MSP3400C datasheet(39/73 Pages) MICRONAS

39 / 73 page

MSP 3400C

PRELIMINARY DATA SHEET

MICRONAS INTERMETALL

7.1.21. Equalizer Loudspeaker Channel

Band 1 (below 120 Hz)

0021hex

Band 2 (Center: 500 Hz)

0022hex

Band 3 (Center: 1.5 kHz)

0023hex

Band 4 (Center: 5 kHz)

0024hex

Band 5 (above 10kHz)

0025hex

+12 dB

0110 0000

60hex

+11 dB

0101 1000

58hex

+1 dB

0000 1000

08hex

+1/8 dB

0000 0001

01hex

0 dB

0000 0000

00hex

RESET

–1/8 dB

1111 1111

FFhex

–1 dB

1111 1000

F8hex

–11dB

1010 1000

A8hex

–12 dB

1010 0000

A0hex

With positive equalizer settings, internal overflow may

occur even with overall volume less than 0 dB. This will

lead to a clipped output signal. Therefore, it is not recom-

mended to set equalizer bands to a value that, in con-

junction with volume, would result in an overall positive

gain.

Equalizer must not be used simultaneously with Bass

and Treble (Mode Tone Control must be set to FF to use

the Equalizer).

7.1.22. Automatic Volume Correction (AVC)

AVC

on/off

0029hex

[15:12]

AVC

off and Reset

of int. variables

0000

0hex

RESET

AVC

1000

8hex

AVC

Decay Time

0029hex

[11:8]

8 sec

(long)

4 sec

(middle)

2 sec

(short)

20 ms (very short)

1000

8hex

0100

4hex

0010

2hex

0001

1hex

Different sound sources (e.g. Terrestrial channels, SAT

channels or SCART) fairly often don’t have the same

volume level. Advertisement during movies as well has

mostly a different (higher) volume level, than the movie

itself. The Automatic Volume Correction (AVC) solves

this problem and equalizes the volume levels.

The absolute value of the incoming signal is fed into a

filter with 16ms attack time and selectable decay time.

The decay time must be adjusted as shown in the table

above. This attack/decay filter block works similar to a

peak hold function. The volume correction value with it’s

quasi continuous step width is calculated using the at-

tack/decay filter output.

The Automatic Volume Correction works with an internal

reference level of –18 dBFS. This means, input signals

with a volume level of –18 dBFS will not be affected by

the AVC. If the input signals vary in a range of –24 dB to

0 dB the AVC compensates this.

Example: A static input signal of 1 kHz on Scart has an

output level as shown in the table below.

Scart Input

0dbr = 2 Vrms

Volume

Correc-

tion

Main Output

0dBr = 1.4 Vrms

0 dBr

–18 dB

–18 dBr

–6 dBr

–12 dB

–18 dBr

–12 dBr

–6 dB

–18 dBr

–0 dB

–18 dBr

–24 dBr

+ 6 dB

–18 dBr

–30 dBr

+ 6 dB

–24 dBr

Loudspeaker Volume = 73h = 0 dBFS

Scart Prescale = 20h i.e. 2.0 Vrms = 0dBFS

To reset the internal variables, the AVC should be

switched off and on during any channel or source

change. For standard applications, the recommended

decay time is 4sec.

Note: AVC should not be used in any Dolby Prologic

modes, except PANORAMA, where no other than the

loudspeaker output is active.

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