Manley MAHI MONOBLOCK AMPLIFIER User Manual

MANLEY

LABORATORIES, INC.

THE MAHITHE MAHI

THE MAHI

THE MAHITHE MAHI

OWNER'S MANUALOWNER'S MANUAL

OWNER'S MANUAL

OWNER'S MANUALOWNER'S MANUAL

TUBESTUBES

TUBES

TUBESTUBES

brought to you by the clever folks at:

MANLEY LABORATORIES, INC.

13880 MAGNOLIA AVE.

CHINO, CA. 91710 USA

TEL: [phone]
FAX: [phone]

email: [e-mail]

website: www.manleylabs.com

RULERULE

RULE

RULERULE

REV 11-1-2005

CONTENTS

SECTION PAGE

INTRODUCTION 3

MAINS CONNECTIONS 4

GETTING STARTED 5

MOVING RIGHT ALONG 6

LEARNING ABOUT TUBES 7

BIASING YOUR AMPLIFIERS 8

SIMPLE TROUBLESHOOTING 9

REPLACING A TUBE OR LAMP OR FUSE 10

TUBE FAQ 11

MORE SILLY VACUUM TUBE QUESTIONS 12

OPTIMIZING YOUR SOUND SYSTEM 13 & 14

CREDITS 15

SPECIFICATIONS 16

WARRANTY 17

WARRANTY REGISTRATION 18

2

INTRODUCTION

THANK YOU!...

for choosing the Manley MAHI monoblock amplifiers for your loudspeaker driving requirements. You have possibly
chosen this product because you auditioned it in a store or heard it at a hi-fi show and were impressed with the sound.
It may have been the right combination of price, power, features and styling for you. It may have been because you
know the Manley Labs reputation for quality, reliability, and integrity. If any or all of these were the reasons, you
made a good choice and for that, we thank you.

The MANLEY MAHI is designed to bring unbalanced RCA-type line inputs up to speaker-driving levels in the
simplest and most direct way possible. This is accomplished in only three active stages through the judicious use of
vacuum tubes, whose purpose-designed applications in audio amplification are pressed to full advantage here.

The MAHI’s circuitry contains many subtle and overt refinements that promote uncolored and revealing musical
reproduction of the input signal. The MAHI is a follow-on model from our previous "50 watt monoblock" model
which was a monoblock version of our famed STINGRAY stereo integrated. The name "50 watt monoblock" and its
chassis got somewhat boring and dated after awhile, so new for 2003 we brought this wonderful little champ up-to­date with our current direction in clever styling while retaining the circuitry basically as it was as to not screw with
success. But doncha know, we couldn't resist making a few improvements...

The MAHI now features Triode-Ultra Linear mode switching as standard whereas before it was a state secret option
on the 50's. Now you can choose whether you'd like to be seduced by a sweet 20 watts of triode operation or whether
you prefer the ballsy-er control of 40 some-odd watts of UL. The other switch on the top deck is a Variable Feedback
switch allowing the user to choose how much negative feedback is being applied to the amplifier for sonic variation
and optimisation of speaker-to-amplifier interface. New for the MAHI we greatly increased the B+ capacity with a
hefty bank of 1200uF filter caps. This now provides for nearly 180 Joules of energy storage which audibly equates to
tighter and more rock-solid authority in the bass region. The MAHI’s output transformer is built right here in our own
Manley Magnetics department and is the same one used in the acclaimed Stingray. Low levels of noise, distortion, and
negative feedback are partnered with the naturally high dynamic range of tube electronics which makes the MAHI
really jump to life.

Please read over this entertaining and enjoyable owner's manual carefully as it contains information essential to the
proper operation and maximum enjoyment of this instrument. Many of the remarks contained herein are especially
pertinent if the MAHI is to be your first long-term encounter with a vacuum tube power amplifier.
Thank you again, and please enjoy your new Mahis! (and the clever Owner's Manual.)

UNPACKING: Unpack the amplifiers carefully by removing all the custom foam packing material and make sure that
all supplied accessories are present. Carefully examine all items for any possibility of shipping damage. All of the
tubes are already installed and should have survived the journey protected by their very own grey foam insert. They
should be standing at attention in their sockets, and should show no signs of distress such as chipped glass, loose
internal components or obvious breakage. If the amplifier is damaged or fails to operate, notify the shipper or your
dealer or us or your local authorities immediately. Or if you suspect The Shipping People threw it off the airplane and
onto your front porch whilst flying overhead at 30,000 feet, notify the shipping company without delay and complain
to them as we only guarantee this unit to be able to survive a drop of 23,487 feet or less.

Your MAHI's were packed by Manny Q. with extreme love and each box includes the following components and
accessories:
a) 1 each, 6 foot IEC 3-conductor power cable (that you will probably replace with an expensive audiophile cord anyway.)
b) 1 each, Owner’s Manual per pair (that we hope you will keep reading.)

It is prudent to retain the shipping materials for future use, as they are custom-formed for the amplifier and
will greatly minimize the chance of shipping-related damage should you ever need to put your precious
MAHI's in the careless hands of The Shipping People again. We have heard that certain rodents might enjoy
munching on the packing foam. We are sorry to report that we do not warranty the packing foam against
attack by mice, rats, or other hungry critters, hungry children, hungry neighbors, etc. Try glue traps or
spring-traps loaded with peanut butter to eliminate these unwelcome freeloaders from your property.

3

MAINS CONNECTIONS

Your MAHI's have been factory set to the correct mains voltage for your country. (Well, that is what we intended to
do when we knew where they would be initially shipped.) The mains voltage that we built these MAHI's to operate
with is marked on the serial badge, located on the rear of the chassis. Check that this complies with what comes out
of your wall.

There is no voltage changeover switch! The power transformer's primaries must be either wired in parallel for 120v
operation or in series for 230v or 240v countries so be sure to check the sticker and the serial number voltage
indication for proper mains voltage. Failure to properly comply with mains voltage requirements can cause exten­sive damage to the system, which of course would not be covered by the warranty. If you relocate from, say, a 120v
country to a 240v country, you will need us to rewire the MAHI's power transformer for you or get instructions from
us to perform this operation if you happen to be as good at soldering as we are, or know someone who is. We are
not telling you how to do this in this Owner's Manual because you need to pass a battery of tests for us before we
will let you play with soldering inside the amplifiers. Contact [e-mail] for more details.

