Marantz SR4000 Service Manual - Page 39

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DOLBY PROLOGIC TEST DESCRIPTION

- The intention of this description is to explain the most important performance measurements for

DPL

(

D

olby

P

ro-

L

ogic)

sets for service.

- Test instruments (recommended) :

- Dolby Prologic test CD

4822 395 10216

- AC mv meters (4x) L, C, R, S

- Oscilloscope (double beam)

- Distortion meter

- CD player.

WARNING:

Be sure that the ground connection (-) of each instrument is

not connecteded

with

the safety earth

⊥

connection. To avoid damage to output amplifiers (balance type)

Use only cinch (input) ground connection

STARTING CONDITION :

-

Replace the loudspeakers for all four output amplifiers with loud resistors according the output impedance for each

amplifier (or use 8

Ω

as standard loudresistor).

-

Set

volume to min. position

-

Set Bass + Treble at 0 db .

-

Select Surround <Prologic> .

-

Select “LARGE” size for Center channel.

-

Set time delay in Surround channel at 20 msec.

-

Dolby Prologic test CD in CD player.

SERVICE TEST DESCRIPTION

Test 1 :

Output and balance setting for all four channels

Select track 2 :

Adjust L, C, R and S for

≈

1W output on the loudresistor with master volume. Adjust with

L/R balance and

Centre/Surround “TRIM” all four channels to equal level (equal meter readings)

Note:

1Watt output corresponds with 2.83V across 8

Ω

P = U

≤

/R

→

U =

√

P x R =

√

1x 8 = 2,83V

Test 2 :

Frequency response for Left and Right channel

Requirement : -3 dB points at

≤

50 Hz and

≥

15 kHz

Select track 3:

measure (and note) the overall gain of Left channel across the load resistor.

Select track 4:

measure (and note) the overall gain on Right channel across the load resistor.

Test 3 :

Frequency response for Center channel

2 possibilitie :

1- Center size “LARGE” requirements :

-3 dB at

≤

50 Hz and

≥

15 kHz (same as L/R requirements)

2- Center size “SMALL” requirements : -3 dB point at

±

100 Hz and

≥

15 kHz (the difference is the

roll-off behaviour of the bass frequencies).

Select track 5 :

measure (and note) the overall gain of Center channel across the load resistor in “LARGE” size (only in sets with

this option) and repeat this measurement in “SMALL” size.

Test 4 :

Frequency response for Surround channel

Surround requirements : -3 dB point at

≤

100 Hz and

±

7 kHz (6 kHz ... 8 kHz)

The difference is the roll-off behaviour of the high treble frequencies.

Select track 6 :

measure (and note) the overall gain of Surround channel across the loud resistor.

Test 5 :

Modified Dolby B type NR decoding freq. response of the Surround channel

Requirement : Roll off behaviour at

±

5 kHz related to 100 Hz.

In this case use 100 Hz as 0 dB reference gain.

Select track 14:

measure (and note) the overall gain of Surround channel across the load resistor.

Note :

The output level on track 14 =

-35 dB below the 1W output reference of the Surround channel.

Test 6 :

Total harmonic distortion measurements for Left, Center, Right, Surround channels for 1 Watt output

Note :

If necessary use a special CD test filter 20 Hz ... 20 kHz between the output channel and the distortion meter

to prevent spurrious products out of audio waves (> 20 kHz) from to the CD player in test.

Select track 3 :

Measure distortion at 1 kHz across

the Left channel.

Output load resistor : requirement THD < 0,3 %

Select track 4 :

Measure distortion at 1 kHz across the Right channel.

Output load resistor : requirement THD < 0,3 %

Select track 5 :

Measure distortion at 1 kHz across the Center channel.

Output load resistor : requirements THD < 0,3 %

Center size “LARGE” (if exists) and repeat for center size “SMALL”

Select track 6 :

Measure distortion at 1 kHz across the Surround channel load resistor.

Note :

time delay setting = 20 msec.

Requirement THD = < 0,5 %

Test 7:

Signal to noise measurements for Left output amplifier

Select track 3 :

Use 1W output

at 1 kHz on the Left channel output loud resistor as 0 dB reference.

Select track 13 :

(silence) and measure the S/Nratio.--->with ccir/arm filter

Requirements for Left channel

≤

-65 dB

Test 8 :

Signal to noise measurements for Right output amplifier

Select track 4 :

Use 1W output at 1 kHz on the Right channel output loud resistor as 0 dB reference.

Select track 13 :

(silence) and measure the S/N ratio.

Requirement for Right channel

≤

-65 dB

Test 9 :

Signal to noise measurements for Center output amplifier

Select track 5 :

Uuse 1W output at 1 kHz on the Center channel (size “SMALL” or “LARGE”)

Select track 13 :


Requirement for Center channel (size “SMALL” or “LARGE”)

≤

-65 dB

Test 10 :

Signal to noise measurements for Surround output amplifier

Select track 6 :

Use 1W output at 1 kHz on the Surround channel output loud resistor as 0 dB reference.

Select track 13 :


Requirement for Surround channel

≤

-55 dB (in all positions between 15 msec ... 30 msec in sets with variable time

delay ).

Cross-talk (channel separation) between adjacent and opposite channels

2 possibilities :

1- Centre size “LARGE” (use 1 kHz tone)

Test 11a:

Select track 3 :

For 1 kHz in Left channel and measure the crosstalk in Center, Right, Surround.

Requirement : < -25 dB

Test 12a :

Select track 4 for 1 kHz in Right channel and measure the crosstalk in Surround , Left, Center.

Requirement : < -25 dB

Marantz SR4000 Service Manual - Page 39

Dolby Prologic Test Description

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