Marantz SR3000 - DOLBY PROLOGIC TEST DESCRIPTION

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DOLBY PROLOGIC TEST DESCRIPTION
- The intention of this description is to explain the most important performance measurements for DPL (Dolby Pro-Logic)
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 :
(silence) and measure the S/N ratio.
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 :
(silence) and measure the S/N ratio.
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