Introduction

A sound card, also known as audio interface, converts between analog to digital signals and vice versa. Without it, a computer doesn’t understand how to handle the signal. There is also no jack to plug your equipment into.

New technology has integrated digital inputs and outputs like SPDIF and ADAT but we won’t go into much details in this article.

An audio interface is an important part of podcast gear. Some computer has a built-in sound card into the motherboard and this is enough to get you started in podcasting.

Basic Terminologies and Facts

The quality of audio equipment is expressed in bit depth (in bit)/sampling rate (in kHz) pair. For instance, 24/96 simply means that the interface is able to handle as much as 24 bits of digital information in each of the sample rates. At the same time the interface can process sampling rates frequency of up to 96 kHz.

In real world, a 96 kHz sampling rate can accurately represent frequencies of up to 48 kHz — half of the actual sampling rate. Normally, humans cannot hear beyond 20 kHz anyway so even with an equipment with the quality of 24bits/48kHz, you are still able to record audio of decent quality.

For your reference, DVD quality sound uses 48 kHz, while audio CD uses 44.1 kHz.

Types of Audio Interfaces

Current computer system allows three types of audio interfaces:

1. PCI interface - This is the type of interface that is referred to as sound card, because it is the most common type of its kind. These cards are inserted into one of the PCI slots on the motherboard.
2. USB interface - As the name implies, a device of this kind is connected to the computer through an USB port.
3. FireWire interface - Like USB interfaces, but FireWire interfaces are connected to FireWire port.

It is important that if you have or plan to acquire a microphone with no mic preamp (or mic pre) then you require a preamp either built-in the sound card or a separate preamp.

A tip: Alternatively, if you have a preamped mic or a separate preamp, then look for manufacturers which provide non-preamp interfaces. Sometimes they offer a product with double inputs with the same price, but without preamps.

We will cover about preamps later in the microphone article.

PCI Audio Interfaces

This type of interface ranges from a lower end to high end cards. As I said earlier, a built-in computer sound interface can get you started in podacsting instantly. With a moderate quality microphone you can achieve a good quality recording.

A low end sound card costs from $10 or less.

Typical sound cards come with 1/8″ mono or stereo jacks. In case of the latter, you can split the left and right tracks using a converter. Depends on the device you are going to connect to the card, you probably want a stereo 1/8″ male to two mono quarter inch — either male or female — converter.

Middle-end cards range from $100 or less to a few hundreds. With 24-bit/96kHz, you can have a low latency audio interface with multi-effects, popular API supports, and multiple types of input jacks.

For about $100, EMU-0404 audio interface card offers the most value with clean I/O, 24-bit/48kHZz and audio software package on CD-ROM.

A high-end solution could possibly cost $600 or more, which includes 24-bit/192kHz in quality and other nifty features. Another EMU card, EMU-1212M represents a terrific value of 24-bit/192kHz, digital I/O, ADAT and FireWire for $200.

USB Interfaces

As USB ports become more common nowadays, we have a wide range of selections for audio/midi interfaces. Some of the popular brands include Edirol, Digidesign, M-Audio, and Tascam. This is not an extensive name of brands but the one I frequently encounter and have some experiences working with.

Some devices are compact and quite complete. The portability makes it very convenient to carry while travelling.

Tascam US122, for instance, has 2 line level inputs, which is switchable to guitar level. It also includes 16 channels of MIDI I/O, headphone output with self-powere USB for $150.

If you opt for an USB interface, prepare to spend between $150 to $200 for a simple home studio. More advanced podcasters would expect to spend $500 or more for an interface.

A Digidesign MBox 2 includes more features and varieties in jacks, including RCA, XLR with phantom power and mic preamp.

Unless you are looking for more advanced features with more inputs/ outputs, chances are a mid-end product is enough for you.

FireWire Interfaces

FireWire port allows extremely high transfer rate over a thin wire. FireWire interfaces are great options but expect to spend more because they usually are more sophisticated.

FireWire interfaces range from $200 to $1300.

An example of high quality FireWire audio interface is Tascam FW1884, which allows 18 simultaneous inputs, word clock in and out jacks, balanced XLR analog mic/line inputs with high quality mic pres and others.

Which Option?

After going through the basics, the types of interfaces and some options, you might be confused as to what to choose for your digital audio workstation.

Realize that for some people who only want to record voice only podcast — probably with a bit of intro and outro PodSafe music — can get away with a low or mid-end PCI interface.

USB interface, on the other hand, is compact and portable. For now, leave FireWire options for pro.

The problem revolves around how many inputs you need. For instance, if you frequently invite others to join your podcast for an interview or as a guest podcaster, it is best if you can provide two separate microphones. Each of them requires one mic input.

Current MIDI keyboard owner will love to have a MIDI input to record their creations.

My rule of thumb is: buy an interface with more inputs and outputs than you require now. It is very common that people think a simple interface is all they need, only to find out a few months later they were wrong.

Beware of Some Problems

A minor but disturbing problem is latency, which more likely to appear on USB interfaces.

Make sure that your computer supports high speed USB 2.0 ports instead of previously more slower version. A decent computer system with the right driver and APIs might solve the issue.

Only a few people reported about USB latency. But, just to be on the safe side, check with others or find a community and ask about it.

PCI interfaces are fast because they are punched directly on the computer’s mainboard.

A microphone without a preamp will need an external pre. Some interfaces have it, so you don’t have to buy a separate one.

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