Adc Paragraphic Service Manual
Service Manual
STE~E() F~E()UEN(]Y
Audio Dynamics Corporation
E()UALllEfl
~---------------CONTENTS----------------~
PAGE
ELECTRICAL PERFORMANCE SPECIFICATIONS 3
CIRCUIT DESCRiPTION , 4-9
SWITCH FUNCTIONS 0-12
DISASSEMBLY INSTRUCTIONS 2
BLOCK DIAGRAM .
ADJUSTMENT PROCEDURES '-
CALIBRATOR SCHEMATIC.................................. . . . . .. .. -
TROUBLESHOOTING - SYMPTOM· CAUSE/REMEDY
AMP P. C. B. (TOP
POWER SUPPLY
SWITCH (L) P. c. B. (TOP
SWITCH (R) P.c.B. (ROP
SLIDE VOLUME (L) P.c.B. (TOP
SLIDE VOLUME (R) P. C. B. (TOP&BOTTOM VIEWS)
ELECTRICAL PARTS LIST
EXPLODED VIEW PARTS LIST 35-36
MISCELLANEOUS PARTS LIST 37
SCHEMATIC DIAGRAM
EXPLODED VIEW
&
BOTTOM VI EWS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ~
&
METER P. C. B. (TOP
&
BOTTOM VIEWS) 21
&
BOTTOM VIEWS) 22
&
&
BOTTOM VI EWS) ~
BOTTOM VIEWS)
i7- ':'
23
24
25-34
38-39
40-41
-2-
ELECTRICAL
PERFORMANCE
SPECIFICATIONS
(Unit)
(Nominal)
(Limit)
Frequency responseat flat position,
Input level=0.775 V
(Hz)
5-100 K~U dB
5-100 K~?:5dB
Control Frequency accuracy
at 26, 32, 39 Hz
at 47, 56, 68 Hz
at 84,100,120 Hz
at 150,180,215 Hz
at 260,320,390 Hz
at 470, 560, 680 Hz
at 840, 1 K, 1.2 KHz
at 1.5 K, 1.8 K, 2.15 KHz
at 2.6 K, 3.2 K, 3.9 KHz
at 4.7 K, 5.6 K, 6.8 KHz (%)
at 8.4 K, 10 K, 12 KHz
at 15 K, 18 K, 21.5 KHz
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
(%)
±5 ±10
±5
±5
±5
±5
±5
±5
±2.5 ±
±2.5
±2.5 ±
±2.5 ±
±2.5 ±
(Output level=0.775 V)
Control rangeat 0.775 V Input
(dB)
+13.5
-13.5
-12~~.5
Harmonic Distortion at 1 V Output
from 20 Hz to 20 KHz
Hum and Noise ratio at 1 V Output
(%)
(dB)
0.018
90
(Input shorted) (I HFA)
Dynamic Range into 10 Kn load
(V/rms)
10
(All Controls should be Flat)
Input Impedance (Kn) 75
Output Impedance at 1 KHz (n) 10
Intermodulation Distortion at 1 V Output,
70/70 KHz at 4/1 ratio (%) 0.02 0.05
Meter tolerance (Frequency at 1 KHz)
at+12dBpoint (dB) ±0.5 ±1.0
at OdBpoint (dB) ±0.5 ±1.0
at-12dBpoint (dB) ±0.5 ±1.0
at other points (dB) ±1.0 ±1.5
±10
±10
±10
±10
±10
±10
5
±
5
5
5
5
+12~~·5
0.04
85
9
NOTE: When each control range is measured, all other controls should be at center (0 dB).
- 3 -
SOUND SHAPER THREE CIRCUIT DESCRIPTION
MAIN POWER SUPPLY (Refer to Figure A)
Power Transformer T 1001 provides three tapped secondary windings.
One delivers +26.4 V /- 26.0 V DC at +104/-137 rnA (no
capacitor circuit consisting of a bridge rectifier D701 and C73,C7
The second delivers -25.2 VDC at -1.1 rnA (nominal)
circuit consisting of rectifier D709 and C715. This voltage supplies - e
TR201.
