QSC PL-9.0-PFC Schematic
_VTOP
B2_P
B2_N
B3_P
32
1
+
EL2257C
E
14
114
U11:3
EL2257C
IX2
DR2
14
13
C
-
U11:1
DS
G
32
1
+
EL2257C
E
13
C
-
U14:1
56
7
+
EL2257C
E
9
8
C
-
U11:2
DS
G
This connects to
chassis gnd at the
rear panel.
_BOP
56
7
+
EL2257C
E
9
8
C
-
U14:2
1 2
_SPK
_SPK_GND
DS
G
1
2
_BGND
EL2257C
EL2257C
U13:2
56
7
+
E
9
U12:2
8
C
-
DS
G
56
7
+
E
9
8
C
-
EL2257C
EL2257C
13
13
U13:1
U12:1
32
1
+
E
14
C
-
B1_P
114
U12:3
EL2257C
B1_N
IX1
DR1
32
1
+
E
14
C
-
B3_P
DS
G
114
U14:3
EL2257C
IX3
DR3
DS
G
_VBOT
PM_REF
DS
G
DS
G
114
U13:3
EL2257C
IX4
DR4
ITEM NO.QTY PART NO. DESCRIPTION VENDOR
IX1
DR1
DR3
IX3
IX2
DR2
DR4
IX4
C129
22u-25V
C125
PM_REF
22u-25V
_BOP
_BGND
_VBOT
_VTOP
U21:1
14
13
CA3054M96
U21:3
5
CA3054M96
1
2
3
4
_BGND
_BOP
_VBOT
_VTOP
U21:2
8
9
11
12
CA3054M96
_BGND
7
6
_BOP
_VBOT
C126
22u-25V
B3_N
CWCCW
W
DN_DRV
HOT
UP_DRV
I_MON
DIFF_AMP_BIAS
_V200
_N_STEP
Values shown preclip a fixed
5 volts below the rails up to
15 amps of output current.
After that, preclip advances
120 mV per ampere output,
for 12v preclip at 70 amps.
CLIP
Gain = 1/37.5
6
5
650mV pk
excursion
3
+
1
2
-
5V=187V
Positive = Clip
7
+
5
+
7
6
-
2
-
1
3
+
2
1
3
+
VP
VN
0.84 atten.
5.95Vpk
clips amp.
3
+
2
-
CLAMP_SIG
1
_BOP
MUTE
With values shown, the effective
step switch time delay is 4us
flat out to 50 KHz.
-POL-
5
+
6
-
3
+
7
14
10 12
9
+
15
16
13
-
VP
2
-
VN
P_ISENSE
N_ISENSE
_SPK_GND
1
+POL+
Closed loop gain
=37.5 or 31.5 dB
5.0 Vp=187.5 Vp
-POL-
_BOP
_SPK
PRE_LIM
REREF
-POL-
Gain = 1.67
Limiter is shown in "fast clip-tracking"mode.
To convert to a slow attack/release limiter,
open the 3 places shown shorted with lines,
and make the connection shown by the
arrow line.
+15V_
84
5
+
6
-
-15V_
VP
-POL-
7
-POL-
116
3
7 5
8
VN
+
2
1
4
-
VP
VP
GAIN_RETARD
10 Vpk clips the amp
with NO LOAD.