The MAINS FUSE may be checked by first disconnecting the IEC mains cord from the power supply’s power inlet
plug. Then gently push the light grey fuseholder retainer clip located next to the IEC power socket. The fuse and
cap should spring outward toward your fingers. The fixed silver springy looking thing is NOT the fuse. Leave that
alone. The fuse is a glass or white ceramic thing with silver end-caps. Inspect the mains fuse for the proper rating;
change if necessary. Refer to the fuse rating chart in the specifications section of this manual. If you do not know
what a blown fuse looks like, you may measure for continuity across the fuse ends. If your meter reads “OL” when
you measure across the fuse, that means “Open Leads” and that would mean the fuse is blown. A blown fuse usually
indicates A Very Bad Thing occurred. If this has happened to you, try to figure out why it may have happened.
(Using a Fast Blow fuse when we have specified a SLO-BLO fuse is one reason, output tubes running away into
never-never land are another reason.) If you have no idea why a fuse might have just blown on its own, you might
want to consult with Manley Labs or your dealer for further advice as Something Very Bad might have occured, like
the power transformer might have decided to retire early.

One way this could happen is by running the wrong mains voltage into the unit. Be sure not to do that.

If you live in a strange place...

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 EARTH terminal
BLUE NEUTRAL terminal
BROWN LIVE 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 OR SWITCH ON THE MAINS SUPPLY UNTIL ALL OTHER
CONNECTIONS HAVE BEEN MADE. (...or else...)

4

GETTING STARTED

PREPARATION FOR INSTALLATION

Budget a suitable space in which to place the amplifiers and associated interconnect and mains power cables. This space
should be free of strong external magnetic and RF fields, and reasonably removed from strong loudspeaker-generated
acoustical fields. This space should also be free of excessive heat or dust and large enough to permit easy flow of cool air
to the top, bottom and sides of the amps. Do not connect the MAHI's to the AC mains until the other interconnections and
items outlined below have been completed.

Keep other associated equipment some distance away from the amplifiers. This will help keep airflow unrestricted, and cut
down interference from radiated magnetic hum fields that can eminate from certain power supplies. Notice that the output
tube’s glass envelopes are capable of reaching high temperatures, depending on operating circumstances. As with other
equipment of this sort, it is best to keep the MAHI out of reach of pets or children, or be careful to keep children and pets
away from the amplifier when in use.

People sometimes ask us why we don't supply a cage to protect children and pets from the scary exposed tubes. I always
answer that I grew up with a tube receiver and survived ok and a cage would look ugly. The only physical harm that came
to any of my family growing up from that tube receiver was once The Moving People dropped it on my mother's toe and
broke it. (Broke the toe, not the receiver. It worked fine for many years after that. And Mom's toe is fine too.) And so did
my little nephew who had one of my amps with scary exposed tubes from the time he was a wee lad. He not only survived
and is in college now, but when he was three years old he knew how to fire up the whole hifi even before his mom did. So
don't under estimate how smart your kids or pets are unless they are already prone to burning themselves on light bulbs. Or
just put these little amps up on a tall shelf out of the way. Actually I'd be more worried about little kids breaking my $3000

moving coil cartridge needle. Or The Cleaning People...

Before plugging in your interconnects, take a quick visual inspection of the tubes. Sometimes either through shipping or
unpacking things get jostled. Make sure all tubes are firmly in their sockets. You might also verify that none have turned
white inside. That indicates that air has leaked inside the tube (or the vacuum leaked out!). Though it is rare, a tube is
sometimes cracked or broken in shipping. It would need to be replaced before powering up the unit. Give us a holler if this
happens to you.

RCA INPUT

The MAHI has a single-ended input stage and therefore only accepts an unbalanced RCA input. Balanced XLR inputs are
not provided as that would necessitate adding more "stuff" such as IC's or transformers to the existing circuitry and for this
amplifier, we are going by the "less is more" philosophy. If you only have balanced XLR outputs on your preamplifier,
please check with its manufacturer as to how it would prefer to be hooked up into an unbalanced load. Some transistor
balancing circuitry wants to see Pin 3 of the XLR lifted while other circuitry, such as transformer-coupled line stages must
have their Pin 3 grounded. XLR female to RCA male adaptors are available if you need to make a conversion. The MAHI
does not invert polarity.

The MAHI is a sensitive amplifier. (It's soooooo sensitive.) With the Feedback switch set at MIN, less than 175 millivolts
RMS into the RCA jack will produce full output power. And there is no mute switch. So make your connections before
you power up the MAHI. Otherwise you'll get a big loud noise. That might scare your kids or pets. And keep them away
from your scary exposed-tube amplifier. Ah!

SPEAKER CONNECTIONS
Never operate the amplifier without a speaker load, or suddenly disconnect the speaker load
while the amplifier is producing a signal. This risks punch-through of the enamel insulation
covering the transformer’s internal magnet wire. Permanent damage to the output transformer
may result and for that, you will be made to pay dearly, dear.

So there you have it. The beautiful WBT binding posts fitted to the MAHI are for hooking up your speakers cables. RED
is positive and WHITE is negative. Get these to your speakers by way of nice speaker cabling terminated with bare wire,
bananas, or spades. The WBT's feature a nice slipping clutch action which will clamp down on your terminals without
spinning them. No need to tighten them like a gorilla or you might break something. Consider yourself well warned.

5

MOVING RIGHT ALONG...

NOW THAT YOU HAVE ALL YOUR CABLES PLUGGED IN, you may now connect the IEC power cord to the

MAHI and to an energized power outlet.
Fire up all your upstream devices first: sources, preamplifier, and such and allow them all to finish their turn-on cycles
so your MAHI will not be amplifying any of their waking-up noises. My nephew was able to master that turn-on sequence
thing when he was a wee lad of only 3 years old. I swear.

Once your front end components are stabilized, you may now switch ON your MAHI's. The mains power switch is
located on the back of the chassis right at the IEC power inlet. You shouldn't need to turn the Mahi around or get
yourself behind it. You should be able to "feel" the rocker switch located next to the AC power cord. (We stuck the
power switch way back there to keep the noisy mains furthest away from the input circuitry.) Flip the switch away from
the power cord to turn on the Mahi or towards the power cord to turn off the unit. The MANLEY MAHI badge will light
up. Sometimes you might see a flash out of the little input tube's heater as it turns on. That's normal so don't worry about
it. I told you, stop worrying about it!