The third delivers 60 VDC at 87.5 mA (nominal) from full-wave
ing of rectifiers D702, D703 and C704.
i
all fro
fro a
rectifi
a full-wave bridge rectifier -
4.
- CI
e roc"ifier - cspactitor
cireui , e base of
co
The voltage which is rectified by D701 provides both bases of TR703
andR717.
TR703/TR705 and TR704/TR706 consist of voltage-regulator circuits 'or
voltages.
These regulator circuits provide approx. +15.4 V/-15 V DC to LED Meter ana 5"
Control circuit which are constant and independent of the load current.
The reference voltage of this circuit is obtained from Zener Diode D708. The base voltage of T
is supplied from the voltage divider R708 and R709.
TR703 turn-on is determined by comparing the output voltage to the reference voltage and is
controlled by changes in collector current of TR705.
Voltage, which is rectified from D702 and D703, divider network R702 and R705 provides approx.
50 VDC. This is filtered further by C703, R704 and fed to the base of divider transistor TR701
which is connected to TR702 in a Darlington emitter-follower configuration. The reference voltage
of this circuit is obtained from Zener Diodes D704 and D705 (Approx. 44 VDC).
The emitter of TR702, decoupled by C701, provides approx. 41.5 VDC to the Equalizer and Meter
circuits. The collectors TR701 and TR702 are returned to 57.4 VDC through R701 which limits the
transistor collector circuits.
The Darlington connection of TR701 and TR702 provides a low output impedance. The base of
TR701 presents negligible loading on the voltage divider network, hence the ripple voltage at
TR702 emitter is small. Except for the small base current into TR701, the full load current flows
through R701.
c T
- 4 -
Figure A
LED METER COMPARATOR CIRCUIT DESCRIPTION
Power Supply and bias configuration (Refer to LED METER circuits)
The power supply for the LED Meter Comparator circuit consists of full-wave rectifiers, which
provide plus (+) and minus (-) +15.4/-15 VDC to each of IC802 through IC814.
LED indication level is provided from the Zener diode D71 0 (-5.6 VDC).
The +15.4/-15 VDC source is applied to LED comparator ICs IC802 through IC814.
The -5.6 VDC source provides a stable voltage to VR801 (L) and VR802 (R) for LED Meter
indicator level.
OPERATIONAL AMPLIFIER FEEDBACK CIRCUIT (Refer to Figure B)
Signal to the (-) input causes a change in output that is inverted in phase relative to the input.
Signal to the (+) input causes a change in output that is in phase with the input.
With no signal to Rin, the (+) input sees 0 Volts through RB, causing the output to be positivegoing. (-) input voltage is equal to (+) input voltage
When the output reaches 0 V, the (-) input also sees 0 V-through resistor RF and further output
change is inhibited. The output, (+) input and (-) input are now all 0 V.
The (-) input remains at 0 V regardless of the signal into Rin.
Example: An input more positive than 0 V to Rin causes the output to be negative-going. The
output continues to drop until the feedback through RF is lowered by an amount sufficient to equalize the imbalance between the (+) and (-) inputs causes by the input
signal. Because of the amplifier's high gain and speed, the imbalance between the (+) and
(-) inputs is always small.
(=
0 V) - known as Imaginal Short.
Since the voltage at the (-) input is always at 0 Volts, the (-) input is effectively at AC ground.
Therefore, the entire input signal appears across Rin and the entire output signal appears across R
Since the (-) input voltage is always 0 V the current into the amplifier's (-) input is constant. Since
this current is supplied by Rin and RF any change in current due to input signal through Rin is
offset by an opposite and equal change of current through RF.
For AC signal currents, if we ignore the negative values indicating signal inversion, the gain of the
amplifier can be calculated as follows.
I (Rin)
NOTE: RC4709 of this circuit operates from split power supplies. [plus (+) supply at Pin No. 14
=
I (RF) Since
and minus (-) supply at Pin No.7].
