Manley 120 Watt Monoblock Amplifier Specifications

Manley Laboratories, Inc.
13880 Magnolia Ave.
Chino, CA. 91710
tel: (909) 627-4256
fax: (909) 628-2482
for choosing the Manley 120 Watt Monoblock Amplifiers. Designed around the concept that less is
more, the Manley 120 Watt Monoblock Amplifiers very fine components, with the shortest and
cleanest signal path possible, and with the use of our own milling equipment we can provide you
with an amplifier that looks as good as it sounds. We have developed a magnetics winding
department right here at Manley Labs where we design and wind the audio transformers.
Thank you again, and please enjoy!
The Manley 120 Watt Monoblock Amplifiers 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 amplifier, such
that a constant flow of air can flow throughout the ventilation openings. We also recommend that
the amplifier and preamplifier be placed at least 10 inches apart. Do not place amplifiers directly on
high pile carpet or any other surface that will block the ventilation holes.
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
Tubes may become loose during transit. Straighten and press down each tube before plugging the
amplifier into the mains socket. Furthermore, NEVER touch the tubes after the amplifier has been
switched on, the tubes become very hot during operation and should only be handled after the power
has been turned off and the tubes have cooled.
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 colored wires should be connected to the appropriate plug
terminals in accordance with the following code.
As the colors of the wires in the mains lead may not correspond with the colored marking identifying
the terminals in your plug proceed as follows;
The wire which is colored 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 colored GREEN or GREEN and YELLOW.
The wire which is colored BLUE must be connected to the terminal in the plug which is marked by
the letter N or colored BLACK.
The wire which is colored BROWN must be connected to the terminal in the plug which is marked
by the letter L or colored RED.
We do not ship the amps with the output tubes inserted to prevent breakage. Before plugging
in anything, locate the 2 tubes (KT-90s or 6550s) packed with the amp and insert them in the two
large tube sockets. The sockets are marked 1 and 2, the tubes are marked 1 and 2 - Put 1 in 1 and 2 in
2. This configuration is how the amps were tested and adjusted. Otherwise you will have to re-bias.
You should remove these little labels from the tubes and amp chassis as they are not needed now and
they may bake on permanently if the amp is run for a reasonable amount of time with them on.
Verify that the smaller tubes are sitting straight in their sockets.
Setting up your amplifier is rather easy.
1. Connect all source components (turntable, CD, Tuner, Tape DAT, etc.) to your preamplifier.
2. Connect the interconnects from the output of the preamplifier or switching center to the
RCA input on the top rear of the amplifier.
3. Connect the hot or "+" speaker cable to the red binding post and the common or "-"
speaker cable to the black binding post (See diagram 2). 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 breaak the connection
inside the amplifier.
4. Insure that the "mains" switch on the front panel is in the "off" or "0" position.
5. Turn on Preamplifier and any source components you plan to use.
6. Plug amplifier into wall outlet.
7. Turn on the amplifier and allow it to 'warm up' a minute or so before playing any audio
8. Turn up the volume and enjoy.
You have two amplifier modes - triode and ultralinear. Triode is about half power but is a
less complex audio path which suits some peoples tastes and speakers. Quiet music or
efficient speakers work well in this mode. Damping factor is slightly lower. Ultralinear is
a more common amplifier mode that allows more power, higher damping factor and a
wider range of speakers to be used. Before switching, turn off the amps to prevent
thumps and unwanted noises. Try both - Use the mode that suits you. Best performance
of tube amps is after they are well warmed up, generally about a half hour after powering.
You should get years of use from the tubes. Some statistically last less long and some last for
30 years. Checking bias every month usually will show you if they are drifting and
performing within specification. Excess noise and microphonics, a tube turned white or
not glowing are also big clues a tube needs to be replaced.
The Manley 120 Watt Amplfier uses a variable "fixed bias" system that requires very little attention.
If you wish to adjust or check the bias, complete the following steps. For this procedure you will
need a multimeter to read millivolts (less than 2 volt range) and a small flat screwdriver.
Looking at the front section of the top plate of the amplifier, you can see 2 red tip jacks and 1
black tip jack. To measure the current draw of each output tube place the positive probe (red) into
the red tip jack for the tube you wish to measure and the negative probe (black) in the black
(GROUND) tip jack and set the meter to read 'millivolts'.
