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C 272 SERVICE MANUAL
STEREO
AMPLIFIER
NAD
STEREO
C 272
AMPLIFIER
SPECIFICATIONS
STEREO MODE
CONTINUOUS AVERAGE POWER = 150 W (21.8 dBW)
OUTPUT INTO 8 OHMS OR 4 OHMS
(Min. power per channel, 20 Hz 20 kHz, both
channels driven, with no more than rated
distortion)
Rated Distortion = 0.03%
(THD 20 Hz 20 kHz)
Clipping power = 170 W
(maximum continuous power per channel).
IHF dynamic headroom at 8 ohms = +2.3 dB
IHF dynamic power
(Maximum short term power per channel) 8 ohms: = 230 W (23.6 dBW)
4 ohms: = 410 W (26.1 dBW)
2 ohms: = 520 W (27.2 dBW)
Damping factor > 150
(ref. 8 ohms 50Hz)
Input Impedance R = 20 kohms
C = 470 pF
Input sensitivity (for rated output into 8 ohms) 1.2 V¡À0.1V
Voltage gain 29 dB
Frequency response 20 Hz 20 kHz ¡À0.3 dB
- 3 dB at 3 Hz/70 kHz
Signal / Noise ratio, A-weighted > 100 dB ref. 1 W
> 120 dB ref. rated power
BRIDGED £¨ MONOPHONIC£©MODE
CONTINUOUS AVERAGE POWER 330 W 25.2 dBW£©
OUTPUT INTO 8 OHMS
(Min. power per channel, with no more than rated distortion)
IHF dynamic headroom at 8 ohms 3 dB
IHF dynamic power 8 ohms: 800 W (29.0 dBW)
IHF dynamic power 4 ohms: 1200 W (30.8 dBW)
DIMENSIONS AND WEIGHTS
Net Weight 12.5 kg ( 27.5 Ib)
Shipping Weight 14.2 kg ( 31.3 Ib)
Dimension (W × H × D) 435 × 133 × 350 mm
ALIGNMENT PROCEDURE (C272)
I. INITIAL ADJUSTMENT (No load connected)
A. OUTPUT OFFSET VOLTAGE
1. Connect a DC Millivoltmeter to L Channel TP2 (DC) and TP8 (GND).
2. Turn unit "ON" and adjust VR301 (100ohms) to get a reading of 0V+/-30mV.
3. Connect a DC Millivoltmeter to R Channel TP5 (DC) and TP7, then adjust
VR401(100ohms) to get a reading of 0V+/-30mV reading on meter.
B. IDLING CURRENT
1. Connect a DC Millivoltmeter to L Channel TP1 (IDL) and TP3 (IDL), then adjust
VR302 (500 ohms) for 6~7.5mV reading on meter.
2. Connect a DC Millivoltmeter to R Channel TP4 (IDL) and TP6 (IDL), then adjust
VR402 (500 ohms) for 6~7.5mV reading on meter.
II. ISC ADJUSTMENT (WITH LOAD CONNECTED)
1. Connect a DC Millivoltmeter to Power Board CB725, and connect 4 ohms load to
both L&R speaker output terminals. Then feed 20kHz signal to Fixed In RCA.
2. Turn unit "ON" and try to get 15W on speaker output terminal. Then adjust VR701
(82kohms) to get a reading of 0V+/-10mV.
3. Change the load to 8 ohms and try to get 160W on speaker output terminals.
Then adjust VR701 (82kohms) to get a reading of 1.4V+/-30mV.
III. FINAL ADJUSTMENT
Repeat procedure A and B for offset voltage and idling current alignment respectively.
R101 +V68L +V64L
Q305 R309
220 MF 2SA1015 R334 R348 R350 R352 R354 R368 C317 10u R364
100 MF 1% D303
C101 2K2 75 0.2 0.2 0.2 0.2 0.1u 50V 6K8 C322
RCA1A VR301 R307 1N4148
R102 C309 2SA1015 3W FP C311 1W FP 1W FS 1W FS 1W FS 1W FS 100V C321 10u/100V
2SA1015
FIXED-L 2M2 R310 180 910 MF 1%
100P 10K 0.1u Q309 100uF
RV1A RV1B 1 D304
1K 100V
R201 1K 1N4148 R333 10K R335 10K
D307 Q326
A1
A2
220 MF 2SB649A BAV21 C313
R370 100 R306 100 C305 Q310 IC301 470P R363
C201 LSCP D309
RCA1B R202 22P/500V R332 TL431 1N4148 22K
FIXED-R 2M2 R325 100 R311 Q304
R205
100P R105 18V 1K 510 500V Q319 Q321 Q323 Q327 22K
LSCN R305 2SC1775 R324 1W FP L301 10uH
0 0 D301 Q317 2SA1943 2SA1943 2SA1943 2SA1943 R365 CZ707