1=
g_
E (Rin)=E (RF)
R'
Rin RF' Rin E (Rin)
__B__E
=
E (RF) GAIN
AMP OUTPUT
F •
BASIC OP. AMP. FEEDBACK CIRCUIT
Figure B
- 5 -
PRECISION HALF-WAVE RECTIFIER AND AMPLIFIER CIRCUIT (Refer to Figure C)
The basic fau It with diode rectifier circu its is that the diodes do not conduct until a specific voltage
is reached. The above circuit eliminates this problem and also amplifies the output.
Referring to the basic circuit, note that: (1) With no input signal 0801 is conducting slightly to
establish 0 V DC at
amount of feedback exists. Therefore, the gain of the amplifier is very high. Lessthan one millivolt
will cause the output to change by a volt or more. Operation is as follows:
a positive-going change in the amplifier output. Since the gain is high until 0801 conducts fully, the
amplifier output jumps to 0.2 Volts long before the input reaches a millivolt (in a very short time).
At this point 0801 is fully conducting, has a low impedance compared to RF (n), and exhibits a
0.2 V drop across it. The rectifier output is now -85 mV DC. Since the feedback loop (RF) has
been completed by 0801 any further decrease in input voltage is amplified by the ratio of RR'.(n)
which is approximately equal to 5 for this circuit.
A positive input causes the output to decrease in a manner similar to just described except the
feedback is through 0803 and RF (p). The amplifier output is blocked from appearing at the
rectifier output by 0801 (0801 is reverse biased with respect to the following stages which are
returned to the 0 V DC line).
In this manner, appearing at 0801 cathode are negative half-wave pulses whose amplitude is directly
proportional to the input signal level.
The following refers to the complete schematic:
The negative pulses at 0801 cathode are filtered into an average DC voltage by R809 and C807, and
this voltage serves as input to the LED meter comparator.
A (-)
input and 0 V DC atAout; (2) When 0801 is barely conducting a small
A
negative input causes
In
R803 and 0803 serve to maintain positive feedback around RC4709 during the positive half-wave
excursions of the input signal. As the amplifier's output is positive during this time, 0803 is forward
biased (0201 is off) and the feedback path now consists of R803 and 0803. The amplifier is thus
kept out of saturation and free from oscillations throughout the full input cycle.
Bias circuit uses split power supply which provides +15.4 V DC at Pin No. 14 and -15 V DC at
Pin NO.7 on IC801.
r-_R_F-"/V(N"y-e_g_.)
RF(Pos.)
----.--0
0803
(AMP OUTPUT)
RECT IFIE R
OUTPUT
0801
BASIC OP. AMP. RECTIFIER-AMPLIFIER CIRCUIT
Figure C
COMPARATOR CIRCUIT FOR LED LEVEL METER DESCRIPTION
Comparator circuit operation
Comparator circuit consts of 13 IC's MJM-4588DM.
Comparator operates by comparing the (-) input level to (+) input level, in which output voltage is
changed from minus to plus Voltage. Thus DC currents flows to each LED.
- 6 -
With no signal, (-) input level [No.2 (L) or No.6 (R)1is kept to 0 V DC.
(+) input level [Pin NO.3 (L) or Pin No.5 (R)l of IC814 is kept to minus DC voltage (about
-45 mV) by half-wave rectifiers through VR801 (L) [VR802 (R)l and VR805 (L) [VR806
Thus, the output voltage of IC814 [Pin No.1 (L) or No.7 (R)1is kept with minus DC voltage.
When minus DC voltage is applied to (-) input, and causes the (-) input voltage to be greater (or
equal) to the (+) input voltage, the output appears as plus DC voltage. (V3:s. V2)
Thus LED D925 (L) and D926 (R) are lit at -12 dB points. But D901 through D924 are not lit
because the input voltage is too low.
Each LED conducts with a (-) input level which is determined by VR801 (L), VR802 (R) (IC802),
R813 (L), R814 (R) (IC803), R817 (L). R818 (R) (IC804), R821 (L), R822(R) (IC805), R825(L),
R826 (R) (IC806), R829 (L), R830 (R) (IC807), R833 (L), R834 (R) (IC808), VR803 (L), VR804
(R) (IC809), R839 (L), R840 (R) (IC810), R843 (L), R844 (R) (IC811), R847 (L), R848 (R)
(IC812), R851 (L), R852 (R) (IC813), R855 (L), R856 (R) (IC814).
