Month: November 2019

Blog Entry, Technology

Audio Interfaces

OK so if you’ve been playing the home game I left your cords dangling at the end of that last post on ports. Time to grab your cable and stick it into something!! You’re thinking about sex again aren’t you? Ugh you people.. Audio interfaces people!!!! Lets talk dirty about those.

So what is an audio interface? Don’t I have one built into my computer? Why are you making spend more money on stuff?!?! So you have a sound board built into your computer most likely, but those are not intended to connect to musical instruments and professional microphones and equipment, so we need something to do that properly.

So what are we looking for when we buy an audio interface? Well that depends on what you are planning to do. Let’s take a look at a simple entry level interface and see what we have. I’m using a Presonus Audio Box as an example, but there are a number of other good ones out there, the Focusrite 2i2 comes to mind as well. You will see on the front there are two jacks on the front. It is a combination Microphone/Instrument jack so you can plug either into it. What is not on there is a Line input so you can plug keyboards or the such into it.

This is a good time to discuss the differences between them. Microphones typically use a type of jack called XLR. This is what it looks like:

So if you are planning on mic’ing anything you will need to be able to support that with the right connection. Now there are many different types of mics, which we will discuss in depth later. Some types of microphones require power, 48 volts to be exact which is why that 48v button appears. Depending on the manufacturer that also may be referred to as the much cooler sounding Phantom Power. Now what comes out of microphones is an extremely quiet signal, which means it needs to be amplified before it can be amplified, hence the term preamp.

Microphone preamps are a discussion all within themselves, and standalone preamps can run hundreds, thousands, into tens of thousands of dollars for some of the boutique preamps. Ever seen Sound City by Dave Grohl? If not you should, but one of the reasons that board sounds the way it does is because of the legendary Neve 1073 preamps in it. You are not getting that with a budget interface, what you are getting are transparent clean mic pres. What that means is that the microphone preamps don’t colour the sound of the microphones these days. The technology has come a long way and pretty well any audio interface you buy these days is going to sound light years ahead of what was made in the past.

Now back to that jack, see the whole in the middle? That’s for an instrument, as in a guitar. It’s called a Hi-Z plug. Looks like the same quarter inch cable that would plug into the back would plug into that. It would, but this is a great time to talk about impedance.

This a really geeky topic, but I’ll do my best to explain it using plain english. In an electronic circuit you need something to prevent electricity from moving. That is called the impedance, in the old days that number would vary and as a result sounds would change and it’s what would help give vintage equipment an identifiable sound. These days everyone sticks to defined numbers for consistency and so things will work the way they are supposed to. Microphones have a specific impedance, as do instruments like guitars and basses, as do external pieces of equipment like compressors and external mic pres.

Now there are pieces of equipment like a DI box that will let your guitar plug into your mic pres, but why add more equipment if you can have it right out of the box? So I would suggest looking for an interface that has a mic pre, a Hi-Z input for instruments and line inputs and outputs for other gear you may have. Another note here to complicate matters, consumer grade equipment like CD players and turntables, and things that have RCA jacks on them are not meant for pro audio grade line inputs, so if you are going to be using that, add those onto the requirements you need for your audio interface.

OK, the MIDI port on the back. Another should have, or must have if you are planning on connecting keyboards that use that. Most keyboards these days will have USB on it as well, but honestly I do find having Midi ports handy.

So you got stuff hooked up and you want to play. Let’s talk about some of the other things going on with audio interfaces. In this case that little knob called mixer, which has input or playback. This will hearken back to my last post and the nasty little subject of latency.

Latency is the time it takes your system to receive the signal, send it to the computer, process it, and then send it back. If it’s low, you won’t notice it, if it’s not, you will hit a note, and then a split second (or longer), you will hear it. Obviously this can be a horrible thing. To mitigate that manufacturers add a mix signal so you will hear what you are playing as you play it by using the signal before it gets sent to the computer. Totally reduces latency but you will not hear the processed signal (so think if it’s a guitar and you’re adding distortion, you will hear the dry undistorted signal).

I have found this problem to be most prevalent in USB devices on Windows. More often than not it can be resolved by properly tuning a system, but it depends on your setup.

That’s the basics. Now things to consider are. Are you planning on expanding in the future? Under Windows you are limited to one interface at a time if it’s USB. With Firewire and Thunderbolt you can daisy chain interfaces that support it. So I have an Apollo, and an Apollo Twin, they connect to each other, and one cable to the PC(or Mac) and I have one big Apollo unit. Likewise I have a pair of firewire Presonus 16.4.2 mixers that connect to each other and then the computer to form one big 32 channel mixing board/audio interface. So you may want to see if you’re units can be daisy chained, or if they support ADAT. What is ADAT, why let me tell you.

The ADAT standard was created by Alesis as a digital replacement for analogue tape and stands for Alesis Digital Audio Tape. Back then they used VHS tapes to digitally store the audio data. The tape part has disappeared but the tiny optical connectors stuck around and is still widely used today for expansions of digital audio interfaces. Initially there ADAT maxed out at eight channels of 48khz 24 bit audio, but through a process called SMUXing (basically using two ADAT ports) you can achieve 8 channels at 96khz 24 bit, or 4 channles at 192 Khz 24 bit.

If your interface supports ADAT, you can then use something like a Focusrite Octopre to add 8 additional channels of audio to your interface.

Damn, that’s a lot of information. Now some advice. I’ve gone through a ton of different audio interfaces, mistakes were made. For me personally I find myself using my Universal Audio interfaces the most, however if you are just starting out, you DON’T need a high end interface. As a matter of fact I would argue you are better off getting something inexpensive and learning how to get the best sound out of that. As mentioned earlier audio interfaces these days are light years ahead of what was offered in the past in terms of sound quality so you can get an amazing sound out of pretty well anything you buy these days with a little work.

What you should keep in mind is what you plan on doing with it. If you are in a bedroom recording yourself a two channel interface should be enough. If you are a drummer you should really start at eight channels and make sure you have an ADAT expansion port on the back to add additional channels of audio should you need it. Regardless get in there and start recording….. Oh wait! You need software for that, which means next up DAW software!