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Why should you buy a high quality audio interface?A high quality audio interface is the biggest factor affecting how your audio is going to sound. All other things being equal — a high performance computer, high end speaker monitors, quality recording software, microphones and instruments — your audio interface is the most important factor in the recording chain. What makes a good audio interface and what should you look for? 1) Quality of the DACs (Digital Audio Converters)High fidelity analog/digital converters should capture your analog audio signal in the finest detail and then reproduce it accurately. The better the resolution — the better your sound reproduction will be. (See Digital 101.) 2) Meaningful specificationsEach electronic component on a circuit board adds a very small amount of noise to the signal. Fewer components means a shorter audio path and more recording clarity and transparency. When comparing the specifications of different audio interfaces, make sure that you're looking at the specifications of the overall interface input to output, not specs at the component level. (See Digital 101.) 3) Total Harmonic Distortion or THDTotal Harmonic Distortion or THD is an amplifier or pre-amplifier specification that compares the output signal of the amplifier with the input signal and measures the level differences in harmonic frequencies between the two. The difference is called total harmonic distortion. Lesser THD allows the components in a loudspeaker, amplifier or microphone or other equipment to produce a more accurate reproduction by reducing harmonics added by electronics and audio media. Total harmonic distortion is measured as a percentage, such as 0.004% THD. This means that the level of harmonic distortion is 0.004% of the total output signal. The lower the percentage the better. 4) Input and output dynamic rangeYou should look for “A weighted” measurements. Our human ear is far from linear, dynamically speaking, especially in the low frequency and high-mid frequency regions. An “A-weighting" filter is commonly used to emphasize frequencies around 3–6 kHz where the human ear is most sensitive, while attenuating very high and very low frequencies to which the ear is insensitive. This is shown in the diagram below by the blue line. (For more discussion on A-weighting click on the diagram below.)
For us, the area of interest lies between the 80 and 120 dB curves. (For more discussion about dynamic range see Digital 101.)
5) Frequency responseFrequency response is a specification used in amplifiers, pre-amplifiers or other audio components to measure how uniformly it reproduces sounds from the lowest tones to the highest. An amplifier or other component should preserve the loudness relationship between various instruments and voices and should not over- or under-emphasize any frequency or tone. This is known as flat frequency response. For more details, check out this tutorial from Faber Acoustical using our Indigo io and AudioFire 4: 6) Clock source and digital jitterThe jitter should be the lowest possible (in nanoseconds) for ultra low distortion and accuracy. 7) Driver stabilityWindows drivers and Mac software should be stable and updated regularly. 8) Well designed interfaceThe interface should be well designed with a solid metal case to protect the electronics inside from bumps and dents. References: http://www.system1audio.com/images/fletchermunson.gif |
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