Mark Levinson Stereo Amplifier JC 2 User Manual

INSTRUCTION MANUAL  
for the  
JC-2 PREAMPLIFIER  
 
INSTRUCTION MANUAL  
for the  
JC-2 PREAMPLIFIER  
1. INTRODUCTION  
The MARK LEVINSON JC-2 PREAMPLIFIER is the distillation of years of  
scientific research and careful listening. The amplification circuitry  
designed by John Curl combines the advantages of class A, completely  
complementary push-pull operation, high open-loop bandwidth, and low  
feedback configurations in order to approach perfect solid-state pre-  
amplification of the most demanding recorded musical material. Hand-  
matched active and passive components not previously used in consumer  
audio equipment eliminate subtle forms of error and distortion which  
plague sensitive ears.  
Mark Levinson Audio Systems utilizes the finest test equipment in its  
product development program. More significantly, a large number of our  
staff participate in the evaluation of these developments and refine-  
ments. When a product is made available, it is only after it has proved  
itself on a wide variety of sophisticated sound systems. To realize the  
full potential of these developments is a laborious and difficult task.  
But - here is a true designers choice for the classic system.  
2. UNPACKING THE JC-2  
Inspect the unit for damage. It should be physically free of dents and  
scratches. If the unit has incurred any damage, contact your dealer  
immediately. Retain all packing material for future shipping. Ship-  
ments made in anything other than the original carton will invalidate  
the warranty, unless authorized by factory.  
3. INSTALLATION  
3.1. Connectors  
The JC-2 is equipped with phono connectors for all audio inputs and out-  
puts. There are two cannon receptacles for connection to the power  
supply. A binding post is provided for ground connections to the chassis  
of the JC-2.  
 
3.2. Power Supply Connection  
The power supply for the JC-2 is mounted in a separate chassis to eli-  
minate hum pick-up.  
Check the voltage the power supply comes a cable with a three  
power supply label to be sure they correspond to the voltage of  
the power source being used.  
From one end of the power supply comes a cable with a three  
prong AC plug on the end of it. Connect this end to a wall  
outlet, using a ground adapter plug if your wall outlet will  
not accept three prongs. From the other end of power  
supply comes a cable with a cannon connector on the end of  
it. Connect this end to the four-pin male cannon connector  
on the rear of the JC-2. This should be done before connecting  
the JC-2 to the power amplifier because there is a transient  
thump when power is first applied to the unit.  
POWER SUPPLY CONNECTOR PIN CONFIGURATION: Pin 1 - ground  
Pin 2 - + V  
Pin 3 - - V  
Pin 4 - no connection  
3.3. Rack Mounting  
The JC-2 may be mounted in a standard 19" relay rack. (The rubber feet  
may be unscrewed if necessary.) 10-32 screw should fit the threads on  
most racks. Be sure to use nylon washers when mounting the JC-2 so as  
not to scratch the unit.  
4. OPERATION  
4.1. Description of Controls  
INPUT SELECTOR - selects any one of six inputs. AUX., TUNER, TAPE 1,  
TAPE 2, and REMOTE PHONO are all high level inputs. PHONO 1 is an RIAA-  
equalized low level input. The REMOTE PHONO input is an unequalized  
high level input. It is intended for use with phono systems having  
their own amplification and equalization, such as the EMT turntable/  
cartridge system, or certain of strain gauge cartridge.  
INPUT/MONITOR - switches between the program source at the input selector  
or either of two tape monitor inputs. This switch will not affect the  
tape outputs. When making copies from one machine to another through the  
JC-2, the playback machine should be directed through the input selector  
rather than the input/monitor switch. Tape copies can be made in this  
manner without degradation of signal because there are no amplifiers  
between the input selector and the tape outputs.  
 