STOP WORRYING ABOUT EVERYTHING AND JUST GET LISTENING! Once audio is first heard from the
Mahi's, please notice that it takes about 45 minutes of warm-up time for the system to reach thermal equilibrium. During
this warm up time, go walk your dog, make dinner, or play some lite pop music. Some Elvis "Blue Hawaii" would be a
fun choice. Or even Don Ho. Well, what you listen to is up to you.

POWER DOWN (What? So soon?) (No silly, when you're done, unless you just wanna practice!) As a rule, power up
your amplifiers last, power down them first so they do not amplify any stray noises which could occur upstream from
source components powering up or down. Additionally, it is best to cut power to the Mahi when not in use rather then
leaving the power on indefinitely. This will enhance tube and system life. The tubes should last thousands of hours under
normal conditions. Especially if you check your BIAS every once in awhile. Keep reading to learn more about tubes and
then on page 8 you can learn about biasing your Mahi's.

(Unless you live in California and are in the middle of a Rolling Greyout®™.)

TRIODE vs. UL vs. TETRODE: The MAHI output tubes can be switched to run in TRIODE mode or Ultra-Linear
mode. Number one thing though, we really recommend that you TURN OFF the amplifier and count to five BEFORE you
throw this switch. Triode is when the screen grids are hooked up to the plates of the EL84's. Triode mode is known to be
very sweet and seductive sounding, but alas, it is a more inefficient way to run the output tubes. You only get about half
the power in Triode as you would in Tetrode. Ultra-Linear, often called "partial triode," is when the screen grids are
hooked up to a special taps on the primaries of the output transformer. These UL taps are located somewhere special
between the center tap and the outside anode taps. Tetrode (or Pentode) operation is when the screen grids are hooked up
directly to the center tap B+ of the output transformer. We don't give you that choice here but we want to tell you about
it to help you understand more about UL. The sound of Tetrode mode is a little rougher and less refined than triode, but
way more powerful, and sometimes, you really need more power. What is great about Ultra-Linear is you get the best of
both worlds and how much of each world we choose to allow into the final result is dependent on where we choose to
put the UL taps when we are designing the output transformer. The closer we choose to put the UL taps to the outside
windings, the more triode-like the UL mode will be. The closer we put them to the center tap, the more powerful tetrode­like they will be. For this little amplifier's UL taps, we found a place where we felt the best balance of the two extremes
would be so you still get lots more power, and it still is sweet, and it also has that driving and boogie-ing character that
makes your toe tap. And again, remember, it is best if you TURN OFF the amplifier, count to five, throw the Triode-UL
switch, and then power back on the amplifier if you want to compare between triode and UL modes. Most people find a
preference and stick to it. You are free to do as you choose. It's a free country.

VARIABLE FEEDBACK: Some global negative feedback is employed in the MAHI. A bit of the output signal is taken
off the final speaker outputs and is routed back to the input stage. The entire circuit, including the output transformer and
some loudspeaker back-EMF, is thus included in the feedback loop, all 3dB's (MIN), 6dB's (STD), or 10dB's (MAX) of
it, which ain't that much actually compared to some amplifiers we could mention. You can choose how much negative
feedback is applied with the Variable Feedback switch. Negative Feedback alters the slew rate or "speed" of the amplifier.
Feel free to experiment with this switch any time, even while playing tunes, even for different music. Use your ears and
pick whatever setting you like, whenever you like. Knock yourself out.

TUBES RULE! While we could lauch into a whole lecture about the technical advantages of vacuum tubes, such as high
headroom, big Joules, graceful overload characteristics and all this stuff, I'd rather get down to what's really important:
Music is an emotional thing. There's no "right" or "wrong." Whatever gets your toe tapping is what is "right" for you. We
enjoy working with vacuum tubes because we find we can get them to translate this emotional connection from the tunes,
through hunks of steel, through the air to your ear where it reaches the enjoyment central station of the brain and then
gives you those goosebumps. Try to measure THAT! Nah, don't. What we'd like you to really do is to enjoy years of
fabulous music through your Manley MAHI's.

6

While we're at it, and since this is a TUBE Amplifier, let's TAWK
about TUBES: As with all tubes, certain parameters degrade with age.

This is due to decreasing cathode emission, a natural process found in all
tubes. There are just so many electrons on that cathode and one day, they
will have all jumped off. An excessive increase in noise level or very
unstable output tube bias can indicate the need to replace a tube. The
electrolytic capacitors will probably eventually dry out or start leaking
and need to be replaced. Maybe in 15 to 20 or 30 years you will need
to do this but don't worry about this for now... didn't I tell you to stop
worrying?

But I do worry: How long will these tubes last? We can’t say for sure.
Nowadays, as in years past, bad tubes do emerge from the manufacturer’s
assembly lines. Some tubes die prematurely while others, especially
small ones like the 12AX7, AU, AT and so on can last for more than 30
years of continuous use! The chief determinants of tube life expectancy
are the stringency of the particular application, and the initial build
quality of the tube itself. The average for the tubes in the MAHI should
to be around 2000+ hours for the output tubes, hey, maybe lots more,
depending on usage, more for the input and driver tubes. We've seen
60,000+ hours on a set of tubes, but we're not trying to get your hopes
up as it is better for the life on your tubes to exceed what we tell you they
will do so you will feel better when they do and be all surprised.

How can I tell when I need to replace them? Most problems relating
to the output tubes will show up while performing the bias procedure (on
the next page). Tubes that cannot be adjusted within the specified range
or have a very unstable reading are should be replaced. If the tube’s plate
(the grey metal rectangular box-like part most visible from the outside)
is glowing cherry red or orange, then the tube is severely overheated.
Check its bias immediately; if unable to adjust, then turn off the amplifier
right away and replace the tube. The input and driver tubes can become
noisy (hiss) or the amplifier may exhibit audible distortion; substituting
known good tubes is the best way find the bad one. You got 2 channels
to play with! They all can't be bad at once.