With an increase in minus DC voltage, provided to the (-) input, each LED is lit in sequence from
D923, D924 to D901, D902.
mn
CIRCUIT DESCRIPTION
FREQUENCY EQUALIZATION
The input signal is fed into TR101 base. TR101, an emitter follower, provides the high input im-
pedance required by the signal source. The low output impedance of TR101 is required to drive
a voltage divider formed by R111 and the sections of the frequency control pots between the cut
end of each control and its wiper. The wiper of each control effectively qrounds only those free
quencies resonated by the series traps (coil, capacitor and resistor from wiper to common). Thus,
the voltage division which occurs can be different for each frequency and depends on the frequency
control settings.
TR103, TR105 and TR107 are connected so that the voltage at TR105 base always follows the
voltage at T R 103 base. For example: An increase in voltage at TR 103 base causes the conduction of
TR 103 and TR 107 to increase, and feedback base drive of TR 105 to increase, until the voltage at
TR105 base is equal to that at TR103 base. Conduction cannot increase beyond this point since
the emitter voltage supplied by TR105 then tends to make TR103 conduct less. Conversely, a de-
crease in voltage at T R 103 base causes a corresponding change at T R105 base.
The output voltage is taken from TR107 collector and is also fed back to TR105 base through the
voltage divider formed by R115 and the sections of the frequency control pots between the boost
end of each control and its wiper.
For each frequency, moving the control pot off center towards boost causes an increase in the
amplitude of the signal presented to TR103 base and a decrease in the negative feedback to TR105
base. The gain is thus increased. Since the signal amplitudes at the bases of T R103 and T R 105 are
always equal, the output signal divided by the feedback attenuation (R 115 and boost sections) is
approximately equal to the input signal amplitude divided by the input attenuation (R 111 and
"CUT" sections). By following a similar line of thought, it will be seen that when the controls are
centered the gain is unity; and when the controls are towards cut, the gain is less than one.
The resistors in series with the series resonant circu its are used to increase the bandwidth or lower
"Q",
the
viding a smooth overall response. The resistors are of different values so that the total series
resistance of each circuit (coil and resistor) is approximately the same. The ratio of the total series
resistance of the resonant circuit to the base resistor of TR 103 and TR 105 determines the maximum
boost or cut obtainable.
of each circuit so that the effect of controls of adjacent frequencies overlap, thus pro-
- 7 -
SIGNAL GAIN CONTROL CIRCUIT
Signal Gain Control circuit consists of T R109, 111, 113 and 115 (L ch) and TR 110, 112, 114 and
116(Rch).
This circuit configuration is identical to the Frequency Equalization circuit. For operating, see
"Frequency Equalization description" section.
The input signal is fed into TR 109 base.
TR111, TR113 and TRl15 are connected so that the voltage at TR105 base always follows the
voltage at T R111 base.
Total gain can vary from negative feedback value which consists of R135, VR101 and R143 (L ch)
[R136, VR102 and R144 (R ch)].
When base voltage of T R111 is equal to basevoltage of TR 113, the gain is unity.
COMPARATOR CIRCUIT FOR SIGNAL GAIN CONTROL'INDICATOR(LED}
Comparator circuit consists of three IC's NJM 4558DM.
Comparator operates by comparing the INPUT signal to output of TR 115. These signals are
supplied to Pin 6 and Pin 2 of IC201 (Lch) [or IC202 (Rch)] . Both input levels are doubled to
output terminals (Pin 6 to Pin 7 and Pin 2 to Pin 1).
Output of Pin 7 is positive, half-wave rectified by D203 and filtered into an average plus DC voltage
(+)
by C207 and R221, and this voltage is applied to
In the same manner, the output of pin 1 is positive, half-wave rectified by D201 and filtered into
an average plus DC voltage by C205 and R233, and this voltage is applied to the (-) input at pin 2
of IC203.
Thus, the difference level between Pin 2 to Pin 3 appears at Pin 1 of IC203. This voltage at Pin 1
servesas input to the Signal Gain Control indicator LED.
