MANLEY
LABORATORIES, INC.
OWNER'SMANUAL
MANLEY REFERENCE
DIRECT INPUT
50/50
STEREO AMPLIFIER
MANLEY LABORATORIES, INC.
13880 MAGNOLIA AVE.
CHINO, CA. 91710
TEL: (909) 627-4256
FAX: (909) 628-2482
CONTENTS
SECTION
PAGE
INTRODUCTION
3
MAINS CONNECTIONS
4
CONNECTING YOUR AMPLIFIER
5
DIAGRAM TOP OVERHEAD VIEW
6
DIAGRAM REAR VIEW
7
DIAGRAM FRONT VIEW
8
BIAS PROCEDURES
9
OPERATIONAL NOTES
10
SPECIFICATIONS
11
WARRANTY
12
WARRANTY REGISTRATION
13
INTRODUCTION
THANK YOU!...
for choosing the Manley DIRECT INPUT 50/50 Amplifier. Designed by David Manley, the Manley DIRECT
INPUT 50/50 Amplifier uses only the best available components, with the shortest and cleanest signal path
possible, and with the use of our own in-house CNC machine shop we can provide you with a amplifier that looks
as good as it sounds.
The circuit and the components used have been chosen carefully after years of development and refinement for
reliability, constancy and most importanly, musical, accurate, and emotional delivery of the sound. The circuit
topology is similar to other designs in the MANLEY range. This amplifier is configured for the more powerful
tetrode operation mode with a separate regulated screen supply which allows a wider range of EL34s to be used as
the screens are run at safer lower and constant voltages . We emphasize big, beefy resevoir capacitors in the high
voltage supplies giving plenty of instant energy for dynamic performance of transient peaks and bass performance
which often exceeds that of rival solid-state amplifiers. We run high voltages on the plates of the output tubes and
are thus able to run them at lower current which will result in longer life for the output tubes. Each output tube has
its own bias adjust, and the procedure for adjusting each tube's current draw is described in this manual. The
multi-sectioned output transformer has been factory set for an optimum 5 ohm load which will drive most
speakers comfortably. This amplifier with its built in selector switch, record output, and precision stepped
attenuator becomes the efficient and compact heart of a system which should bring you years of pleasure.
Thank you again, and please enjoy!
GENERAL NOTES
LOCATION & VENTILATION
The Manley DIRECT INPUT 50/50 Amplifier must be installed in a stable location with ample ventilation.
Allow a minimum of 2 inches of clearance on the top and sides of the amplifiers, such that a constant flow of air
can flow. Do not place amplifiers directly on high pile carpet or any other surface that will block the ventilation
vents underneath the amplifiers. If you have small children or pets, you should consider placing the amplifiers out
of reach to prevent damage to the amplifier or damage to your small children or pets by the amplifier as the tubes
do get hot during operation.
WATER & MOISTURE
As with any electrical equipment, these amplifiers should not be used near water or moisture. If liquid enters the
amplifier, it must be immediately returned to your dealer for servicing.
SERVICING
The user should not attempt to service the amplifier beyond that described in the owner's manual. Refer all
servicing other than biasing and tube replacement to Manley Laboratories
SPECIAL NOTES
Tubes may become loose during transit. Straighten and press down each tube before plugging the amplifier into
the mains socket. Furthermore, do not touch the tubes after the amplifier has been switched on, as the tubes
become very hot during operation and should only be handled after the power has been turned off and the tubes
have cooled.
WARNING!
!
TO PREVENT THE RISK OF ELECTRIC SHOCK
DO NOT OPEN THE CABINET
REFER SERVICING TO
QUALIFIED PERSONEL
MAINS CONNECTIONS
Your amplifier has been factory set to the correct mains voltage for your country. The voltage
setting is marked on the serial badge, located on the rear panel. Check that this complies with
your local supply.
