Jacksmith39.files.wordpress.com



Jack Smith15111855 22/09/2015Audio InterfacesResearch Task 2What is an Audio Interface and why bother using one? An audio interface, or an AD/DA converter is a conversion tool that changes analogue inputs to a digital output (computer) or an analogue output (speaker). Because pretty much all recordings are edited digitally now, this is essential equipment. It works by obtaining electrical signals generated from the microphone’s diaphragm and converting it to a digital signal in binary for the computer to use (AD). If the user wants to listen back to it, the audio interface would convert the digital signal back to analogue (DA), and the sound would play out of the speakers. 1104900249491500How are Audio Interfaces connected to a computer? Audio interfaces are usually connected to a computer via a Firewire, USB or PCI connection. A USB 2.0 connection (the most common today) can record multiple tracks at once at an incredibly high sample rate (480Mbps), whereas a USB 1.1 connection (the original, least advanced) can only record 2 tracks at one time at a comparatively terrible 12Mbps. Plus, every computer has a USB port so it is easy to obtain. A Firewire connection however, can record multiple tracks at 400Mbps, but instead of sending the information in ‘packets’ of information like a USB connection, the firewire keeps a constant stream, meaning the audio will be processed more efficiently. If you do not have a firewire port on your computer, you have to purchase a third party port. PCI is a hardware card attached to the motherboard on a computer. This type of interface is very efficient because it has next to no latency. However, it has to be installed inside a computer tower, which makes it very inefficient for mobility. My personal favourite is a USB connection, because of its impeccable speed of 480Mbps, and even though it sends information in packets and not a constant stream, it still shows an incredibly high quality.851535148844000Analogue and Digital signals. The difference between analogue signals and digital signals is that analogue signals work based on electrical signals sent directly from the diaphragm, when it vibrates between positive and negative fields of energy. Analogue signals continuously change in amplitude or frequency, whereas digital signals can only have two states, on (1) or off (0). This is because digital signals rely on binary code, which can only handle 1s and 0s. Analogue would usually be stored on a magnetic tape, however, digital signals can be stored on a hard drive, allowing for more memory. An analogue signal has a continuous signal, whereas digital signals are small sound samples recorded thousands of times a second. Pre-amps (Make sure you talk about signal to noise ratio in this section). Because microphones usually generate weak audio levels, a pre-amp is needed to amplify that weak signal to a signal that is better for the user. Some pre-amps can introduce unwanted hissing or background noise due to their circuitry. When deciding on a pre-amp, it is important to keep in mind this signal-to-noise ratio. This is an indication of how much noise is produced by the pre-amp’s circuits. The lower the ratio, the better. For example, the M-Audio ProFire 2626 interface creates a signal-to-noise ratio of -109dB, meaning that the background noise is -109dB quieter than the gain before it distorts. Some pre-amps can be noisier than others if it has higher gain. A good pre amp would have a low signal to noise ratio, where you can turn up as much gain as is needed without background noise being heard. 131127567443350015392404340860001194435137414000Types of audio connections found on audio interfaces. The most common audio connections on audio interfaces are XLR connections. These are 3 pin, industry standard connectors with a balanced audio signal, meaning that it uses balanced lines. This connection is great for recording sound because it allows long cables to be used while reducing external noise that may be presented in the use of such long cables. You can join multiple XLR cables together to improve length, without any noise degradation. These are usually input connections, and include a “male” and “female” connector, a male having outward facing prongs and a female having holes to slot them into. A TRS connector, or a ‘Jack’ connector is used mainly in output, for listening to audio playback. It is mainly used for analogue signals. They are called TRS connectors because the T stands for tip, the R stands for ring and the S stands for sleeve. The most common arrangement is to have the male plug attached to the cable and the female (socket) inside the equipment. They usually have 2 rings around the end, for stereo listening.An RCA connector, or a ‘Phono’ connector is also used for output, and are known as A/V Jacks (Audio/Visual). It is less convenient than that of a TRS connector because it takes up more space and uses more wire. It also has more disadvantages. It creates a loud buzzing noise because of the signal connection being made before a ground connection is established. Another problem is that each signal requires its own plug, yellow for video, white for left audio and red for right audio, for stereo listening purposes. You would also need more of these cables if you wanted to use it for input as well as output, leading to a lot of confusion over which wire goes where. It is an unbalanced connection so if you tried connecting this type of wire together, it would introduce a lot of unwanted background noise, which is why this input is not preferred in the professional music industry. This type of input gives off a very low level output signal, meaning a pre amp would have to amplify and equalise it. 85280596837500A S/PDIF connector is used to carry compressed digital audio, such as a .mp3 file and play it as a surround sound, and is used as an output.A MIDI connector allows instruments and computers to connect with each other. It is used as both an input and output connector. They usually connect computers to keyboards or other electrical instruments, like a V-drum kit. Sample Rate and Bit Depth. A sample rate is the amount of times per second that a clip of music is sampled. A sample rate of 44.1kHz means that sound is ‘snapshotted’ 44,100 times per second. The higher sample rate, the better. This is because more information is captured, leading to a higher quality. When the interface converts the digital audio back to analogue, the empty space between each sample is made smoother. When there is a higher sample rate, there is less empty space between these samples, which means improved smoothing and better sounding audio. Latency. Latency is the delay between input and output. All digital audio systems produce this. This can cause problems when recording. For instance, when recording vocals, the singer will hear their voice live and then hear the delayed signal coming back from the digital audio workstation. This delay makes it hard to hear their own pitch and keep the timing. These problems can be resolved by hardware direct monitoring. This lets you monitor direct from the audio interface, before any latency is introduced. To use this, the vocalist will select which live inputs and software returns they want to hear while parison. The M-Audio M-Track Eight audio interface with integrated preamp has 8 XLR balanced microphone inputs, with a signal-to-noise ratio of 111 dB. It uses a USB 2.0 connection to the computer, meaning fast connection. This is great for a full band, or a large music ensemble. It has an extremely low latency through speakers or headphones.However, the Focusrite Scarlett 6i6 only has 2 instrument inputs, meaning it can only record duos or very small bands. It has a signal-to-noise ratio of -122 dB, and it also uses a USB 2.0 connection. It has apparently “the lowest latency in the business” so that gives only one slight advantage to the M-Track Eight, other than that, I’d personally say that the M-Audio M-Track Eight is a better audio interface.BIBLIOGRAPHY : All About Audio Interfaces (Vol 2) ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download