TAPE 1/TAPE 2 - selects either tape input 1 or tape input 2 for the input/  
monitor switch.  
MONO/STEREO - selects either a mono or a stereo mode at the main outputs.  
HIGH/LOW - selects either 21dB gain (HIGH) or 11dB gain (LOW) in the  
output stage. Line level inputs should generally be used only with the  
low gain setting. Low level phono inputs can be used with either HIGH or  
LOW depending on the output level of the phono cartridge. If when using  
the low gain position, the output level control is set close to maximum  
for a pleasing level, i. e. above 7 or 8, turn down the output level and  
switch to the high gain position. This will give a broader range of  
operation for the output level control. Conversely, if in the high gain  
position the output level control is set below 1 or 2, switch to the low  
position.  
This switch does not affect the tape outputs.  
BALANCE 1 and 2 - these switches are used to precisely set channel balance  
for a correct stereo panorama. There is a total range of nine dB in one dB  
steps for each channel. The normal position for these controls is 0dB.  
At this position there is a gain in the output stage of 11dB in the LOW  
gain setting, and of 21dB in the HIGH gain setting.  
These controls do not affect the tape outputs.  
OUTPUT LEVEL - adjust volume at the main outputs for both channels  
simultaneously.  
5. OPTIONS  
5.1. The JC-2 Modular Plug in Phono System (from S/N 1122)  
The basic JC-2 Preamplifier contains two extremely high performance  
ultra-low noise amplifiers encapsulated in special thermal epoxy. The  
external regulated power supply and the internal active filter in the  
JC-2 make it possible to incorporate very high gain phono circuitry with  
great immunity to hum pick-up and other power supply noise. A series of  
plug-in cards is available, containing equalization and other circuitry  
to match the characteristics of the phono section to practically every  
cartridge available now and in the future. The basic amplifiers and the  
plug-in cards feature gold-plater pins and sockets for highest reliability.  
As part of this system, MLAS offers a revolutionary moving coil cartridge  
amplifier which provides DIRECT input, WITHOUT BOOSTER AMPLIFIER, of even  
the lowest output MC cartridges. The input stage accepts 7 millivolts at  
1kHz, and 70 millivolts at 20kHz, which allows enough headroom for the  
highest peaks it is possible to encounter (80cm/s). Transient distortion  
has been greatly reduced, giving a significant increase in transparency  
and openness of sound. This system includes one JC-1SM plug-in card and  
two Universal Phono plug-in cards (see below).  
 
UNIVERSAL PHONO PLUG-IN CARDS  
System:  
Gain:  
36dB  
Overload:  
1kHz  
20kHz  
900mv  
A
B
C
Two UP-1A cards are normally sup-  
plied with the JC-2 unless other-  
wise specified. This system accepts  
Input impedance: 47kOhms.  
100mv  
The UP-1B system offers lower  
sensitivity but increased head-  
room for the highest output magne-  
tic phono cartridges.  
30dB  
220mv  
1.6v  
This set provides exact equalization  
for the Brüel & Kjaer series of cartridge  
measurement records. Information on  
request.  
D
E
F
This system includes two UP-1D cards  
and a JC-1SM module. It offers  
DIRECT moving coil cartridge input.  
70dB  
7mv  
70mv  
Provides equalization and DC current  
source for certain gauge cartridges.  
Information on request.  
Flat response amplification. Specify  
application and requirements.  
The JC-2 may be ordered with any set of these plug-in cards. Alternate  
sets may be purchased at any time. Custom UP-1 cards can be supplied;  
contact the factory regarding your special application.  
Frequent changing of the cards is not recommended, but may be done.  
If you have any questions concerning the characteristics of a certain  
cartridge, please contact your dealer or the factory with regard to  
appropriate plug-in cards.  
5.2. Wood and Lexan Case  
A special case of original design is available for the JC-2 Preamplifier.  
The engraving on the top plate of the JC-2 is visible through a lexan  
window inset into the of the case.  
 