Export units for certain markets have a moulded mains plug fitted to comply with local
requirements. If your unit does not have a plug fitted the coloured wires should be connected
to the appropriate plug terminals in accordance with the following code.
GREEN/YELLOW
BLUE
BROWN
EARTH
NEUTRAL
LIVE
terminal
terminal
terminal
As the colours of the wires in the mains lead may not correspond with the coloured marking
identifying the terminals in your plug proceed as follows;
The wire which is coloured GREEN/YELLOW must be connected to the terminal in the plug
which is marked by the letter E or by the safety earth symbol or coloured GREEN or GREEN
and YELLOW.
The wire which is coloured BLUE must be connected to the terminal in the plug which is
marked by the letter N or coloured BLACK.
The wire which is coloured BROWN must be connected to the terminal in the plug which is
marked by the letter L or coloured RED.
DO NOT CONNECT/SWITCH ON THE MAINS SUPPLY UNTIL ALL OTHER
CONNECTIONS HAVE BEEN MADE.
CONNECTING YOUR AMPLIFIER
Setting up your amplifier is rather easy.
1. Connect all LINE LEVEL source components (CD, Tuner, Tape, DAT, etc.)
to the designated RIGHT & LEFT inputs on the back of the amplifier.
2. Connect the hot or "+" speaker cable to the red binding post and the common
or "-" speaker cable to the black binding post (See diagarm 2) of each channel. Ensure that the other end of the cable is connected correctly to the
speaker. Tighten the binding posts by hand. If you use a nut-driver (3/8")
do not over-tighten the posts or you may break the connections inside the
amplifier.
3. Check that the volume control is in the minimum counter clockwise position
and/or the MUTE switch is engaged DOWN.
4. Ensure that the "mains" switch on the front panel is in the "off" or "DOWN"
position.
5. Turn on any source components you plan to use first.
6. Plug amplifier into wall outlet.
7. Switch the mains power switch to the ON position and allow the amplifier a
minute or so to 'warm up'.
8. If the MUTE switch is engaged, the red mute LED will illuminate. Throw
this switch UP to the operateposition.
9. Turn up the volume and enjoy.
10. After your listening session, be sure to mute the amplifier and turn off the
power BEFORE powering down any source components. You do not want to
amplify potential noises your source components may create on turn-on/turnoff.
INPUT
RCA
OUTPUT B+ MAINS IEC MAINS
FUSES
IN
TUBE BIAS ADJUST POINTS
1
2
3
4
6414
1
6414
3
2
12AT7
4
12AT7
Amplifier Overhead View
with top cover removed
OUTPUT TUBES:4 x RUSSIAN 6CA7/EL34
The 6CA7's used are the Russian up-rated 6CA7's. This has been proven to be the rugged and reliable of this type and
we strongly emphasize that only the RUSSIAN 6CA7's should be used in this amplifier. The MANLEY DIRECT INPUT 50/50
has been thoroughly optimised around this tube. Use of unapproved tube types can and will void your warranty.
DRIVER TUBES: 2 x 6414
The 6414 is an American military uprated version of the 12BH7A with increased current drive.
INPUT TUBES: 2 x 12AT7WA
The 12AT7WA has several equivalent numbers, (12AT7, 12AT7A, 6201, ECC81, etc.) Any of these types may be
used. We have selected this 12AT7WA very carefully for noise, microphonics, and constancy. Replacement tubes of premium
quality are always available from MANLEY LABORATORIES.
RIGHT
CHANNEL
MAINS
FUSE
SLO-BLO
RCA
INPUTS
LEFT
CHANNEL
RECORD
OUTPUTS
AUX
AUX
CD
MAINS
IEC
RCA
INPUTS
CD
TAPE
TAPE
TUNER
TUNER
SPEAKER
OUTPUT
BINDING
POSTS
REAR VIEW OF AMPLIFIER
FRONT VIEW OF AMPLIFIER
MANLEY
AUX
CD
TAPE
TUNER
DIRECT INPUT
50/50
STEREO AMPLIFIER
READ BIAS
VOLUME
GROUND
1 2 3 4
MUTE
SWITCH
POWER
SWITCH
FRONT VIEW OF AMPLIFIER
MUTE
LED
SHOWING BIAS MEASUREMENT POINTS
MANLEY
POWER
LED
BIAS PROCEDURES
The Manley DIRECT INPUT 50/50 uses a fixed bias system that requires very little
attention. If you wish to adjust or check the bias, follow the following steps.
