Recording Guitar and Bass: Reduce the Noise
By Anderton |
Quiet is good—and these tips will help get you there
by Craig Anderton
Noise comes in many guises: there’s hiss from preamps, clicks and pops from digital clock mismatches, hum from bad shielding, and (unfortunately) a whole lot more. As a result, there’s no one way to get rid of noise—different problems require different solutions. The secret to a quiet recording is to find, then minimize, each noise source.
When you’re chasing down noise, wear headphones to hear more detail in the sound. Then, start from your final output and work backward. Turn up individual faders, enable/bypass EQ, vary the mic preamp gain, etc. to help isolate the main contributors of noise. Following are tips on reducing noise.
REDUCING NOISE AT THE SOURCE
- Set your instruments’s level control up full. The more signal feeding an amp or preamp, the better.
- Transformers, computers, hard drives, etc. can leak interference into pickups. Angle your axe away from noise sources, but note that even the slightest movement could allow noise to re-enter. A wireless tablet controller or wireless keyboard may allow you to get far enough away from your computer to reduce noise considerably.
- While recording, turn off any digital gear that’s not in use if it contributes interference. Even LCD monitors can radiate noise; some players have learned how to record using keyboard equivalents to allow for turning off the monitor during the actual recording process.
- The fewer fans, the better. Some graphics cards are fanless, like the ATI Radeon HD5450 (Fig. 1), which makes them well-suited to the studio.
Fig. 1: Look ma, no fans: the ATI Radeon HD5450 is one of many graphics cards that doesn't have a fan, which helps reduce noise in the studio.
- Solid-state drives—while more expensive than conventional hard drives—make no noise and run cooler.
- If you have a hard drive running for backup, turn it off while recording. Back up to a USB stick, then copy over to the hard drive after the session is over.
- Fluorescent lights and dimmers can cause interference. Incandescent and LED lamps are quieter.
- Humbucking pickups are less sensitive to external interference than single-coil pickups, but they still somewhat susceptible to noise.
HARDWARE SIGNAL PROCESSORS
- Any signal processor fed directly from your instrument should have a high input impedance (250K ohms or higher). This prevents loading down the pickups; loading reduces level as well as high frequencies. Note that this is not an issue with active pickups.If miking your amp is too noisy, try going direct into the console or recorder with a preamp that has “character,” or an amp emulator. This is usually quieter than miking a tube amp, although a high-gain hardware processor or even a software amp sim will amplify noise entering your axe as surely as any physical amp.
- If you’re feeding a processor designed for studio applications, unless it has an “instrument” input you may need to precede it with a compressor, preamp, or other effect designed specifically for guitar- or bass-level signals. This will “condition” the signal, allowing it to drive the studio-oriented effect while maintaining a good signal-to-noise ratio.
- Hit the processor inputs with as much signal level as possible, but be careful. Some effects monitor the level coming into the unit, so if the effect being used adds a lot of gain (e.g., a very resonant filter) and overloads the internal DSP, this won’t show up on the meters – yet the sound will be distorted. It’s best if your processor can monitor the DSP output as well as the input.
- With inexpensive “stomp boxes,” using batteries instead of AC adapters will sometimes give less hum.
These tips apply to playing live, as well as to using a hardware mixer in the studio.
- Turn down all unused channels, subgroup level controls, and effects returns. Even if there’s no input signal, turning up a fader can contribute noise.
- Some systems let you choose between –10 dB and +4 dB as a nominal signal level. Using +4 dB sends more level through the system, which can improve the signal-to-noise ratio. However, be consistent: if you choose +4, then everything should run at +4. You also need peripheral equipment that can run at this level.
- Check each of your effects returns. Reverbs in particular are notorious for dumping noise into the master output bus. If an effects unit has internal noise gating, sometimes adjusting the threshold up a little from the factory setting will cut out residual hiss.
- Use proper gain staging. Initially set the master output and channel faders to unity gain (usually indicated as 0 dB). Use the channel strip gain trim controls to bring any input signals up to the proper level. If the trim control can’t go high enough, it’s better to bring up the associated channel fader than the master.
- To boost mic gain, consider using pro-grade transformers as an alternative to active mic preamps. The pros and cons of each are controversial, but the short form is that transformers can color the sound, while preamps add noise. However, coloration is in the ear of the beholder, and is not necessarily a bad thing. In fact, a quality transformer can serve as a signal processor that “warms up” the signal, particularly with bass.
REDUCING NOISE IN DAWS
- A steep (e.g., 48dB/octave) lowpass filter can take down the highs, and the hiss along with it.
- Not all noise is in the high frequencies—consider hum with guitar. Again, a steep filter—this time in highpass mode—can help get rid of low-frequency and subsonic noise (Fig. 2).
Fig. 2: Trimming the extreme low and high frequencies from a guitar part using Sonar X3's lowpass and highpass filters.
- Deleting the spaces between notes, then adding a short fadeout from the note into the silent part, is time-consuming but can really clean up a part. Some programs include an option to “strip silence” which automates the process, but check to make sure it’s not causing an unintended consequences (e.g., an overly abrupt decay).
- There are many “restoration” processors, like iZotope’s RX (Fig. 3), the noise reduction tool in Sony Sound Forge, and several tools in Adobe Audition. Some of the most effective versions work by taking a “noiseprint” of a part of the track that consists only of noise (or hum), and removing only that component from the overall sound.
Fig. 3: iZotope's RX suite of noise reduction tools (the current version is RX3) is effective at de-noising, as well as removing crackles, clicks, and other artifacts.
Okay . . . now your system should be a lot quieter. Granted, if your music is great, no one’s going to care too much about a dB or so of noise. But why not go for as pro a sound as possible? All it takes is a little effort.
Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.