All tubes are “microphonic” to some extent; that is, they will make
ringing noises through the speakers when tapped or vibrated. Here again,
substitution will determine which one is overly sensitive to mechanical
vibration. Obviously, any tube that is totally dark inside while powered
up or is cold to the touch (careful!) is defective, or not making good
contact with the heater contacts in the tube socket.

Most tubes have a silvery coating deposited on some area inside the glass
bottle. This coating is put there by the “getter”, and its job is to soak up
or “get” contaminants, such as air molecules left over inside the glass
envelope during the tube’s manufacture, and help keep the vacuum hard.
(Ooooh. You said "hard.") If the getter material has turned white
(compare to another tube), then the tube has lost vacuum (or gained air!)
and is definitely bad. Replace at once. Don’t turn the amp on. Throw the
tube out. Or shoot it.

Do I need to replace them all at once?

No, at least not with these amps, or unless all the tubes have clocked
some thousands of hours of use. Some tube amps do require that if one
tube has to be replaced that a complete matched set put in. All Manley
amps use individual bias trims for each output tube which allows a single
tube to be replaced. Absolute best performance is achieved when the
tubes are most similar, both in bias requirements and transconductance
characteristics. We batch them and label each tube so that in the event
of a replacement you can get one from Manley of similar characteristics
as the others in your amp. We need that hand written number on the top
of the tube (Output tubes only. We know what we need to give ya for
input or driver tubes).

Does the “sound” of the amp change as the tube ages?

Yes, but not too much, and even then, given good tubes, it is fairly
strongly related to the amp design. The tubes can be allowed to reach
their technical life limit, or they may be replaced more frequently
depending on the listener’s taste and accompanying equipment. In
general, the band edges will suffer first, with very gradual loss of the
deepest bass and ultrasonic treble. The MAHI is designed to meet
stated power bandwidth specifications at 80% of rated output power
at the end of useful tube service life. By way of contrary tube
application contrasts, it is not like big guitar amps where tubes are
replaced every 6 months for reasons of “tone”. The MAHI’s tubes are
strong, allowing a very long life and less change between old and new
tubes. This is where that figure of 2000 hours, or 4 to 5 years of use
comes from. You may notice an improvement between tubes this old
and new tubes depending on how critical you are. Keep in mind the
sound of new tubes changes most in the first weeks of use before they
can be considered “broken in”. At first they may sound a little “tight”
and “direct” (like some people we know).

Is it difficult to replace a tube? Yes, but only if you have trouble
replacing light bulbs. It is super easy. Turn off the power. Just let the
amp cool a few minutes so that you don’t burn your pinkies. It helps
to wiggle the tube gently rather than pulling it out straight. Use some
terry cloth material or an oven mitt if time is pressing.

Even if you don’t consider yourself “technical” you probably have
more technical ability than your parents and they used to fix the
family TV set by taking out the tubes and putting them through the
tube tester at the local pharmacy. It is almost as easy to re-insert a
tube. Just make sure it is correctly lined up with the socket and you
don’t bend a pin. Notice that the 9-pin miniature tubes have a gapped
set of pins, making a rotational installment error nearly impossible.
The larger 8-pin or octal-based tubes have no gap in their pin sets,
but instead have a larger keyed center pin formed from the inert
plastic plug material. The key makes insertion of the tube into the
socket nearly impossible unless the key lines up with the matching
hole in the amp’s octal socket. Notice that octal tubes which have
damaged or missing keyed center pins should NOT be used, since
some output tubes internal wiring can cause dramatic equipment
failure by short-circuit if incorrectly fitted to the amp’s sockets. But
you don't have any octal tubes in this amp so don't worry about that.

You can wiggle the tube when reinserting too. If you had a solid state
amp (heaven forbid!), transistor replacement would merely be
chapter 1 in the saga. You would have to open it up, diagnose the bad
transistors and burnt resistors, de-solder 'em, find replacements
(good luck on locating those germanium beasties) re-solder 'em, and
hold your breath as you turn it on. Best have your Platinum credit
card handy for ordering more. Or you could send it back, be without
music for a few weeks, pay for service by the hour and be ready to
administer nitroglycerine tablets under the tongue when it fries
again. (Sarcastic? We're not sarcastic!)

That's why TUBES RULE: If you need a tube, or set of tubes,
Manley Labs will be happy to sell you matched sets at a good price.
And if you prefer to send the unit back for repair or adjustment, our
warranty covers most everything except tubes (6 months only please)
and abuse (7 months only-- just kidding). Plus we handle ground
shipping back to you (unless you live overseas, cuz there's no ground
service!) Repairs usually take less than a week. Could we do more?
(That's a rhetorical question. It's late. Just keep reading...)

7

BIASING YOUR AMPLIFIERS

DON'T WORRY! IT IS SUPER-EASY!

Convenient test points for checking the standing current of each EL84 output tube is available on the top of the
chassis, near the output tubes. The test points are connected to each tube’s 10-ohm cathode resistor (inside).
Everything is clearly labelled on the chassis because we know you guys are prone to throwing away informative
Owner's Manuals.

Tube bias is a frequent source of confusion and misinformation, especially as it pertains to output tubes. This is
partially due to the practice of using the term ‘bias’ for many situations throughout the electronics industry in
general, along with the nature of the requirements needed to provide a proper electrical environment in which to
efficiently operate a given audio output tube. Here, therefore, is a concise (oh really, Mitch?) picture of what is going
on in the EL84 output tubes when the “bias” control is adjusted…

When the amplifier power is switched on, several voltages are quickly developed by the amplifier power supply.
Around +400 volts DC for the plate, and about –25 volts DC, low current and low power, for the control grids. Six
and 12 volts are also applied to the appropriate tube filaments. All of these voltages are referred to the output tube
cathode voltage, which is usually within a few volts of circuit ground or chassis potential

The heater (orange glowing filament) of the tube inside the cathode sleeve rises to about 1200 degrees C. This heats
the special oxide coated nickel cathode sleeve and, after 10 or 20 seconds, the oxide produces a generous cloud of
electrons, which are negatively charged. The electrons are strongly attracted to the large positive plate, which is
beckoning them from across the vacuum with an irresistible +400 volt potential. Notice here that, as usual, the
differing charges, plus-to-minus, attract, and like charges plus-to-plus or minus-to-minus repel. Without some
control, the tube is in danger of running at full cathode current, which due to prodigious input power from the 400V
power supply, would lead to red-hot plates and quick tube destruction. Now the control grid is used to throttle back
this hazardous situation, by the careful application of a negative voltage to the control grid. This applied negative
grid voltage, Mr. Bias, retards the flow of electrons from the cathode to the plate by repelling the cloud of electrons
around the cathode with a like charge, minus-to-minus, and confining most (or all) of them to the space between the
cathode and control grid. Much like a Venetian window blind is used to control sunlight entering a room.