For example, when the input level at Pin 2 is small compared with Pin 3, the output at Pin 1
appears as positive voltage (approx. 13.6 V DC).
Thus, LED D1003 will light but D1002 will not.
When the input level at Pin 2 is greater compared with Pin 3, the output at Pin 1 appears as a
negative voltage (approx. -12.3 V DC).
Thus, LED D1002 will light but D1003 will not.
input at pin 3 of IC203.
When the input level at Pin 2 is equal to Pin 3 input level, the output will appear as zero, and thus
both LED's D1002 and D1003 will light. In this case, the gain is unity. (Figure D)
OSCILLOSCOPE
f--o
~
[1]
Po
SS-3
c::=
o
o
0
AUDIO OSC. FREQUENCY AC V.TV.M.
(20. 20KHz) EQUALIZER
o-+--©-
INPUT OUTPUT
MH 0illiMMIIlII
::>
BBBBBBBBBBBB @ @BBBB88BBB888 ~
I- I-
:;)
:;)
Q. Q.
Z ~ 0209 0210
01002 01003
§
c:::;
----@
,---
f
Figure D
-8-
POPPING NOISE PROTECTIVE CIRCUIT
This circuit eliminates the popping noise in the speakers when the power switch isturned "on" or
II
off".
This circuit consists of TR201, TR202, TR203 and a Reed Relay.
When power is switched "on", -0.5 VDC is provided to the baseof TR201 through R238. TR201
will turn off. After about 6 seconds, TR202, TR203 will turn on. Thus the Reed Relay will restore
connections to the OUTPUT Terminals.
When the power switch is "off", 1.7 VDC is provided to the baseof TR201 through R237. TR201
will turn on, TR202 and TR203 will turn off. And thus the Reed Relay will disconnect the
OUTPUT.
LED METER OPERATING CHART
AC INPUT AT VR301
(Max. CW)
mV RMS @ 1 KHz
SeeNOTE 1.
12 mV
15 mV
19 mV
24 mV
29 mV
35mV
46 mV
65 mV
74 mV
100 mV
120 mV
150 mV
190 mV
RECTIFIED DC V
AT C807 (-) INDICATION CURRENT EACH LED
SeeNOTE 2. SeeNOTE 3.
-53 mV DC -12 dB
-76 mV DC -10dB
-102 mV DC
-132 mV DC -6 dB
-166 mV DC -4dB
-205 mV DC
-278 mV DC OdB 2.63 mA
-395 mV DC +2 dB 2.63 mA 1.84 V DC
-453 mV DC
-618 mV DC
-740 mV DC +8dB 2.63 mA
-940 mV DC +10 dB
-1.18 V DC
LED METER LED METER
(mA)
2.63 mA
2.63 mA 1.84 V DC
-8dB
2.63 mA 1.84 V DC
2.63 mA
2.63 mA
-2dB
+4 dB
+6 dB
2.63 mA
2.63 mA
2.63 mA
2.63 mA
+12 dB
2.63 mA
VOLTAGE ACROSS
DC VOLTS
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
1.84 V DC
Rectified DC V and LED Meter data for actual levels used for LED Meter indication. (LED "ON"
condition)
NOTE:
1. AC signal applied to INPUT jacks of Equalizer.
BY-PASS/EO switch to EO, METER switch to IN, LINE/REC to REC and MONITOR to OUT.
2. Rectified DC voltages measuredfrom C807 (-).
3. Indicated voltages across each LED indicator are obtained with LED Meters calibrated as
specified in the CALIBRATOR PROCEDURE section of this manual.
