Beginner FAQ on Audio Interface Preamps, Analog gears and DI Boxes

I received this common inquiry by mail, so I decided to write a post on this to clarify these common questions.

Hi

I read your article about how to make quality recordings and have a couple of questions.

First I am planning buying an audio interface with built-in preamps and wonder which is best. I have read some reviews about presonus fireproject and motu and mackie onyx, and its very confusing to choose one.

I also wonder if I need some external effects like compressor and processor between the different instruments and the audio interface.

Many internet sites are writing about using DI boxes when recording guitar and bass, and compressor on drums and vocal.

Thank you in advance.

Importance of Preamps on Audio interface

First, buying an audio interface with built-in preamps should not be that hard. You can refer to this article buying an audio interface tips for beginner.

I cannot advise you which is good or great because of the lot of factors involved, such as your budget, number of inputs, etc. But since you are talking about quality of recordings and the importance of having a quality signal chain; I would put a strong importance on the quality of the pre-amps.

Researching further, I found out that some audio interface have decent and award winning preamps, such as Focusrite. I do not know with the others, but currently I am using Saffire Pro 40 which is a great sounding audio interface.

Saffire Pro 40 has eight inputs, although this might look too much for your needs, you can use one with lesser inputs. Manufacturers such as Focusrite use the same preamps both in their high-end and low end audio interface. So for example, if you purchase a Saffire USB 6 (one of the cheapest on the Focusrite line of audio interface) it uses the same preamp with the Saffire Pro 40; only that it has two inputs.

If you plan to buy another brand whether Presonus, Mackie or M-audio, try to read their manual or reviews and make sure you got a decent sounding preamps.

Importance of having analog effects on the signal chain

Analog effects add warmth and realism to your recordings. Most of the time, producers are too obsessed with software effects (plug-ins, etc) only to complain the project lacks the analog warm sound at the finish.

One very simple tip is to use analog effects on your recording. So yes, it is advisable to use analog gears like compressors, EQ before recording if that makes the recording sound great.

You can connect it as follows:

Instruments (guitars, for example) == > Analog effects (compressor, EQ) == > Audio Interface Input (preamp) == > Computer (DAW)

You can even record all instruments using this technique and get the benefits of having a few processes during the mix (such as EQ and compression).

A common example is live band recording. EQ and compressors can be applied on the guitar and bass guitar as analog effects and adjust for good sound before recording. EQ can be applied to increase clarity not only the guitars, bass but on the vocals also (cutting on the guitar EQ band, not on vocals).

The same technique with the drums while only the vocals are recorded dry (without any effects). During the mixing stage; bass, guitars and drums do not anymore need digital effects since they already sound polished before being recorded.

Only the vocals needs a little processing, so the overall result of your mix is warm and great sounding because of less digital effects applied.

Importance of DI boxes in recording guitars and bass

DI boxes are important for getting a great recording sound for guitars and bass. The function of the DI is to convert a high impedance input to a low impedance output. This is necessary for getting a nice sound as impedance miss-match can result to an awful guitar and bass sound.

You need to use a DI box when recording guitars and bass to a low impedance microphone input of the preamp. A common example is the audio mixer microphone preamp XLR input. See screenshot of the sample audio mixer (Behringer Xenyx series):

As what you have noticed the mixer preamp requires a low impedance XLR input. Supposing you are recording a passive bass guitar and need to have a strong and clean signal; you can record it as follows:

Passive bass guitar == > DI box == > Audio Mixer XLR preamp input

Passive bass guitar have high impedance but very weak signal output (instrument level signals), so a DI box would convert this to low impedance output suitable for microphone preamps input. And then the preamp would boost it to line level signals. Read this tutorial on difference of line, instrument and microphone levels if you are familiar with these terms.

DI box are inexpensive yet very useful recording gears. One of the commonly used DI box is Pyle-Pro PDC21.

However some audio interface has the capability to recognize instrument level inputs such as Saffire Pro 40. This audio interface has an “instrument” level button that when pressed (see screenshot below in yellow box), it will automatically adjust impedance when a high impedance input is connected for recording (such as a bass guitar).

In this case, you do not need an external DI because the audio interface should handle the impedance matching pretty well. But bear in mind that not all audio interface has this feature.

Content last updated on July 25, 2012