When you adjust the “bias” control, the control grid is being made slightly less or slightly more negative. How much
this electronic venetian blind has been opened or closed may be observed by watching the cathode current with a
voltmeter at the tube’s test point. The higher the current, the more open the “blind” or valve setting, hence the higher
the voltmeter reading. Notice that contaminants in the vacuum and other factors can sometimes conspire to reduce or
eliminate the effects of the negative voltage impressed on the control grid, which can lead to runaway over-current
conditions and ultimate tube failure.

OK, Mitch, that's enough for now. My eyes are glazing over. HOW DO I CHECK THE BIAS?

Checking the standing current may be performed by connecting a DC millivolt meter between a test point and chassis
ground, with the positive red meter lead to the test point, amplifier on, and zero audio signal present. Just leaving
your preamplifier turned off is not not a bad idea. Adjust the corresponding bias trim control until a meter reading of
250 millivolts is attained. This corresponds to 25 milliamps of standing current because Ohm's Law tells us that

0.250VDC divided by 10 ohms (the cathode resistor) equals 25mA. Changing the standing current through one
output tube may slightly alter the amount of current flowing through the neighboring tubes. Therefore, check the
remaining output tubes and readjust as necessary. Turn off the amplifier and replace any tube that cannot be brought
to the correct standing current when varying its bias adjustment control. Do not let the standing current exceed 50
milliamps (500 millivolts) except briefly as necessary during the adjustment procedure or you might be in for a
surprise. (And we're not going to tell you what that surprise might be or it will spoil it for everybody.)

You should expect extended life from the tubes in your MANLEY MAHI amplifiers if you adhere to the procedures
described above, and check your EL84 standing current at least once every 2-3 months. Generally, the longer the
tubes operate, the less they should need standing current level inspection. And when that sad day comes, and the
tubes have reached their lifetime service limits, be of good cheer, for should you ever need replacements we stock all
the tubes used in these amplifiers, pre-screened and tested, and at very reasonable prices too! Oh yes!

8

TROUBLESHOOTING

Here are some suggestions to try out in the event you encounter some of the symptoms below.
If you encounter some other symptoms, then maybe you have some other problems that we don't know about.

HUM: Forgot the words. Try a mains ground adapter if they are legal in your country. They are also called 3
pin to 2 pin adapters or “cheaters” and are available in hardware stores. There should be one ground in your
system and only one. If two or more pieces of gear have 3 pin AC mains cables, and they are grounded into the
wall, a ground loop can occur which will usually cause hum. Either the preamplifier OR the power amps, when
sharing an earth connection, are probably the best ground reference for your system, but not both or all of
them.

HISS: Stray snakes in the room. Plug a shorted RCA plug into the input. Did the hiss stop? If so, then the
source of the hiss is something upstream from the MAHI. If the noise level is the same, then the problem is in
the MAHI - probably a noisey 12AT7 or 6414. Try swapping (with the power off please) one tube at a time
across to the other channel to see if the hiss moves over there. If it did, then you found the troublemaker and
you can contact us and we will report him to the proper authorities and send you a tube. And maybe sell you
some spares for next time.

OUT O' BALANCE: Mom told you not to put anything smaller than your elbow in your ear. The two
speakers sound different. Make sure you have both amplifiers' MODE and FEEDBACK switches set to the
same positions. It may be the CD or source and the way it was recorded. First try a different source, or switch
the source to the mono mode if possible, and listen for any level shifts. Notice that each MAHI’s overall gain
is carefully checked at the factory, and should be within 0.25 dB (or better) of each other. Next try swapping
the inputs. Power down and swap left and right inputs. If it is the source, then the problem will “follow” the
swap. Return them to normal (L=L). Power down again and next try swapping the speaker connections by
putting the left speaker wire in the right terminals and right wires into the left terminals. If the problem
switched sides then one MAHI is suspect; if the problem stayed on the same side it is probably a damaged or
fatigued speaker or some crossover switch that got changed by The Cleaning Lady.

NO SOUND, NO PILOT LIGHT, TUBES DARK: Did you pay your Edison bill? Check the MAHI's AC
Mains fuse. Check AC power cord. Is the amp plugged into a working electrical outlet? (This has happened to
everyone at least once!).

NO SOUND, PILOT LIGHT ON, TUBES LIT: Forgot to lower needle onto record. Check speaker
connection and input connection (exchange with the other channel). Take a bias measurement. Do all bias test
points read zero volts? If so, the B+ fuse is blown. CAREFULLY INSPECT ALL OUTPUT TUBES BEFORE
REPLACING THE B+ FUSE because you probably blew one. That B+ FUSE info is on the next page, page

10. (See also “Replacing Tubes” on page 7 if you forgot already what a blown tube might look like).

ONE OUTPUT TUBE WILL NOT BIAS: It doesn't want to. Try to will it to comply. If the bias on ONE of
the tubes will not adjust at all or reads zero volts, and the tube filament is lit, try replacing replace that
particular tube. If the reading still is way off or reads zero, turn the amplifier off. Set your multi-meter to
“ohms” (the Omega sign) instead of “DC volts” (NOT the wavey line, that's AC volts!). Now measure the bias
test point resistance (that's what Ohms do) between the red test point and the ground test point. It should read
approximately 10 ohms. If it reads very high or not at all, then the 10-ohm cathode resistor connected to the
tube has become hurt by that tube not being nice to it. One function of this resistor is to act as the final safety
valve in case of a shorted (not nice) output tube, preventing damage to the rest of the amplifier should a short
occur. Replacing this resistor can be done by anyone with adequate soldering skills. We recommend
contacting our service department here at the factory for specific instructions on how to do that because we are
only giving you enough information in this owner's manual to almost be dangerous.

