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Audio interfaces - the *one* feature that manufacturers don't want us to know about

There are so many different audio interfaces available, some claim to be better than others. But take the lid off the box and will you find that they are all pretty much the same inside.


You may have been in recording long enough to remember the Alesis ADAT 8-track modular digital recorder, which was a breakthrough in performance/price ratio in digital audio, but unfortunately not particularly reliable.

Then other companies started making ADAT recorders, Fostex, Panasonic and even Studer. But take off the lid, and what you would find inside would be an Alesis ADAT, made in the Alesis factory and dressed up in fancy clothes.

Something similar is happening with audio interfaces. Every audio interface has analog-to-digital converters, so the signal from the microphone or instrument can be converted to digital form.

Conversion from analog to digital is still an area where leading-edge development is taking place. There is no such thing as a perfect converter, and since they are not perfect, they must all have their own distinct sound.

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So that means that every audio interface should sound different, purely because of the converters.

Well let's lift up the lid and find out a little more...

The design and manufacture of analog-to-digital converters is rocket science. In fact it's beyond rocket science. Where much audio design, both analog and digital, can be done in a back room, and manufacturing done in a factory that could have been making sewing machines, the design of converters requires the best brains in the world. And people with the best brains are few in number.

And manufacturing an analog-to-digital converter requires a state-of-the-art semiconductor facility. You can't build one overnight in an industrial unit.

So you can take it then that audio interface manufacturers don't design and build their own converters. Not even Digidesign do that.

So what do they do?

Answer - they buy converters from a very small number of manufacturers who have the expertise and manufacturing capability, such as Analog Devices, Burr-Brown, Cirrus Logic and AKM Semiconductor. And because these manufacturers are so few in number, you will see their converters across the range of audio interfaces.

So an audio interface basically consists of a standard converter dressed up in a fancy box. All the manufacturer is responsible for is the preamps and the FireWire, USB or PCI output to the computer.

No manufacturer states in their specifications which converters they use, so obviously it's something they want to keep quiet about, probably for marketing reasons.

But maybe they should - maybe they should even show off the converter behind a transparent panel - maybe even back light it with a couple of LED's ;-)

In a world that inherently must combine analog and digital audio, the analog-to-digital converter is all-important, and we deserve to know its source.

By the way, if you do know for sure the make and part number of the analog-to-digital converter used in any pro audio interface, either through the manufacturer's specification or because you have taken the top off and looked for yourself, please let us know at

By David Mellor Tuesday December 20, 2005