4. All DC voltages arewithin±10%, measured with AC\VTVM and DC Voltmeter (over 10 Kn/V).
l
- 9 -
SWITCH FUNCTIONS
(Applicable to LEFT or RIGHT CHANNEL)
LlNE-REC and MONITOR SWITCHES "IN"
INPUT
LlNE-REC
21 20
- - - - ~- - .....--------41~
BY-PASS
8 9
IN lOUT
BY-PASS
12 11
MaN
16 17
~
--------
EQUALIZER/SIGNAL GAIN CONTROL CIRCUIT
TR101,103,10S,107,109,111,113,11Sand
CONTROLS
p
L-AAA___J
Figure 1
LINE-REC SWITCH "IN"
BY-PASS
12 11
~ • • •• OUTPUT
INPUT
LlNE-REC BY-PASS
21 20
24 23
MaN
8- 9
EQUALIZATION/SIGNAL
GAIN CONTROL CIRCUIT
IN OUT
Figure 2
LINE-REC, MON ITOR and BY-PASS SWITCH ES "OUT"
INPUT
2
MaN
24 23
LlNE-REC
BY-PASS
8 9
IN OUT
EQUALIZATION/SIGNAL
GAIN CONTROL CIRCUIT
BY-PASS
12 11
~ r'
_/
7
TAPE
OUT
LlNE-REC
i ·
MaN
OUTPUT
MONITOR SWITCH "IN"
LlNE-REC
""PUT ...... ,
2
Figure 3
MaN
22 23
Figure 4
-10-
11
BYPASS 12
IN OUT
EQUALIZATION/SIGNAL
GAIN CONTROL CIRCUIT
LlNE-REC
15 14
OUTPUT
BY-PASS SWITCH "IN"
INPUT
MON
24 23
BY-PASS
8 7
BY-PASS
10 11
EQUALIZATION/SIGNAL
GAIN CONTROL CIRCUIT
Figure 5
BY-PASS and MONITOR SWITCHES "IN" MON
MON BY-PASS BY-PASS L1NE-REC
INPUT OUTPUT
22 23 8 7 10 11 15 14
LINE-REC
EQUALIZATION/SIGNAL
GAIN CONTROL CIRCUIT
MON
18 17
L1NE·REC
IN OUT
IN OUT
Figure 6
METER SWITCH "IN"
BY-PASS/EO SWITCH TO "BY-PASS"
Figure 7
LED METER INDICATES SIGNAL AT OUTPUT JACK WHEN METER SWITCH IS "IN".
METER SWITCH "IN"
BY-PASS/EO SWITCH TO "EO"
METER ::
HALF-WAVE
RECTIFIER
AND
COMPARATOR
CIRCUIT
BY- 29
PASS
OUTPUT
OUTPUT
27
26 BY-
30
R145
(R146)
-B line (-5.6 V)
PASS
Comparator
LED METER
Figure 8
WHEN BY-PASS SWITCH IS "IN", LED METERS INDICATE AT 0 dB POINTS ONLY, REGARD-
LESSOF OUTPUT SIGNAL.
NOTE: RIGHT CHANNEL LED METER INDICATES OUTPUT OF SOUND LEVEL METER
WHEN CONNECTED TO SLM JACK. (METER SWITCH IN EITHER POSITION)
- 11 -
METER SWITCH "IN"
BY-PASS/EO SWITCH TO "EO"
INPUT
BY-PASS
~-------------------+~ ,
L..-.-+---!a
EQUALIZER
SIGNAL GAIN
CONTROL CIRCUIT
r--------------------,
I
, I
~ J
SIGNAL GAIN CONTROL
COMPARATOR
>--!,-----i
I
I
,
,
,
,
,
SIGNAL GAIN
LED
01003
(01005)
01002
(01004)
Figure 9
WHEN BY-PASS SWITCH IS "IN" AND METER SWITCH IS "OUT", SIGNAL GAIN CONTROL
LED DOES NOT INDICATE REGARDLESS OF INPUT SIGNAL.
DISASSEMBLY INSTRUCTIONS
1) To remove chassisfrom metal cabinet
a) Remove four screws- two from each side of cabinet asshown in Figure A.
b) Remove five screws that fasten the rear panel to the metal cabinet. (See Figure B.)
2) Removal of Front Panel
a) Remove chassisfrom metal cabinet asdescribed in 1).
b) Remove the four screwsfrom the top (Figure C) and four screwsfrom the bottom (Figure D)
of the Front Panel.
c) Remove knobs and pull panel off.
NOTE: If required, remove one screw (painted red) from the top of the Front Panel as shown in
Figure E.
Figure A
Figure C
Figure E
Figure B
Figure D
-12-
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