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Unless you have such an installation and have a hum problem you can’t solve by other means (ie: using balanced input and output connections), leave the ground jumper strap in place. 5. CONTROLS 5.1 Low Shelving Filter (Filter No. 1) 1. Low Shelf Level The nature of a shelving filter is such that the frequency response ramps up to a plateau and then levels off again, hence the term “shelf”. This level control knob adjusts the boost or cut of the signal below the tuned filter frequency as selected by its outer concentric frequency knob. The level which is indicated on the panel dial is the decibel level of the flat portion of the shelf. (see drawing) 2. Low Shelf Frequency This control adjusts the frequency below which the shelving filter affects the level. The frequency which is indicated on the panel dial is the midpoint of the shelf’s sloping response. 5.2 Parametric Filters (Filters No. 2-6) 1. Range Switch Each parametric filter has a normal center frequency range of 200Hz-20KHz. Depressing the range switch divides the center frequency by 10, providing a range of 20Hz-2KHz. 2. Level Control The band of frequencies selected by the frequency and bandwidth controls are increased or decreased up to 15dB by this control. 3. Frequency Control This outer concentric knob adjusts the center frequency of the filter action. Tick marks on the face panel are calibrated to ISO 1/3 octave center frequencies. 4. Bandwidth Control This inner concentric Knob allows control of the width of frequencies around the center frequency (sometimes called “Q”), and is a key reason parametric equalizers are such a precise tool. With it, you can affect a wide (3.3 octaves) response, or a narrow (.05 octaves) band. To give an example, you could effectively boost or cut by 15dB a middle C on the piano without affecting the adjacent B or D at all! 5. EQ In/Out Switch The individual filter is engaged by depressing this switch. Since the filter is bypassed when the EQ switch is out, it is recommended that the EQ switch be out when no filter action is required. This is preferable to “zeroing” the level control when considering optimum noise performance. Low Shelf Level Response Operating Manual - PQX 571 and PQX 572 Parametric Equalizer 5.3 High Shelving Filter (Filter No. 7) These concentric controls work the same way as the low shelf controls described in (1) and (2) except the filter response starts at the center frequency selected and continues up in frequency. 5.4 Master Level The overall gain of the equalizer is adjusted by this control. The master level gain stage is placed prior to any filter stages so that increasing the master level will not amplify filter noise. If the Master EQ switch is out, the level control has no affect. Signals are then simply routed through the equalizer at unity gain. 5.5 Clip Indicator This red LED illuminates when an amplifier in any of the filters comes within 3 dB of clipping, includ- ing those filters which are not engaged. The maximum signal level through the PQX equalizers is greater than +22 dBu. Parametric Filter Frequency Control Parametric Filter Level Control High Shelf Level Response Parametric Filter Bandwidth Control Operating Manual - PQX 571 and PQX 572 Parametric Equalizer Mixer PQX 571 Parametric Equalizer Crossover Power Amplifier Compressor - Limiter Typical Sound System Design 6. TYPICAL APPLICATIONS 6.1 Connecting Into a Sound System Typically an equalizer is used in a sound system which has a mixer or some other sort of preamplifier. In such cases, the equalizer normally should be connected after the mixer but before any electronic crossovers or limiters. The PQX equalizers are line level devices designed to operate at nominal +4 dBu signal levels; therefore, the equalizer should not be connected directly to microphones, phonograph players or low level musical instruments. 6.2 General Tone Control The parametric equalizer is a very useful device for general tone shaping because the filter’s center frequency, bandwidth and level are all continuously variable. To use the power of the equalizer effectively, you need to translate your idea of the tone you want to produce into a range of numerical frequencies. This is simple after a little practice. Here are a few references which are useful for starting points: Very low bass (the “wind” in a kick drum, almost felt as much as heard -40Hz-80Hz. The low register of a male voice - 200Hz The low register of a female voice - 350Hz Lower midrange (“warmth” frequencies) 400Hz- 1KHz Upper midrange (“harshness”, snare drum “bite”, “hot” sound) -2.5KHz-4KHz. Sibilance (“sss” sounds, cymbal “sizzle”) - 8KHz15KHz. Try using these starting points as a guide when you want more or less of these types of sounds. Adjust by ear from there. It is always a good idea to remember that a little equalization usually works out much better than a lot, and that there are many audio problems which cannot be solved with equalization alone. 6.3 Feedback Control The...

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