AMR 64 Manuel d'utilisation - Page 4

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Mid Frequency EQ: Is a quasi-parametric type

(often referred to as "sweepable") of equalization.

Unlike "fixed" frequency EQ, this allows the opera¬

tor to adjust (tuning like a radio) to the specific

frequency range or desired sound. This is a very

flexible type of equalization that is preferred by

many mixing engineers. The operation incorporates

two controls: Mid Shift: Used to adjust (or select) the

center of the frequency range (adjustable from 200

Hz to 5 kHz). Boost/Cut: Used to select the amount

of boost or cut for the mid frequency section of the

equalizer.

About Sweepable Equalizers

The Mid Frequency EQ section of the AMR 64 utilizes a sweep-

able type equalization circuit. Such equalizers provide a continu¬

ous adjustment of frequencies within the equalizer's operating

range (unlike normal fixed-frequency equalizers that offer one or

a handful of preset fixed frequencies). The sweepable type on the

AMR 64 will allow the range to be adjusted anywhere between

200 Hz and 5 kHz. You first determine if you wish to boost or cut,

then simply apply a moderate amount of boost or cut (+5 or -5 dB)

and adjust the frequency control to the desired frequency range.

This moderate amount of boost or cut will allow you to hear the

affected frequency range quite easily, thereby allowing you to

place the equalizer within the desired frequency range. Once you

have identified the desired frequency range (by this method),

then readjust the Boost/Cut Control (up or down) to the desired

amount. A set of graphs are shown to indicate the operational

characteristics of the sweepable midrange section of the AMR 64

equalizer.

Fig.

Characteristic EQ Curve of the Sweepable Midrange

+10 dB

0 dB

-10 dB

100

200

500

10K

20K

Fig. #2

Sweepable Midrange EQ @ 250, 500, IK, 2.5K, and 5 kHz

+10 dB

0 dB

-10 dB

100

200

500

10K

20K

(Frequency/Hz)

High Frequency EQ: This is a shelving-type equal¬

izer for boosting or cutting high frequencies up to 15

dB.

Low Frequency EQ: This is a shelving-type equal¬

izer for boosting or cutting low frequencies up to 15

dB._

About Shelving Equalizers

The High and Low Frequency Equalization of the AMR 64 utilize

a shelving-type equalizer circuit. While referring to the EQ graphs,

you will see that slight amounts of boost or cut affect only the

extreme high or low frequency ranges. If you will refer to Figure

#3, you will notice that a 5 dB boost at 50 Hz has little effect at 200

Hz, while a 15 dB boost at 50 Hz will boost 200 Hz by approxi¬

mately 6 dB. The same is true with the high frequency equalizer in

Figure #4 - a 5 dB boost at 10 kHz will boost 1 kHz approximately 3

dB, while a 15 dB boost at 10 kHz will boost 1 kHz approximately 6

dB.

With larger amounts of boost or cut, low frequency shelving

equalizers will affect the frequency ranges above as well as

below the indicated frequency of 50 Hz. Likewise, with larger

amounts of boost or cut, high frequency shelving equalizers will

affect the frequency ranges above and below 10 kHz.

Fig. #3

Auxiliary Master Send Control: This is a Master

Level Control for the Auxiliary Send Section of the

mixer. The mix is determined by the settings of the

six Auxiliary Send Controls on each input channel.

The Master Level Control will allow the overall level

to be increased or decreased without chang ing the

mix of the individual Auxiliary Send Controls on the

inputs.