Your Guide to Audio Interfaces

What is an Audio Interface?

Audio Interfaces handle the conversion of audio sound signals from analog to digital and back from digital to analog. It is all 0’s and 1’s. Computers are digital and only deal with digitally encoded data. In the music world, this means digitally encoded music and other sound signals.

With computers being so powerful, it is easy to forget that under the covers they are really only dealing in binary code. So any music that makes it way into your computer must be encoded in some manner to be stored or used. MP3 is a common encoding. WAV is another. We will talk more about those below, but for now just realize that music inside of your computer is encoded.

What about the music or sounds we hear our computer making? If sound is all digitally encoded, how is sound produced?

The earliest and simplest way computers produce sound from digital encodings is via a sound card. Most computers will have an elementary sound chip embedded on the motherboard to perform this operation. These cards or chips perform the conversation of digital sound to an analog sound. This might only be at a very low level (voltage) for use with a headphone or earbuds. That signal is analog; a varying voltage signal.

All modern computers will at least handle stereo signals where you will have a left and a right channel. Many computers might also have built in speakers and can produce a strong enough signal to drive those speakers at a reasonable level.

Sound Cards

Sound cards were the first audio interfaces. They allowed for converting music and sound from a digital format to an audio format and, generally, from an audio format back to a digital format. And they are still useable for these features, whether they are built-in capabilities of your computer or specific sound cards added to a desktop machine.

Modern Audio Interfaces

Sooner or later, serious music enthusiasts realize that they want to acquire a digital audio interface that provides the ability to further manipulate the audio files. The picture below shows in a schematic type of form how an audio interface relates to audio and music processing.

The audio interface in the converter sitting between the analog world (instruments, microphones) and computers. They also have features for converting back from digital to audio format.

With so many different signal types and connection type, the main selection of an audio interface is to understand how you’e like to use it. You will need to ensure it can handle all your input and output devices and also be able to plug into your computer.

An excellent audio interface is important for any musician or producer since the majority of standard sound cards do not provide professional-quality sounds. An audio interface can broaden the potential of a recording system with a multitude of monitoring selections, input/output, and MIDI connection. The selections that are available are at times confusing though. This is why we created this article to further explain these devices.

Connections for Audio Interfaces

USB audio interface

USB audio interface is the most reasonably-priced device among audio interfaces and is the most widely-used product as well. USB or Universal Serial Bus is a kind of format that is capable of connecting a broader selection of external devices to a computer. Over the years, the USB standard has kept getting better. The USB 2.0 and 3.0 are now the primary standards for data transfer to computers.

However, if you are considering using the USB type, keep in mind that this kind of interface can be limiting for users who want to operate with higher resolutions or a variety of input and output.

Majority of USB interfaces are restricted to a smaller number of ins and outs and they also provide inadequate amount of channels to and from the PC. However, if you tend to work on a PC without any outboard gear, the USB audio interface is highly recommended.

FireWire audio interface

FireWire audio interface uses IEEE 1394 or a FireWire connection cord. This costs more than the USB type but provides a faster connection. A plug and play system with higher bandwidth and low latency benefits more from a FireWire interface as compared to a USB. Its speed is comparable to the USB 2.0.

However, the unit manages heavy information traffic in a more effective manner. This is ideal for units operating with lots of data such as DVD players and camcorders. FireWire also presents more input/output and provides bigger sample rates as compared to the USB type.

PCI audio interface

The PCI type uses an expansion card that mounts onto a desktop computer and utilizes a break outbox or cables to link up audio units. One benefit of PCI unit is its speed and its capability to operate a multitude of outputs and inputs. This particular format, however, requires users to open their computers in order to install hardware. It is also utilized chiefly for tower-based PC configurations thus it would not work with iMacs or laptops.

Although it presents excellent stability for information transfer, setting the whole thing up is typically complicated because as mentioned previously, it requires opening the computer.

Cardbus/PCM-CIA audio interfaces

Cardbus and PCM-CIA connections are not quite as accessible as the other audio interfaces mentioned here but there are a number of companies that make decent interfaces featuring this format. This is a great tool to use for mobile users who are not fond of using an external box to connect to their laptops.

Selecting the Best Audio Interface that Fits Your Needs

Selecting the best audio interface might seem like hard work, but it really comes down to matching your needs to the market. It can be a little confusing because there are many factors that you need to take into account from connection kinds and formats to input/output configurations.

This handy guide would hopefully steer you in the right direction by helping you pass through the selections that you require and find a good audio interface that works for you.

Importance of an Audio Interface

It is important to have an audio interface that works well. This is a factor that benefits producers and musicians who want to have access to recording equipment without spending studio time and compromising sound quality. You can use sound cards but if you are after recording music, an audio interface is best for the task.

Majority of sound cards only offer consumer-quality stereo line input and output and a headphone output. Too much latency, radio and electromagnetic obstruction can greatly influence audio in and out and this is often the case with sound cards.

Although sound cards are excellent for connecting hi-fidelity speakers and compressed audio playback, you would need to get a dependable audio interface for keeping track of decent audio and recording procedures.

Selecting Proper I/O Configurations

Input and output configuration is a crucial factor in selecting an audio interface. It may be best to think about what kind of audio processing you want to do on the computer and what software you will be using to do it. For example, Audacity is a very nice open source, multi-track audio recorder and editor that is free and runs on Windows, Macs, and Linux. Depending on your needs, this might be enough.

The amount of I/O and the appropriate kind depend completely on what you are planning to record. The selection of audio interfaces encompasses everything from 2-channel PC units to setups that can record lots of channels.