9

MAINS FUSE: If this has blown, A Very Bad Thing has occurred. See page 3.

B+ FUSE: The B+ fuseholder is located on the rear chassis near the speaker binding posts. If all of the

sardine NONE of the tubes show any bias reading at all, and the lights are on, and no tunes will play, you
might have popped a B+ fuse. This fuse is here to protect the output transformer from a rogue tube or some
other strange event. Before replacing it, stop and think a minute if you noticed anything, like a bang or crack
noise coming from the speaker. Or maybe you notice one of the tubes looks cracked or sick. Or maybe you
smelled something funny? And saw a tube take off and glow bright red or orange? Any of these events could
be a tube "running away". If you are aware of what went down and can clearly see the offending tube, then
yes, do replace the bad tube and then replace this B+ fuse. Always check the bias on a new tube as the
amplifier warms up and watch him closely like a new puppy to make sure he behaves for the next little while.
The fuse is a 4/10th Amp, 250v MDA 4/10 SLO-BLO (time delay). The size is 1/4" x 1 1/4". Only use a
ceramic fuse here as the glass ones sometimes flame out or crack. Do not use a Fast Blow fuse or you will be
replacing them on every downbeat. And remember those 400 volts we mentioned? They are living here on
this fuse, so you had better MAKE SURE THE AMPLIFIER IS OFF AND UNPLUGGED AND
DISCHARGED before you play with this!

SWAPPING TUBES: Three tube types that are electrically and plug-socket compatible with the 12AT7A
dual triode include the 6021, 6679, and the ECC81. There is no exact replacement for the 6414 dual triode,
although the 12BH7 or 12AT7 are pin-compatible substitues, so in a pinch you can jam one of those in to get
you by for a few days. The 6414 is really the best choice here, for this circuit, trust us. Actually think long
and hard before just trying to score some golden lovely tubes on ebay for $125 each. Are they really what
they claim to be? (Paint can be scraped off or applied at will.) Are they really new? (Hard to tell sometimes.)
Are they tested? Were they tested for optimum performance in a Manley MAHI? We didn't think so. By
virtue of our experience, testing, and selection we do recommend you obtain replacement tubes from the
factory. We will indeed be looking after the best interests of you and your MAHI in our tube selection
travails.

Digging around inside:

Yes there are user-servicable parts inside! (Contrary to what The Safety Regulatory People tell us to declare
on the rear of the chassis, and you have to be a handy kind of user...) But, as with other vacuum tube based
products, there is also high voltage present. Therefore caution must be used when covers are removed;
otherwise there could be Shock Hazard. Probably not enough to kill you. Only enough to severely annoy you
should you inadvertently grab onto the B+ volts. As with all mains-powered gear make sure the mains power
is off and mains cord is unplugged if you are planning to get inside and dig around in there. If the amp has
been powered up within the last 15 minutes stop! and let the large electrolytic capacitors discharge otherwise
you could still get a shock even though the unit is unplugged. Really! You will need a #1 Philips screwdriver
to remove the bottom cover screws. Use one hand only when reaching into the enclosure or touching any
components inside. Keep the other hand away from the amplifier, preferably in your pocket. For real!

BACKLIT BADGE LAMP REPLACEMENT: If the tubes are glowing and you have tunes but the
MANLEY MAHI badge fails to light up, you may have a burned out badge bulb. This little light bulb looks
like a fuse but it is really a light bulb so don't try to put a fuse in there. It is sometimes called a "fuse-lamp"
and is 1/4" diameter by 1 1/4" long. It is a 12volt, 0.15 Ampere incandescent lamp. If you need a new one
and can't find one readily, you can guess that we probably have plenty in stock and you could order a new
one from us. After removing the cover, use a small slot driver to help pry the badge’s fuse-lamp straight
down out of the clip holder. It is of course located right behind the MANLEY MAHI illuminated badge
under the aluminum bracket. Don't crush & break the glass. NOTE! MAHI's shipped after 5/2003 use

LED's to light up the badge, so guess what? You will never have to replace these! Hooray!

Please direct any other more involved questions regarding the guts of the MAHI to

MANLEY LABS Tech Support for further assistance.

Taking advantage of the amazing technology of email: [e-mail]

is the best way to reach us, because we might be eating lunch or something.

10

TUBE FAQ

A few general all-too-frequently-asked vacuum tube questions from the
manleylabs.com FAQ as found on our website are answered here in case you don't
have internet access (which we don't doubt because after all you bought vacuum
tube amplifiers, didn't you?):

(Don't take that comment personally. EveAnna still drives air-cooled Volkswagons... We're not perfect either.)

FAQ #16. Do you sell tubes?

I don’t know what you’re talking about.

FAQ #16a. I need to retube my Manley amplifier. Do you sell tubes?

Sorry. Just kidding. Yes, of course we do. We have about 100,000 tubes in stock of the several major
types we use.

FAQ #16b. Why should I buy tubes from you?

We are only as good as our worst tube. We are very selective about which tubes we use in Manley
products and we have several different testing and burn-in jigs to test for certain parameters which will be
most important for that tube in a given circuit. We will test and select a tube set for you that will be
optimized for your Manley piece of gear and in most cases, your tube set will actually be tested in another
one of what you have.

FAQ #16c. Are tubes expensive?

Not especially. Although I might have made a killing in the stock market had I invested the money I
instead put into finding and stocking these large quantities of tubes ten years ago when the USA military
were dumping their stocks of NOS JAN vacuum tubes. Seriously, there is the stocking cost to consider in
the cost we must charge, development charge of the computerized test jigs we built, then more importantly
the time it takes one of our guys to run a little tube through its qualification procedures. Remember, a
given tube cannot be improved during testing. It is the way it is, and one hopes it stays that way. It can
only be selected, and in selecting that tube that will work really well for your piece of gear, we probably
had to throw away several. In some cases we might have had to go through 30 tubes to find the quietest
one, or the one with the lowest microphonics, or the one with the best internal matching, depending on
what parameters are important for that circuit. That is all factored into the cost somewhat, but no, overall,
we don’t charge enough for replacement tubes.

FAQ #16d. NOS? JAN? What does that mean?

