G

Gain

How much an electronic circuit amplifies a signal is called its "gain". In most specs or references you will see gain expressed as a decibel value (i.e. 6 dB of gain). Occasionally, you may sometimes see gain expressed as a straight numeric ratio (a voltage gain of 4 or a power gain of 2).

Gate

A dynamics device whose function is to remove unwanted audio material below a certain threshold. Some type of "gain cell" is employed (usually a VCA) that can raise or lower the volume of the audio going through the unit. When the signal falls below a certain threshold that is set the gain cell will quickly drop the audio level down to a predetermined level. This level is usually very low, or even off, but in some applications it may only be a reduction of a few dB. The reason they are called gates is because when they "close" it sounds as if the audio has suddenly stopped, or has been "gated." Now, it is possible to set many gates for slower response time so the effect is not as sudden, but often a sudden change is what is desired. Gates are often used on drum tracks to prevent bleed from other nearby drum mics, and they are sometimes used on noisy sources so when the desired audio signal stops the noise is automatically muted. The gated reverb sounds made popular by Phil Collins and Peter Gabriel in the 1980's were the result of running a reverb's decay through a gate. When the reverb level fell below a certain threshold the sound would abruptly cut off.

GFI

A special type of AC circuit breaker designed for increased safety. A GFI compares the current on the hot AC lead to the neutral AC lead. If there is any difference then that means there is a problem and the current should be shunted to ground. A GFI breaker is designed to VERY quickly open and interrupt the power should this condition arise. This is better than simply shunting dangerous current to the safety ground because even when current is going to ground in a normal system the breaker will not open until its current capacity is surpassed. If you happen to be in the path of this current then...well...that would be bad. A GFI interrupts the current flow before significant amounts try to find a path to ground.

Gooseneck

A flexible, spiral, metal coupling usually between 8 and 18 inches long that can be used to attach a microphone to a stand. The gooseneck is flexible and allows the microphone to be oriented in almost any direction. Most metal goosenecks squeak when moved so it is generally not possible to move them while the microphone is in use. Recently, however, manufacturers have started using rubber and plastic compounds to build goosenecks that can be move without generating excessive noise in the microphone.

Granular Synthesis

A sophisticated (and esoteric) form of additive synthesis (see WFTD archive Additive Synthesis) combining sound elements called "grains," which are used to make up sonic "events." Events are time sliced into "screens" that end up containing the amplitude and frequency dimensions of hundreds of events. Very complex sounds can be created using this technique, but the computational power required to generate them is so great that it has not been practical to use this form of synthesis in any commercially available hardware machines.

Graphic Equalizer

A type of EQ that is configured to provide a graphic display of the EQ settings. Years ago equalizers were all rotary knob based. When units began to arrive on the scenes that had 15, 30, or even 45 bands (frequencies) they could EQ at once it became difficult to see what was going on at a glance. Looking at a row of 30 knobs to get an overall idea of the EQ curve is pretty difficult. So equalizers that used sliders instead of knobs were developed and quickly won the favor of engineers due to their improved ergonomics. People liked how easy it was to see the overall EQ curve at a glance, but they also just liked using sliders more than knobs (something that we'd already figured out about mixers). The ONLY thing that makes an EQ "graphic" is this configuration of being able to see the curve at a glance. Contrary to popular belief there are graphic EQ's that have the same features as parametric EQ's, including Q controls and sweepable frequencies. Most graphic EQ's, however, only give you control of cutting or boosting a pre-selected set of frequencies at a pre-selected Q.

Green Book

Also known as CD-I or CD Interactive, this book is a subset of the White Book. It specifies an operating system, an API (Application Programming Interface) and playback hardware. Philips is the only manufacturer supporting this technology.

Ground

• The hard stuff you hit when you fall out of an airplane.
• In electricity, a large conducting body, such as the earth or an electric circuit connected to the earth, used as a reference zero of electrical potential.
• A conducting object, such as a wire, that is connected to such a position of zero potential for the sake of "grounding" an electronic device.
• Grounding - What a quarterback does with a football when he sees Reggie White coming at him.
• Verb - to "ground" something means connecting it electrically to ground.

In electricity an electrical path to ground is provided by code at all electrical outlets for safety. In the event of a failure or circumstance that might normally cause the operator (or anyone coming in to electrical contact with connected equipment) to be the return path for the electrical current the ground can shunt this current away safely and return it to earth, which is where it is trying to go anyway. The alternative of the operator being the return path can cause electrocution.

In audio, ground usually refers to either the electrical ground mentioned above, or to an audio shield. An audio shield is not always a ground and should never be used as a safety ground. That they are often at ground potential is a function of how they may be connected to other equipment. Many audio devices have the ability to disconnect their signal paths entirely from electrical ground as a way to prevent hum or ground loop problems.

Ground Lift

In some situations, it may be useful or become necessary to defeat a signal's path to ground. For example, if your studio is plagued with ground loops, or noise issues, breaking a path to ground may solve the problem. Ground lift is a switch found on many pieces of audio equipment which disconnects audio signal ground from earth or chassis ground.

Using ground lift switches is considered to be far safer than the old "3-to-2 prong AC adapter" solution (which we heartily DON'T recommend, see TTOTD from February 24, 1997 for more on this topic). However, occasionally ground lift switching will not be as effective in resolving problems as the brute force AC adapter might be.

Ground Loop

A phenomenon that occurs when an audio (or video) system has multiple paths and path lengths to ground. When a ground loop occurs in an audio system it will manifest itself as a hum. The hum occurs at 60 Hz (Hertz) or some multiple of 60 Hz because that is the line frequency of AC (in the US). In video a ground loop can often shows up as rolling bars (sometimes quite faint) in the picture. The severity of the hum will vary depending upon numerous factors; sometimes it can be quite faint, while other times it can be so loud that it overloads an amplifier. Ground loops have been a problem since the very early days of connecting audio equipment together and there have been volumes of materials written on how to prevent and solve them. Any time one connects multiple pieces of audio gear together that are each plugged into an electrical outlet and connected to each other via signal cables, and possibly even electrically connected by their cases touching or being in the same rack, the risk of ground loops increases. There are many valid schools of thought on stopping them, some of which we will get in to in the coming months. At the most basic level, however, the only way to prevent or get rid of ground loops is to make sure that all of your equipment has only one path to ground. One way people sometimes accomplish this is to utilize AC plug ground lift adapters (a.k.a. widow-makers) on offending pieces of equipment as determined by troubleshooting the system, but this is considered unsafe and we highly recommend against it.

Group Delay

1. The amount of time between when a rehearsal is supposed to start, and when all the members of the band have arrived.

2. A characteristic of electronic components that causes different frequency ranges to be delayed by varying amounts. Typically, highs and mids will be delayed less than low frequencies. By using careful designs, engineers can take advantage of this to reduce true harmonic distortion, and improve sound quality (Oram Professional Audio is a major proponent of this technique).

Guard Band

1. In concept, similar to a guard dog, although the musicians that make up guard bands are often far more ferocious. They are generally employed as protection against polka bands made up of kazoo and accordian players performing Bee Gees hits through Marshall stacks turned up to "11."

2. A thin, unrecorded area between the recorded tracks on magnetic tape. The physical separation provided by a guard band helps to cut down on crosstalk between adjacent signals on the tape. (See also WFTD "Crosstalk")