Keyboard Magazine "In The Studio" Using Noise Gates with Keyboards.
Ah, the bliss of no noise at all ! Well it’s a nice concept but it is seldom that electronic keyboards are free from hiss. Hiss that is then equalized and amplified into more hiss. Electronic keyboardists of the seventies were well aware of the hiss that came with their Fender Rhodes or their Hohner Clavinet. And when we added that phaser, flanger and or chorus unit, it then became untolerable. Yet on records the hiss was absent. Or at least reduced to a level that was far more tolerable to listen to. That is because we have our recording engineers to thank. You know the guys facing that never ending battle against hiss and all the other extraneous little clicks, pops and buzzes. Is it magic? Well not really. Just the gift of being able to harness the power of the "Noise Gate". A device that is so much a part recording today it has been included in most major recording consoles on every channel. Some of you may remember MXR’s "Noise Gate - Line Amp". The little gray box around $100.00 that had one knob called Threshold. This box was a solution to the hiss produced by the Rhodes and clavinet. The problem with a one knob noise gate is that there are no envelope controls. The release and attack of when the gate opened and closed was preset. Now all you true synth people know how useless a synthesizer without any envelope control is. But never the less it was the first affordable unit. Toady there are many units on the market ranging in an average area of about $250.00 but with the features that make a powerful tool. Let’s take a look at some the basic controls found on most noise gates. We’ll start with the Treshold control. This control sets the level at which the gate will open. You could think of a noise as a valve in a heart, a drawbridge that lets sound pass thru whenever that sound is above a certain volume level thus called the threshold. So if the threshold is set for 1db, it will not open untill the level of the sound has reached the 1db threshold. As long as the sound level stays above the 1db threshold point the gate will remain open. When the sound level falls below the 1db point the envelope section of the gate takes over. How fast or slow the gate closes depends on how the envelope controls of the noise gate are set. The most common control found on most noise gates is the release control. Depending on how the release control is set will determine the speed of how fast or slow the volume of the sound will taper off to. For example, the release should be set slower for a ballad than an uptempo song. Playing a Rhodes type of patch during a ballad will probably call for a good deal of ¼ note sustaining chords. A slow release will allow those chords to ring out and die away slowly. On the other extreme a fast funky clavinet riff would require a lightning fast release setting so that the gate will close right with those staccato riffs. If the gate isn’t fast enough the listener would actually be more aware of the hiss present. The apparent sound of hiss turning on and off is appropriately called "breathing’. The art of setting a noise correctly to prevent breathing requires an understanding that the dynamics of the player will have to be reduced so that a good noise gate setting will not be as dependent on the players dynamics. A compressor / limiter is a good tool to even the dynamics out before the signal reaches the noise gate. ( see my article on Using Compression with Keyboards --- issue of Keyboard Magazine) Getting back to fighting the breathing, there is another control called "Attenuation". The attenuation controls how much the sound is attenuated whenever the gate closes. Certain gates have as much as 60 db of attenuation. By setting the attention to a closer amount ( around 10db of cut ) the gate does not close as much or as far and the hiss is reduced but actually still there. It is the total absense of hiss that makes breathing more noticable. The perfect application is when the envelope of the noise gate follows the envelope of the sound. On percussive sounds this is easy. Drums are always recorded with gates. But be carefull when recording live drums. If your gate doesn’t open because your threshold is set too high, your drum won’t get to tape and then there is nothing. Same thing with setting the threshold too high on your keybord. If you play a soft passage be sure that your gate’s threshold is set low enough to open. Another important control is the "Attack" control . This can delay the opening of the gate and can be used to contour the sound. You can take a harsh heavy velocity sounding part and give it the soft curve of a violin on the other extreme. Slower attacks also work well on the reverb unit for your keybords. What you didn’t know that ? Well gates are very much a part of todays reverb effects. For instance if you put a lot of reverb on a staccato percussive keybord part and then set the gates release to be short and the amount of attenuation to full tilt, you can achieve an explosive type of reverb effect. Exactly like the sound of Phil Collin’s snare drum. The reverb is big and then it dies right off making the snare sound even bigger. Another important control is called ratio. The ratio of a noise gate works exactly oppisite that of the ratio of a commporessor/ limiter. Instead of being 2 : 1 the gate’s ratio’s are 1 : 2 and 1: 4 and 1 : 8 and etc. The higher ratio in a noise brings about an interseting phonomema called expansion. Unlike what compression does in smoothing out dynamics, high ratios in a noise will cause expansion and seem to add dynamics to a sound. How much and how these dynamics affect the sound are again dependent on the Attack and Release settings. How fast or slow the dynamics come in to play and how long or short they will last due to the release. Once you start getting on the hiss patrol, it never ends. Keyboards that are digital in nature, upon closer examination will have an alarming amount of hiss. Some keyboards even have noise gates built in to the output stages. The only problem here is that again they are set for slowwer releases and breathing can again be a problem. So even though noise gates may be built in , you still need an additional noise gate to remove the breathing effect. Doubling up ? Well using a noise gate after a noise might seem a little extravagant but this prctice is very much common place in recording today also! Some times the envelope of even the fastest gate may be too slow. By adding a second gate, you can tailor the envelope even closer to that of the orignal sound. Using compression after a noise gate is another interesting effect. You can squash some of the expansion that occurs with high ratio / high attenuation settings. There is even the technique of compressing before the noise gate and after it. Very popular on percussive sounds. I’ve listed some of the many noise gate units available so you can choose which is the right gate for your budget and needs. Good luck and remember no noise is good noise. Dbx 166 - a dual channel noise gate /compressor $ Valey People Dynamite - a dual channel unit $ Drawmer Ds201 - a dual channel unit with de-esser $ Kepex II - sold individually but requires power supply rack Dbx 904 - sold individually but requires power supply rack