Equalizers ____________________ Page 1 of 4 Equalizers ("EQ" for short) have been around in the recording and motion picture work for many years, and in the last ten years or so have become popular items in many home stereo systems. They are more often than not an item included in most small home and semi-pro recording studios. The term "equalizer" is just a ten-dollar name for fancy tone control. On your home stereo, the BASS and TREBLE controls are the normal tone controls; they break the audio fequency spectrum up into broadly-defined "low" and "high" parts (or, slices). With the tone controls, you can vary the relative strengths of the low and high notes you send to your speakers. Graphic equalizers generally cover from 10 to 30 such slices of the sound spectrum. Home type EQ units generally have a seperate but identical set of sliders for each of the two stereo channels; hence, the presence of 20 or more slider controls. Equalizers allow you to break the spectrum up into much more sharply-defined "slices" of the spectrum. The controls each cover a particular slice of the spectrum, and on "Graphic equalizers," they are usually arranged as a series of vertical "sliders" on the front panel. By glancing at the relative positions of the sliders, you can get a quick overall look at how the different parts of the spectrum relate to each other in terms of relative strength. The relative positions of the sliders draw a "graph" of the resulting spectrum (hence, the name "Graphic equalizer"). For example, you might have the sliders on your EQ set so they look something like this (only one channel shown): <----- Bass Mid-Range Treble -----> __________________________________________________________________________ | | | + 12 dB ------------------------------------------------------------- | | 9 -----------------------------------------------------------[ ] | | 6 ------------------------------------------------------------- | | 3 ---------[ ]--[ ]-------------------------------------[ ]---- | | 0 [ ]--[ ]------------[ ]--[ ]----------------------[ ]--------- | | 3 -----------------------------[ ]--[ ]--[ ]--[ ]-------------- | | 6 ------------------------------------------------------------- | | 9 ------------------------------------------------------------- | | - 12 dB ------------------------------------------------------------- | |__________________________________________________________________________| Equalizers ____________________ Page 2 of 4 The relative positions of the controls show at a glance that the mid-lows are boosted slightly above normal, the mid-range is attenuated slightly below normal, and the extreme high frequencies are boosted considerably. This example might be used during playback of an old record or tape, where the "presence" in the original recording is too strong, and where the treble frequencies (such as snare drum brushes and cymbals) need to brought forward from the background. You can, for instance, boost the mid-range slightly for more "presence" in a singer's voice, or perhaps decrease the lower two sliders if the sound is too "boomy." You can set both the right and left channels to have the same "curve," or you can set each channel differently. It all depends on how the record or tape you are playing was recorded, and how you want it to sound -what sounds best to you. Equalizers can be hooked into your system between the pre-amp's LINE OUT and the power amplifier's LINE IN connections. Or, if you do not have a seperate pre-amp and power amp, you can connect the EQ in the "Tape Monitor" loop on your pre-amp or receiver. Here are some ways you can hook your equalizer into your system: Pre-Amp EQ POWER AMP ------------------ ------------------ ------------------ | | | | | | | | | | | | | Line Out|----->|Line In Line Out|----->|Line In | | | | | | | | | | | | | ------------------ ------------------ ------------------ A. Seperate Pre-amplifier and Power Amplifier Amplifier (Receiver) EQ ------------------ ------------------ | | | | | Tape Mon Out|----->|Line In | | | | | | Tape Mon In |<-----|Line Out | | | | | ------------------ ------------------ B. Combined pre-amp and power amplifier or receiver Equalizers ____________________ Page 3 of 4 In both of the above cases, the Tape Out and Tape In on the equalizer are for connections to and from your open-reel or cassette tape recorder: EQ Tape Recorder ------------------- ------------------- | | | | | Tape Out|----->|Line In | | | | | | Tape In|<-----|Line Out | | | | | ------------------- ------------------- When used with recording mixers or consoles, EQ units sometimes are inserted into the "effects loop" circuitry. Many of the larger consoles, however, have connections labeled soley for equalizers, leaving the "effects" loop free for other devices, such as reverb units, echo chambers, delay units, etc. Mixers and consoles generally have seperate controls for varying the amount of relative gain or loss of the effects loop. Each channel usually has its own "send" level control, and the console has an overall "return" level control. Some consoles have an overall "send" level control, too. When used with the "effects" loop circuitry, typical EQ connections for mixers/ consoles might look like this: Recording Mixer or Console EQ ------------------------------ ------------------------------ | | | | | | | | | Effects Send|----->|Line In | | | | | | | | | | Effects Return|<-----|Line Out | | | | | | | | | ------------------------------ ------------------------------ Equalizers ____________________ Page 4 of 4 Typical Equalizer controls: o BYPASS/EQ effectively inserts or removes the EQ, without you having to physically connect or disconnect the cables. With the control turned "off" your equalizer's sliders have no effect; ie., the signal passes through your EQ totally unaltered. Turning the bypass on and off gives you a handy means of hearing just how effective (good or bad) a particular EQ setting will be. o METER/OUT turns the built-in meters (or LEDs) on or off. For instance, you may not wish to see them flashing in a dimly lighted room. o TAPE MON IN/OUT gives you an effective "Tape Monitor" circuit in case your pre-amp or receiver does not have one. (It's extremely rare these days to find a pre-amplifier or receiver which does not have a tape mon loop built in.) o GAIN sets the relative overall gain or loss of the entire EQ signal, not just that of any particular band of frequencies.