New Old Stock. Joint Army Navy. Yes our military used to use vacuum tubes. As long as the glass
doesn’t break, tubes are impervious to a nuclear explosion’s electromagnetic pulse unlike little silicon
devices whose little junctions would go poof!

FAQ #16e. Good to know. How long do tubes last?

Some of them are dead out of the box. Some tubes don’t make it through burn-in and after a few days they
just go noisy or quit. Sometimes UPS sabotages our shipments and after all our testing efforts the tube
arrives broken at your place. Sometimes a tube decides to end it all early and intentionally misbehaves
after a few months. Other tubes are real troopers (like my 98 year old neighbor) and run strong for 30
years. We have documented cases of power tubes in Manley amplifiers going over 60,000 hours non-stop
in recording studios 24/7/365 without a re-tube. In one case in particular, the amplifiers were never turned
off and had their own dedicated air conditioning for the amplifier rack they lived in. This certainly
contributed to their long life.

11

More silly vacuum tube questions...

FAQ #16f. Should I turn off my gear between uses?

While power cycling is a factor for ultimate tube life, there also is a fixed number of electrons that can ultimately
jump off the cathode. In general we do recommend if you aren’t using the gear for more than a few hours you should
power it down. Do you leave the lights on in your house when you are away?

FAQ #16g. But it sounds different when you first turn it back on. What is the warm-up time for this gear?

I generally recommend 45 minutes warm-up time for everything to reach operating temperatures and sound like it’s
supposed to.

FAQ #16h. What about break-in time for new gear?

We burn in the gear for a couple of days before it is shipped out. Folks report that after about a week of break-in that

it sounds better. Some of the more fussy people of course report that full break-in takes much longer....

FAQ #16i. How do I know a tube is broken?

All the vacuum has leaked out.

FAQ #16i.i After the vacuum leaks out, where does it go? Is there some way to
collect it and put it in another tube, to make it last longer?

You have to suck really hard.

FAQ #16j. No really, how do I know a tube is broken?

Usually a tube whose glass has been broken or cracked usually will have a white powdery like substance inside it
where all that silvery stuff used to be. No, it is not cocaine and we didn’t put it there..

FAQ #16k. Does the glass explode?

I haven’t seen it happen. Usually the glass will just crack at the base of the tube if it is going to physically break due
to a sudden change in temperature and “all the vacuum will leak out”.

FAQ #16l. Other than outright failure of a tube, how do I know when it is time to re-tube?

Generally speaking, for the small tubes, if you notice an unacceptable increase in background noise (“hiss”) then the
tube who is responsible for making the gain in the circuit probably needs to be replaced. The tube(s) making the gain
will usually be shorter than the output tube. Common types we use for gain in most of our circuits will be 12AT7,
6201, 12AU7, 5814, 12AX7, 5751, or 6072. The output buffer tube in most of our line-level circuits will be either
the 7044, 6414, or 12BH7. These tubes usually don’t cause too much trouble and either work or don’t work. Turn
the lights off and see if you see the little tubes glowing. Look for one that looks like it has cocaine in it.

For the power tubes in our amplifiers, after a few years if you notice a small revolt going on where several of the
output tubes are misbehaving or getting hard to bias, you might consider doing a full re-tube. Keep the old ones that
did not join the revolution as emergency spares.

FAQ #16m. Can I change a tube myself?

R.T.F.M.
Do you call in specialists to change your light bulbs for you?

12

Optimising Your Sound System

This section is full of Hutch's little hints that may help you get the most out of your stereo - and it may not
cost anything or cost very little. Probably, you know most of this, but hopefully some of it may be new or
refresh your memory or just be refreshing reading in a manual.

A very important factor is your speakers. Hopefully you have good speakers and they are appropriate for
your power amplifier. What is appropriate? Well, with 50 watt of tube power per side and probably a limited
budget we would hope for reasonably efficient speakers so that the system will get loud enough for the music
you listen to. The "spec" to look for is "sensitivity" or "efficiency". A speaker that is 95 dB efficient will
easily get as loud with 50 watts as 85 db speakers with 150 watts. "85" will do if you only listen to folk or
chamber music. Usually you pay about the same for high sensitivity speakers but in amplifiers more watts is
more $. By the way, many reviewers confirm that 50 tube watts is similar to 100 solid state watts. If you are
buying speakers, it is wisest to carefully listen to them before buying. You will most likely like them longer
if they tend to sound natural and real rather than over-emphasized in some area. In other words, think
"accurate reproduction" not "numbers" and "hype".

The price of speakers is often directly related to the low frequency response. Great lows generally require
deep pockets and plenty of power. Thanks to "home theatre" there are a lot of powered subwoofers available
that won't drain your resources. Get one that connects to speaker outputs so that it follows your input
selection and volume control. This makes connecting them pretty easy.

There are some very interesting speaker tricks. Most people just place them wherever it is convenient.
Spouse approval is a real factor. We suggest that you experiment with speaker placement, then when they
sound 100% better you bring in the spouse and demonstrate the difference. They should be able to hear the
improvement and may totally agree with your choice. You should aim for equal distances between your
listening position to each speaker and from speaker to speaker. The ideal is an "equilateral triangle". Try to
get the speakers off the floor, and away from the walls (both side and back). The angle of the tweeter or
speaker front panel to your face is also critical and experiment with that too. You should be getting a smooth
frequency response so that highs and lows are balanced and mids not too prominent or distant. It should
simply sound "natural". When we buy color TVs the first thing most of us relate to is flesh tones because it is
something we all relate to and know when they are right. The equivalent thing in audio is vocal tone. We
have evolved amazing discrimination for the varieties of human voice and much less for other instruments.
Use a few well recorded CDs with vocals and adjust the speakers to get the most natural voices. If you are
lucky, you will end up with a system that creates a 3D picture of the music that not only has left/right width
but a solid distinct center. It should also make some sounds seem in front of the speakers and some behind.
We have heard some systems with our amplifiers even give an illusion of the height of the individual
musicians. Most rooms are longer in one dimension. Some systems sound best with the speakers across the
short dimension and the listening position part way back but not right at the back wall. Some systems are
better across the long dimension. The only way to find out is to try.