If you are a musician, you might only require a pair of inputs as long as they are appropriate for what you plan to do. The majority of audio interfaces contain 2 or more microphone preamps. If you want to use a condenser microphone, you would want to make sure that the preamps of your interface also come with phantom power. If you want to plug a keyboard or a guitar into the interface, make sure that the interface includes hi-Z inputs.

Furthermore, it is important to remember that line-level I/Os are excellent for connecting headphone amps, studio monitors, and outboard processors.

Digital input/output might not appear to be crucial when you are just starting out in the business. However, they can be significantly beneficial in due course. For example, several high-end 1-2 channel microphone preamps include S/PDIF output. This is already in a digital format and enables users to connect the devices to the audio interface. The signal can then be passed on to your computer for processing. This is definitely a more advanced setup that most casual users will not need.

Another advanced digital format is ADAT Optical Interface, also known as ADAT Lightpipe. It will be available on high-end audio instruments and mixers. A single connection and transmit lots of channels, but again not something the casual user will be needing.

Some Terms that You Need to Know

Drivers

Drivers are software items that allow audio interfaces to get in touch with a computer. They also assist in minimizing latency and in turn users get great sound quality.

Preamps

This means a microphone preamplifier that boosts ultra-small signals from a microphone up to a proper level meant for recording. An excellent recording by a microphone starts with a decent preamp and appropriate input. This one is also called “mic pre.”

Latency

Latency is the obvious pause in tangible sound and the playback that it provides can be off-putting on headphones and speakers. These days, latency does not sound that terrible on computers but common sound cards that are included in those units are not excellent in terms of quality. Therefore, a superb audio interface could enhance this until you do not even recognize any of it.

Direct monitoring

Many audio interfaces feature a switch to facilitate users to perceive the source of the sound in a direct manner. Therefore, if you are recording vocal parts, you would promptly make out your voice straight in the headphones without the annoying delay.

48V phantom power

Several microphones require power to push active circuitry or separate a condenser microphone’s plates. If you want to link up a mic that needs phantom power, then you would be required to buy an audio interface with phantom power switch. However, if you have a dynamic microphone, you would not need a model that includes this feature.

MIDI

Several interfaces contain MIDI in and out. Majority of MIDI controllers operate by means of USB therefore this is not as crucial to acquire like it was in earlier days.

Sample rate and bitrate

The “sample rate” is the number of times per second that a sound is “sampled” to generate digital signals. Higher sample rates feature a higher frequency selection of sounds that can be administered and recorded. The most common sample rate is 44.1 kHz which is capable of recording sounds of up to approximately 22 kHz (half the sample rate).

Each sample of the audio signal is digitized into a digital number. The more bits that are used the higher the accuracy of each reading. These days, any decent encoding will be done at 24bits. This is also known as the “bit depth”. Prior to 2010 you’d also find digital audio equipment that used 16 bit encoding.

So you can probably see that for the best conversion of audio to digital you will want a higher “sample rate” and larger “bit depth”. Again the “sample rate” is how often the audio is sampled and the “bit depth” is how accurately each sample is measured.

To understand how much digital data is being created, you multiply the sample rate by the bit depth to get the BitRate. The quality of the digital encoding is directly impacted by the BitRate. Lets look at some typical numbers.

Typical BitRates

CD (Compact Disks): 1,411 kb/s The standard for CD includes 44.1kHz sampling for 2 channels (Left and Right), with a bit depth of 16bits. This is uncompressed audio and takes up a lot of space. 1 CD can be up to 80 minutes of music which is almost 1 GB of space.

To enable easier storage and handling of audio data, it is often encoded. MP3 is a very popular encoding that you have probably heard of. The MP3 specification allows for a range of bitrates (quality) with the highest being 320 kb/s which is generally referred to as CD-quality. So you can see it is only about 1/5th of the uncompressed size.

Most common listeners would have a hard time distinguishing between raw CD sound an 256 kb/s MP3 files, so it has is generally considered “high-quality audio”.

For comparison, free Spotify streaming streams at 160 kb/s. Personally, this is good enough for me, but most keen listeners will want to be dealing with higher quality bitrates.

Sample Rate Inflation

Up until 2010, 44.1 kHz (44,100 samples per second) was generally always used as the highest sample rate. Even the best-turned humans are not capable of hearing tones that are any higher. Similarly, now most decent equipment will use a 24bit bit depth, although you may still find 16bit.

But, now you are seeing more and more use of high sample rates. 48 kHz has become standard for many people. And, there are some professions that are now running 192 kHz equipment. This is extremely high and will require expensive gear and lots of memory and storage space in daily use.

More Considerations

There are several audio interfaces that are PC or Mac compatible only. Therefore, make sure that you carefully go over the features of each model. Interfaces today contain some built-in software control and will often include a trial version of computer software for editing audio. This feature is convenient and mixing software lets users perform every procedure easily.

These procedures include adding reverb as well as setting up and delaying headphone mixes among others. Furthermore, software control and built-in DSP let users perform those tasks without draining the CPU, affecting DAW software and supplementing latency to the mix.

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Current Top Selling Audio Interfaces

Now that we have discussed the factors that you need to remember while looking for audio interfaces, it is time for some recommendations. Here are some examples of audio interfaces that are constant favorites among musicians and producers.

*Price from:  2023-03-29 at 11:36 EST

Conclusion

The primary decision-making factors that consumers should take into consideration when looking for audio interfaces include required connections and the total number of outputs needed. The number of sound resources linking to the audio interface would decide the number of outputs that are obligatory.

Musicians have their own list of requirements when it comes to purchasing audio interfaces and that would progress in due time. The most important thing is producing great quality music and all these setups are, in fact, efficient at doing that task.