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Audio Interfaces

Brian Toye
August 13, 2011



Audio Interfaces (or sound card).

There are so many (interfaces) on the market. Some cost $100 and some cost $5000. What are the differences? Which ones should you expect to find in an artist’s bedroom and which ones in a pro studio? Let’s start by explaining “what” and interface is, according to the Oxford Dictionary:

1. a surface regarded as the common boundary of two bodies, spaces, or phases.
2. a common boundary or interconnection between systems, equipment, concepts, or human beings.

In the audio world, an interface refers to the piece of equipment that translates the audio signal from the analog world to the digital world (and vis versa). The interface sits at this boundary between both “systems” and translates the signals in both directions, when needed. The devices inside the interface which do the conversions are called Analog to Digital Converters and Digital to Analog Converters (A/D’s and D/A’s for short).

The higher the quality of these A/D’s and D/A’s the truer the analog sound representation in the digital realm. Most converters can work at 192khz and 24 bit these days, although CD quality still remains at 44.1khz and 16bit. So what is the difference between two converters that can both work at 192khz but differ in price by a factor of ten or more? Digital information requires a “clock” in which all the 192 000 samples per second are related to. If this clock is not accurate to a millionth of a second then we will encounter clocking artifacts such as jitter. Such problems can lower the dynamic range and stereo panorama of the sound stage. Thus, when tracking a 90 track production through an M-Audio or M-box interface, which contain low quality converters, this jitter problem is magnified 90 times (or however many tracks u record). If you happen to have an outboard piece of gear such as a compressor or reverb that you wish to use during mix down, then you must come out of the interface into the reverb or compressor and then return back into the computer through the interface again. This process, through low end converters will also lower the overall quality of your overall mix. If you have cheap converters it's best to run through them once to get into the box, and then stay there.

A high end interface, like the new AVID I/O 16 x 16 has a very stable clock and high end converters. Going in and out of this interface should not diminish the dynamic range or the panoramic field of your sound sources. This interface, unlike the m-audio or mbox, does not contain mic pre’s, DI’s or headphone jacks for monitoring. The higher end gear forces you to purchase separate monitoring set-ups and separate front end (mic pre’s, DI’s).

If you are looking for a good quality home recording interface with a decent clock and converter, check out the RME Babyface. Your demos should translate well through this device. Remember, demos don’t have to be more complex than a chord progression and vocal and or beat and vocal. Leave the canvass blank for a producer to bring his/her vision to your writing.

Take home msg: Converters rely on "clocks". All "clocks" are not equal, cheap ones cause jitter....jitter decreases sound quality (dynamic range and panorama)

for more information about jitter see http://www.tnt-audio.com/clinica/jitter2_e.html

another interesting source with further links on the subject

http://www.benchmarkmedia.​com/appnotes-d/jittercu


- Brian Toye -
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