Recording Guitars - Get the Signal?

The most basic element of recording is the signal path. That may sound a little obvious-I mean, everyone knows that you can't record a guitar or voice until you first feed it to the recorder. But it is also one of the most overlooked elements of creating a good recording. As the saying goes, "Garbage in, garbage out": No matter how good your recorder, effects and mixers are, your tracks are going to sound like they were processed through your dog's digestive tracks unless the original signal is of optimum quality.

Professional engineers pay plenty of attention to creating the healthiest signal path possible. One of the most important steps is level and impedance matching. This means that the level coming from the source (e.g., your guitar's output jack) matches well with the input level of the destination (your 4-track's 1/4" input). While the output levels of various guitars, microphones, and preamps vary widely, they fall into three basic categories:

1) Instrument level (-20dB and lower) These sources, like a guitar, have the lowest output. This means that their signals need to be boosted by some sort of preamp before they can reach the level necessary to get a healthy signal to your recorder. Most microphones fall into this category as well, and in the case of some dynamic mics the output can be even lower. Instrument-level jacks are usually unbalanced 1/4" high impedance (for guitar) or XLR balanced low impedance (for microphones).

2) Line Level (-10dB) Commonly referred to as semi-pro or consumer line level. This is the spec most common on home recording gear, including mixers, the unbalanced RCA inputs found on many tape decks, and so on.

3) Line Level (+4dB) +4dB, balanced inputs and outputs are most common in professional applications. Balanced connectors can be either XLR (don't confuse these with mic inputs) or 1/4" TRS (Tip/Ring/Sleeve). TRS plugs look like the plugs on your stereo headphones. Although, as we mentioned, most home recording gear uses unbalanced -10dB connectors, devices like ADATs, TASCAM DA88s, mixers and many soundcards can also accommodate a +4dB balanced signal

The advantage of the higher level/balanced connection is twofold: More headroom means you can feed just about any signal without causing distortion; balanced operation means lower noise. A balanced line usually sounds better than an unbalanced line when you have a long cable run. Problems when the output of the source (your guitar) is a poor match for the input of the destination (your tape deck). Let's look at a couple of common situations.

Example 1:
You want to plug your acoustic guitar, which is equipped with a pickup, directly into your mixer. You see that the mixer has a 1/4" input, a perfect match for your guitar cable. But when you plug in, you find that the guitar sounds lifeless, slightly distorted, and noisy. If the 1/4" input is designed to accommodate a -10dB (or +4dB) signal, the guitar's -20dB output won't drive it hard enough to supercede the noise floor. The problem can get worse if the jack is designed for balanced input-feeding an unbalanced line can cause grounding noise and buzzing.

Example 2:
Here's the opposite problem. Let's say you like to plug your guitar into a preamp such as the Line 6 POD or SansAmp before feeding to your tape deck or mixer. If your preamp's output is too hot, you may overload the mixer or tape deck's input, causing distortion.

The solution to each example's problem is pretty simple.

Step 1)
Find out the optimal level of each piece of gear in your studio. This is usually at the back of the owner's manual.

Step 2)
If your source (guitar) does not match your destination (mixer or tape recorder) in level, impedance, or balanced/unbalanced status, use the appropriate transformer to bring them into agreement. In our first example, we tried to feed a guitar directly into a mixer through a 1/4" line input. The results? Not so good. We'd have done better by connecting the guitar into an external preamp first. We could also have used a direct box to create a balanced signal and match the impedance of the guitar to the microphone input on the board. The mic input is designed to handle the guitar's output level comfortably. In Example 2, our preamp's output was too hot for the mixer. While we could have reduced the level by simply turning down the volume, this isn't always the best way to go. A better solution is to use the level-match switch found on many preamps or other outboard devices. You can find it either on the back panel or, if is a digitally controlled device, in the software. If you know the optimal level of your mixer or recorder's input, you can set your preamp to match. Simple enough, right? No need to get intimidated by recording technology. Check out our Guitarist's Glossary for more clarification of any terms that might be unfamiliar to you. Now that you know how to get signal from your guitar to your board, we'll be ready to tackle recording levels next time around.

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