Each of the two (2) output tubes can have its own bias adjusted by altering its own bias adjust
pot. The numbering sequence for the 2 output tubes runs from left to right, as do the corresponding
tip jacks (measurement points). The bias adjust pots are located on the top side of the amplifier,
therefore it will be NOT be necessary to remove the bottom cover to changing the bias. They also
read left to right.
The first step to setting the bias is to turn on the amplifier and insure that there is zero signal
input. Mute your preamplifier. Don't play tunes. Also, you MUST leave your loadspeakers
connected as these provide an ideal load on the output. Never operate your amplifiers without a
suitable load or speakers attatched. It is recommended that you leave the amplifier on long enough
to ensure that the tubes have reached their stable current draw.
Set your meter to read VOLTS DC. You will be measuring less than 1 volt so set your meter
for a low range if it is not an autoranging meter. Place the probes in the first red tip jack (negative
probes remains in the black tip jack for whole biasing procedure) and adjust the first bias trim pot
located on the left side top deck of the amplifier until you measure approx. 300 mVDC (0.300
VDC). Since you are measuring across a 10 ohm cathode resistor, this would correspond to a 30 mA
bias current. Settings between 275 mV and 300 mV are perfectly OK but try to have each tube the
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.
Follow step five with the other tube. Then go back and recheck again. Check and set the bias
on your amplifiers every day for the first week or any time you retube. Then check every week, then
every month. A red glowing area on the side of the tube usually indicates it is drawing way too much
current. If you see a red spot on the side of the tube, check and reset your bias immediately.
The power switch is located on the lower left hand corner of the front panel. Push the top of the
rocker switch (1) to turn on the amplifier and the bottom of the rocker to turn off the amplifier. The
LED on the right side of the front panel will illuminate indicating that the amplifier is operating. Do
not turn on and off the amplifier in rapid succession.
It is not recommended that you leave your amplifier permanently switched on. This only wastes
electricity and tube life. Your amplifier has solid state rectification and reaches peak operating
condition in approximately 30 minutes.
As with all tubes, their quality degrades with age. This is due to cathode emission, a natural process
found in all tubes. We recommend that you have your amplifier checked every 3-4 years, depending
on usage, sometimes the amplifier will require re-tubing after this time has elapsed, although we
have many cases of extreme long life recorded-- 40,000 hours and still counting!.
The Manley 120 Watt Monoblocks are equipped with a voltage change-over switch located under
the bottom cover. Insure that this switch is set at 110 if your mains voltage is 100,110,120, or 127
Volts. Set this switch to 220 if your mains voltage is 220, 227, or 240 Volts.
Changing the light bulb:
The lamp which back-lights the Manley insert on the faceplate is a fuse-lamp style lamp. Should it
burn out, turn off and unplug the amplifer from the mains first. Then remove the bottom cover.
Carefully pry out the old lamp from its clips and replace with one of the same type. Although it
looks like a fuse, it is really a light bulb!! Don't put a fuse in there!!
The fuse lamp is 1 1/4" x 1/4" 8Volts, 300mA.
Always replace with same type and rating. Should the B+ fuse blow (the fuse nearer to the output
binding posts) this usually indicates a tube has blown. One should visually inspect the pcb to look
for any burnt resistors a blown tube may have taken out. Also a good test is to measure the resistance
of each catode resistor. This is done in a similar fashion to checking the bias, except do this test with
the amplifier turned OFF, and set your meter for Ohms. Each cathode resistor should measure 10
Vacuum Tubes:
2 x KT-90 or 6550 (or good KT-88), 1 x 5751, 1 x 7044
Output Power
120 Watts tetrode, 65 triode
Frequency Response, +/- 1 dB
20 Hz - 50 KHz
Input Sensitivity
1 Volt nominal
Input Impedance
100 KOhm
Load Impedance
5 Ohm. Factory preset for 5 Ohm
S/N Ratio @100W
-100 dB
Power Consumption
120 Watts
360 Watts
Mains Fuse
100, 110, 120V
220, 240 V
W=12, D=10, H=6 inches
W=19, D=12, H=6 (panel=3.5) (rack mount version)
27 lbs (each)
Shipping Weight
Full Power
4 A (Slo-Blo)
2 A (Slo-Blo)
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.
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 labor. 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.
We ask that you please fill out this registration form and send the bottom half to:
CHINO CA, 91710
Or you may FAX it to: 909-628-2482
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 Manley Laboratories.
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