantom power for condenser microphones, and do not provide enough amplification or gain when working with low-level tracks or sounds. For those reasons we recommend the use of a higher quality sound card that features balanced XLR inputs and an adequate microphone pre-amp. Such sound cards allow the direct connection of a professional microphone and high quality recordings with low noise levels.
High quality PCI cards are available for desktop computers. For laptops external sound cards with a digital output (USB of Firewire) are the best choice. Such cards can be connected to a computer easily and have one or more XLR inputs for professional microphones as well as a microphone pre-amp.
A quick and easy solution for all computers is the Shure X2u-to-USB adapter which features an XLR input and a USB output. The XLR input is balanced and the digital output is provided to the USB port of the computer. The X2u is compatible with PCs and MACs and can be operated without the installation of additional drivers.
| INFO: Latency |
| Latency is a delay in the signal path caused by the time required to convert sound from analogue to digital (or vice versa) for processing of the signal. Usually measured in milliseconds, latency can occur at multiple points in the signal path… and it can really add up. |
What this means is that the sound you are hearing when you listen to yourself singing might not be happening in real time. A latency of approximately 4 ms is normally uncritical. With a higher latency the timing of the musicians suffer. E.g. if a singer is supposed to sing to a bandmix and the latency is too high, he
will start singing too late. Standard internal soundcards usually have a pretty high latency (200 ms and more).
While this latency is not critical for podcasting and voice over, it is unacceptable for musicians recording a multi-track song. High-quality sound cards offer a latency of 4 ms and less.
Mixers
A third possibility is using mixers (or “mixing console” or “mixing board”). Small mixers that offer a few balanced XLR inputs are sufficient for home recording. The output of such mixers offers a gain level that is high enough to be connected to the line input of the computer.
Internal PC sound cards normally have an acceptable sound quality at the line input to be used in combination with a mixer. But as the mixers often have balanced XLR outputs, and the sound cards unbalanced inputs, special cables or adapters are necessary. An advantage of a mixer is the option to blend separate microphone signals into one mix. Even though you would normally use a single track for each signal – instrument or voice – a mixer can help to make a quick and easy recording onto one track.