R371 2K2 39K 100K R331 2SC4793 R362
4 10UF/25V 2PIN
L-MU 4R7/FS R336 33 R361 15K 2 +64V
1 5 SW705B C303
1K 1 -64V
SW705A 2 6 F/V SW Q325
F/V SW 3 Q303 R330 R345 C1815 CZ719
R304 C323 TP1
7 10 2SC1775 2200u/6.3V 3R3 1K2 R356 C320 2PIN
100 0.1u IDLING-I 1 LOUT
SW705C 8 11 SW705D C306 1W FP 0.05 22n
R308 2 GND
F/V SW 9 12 F/V SW 5W 100V
33 R317 100V R347
R103 2SB649A
220 MF 150 1% 220 L-FDBK
Q301 Q313 A1015 C315
BUF-R 1W FS L303 1uH
C102 CZ301 Q329 Q330 2SA872 Q316 0.1u
RCA2A R104 R303 R318 R328 R329 100 TP2
2PIN 2SC1775 2SA872
VARI-L 2M2 100 MF 47K 1%MF 100 MF -V64L OFFSET R360 3R3/1W FP
100P Q315 +V68L CZ709
3 LIN 1
R319 R327 KSC2690 8PIN
R203 2 GND 2 R301 C301 10K 0.5W 1%MF +V64L R358
39K R337 100 TP8
220 MF 1 GND 470/MF 10uF R302 GND L-MU 8 MUTE-L
Q302 100P 1W FS R346
22K R359 10/1W FS 100/0.5W MF 7 POS90
C202 CZ301A 2SC1775 R322 9K1 C308 Q314 820
RCA2B R204 C302 6 POS80
CZ61 3PIN 0.5W 1%MF 2SD669A R357
VARI-R 2M2 220P R320 C318 LSCP 5 SC-P
100P 9PIN 0.05
33 TP3 0.1u LSCN 4 SC-N
R338 5W 100V
R312 L-FDBK IDLING-I 3 OVERI-S
1
2SA872 3R3 500
100 2 -68V
1
2
3
4
5
6
7
8
9
C105 +18V -18V C205 Q306 1W FP VR302
1 +68V
10uF 10uF
ROUT
+18V
LOUT
LIN-
LIN+
GND
RIN+
RIN-
-18V
R339 R340 33
R313 R326 4R7/FS Q318 CZ713
39K Q307 100K 2SA1837 2SC5200 2SC5200 2SC5200 2SC5200 2PIN
R341 L302 10uH 1 BG-O
1
2
3
4
5
6
7
8
9
CB61 2SA872 2SD669A 510 C314 Q320 Q322 Q324 Q328
+18M C270-INPUT BUFFER 9PIN +18M Q311 1W FP IC302 R366 R367
2 GND
C304 C307 TL431 470P t=90 C t=80 C -V68L
C103
C104
C613
C612
C204
C203
R314 100 500V
2SA970A 2SA970A 10uF/25V 22P/500V
D302
Q68 Q65 -18M Q63 Q67
C68 C66 18V R315 R343 10K R342 10K
2SD667A R68 R67 2SD667A Q308 Q312 BAV21
63V
63V
10n
0.22u
0.22u
10n
0.1u 0.1u 1K
100uF
100uF
1K MF 1K MF 2SC1815 2SC1815 D308 C312
D305 100u/25V
R620 10/MF R619 10/MF 1N4148 R344 R349 R351 R353 R355 R369 C316
R612 C64 C63 R611 R316 C319
MGND MGND C310 2K2 75 0.2 0.2 0.2 0.2 0.1u
1K 39P ML-FB MR-FB 39P 1K 10K R321 D306 10u/100V
0.1u 3W FP 1W FP 1W FS 1W FS 1W FS 1W FS 100V
R621
C611
1K MF 1% R323
100V 1N4148
R616 MLO MRO R615 100 MF 1%
0 N.I. N.I. 0 -V68L -V64L
Q62 Q61
D63 2SK369 R62 R61 2SK369 D61
1N4148 220 MF 220 MF 1N4148
MLO MRO +V68R +V64R
R610 R69 Q405 R409
C610 C69 2SA1015 R434 R448 R450 R452 R454 R468 C417 10u R464 C422
R618 100/MF 100/MF R617 100 MF 1% D403
1N4148 47P 47P 1N4148 47/MF 2K2 75 0.2 0.2 0.2 0.2 0.1u 50V 6K8 10u/100V
47/MF VR401 R407 1N4148
D64 D62 C409 2SA1015 3W FP C411 1W FP 1W FS 1W FS 1W FS 1W FS 100V C421
2SA1015
R410 180 910 MF 1%
10K 0.1u Q409 100uF
ML-FB MR-FB 1 D404
MGND 2SB647A 2SB647A MGND 100V CZ708
1N4148 R433 10K R435 10K
Q66 Q64 D407 Q426 2PIN
1 +64V
2SB649A BAV21 C413
R406 100 C405 2 -64V
R66 C62 R64 R63 C61 R65 Q410 IC401 470P D409 R463
C67 R614 R613 C65
N.I. 2.2M 2.2M N.I. 10K R411 22P/500V R432 TL431 1N4148 22K CZ705
0.1u 10K 0.1u Q404 510
1% MF 100P MF MF 100P 1% MF 1K 500V Q419 Q421 Q423 Q427 22K 2PIN
D401 R405 2SC1775 R424 1W FP L401 10uH 1 ROUT
18V 39K 100K Q417 2SA1943 2SA1943 2SA1943 2SA1943
R462
R465
2 GND
10uF/25V R431 2SC4937
4R7 FS R436 33 R461 15K
-18M MGND -18M C403
1K Q425
1 GND
Q403 R430 R445 C1815
R404 C423 TP4 2 ROUT
2SC1775 2200u/6.3V 3R3 1K2 R456 C420 CZ718
100 0.1u IDLING-I
C406 1W FP 0.05 22n 2PIN
FT
R408
100V 5W 100V BG-S
Q431 33 R417 R447