Saturday, August 1, 2020

What specs to check out before buying an audio interface


Hello and welcome to this week's article!

This article is to be considered as an expansion of our article about audio interfaces (click here to check it out), and this time we're going to check out a bit more in depth the tech specs.

As per every other tech product, also audio interfaces are placed in the market in various price ranges, which can go from 60 bucks to well over one thousand (or more), and yet they all promise the same thing: to record an input signal, convert it from analog to digital and send it to your computer, usually letting you also plug an output device such as monitors or headphones.

Why the price difference then?
Because of two things: the specs and the support.
Let's start from the support: when choosing an audio interface support gets often overlooked, but it actually is even more important than the specs themselves.
You should thing about keeping the interface for several years, and if the support is not good, if there are bugs they will not get solved (and often in the first release of the drivers there is something to be fixed), or if you change your os (for example to a newer version of windows) and the support is not good, it's very likey that they will not relese the drivers for the new version, making the interface unusable (and this happens more often than you think with cheaper brands, which is infuriating).

Moving to the specs, here are some to check out when choosing an interface (obviously there are many more than these, but these are the most important ones):

Sample rate: this number tells you how often the device checks out the audio signal and records its amplitude, so it's basically the speed at which the analog sound is rendered into a digital signal.
The most common sample rates are 44.1 khz, 48 khz, 96 khz, 192 khz.
In case of 96khz for example, the interface "photographs" the incoming sound 96'000 times per second. 
These sample rates also tell us the maximum frequency the interface can record, which is the half of the sample rate number (for example in the case of 44.1 khz is 22.05 khz, which is still more than the usual human hearing, which ranges from 20 hz to 20 khz).
When recording music, it's suggestable to have an interface capable of recording at least at 48 khz.

Frequency response: this shows you the sensitivity of the device, and tells you the range on which it operates, for example 20 hz to 20 khz. This number is also modified from other factors, for example microphones, which can create a funnel effect.

Bit depth: it tells you how many bits are used for each sample recorded, and this influences the dynamic range of the interface. Having more bits means being able to record with higher dynamic ranges (therefore with a lower noise floor). 
16 bit: it's possible to achieve a dynamic range (theoretical) of 96 db
24 bit: it's possible to achieve a dynamic range (theoretical) of 144 db

Dynamic range: it's the ratio between the loudest signal that can be recorded by the interface and the noise floor, and it's measured in dbA (decibel A-weighted). 
The more dynamic range there is, the lesser the risk (when for example compressing the signal) to raise the noise floor to a point that will ruin our sound. 
In order to avoid these problems, it's suggested to use an interface with a dynamic range of 100 or more dbA.

Gain: often in the interface specs there is written something like "Gain 0-60db", which means that the gain knob can amplify the incoming audio signal up to 60db. If the preamp applies a minimum of +10db to a maximum of +60db, the Gain Range (the distance between the minimum and the maximum) is 50db.

EIN: it's the equivalent input noise, a way of stating the preamplifier noise of a recording device. When recording from a source such a microphone, the signal needs to pass through a preamp in order to raise to the desired gain level, and each preamp has a certain amount of intrinsic noise, which should be as low as possible.
Ein is measured in dbU (which are always negative numbers), and the lower the number, the lower the noise.
EIN is a good system to compare the noise level of two different interfaces, to see which one is better (for example -130 dbu is considered a very low noise preamp, while from -120 dbu up the noise starts becoming noticeable).

I hope this was helpful!