6. SPECIFICATIONS  
Phono Section:  
Gain*  
OVERLOAD POINT*  
1kHz  
1kHz  
36dB  
100mv min.  
*(see also Section 5)  
MAXIMUM OUTPUT  
CHANNEL TRACKING  
FREQUENCY RESPONSE  
18Hz to 20kHZ  
18Hz to 20kHz  
-1.5dB down at  
6v min.  
.5dB ( .2 typ.)  
18Hz, 30kHz min.  
NOISE  
below 10mv, inputs shorted  
below 10mv, 600ohms load  
18Hz to 20kHz:  
85dB  
83dB  
ASA "A" weighted  
90dB min.  
88dB  
INPUT IMPEDANCE  
RECOMMENDED LOAD  
OPEN LOOP BANDWIDTH  
SLEW RATE  
47kOhms*  
10kOhms or higher  
1500Hz min.  
20V/microsecond  
NOISE (JC-1SM)  
Line Section:  
below 1mv input  
better than 85dB  
FREQUENCY RESPONSE  
MAXIMUM OUTPUT  
GAIN  
Flat ±.2dB, 20Hz-50kHz, -1dB at 12Hz, 100kHz  
10V  
HIGH  
21dB  
LOW  
11dB  
NOISE  
INPUT IMPEDANCE  
below 2.5V  
HIGH  
LOW  
100dB min.  
10kOhms min.  
30kOhms  
RECOMMENDED LOAD  
OPEN LOOP BANDWIDTH  
SLEW RATE  
10kOhms or higher  
40kHz  
100V/microsecond (min.)  
POWER SUPPLY  
external ±15V at 300ma regulated and  
filtered. Internal additinal active  
filter for phono section.  
CURRENT  
SIZE  
approx. ±250ma at ±15V  
19" X 2"X 6 1/8"  
WEIGHT  
approx. 6lbs. with power supply  
 
7. WARRANTY  
All MARK LEVINSON products are guaranteed for five full years from date  
of purchase. Parts and labor will be furnished free of charge. The  
manufacture assumes no responsibility for damaged or abused equipment  
and reserves the right to determine cause of defects.  
IMPORTANT: Addendum to Section 4  
An output coupling selector switch is located between the line ampli-  
fiers on the main circuit board. When switched to the right (factory  
set position) the line outputs are AC coupled for driving direct coupled  
power amplifiers. When switched to the left, the line outputs are  
direct coupled for friving AC coupled amplifiers.  
 
NEW DEVELOPMENTS IN THE JC-2  
JC-2 Preamplifiers starting with serial number 2148 differ from previous units.  
They are equipped with lemo connectors, a new power supply (PLS-150), two phono inputs and new  
phono plug-in cards.  
PHONO SECTION  
The standard systems are now A3, D5 and d6. The plug-in cards contain a two-station  
program switch for selection of input and gain characteristics.  
System  
A3  
Rocker Switch  
Function  
Open  
Closed  
1
2
input impedance  
gain  
100k  
30dB  
50k  
40dB  
D5  
D6  
1
2
CRC*  
gain  
CRC out  
54dB  
CRC in  
60dB  
1
2
CRC  
gain  
CRC out  
60dB  
CRC in  
66dB  
System A3 permits optimum loading for cartridges such as the B & O, Grace and Audio Technica  
types which are designed for 100kOhms termination. Certain high output moving coil cartridges such  
as the EMT, the Supex 901, the Satin and the Ultimo, may be used in more efficient systems with the  
40dB gain implemented.  
System D5 and D6 are identical except for the gain. Both offer switchable CRC for flattening the high  
frequency response of certain cartridges like the Fidelity Research FR-1Mk3, the Ortofon SL15  
(original type), and certain other moving coil types (high frequency response varies from batch to  
batch of most MC cartridges.)  
System D5 offers 54 and 60dB gain positions. 60dB gain is the same as previously  
supplied by our System D and D1. 66dB is especially intended for use with low output MC cartridges  
such as the FR-1 Mk2 and Mk3 when used with inefficient systems requiring more voltage gain in the  
preamp.  
WHEN NOT OTHERWISE SPECIFIED, SYSTEM D6 WILL BE DELIVERED.  
Selecting the appropriate gain for the record output level may be accomplished by selecting the right  
phono plug-in systems.  
Note:  
System A3 cards MAY BE USED in earlier units. System D5 and D6 MAY NOT BE USED in  
earlier units. To accomplish the switching facility, differences had to be incorporated in the modules  
which DO NOT ALLOW Compatibility. For detailed information, contact the factory.  
For any questions concerning individual units, give us the SERIAL NUMBER of JC-2 in question.  
*CRC: Cartridge Resonance Compensation. The CRC circuit supplied rolls the high frequency  
response at 6dB per octave, -6dB at 20kHz. In particular, this curve has been successful in improving  
the performance of the FR-1Mk3. Other corrective curves are available on request.  
 
