Ashly PQX-572 Manuel d'utilisation - Page 4

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Operating Manual - PQX 571 and PQX 572 Parametric Equalizer

4.3

Grounding

The terminal strip has two ground con-

nections, one for input ground and one for chassis

ground. The equalizer is shipped with a jumper

strap connecting these two grounds. Normally,

this strap should be left in place so the chassis

and input grounds are connected. In a rack-mount

installation where the equalizer is connected to

other equipment with unbalanced inputs or out-

puts, and the rack itself provides a good electrical

connection between the equalizer chassis and the

other equipment, it may be desirable to remove this strap

to isolate the input ground from chassis ground and avoid

a ground loop. 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.

CONTROLS

5.1

Low Shelving Filter (Filter No. 1)

1. Low Shelf Level

The nature of a shelving filter is such that the fre-

quency response ramps up to a plateau and then levels off

again, hence the term "shelf". This level control knob ad-

justs the boost or cut of the signal below the tuned filter fre-

quency 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.

Low Shelf Level Response

5.2

Parametric Filters (Filters No. 2-6)

1. Range Switch

Each parametric filter has a normal center fre-

quency 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 fre-

quency 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 (some-

times called "Q"), and is a key reason parametric equaliz-

ers 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 adja-

cent 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 "zero-

ing" the level control when considering optimum noise

performance.