For this procedure you will need a voltmeter (a hand held autoranging DMM digital
multimeter is the easiest) and a small flat screwdriver.
1.
On page 8, which shows the FRONT panel of the amplifier, you can see 1 black tip
jack and 4 red tip jacks. To measure the current draw of each output tube place the
POSITIVE meter probe into the first red tip jack and place the negative meter probe into the
BLACK tip jack.
Set the meter to read 'millivolts' DC (direct current).
2.
Each of the four output tubes can have its own bias adjusted by adjusting its own bias
adjust pot. On the top view picture on page 6, you can see the numbering sequence for the 4
output tubes and each tube's bias adjust pot. You'll need to remove the top cover by
unscrewing the screws found on the top and sides of the cover. Do not touch any components
inside the amplifier. Do not adjust any other pots except for the ones pictured on page 6.
High voltages are present even after the amplifier has been turned off!
3.
The first step to setting the bias is to turn on the amplifier and ensure that there is
zero signal input, either leave the preamplifier muted, source signal turned off, volume
control down, etc. In other words, you want to measure the quiescent current of the
amplifier: NO input signal. Also, leave your loudspeakers connected as these provide an
ideal load on the output. (DO NOT EVER OPERATE YOUR AMPLIFIER WITHOUT
SPEAKERS CONNECTED!) It is recommended that you leave the amplifier on long enough
to ensure that the tubes have reached their stable current draw, at least 1/2 hour is
recommended.
5.
Place the red positive meter probe in the first red tip jack . Adjust the first bias trim
pot slowly until you measure 275mV to 300 mVDC (0.275V to 0.300VDC). Since you are
measuring across a 10 ohm cathode resistor, this would correspond to a 27 to 30 mA current
draw for each tube by Ohm's law.
6.
If you are unable to bring the bias voltage down to 300 mV on any tube then we
recommend that the tube be carefully watched or replaced.
7.
Follow step five with the remaining tubes, switching to the next tube measurement
point and adjusting the next trim pot each time. After you have adjusted all the output tubes,
recheck and repeat the procedure as they will drift a little bit during adjustment. Once they
are all set, your amplifier should be in perfect operation.
OPERATIONAL NOTES
TUBE LIFE
You should expect extended life from the tubes in your MANLEY DIRECT INPUT 50/50 if you
adhere to the procedures described above and check your bias at least once every 2-3 months. We
stock all the tubes in these amplifiers should you ever need replacements (and at very reasonable
prices too!)
FUSES
The fuse used in your amplifier are standard 1/4" x 1 1/4" SLO-BLO types. The correctly rated fuse
has been installed at the factory for your country's voltage. If replacing a fuse, always unplug the
amplifier's power cord from the wall outlet and always use the exact same type and ampere rating
fuse as the one you are replacing. Failure to do so will void your warranty and can be a dangerous
fire hazard. NEVER replace a fuse with thick wire, tin foil, gum wrappers, or anything else other
than the correct fuse!