TONEARM CABLE ADAPTOR  
From an effort to simplify the connection of existing turntables to MLAS Pre-  
amplifiers fitted with Lemo connectors, we have developed the CA-1 cable adap-  
tor. The CA-1 is a solid block of aluminum 2X2X .75" machined to exact toler-  
ances and finished in our standard brushed black anodized surface. It replaces  
the phono connectors of any existing tonearm cable and allows connections to  
our preamps with an LL (Lemo to Lemo) cable set. (see page 11 of our 12-1-76  
notice. ) The CA-1 contains two female Lemo connectors. You will need LL.6" or  
LL-3' cables to complete the connection from the turntable to the preamp.  
The CA-1 can be easily installed by anyone who can solder. Tools necessary are  
a write cutter and stripper, a soldering iron and solder, a small screwdriver and  
an allen wrench (included) for tightening the strain reliefs. A provision is made  
for mounting the CA-1 to a turantable base or shelf, with one wood screw.  
For tonearm cables having leads less than .1" diameter, the CA-1 is not necessary.  
Non-crimp style lemo connectors can be installed easily.  
Other applications for the CA-1 include adapting microphone and other kinds of  
cables to Lemo termination.  
Tonearm cables from Japan generally use thick leads due to their interest in low  
capacitance cable. This type cable is not very durable and has some disadvan-  
tages in spite of the claims of its proponents. Those cables terminating in gold-  
plated phono connectors pose a hazard since gold really mates only with gold; gold  
to cadmium-plated phono connectors (the normal type) is worse than the standard  
phono connector to standard phono jack. The CA-1 is designed to accept all dia-  
meters of tonearm cable from the size just too big for non-crimp Lemos up to the  
heaviest Japanese type.  
 
INSTRUCTIONS FOR ASSEMBLING THE CA-1 CABLE ADAPTOR  
1.  
The CA-1 may be mounted to a shelf, cabinet, or turntable base with one  
wood screw. This keeps fragile tonearm leads from breaking or flexing.  
2.  
3.  
Use LL-.6 or LL-3 cables to connect with your JC-2 or LNP-2 preamplifier.  
Cut the phono connectors from the tonearm leads, nothing which wire is left  
and which is right.  
4.  
5.  
6.  
Strip the ends about 1/2" so that a center conductor and shield are prepared  
for each end.  
Insert the wires through the small holes on the edge of the CA-1 so they  
project through the other side.  
Solder the leads to the Lemo connectors, left and right. If the center  
Conductor wire is 26 gauge or smaller, it will fit in the connector pin;  
otherwise, wrap it around the pin and solder it.  
7.  
Pulling the leads back through the CA-1 gently, install the front plate  
with the button head screws and the 1/16" wrench.  
8.  
9.  
Drop the teflon pillows into the strain relief holes.  
Insert the strain relief screws and tighten gently.  
The system you just assembled is the closest thing to having one continuous  
wire from tonearm to the first state of preamplifier electronics.  
 
PLS-150 POWER SUPPLY SYSTEM  
JC-2 preamplifiers with Lemo connectors are equipped with the PLS-150 Power  
Supply. The PLS-150 Power Supply is considerably larger and heavier than the  
ones delivered with previous units. We recommend that it be positioned with  
the cable end facing the wall and the front plate facing forwards. In this  
way, the two LED' s will be visible. these lights indicate that the power  
supply is receiving the correct AC voltage and is delivering the correct DC  
voltage. If the AC light blinks or goes off, this indicates that the AC  
line voltage has dropped to unacceptable levels. If the DC light goes out  
it indicates that the power supply is no longer functioning. Should either of  
these lights go out, contact your dealer or factory for service.  
The PLS-150 Power Supply is a remote sensing design. This means that the  
power supply adjusts the voltage to be accurate at the preamp itself, adjusting  
for any effects of the cable and reducing cross modulation of the audio circuits  
to virtually zero.  
The PLS-150 chassis is removed from its cover by removing the four feet and  
single captive screw on top of the unit. Look inside if you want to, but  
don' t play with it unless you have specific instructions from the factory.  
 

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