CLIP_FEED
VP
LOSS_OF_FEEDBACK
DN_DRV
VN
UP_DRV
8
STANDBY
STANDBY
MSP_VMON
MSP_VMON
D_GND
MSP_IMON
MODE_FLAG
CLIP_
SIG_GNDSIG_GND
CH_IN_NCH_IN_N
CH_IN_PCH_IN_P
I_SET
7
6
5
4
3
2
1
J6:1
1
PWR_GND
PSENABLE_A
I_SET
PWR_GND
PSENABLE_K
POT_TOP
SHED_V SHED_V
+15V
PSENABLE_A
1
2
3
4
5
6
7
8
9
MSP_VMON
MSP_IMONMSP_IMON
-POL-
+POL+
280 KHz LPF
2
-
3
+
PSENABLE_K
1
+POL+
C88
47-10NP-10%
+POL+
REREF
POST_POT_NPOST_POT_N
POST_POT_PPOST_POT_P
PRE_LIMPRE_LIM
+15V_+15V_
SMPS_VSMPS_V
-15V_-15V_
10
11
12
13
14
15
16
C63
22u-25V
C68
22u-25V
B1_P
B1_N
SMPS_ON
PRE_LIM
REREF
PROTECT
-POL-
LOSS_OF_FEEDBACK
STANDBY_LED
CLIP
-POL-
CLIP_FEED
V_MON
+15V
J6:2
2
J6:3
3
J6:4
4
J6:5
5
J6:6
6
J6:7
7
J6:8
VP
VN
8
J6:9
9
J6:10
10
J6:11
11
J6:12
12
J6:13
13
J6:14
14
REREF
POST_POT_N
POST_POT_P
SIG_GND
STANDBY_LED
SIG_GND
VP
VN
+15V
V_MON
PROTECT
PWR_GND
CLIP_FEED
J6:15
15
J6:16
16
CLIPCLIP
PWR_GND
VP
Current gain: 22,460.
3.6 mA total set curent
results in 81A peak output.
Minumum at full cut-back is
250 uA or 5.6A output.
PROTECT
_V50
FAN_N
DIFF_AMP_BIAS
SMPS_ON
MUTE
I_SET
Nominal I_SET = 3ma to 5ma.
Amp is fully on at I_SET>1ma.
Above 3ma fan is unaccellerated.
From 3ma to 1ma speed rises.
Below 1ma fan speed reduces
back linearily to normal speed.
C117
22u-25V
600ms delay to enable audio.
1
2
3
4
C55
22u-25V
Fan idles at 10V up
to 60C. From 60C to
80C fan ramps from
10V to 24V. At 85C
fan V = 28V MAX.
(Note that SMPS can
also speed fan up.)
B3_N
_N_STEP
200ms delay to disable audio.
5
+
7
6
-
VN
GAIN_RETARD
2
1
VP
3
DS
G
6
-
7
186V = 5V
Gain = 1/37.5
5
+
-POL-
VP
STANDBY_LED
PSENABLE_A
_BOP
PSENABLE_K
VN
_BGND
_BOP
_SPK_GND
V_MON
MSP_VMON
HOT=250uA
@ 80 deg C.
HOT
5V = 100 deg C.
1
U1
2.5V-1%
5
SNAPPER PTC
6
-
7
5
3
+
2
-
VP
The "HOT" threshold is 80C
Cutback begins at 100C and
full shutdown happens at 110C.
(+/- 3 degrees)
VN
+
70A = 5V
>5V = Current Limiting.
Total Gain = 16.85dB
2
-
1
3
+
+
7
6
-
P_ISENSE
N_ISENSE
I_MON
MSP_IMON
Clamps caps to 48-54V
_V200
CLAMP_SIG
V_MON
LOSS_OF_FEEDBACK
D S
G
VN
_V150
5
+
7
6
-
_N_STEP
NOTE: This opamp must not
clamp its input terminals
together. TL072 or EQIV!!!
5
+
7
6
3
+
1
2
-
-
VN
5
+
7
6
-
VN
DS
G
_V150
DS
G
_V100
_N_STEP
_V100
5
+
7
6
-
VN
3
+
1
2
-
VN
5
4
3
2
1
PROTECT
SHED_V
I_MON
2
-
3
+
+
1
-
3 volts here signifies
50 amps output, so
load is likely 2 ohms.
1
DS
G
_V50
3
+
1
2
-
_N_STEP
VN
3
2
VN
5
+
7
6
-
VN
B4_P
C49
C19
22u-25V
C33
22u-25V
VN
VP
84
84
VN
84
84
84
C48
22u-25V
C30
C31
22u-25V
B4_N
22u-25V
22u-25V
_V50
_VTOP
_VBOT
_N_STEP
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