SPECIFICATIONS
Vacuum Tubes:
Output Power
4 x EL34 (Output), 2 x 6414 (Drivers),
2 x 12AT7 (Inputs)
51 Watts (@1.5% THD 5 ohm load)
Frequency Response, +/- .5 dB
at 50% rated power
10 Hz - 20 KHz
Input Sensitivity
375mV
Input Impedance
100 KOhm
Load Impedance
5 Ohm (fixed)
S/N Ratio @50W
-80 dB
Power Consumption
220 Watts
360 Watts
Mains Fuse
100, 110, 120V
220, 240 V
Dimensions
W=19, D=10, H=5 inches
Shipping Weight
41 lbs EACH
Quiescent
Full Power (@1.5% THD 5Ω load)
5 A (Slo-Blo)
3 A (Slo-Blo)
WARRANTY
All Manley Laboratories equipment is covered by a limited warranty against defects in materials
and workmanship for a period of 90 days from date of purchase to the original purchaser only. A
further optional limited 5 year warranty is available to the original purchaser upon proper
registration of ownership within 30 days of date of first purchase.
Proper registration is made by filling out and returning to the factory the warranty card attached to
this general warranty statement, along with a copy of the original sales receipt as proof of the
original date of purchase. Only 1 card is issued with each unit, and the serial number is already
recorded on it.
If the warranty registration card has already been removed then this is not a new unit, and is
therefore not warranted by the factory. If you believe this to be a new unit then please contact the
factory with the details of purchase.
This warranty is provided by the dealer where the unit was purchased, and by Manley Laboratories,
Inc. Under the terms of the warranty defective parts will be repaired or replaced without charge,
excepting the cost of tubes. No warranty is offered on tubes, unless:
1. a Manley Laboratories preamplifier is used with a Manley Laboratories amplifier, and
2. the warranty registration card is filled out.
In such a case a 6 month warranty on tubes is available with the correct recording of the serial
number of the preamplifier on your warranty registration card.
If a Manley Laboratories product fails to meet the above warranty, then the purchaser's sole
remedy shall be to return the product to Manley Laboratories, where the defect will be repaired
without charge for parts and labour. The product will then be returned via prepaid, insured freight,
method and carrier to be determined solely by Manley Laboratories. All returns to the factory must
be in the original packing, (new packing will be supplied for no charge if needed), accompanied by
a written description of the defect, and must be shipped to Manley Laboratories via insured freight
at the customer's own expense. Charges for unauthorized service and transportation costs are not
reimbursable under this warranty, and all warrantees, express or implied, become null and void
where the product has been damaged by misuse, accident, neglect, modification, tampering or
unauthorized alteration by anyone other than Manley Laboratories.
The warrantor assumes no liability for property damage or any other incidental or consequental
damage whatsoever which may result from failure of this product. Any and all warrantees of
merchantability and fitness implied by law are limited to the duration of the expressed warranty.
All warrantees apply only to Manley Laboratories products purchased and used in the USA.
Some states do not allow limitations on how long an implied warranty lasts, so the above
limitations may not apply to you. Some states do not allow the exclusion or limitation of incidental
or consequential damges, so the above exclusion may not apply to you.
This warranty gives you specific legal rights and you may also have other rights which vary from
state to state.
WARRANTY REGISTRATION
We ask that you please fill out this registration form and send the bottom half to:
MANLEY LABORATORIES
REGISTRATION DEPARTMENT
13880 MAGNOLIA AVE.
CHINO CA, 91710
Registration entitles you to product support, full warranty benefits, and notice of product
enhancements and upgrades. You MUST complete and return the following to validate your
warranty and registration. Thank you again for choosing to use Manley Laboratories.
MODEL ____________________
SERIAL No. ______________________
PURCHASE DATE ______________ SUPPLIER ______________________
--------------------------------------------------------------------------------------------------PLEASE DETACH THIS PORTION AND SEND IT TO MANLEY LABORATORIES
MODEL:MANLEY REFERENCE DIRECT INPUT 50/50 STEREO AMPLIFIER
SERIAL No. ______________________________
PURCHASE DATE ______________ SUPPLIER _______________________
NAME OF OWNER _______________________________________________
ADDRESS ______________________________________________________
CITY, STATE, ZIP ________________________________________________
TELEPHONE NUMBER ___________________________________________
Serial #'s of Associated Manley Laboratories Equipment ___________________
________________________________________________________________