If you are getting this amazing imaging and soundstage, you may be interested why you have it if you have a
nice vacuum tube amplifier. These are very audible effects that seem to be beyond normal measurement
technique or textbook electronic theory. This effect is directly related to the amount of negative feedback
used in a design. The less feedback the greater the imaging. In transistor amplifiers it has been common
practice to use more than 80 dB of negative feedback. Conventional designs need it because transistors are
not particularly linear devices and it forces the circuit to get low distortion figures as well as very high
damping factors. Tubes are much more linear and inherently low distortion. Tube amplifier designs use far
less negative feedback (less than 20 dB) as a result . We speculate that the negative feedback may have a
negative effect on transient accuracy. It is reasonably documented that the feedback does reduce the lower
order harmonics in distortion but can raise higher order harmonics that are more audible. Feedback also
makes the transition from clean to clipping very abrupt and abundant with high order harmonics. The best
audio devices always seem to be simple & aesthetically balanced, with form following function.

13

More Helpful Hints from Hutch...

You may have bought a great system but there is a good chance that you are only getting a fraction of its
potential. Very frequently we have experienced top quality electronics sounding unimpressive simply
because acoustics were ignored. Even amongst studio engineers, few can really tell the difference between
good speakers in a bad room and bad speakers in a good room - but they all know good speakers in a good
room and very likely so do you. Acoustic techniques are better explained in books on recording studio
construction. You can buy good ready-made acoustical materials and/or build them yourself for a fraction
of the cost. Dollar for dollar, you can expect far greater improvement with acoustic treatment than
expensive interconnects.

Most people think acoustics is about sound-proofing but there is a lot of info available for improving the
reproduction of music. Sound-proofing is usually expensive. Luckily just improving the acoustics in a room
can be pretty painless. You may be able to change or move what is on the floors and walls (without getting
expensive or ugly). The improvements may be dramatic.

Number One on the bad list is parallel surfaces. That pretty much includes most rooms. Parallel surfaces
can support a very short echo that is known as a standing wave. It boosts some frequencies and cuts others.
This effect is often called comb filtering because of the multitude of peaks and dips. One cure is breaking
up the big surfaces with a variety of smaller ones. The good news is that book shelves, curtains, wall
hangings or macrame, plants, furniture and lamps all help. Not only does this balance live surfaces with
dead ones but "checker-boarded" areas also act as a sort of diffuser. You can probably build low cost
effective and attractive diffusers or have them made if you want something better (and more efficient).
Number Two is very unbalanced room treatment. Both too "live" and too "dead" is generally bad. One
might think that wall to wall carpets & curtains is going to be fine but watch out. All that stuff only eats
highs and a little mids, but doesn't do anything to the lows. The lows end up very live in contrast to very
dead highs. One way to balance this is get some thick absorbsion into the corners. Thick absorbsion in the
corners is most effective to lows. The idea is to balance high and low absorbsion. Even normal speech
sounds weird in near empty rooms with plain painted gypsum walls and hardwood floors. The simpler the
decor the more intense the acoustic problems. The only hints we can offer is that the wall behind the
speakers and behind you are often the most important. You can build some simple absorbers. Simply cut
two 4'X8' pieces of 2" rigid fiberglass or open cell foam rubber into 16"X8' strips and wrap some white
cloth around them. Easy, clean looking and cheap. Experiment, lean them against the wall at various
places. Even very experienced acoustic designers experiment, listen then decide rather than attempting to
predict every result. A variation is to use "perf-board" as a backing if you intend to stretch the fabric
reasonably tight. It may also help with hanging the strips to the walls. Perfboard with a one or two inch
space behind it is an alternative front surface to increase diffusion or can do double duty as a simple
helmholtz absorber (for the low mids) and can be effective on the ceiling. You can hang a few up there
either flush or dropped a few feet if you have the height to absorb lower frequencies. The wall behind the
listening position is usually responsible for too much or too little lows compared with the rest of the room.
Read up on slat and membrane absorbers for problems there - the panels described above won't help much
for that.
Number Three is lack of left/right symetry. In order to get the left and right similar sounding and getting a
rock-solid center you should have identical left and right walls and distances. The ideal is a perfectly
symetrical room but this may not be practical. Again, try to achieve this with positioning.
Some of the "test" CDs have a variety of low frequency tones or sweeps. Use them to find rattles and buzzes
in the room. Lamps and fixtures, some cabinets and components can do this. A little tape or glue can often
fix these types of things. If you are getting serious about this kind of thing you can get a variety of test gear
from measurement mics to real time analysers or computer software. These are useful tools but do not
depend on the readings unless you are very experienced using them. Best to use your ears and use the test
gear to verify what you hear and to document the changes. Remember that test gear neither makes records
nor listens to music. Frequency measurement often ignores "time" and exagerates some factors and glosses
over others. Steady tones are virtually useless in real rooms. The more comprehensive tests give complex
data that needs to be correctly interpreted to be useful. Use 'em but don't jump to confusions. Always use
ears too. Ears are fabulous instruments.

14

CREDITSCREDITS

CREDITS

CREDITSCREDITS

MANLEY MAHIMANLEY MAHI

MANLEY MAHI

MANLEY MAHIMANLEY MAHI

An EveAnna Manley Production

Featuring concept, layout and industrial design by EveAnna Manley.

Starring: Paul Fargo for Input Innovations

Hutch for Output Outovations

Mastered by: Baltazar Hernandez

In keeping with our new tradition of naming fresh new Manley HIFI products after aquatic
creatures, we set out to revisit the 50-ish watt monoblock idea to bring you the MAHI.

From our collective creative brains issued forth all the clever circuitry and schematic
design.

Joe Rodriguez heads up the Manley Magnetics department. The special output transformer
used first in the Stingray (which is more or less a stereo integrated version of the MAHI
circuit) resulted from plenty of studied calculations, laborious winding and lamming, and
intensive batteries of tests both on the bench and in our listening environs. All the tunes must
pass through this iron beast before reaching the final speaker destination and so it was an
important thing to do right. We make this little output transformer sound BIG.

Balta did all the circuit board and metal work drawings and assembled the prototypes.

Humberto, Gamma, Martin, Jose-Luis, and Smokey measured and aligned everything as
Quality Control Technicians are prone to do.

You can blame this silly manual on EveAnna and Mitch with some intelligent ramblings
contributed by Hutch. There are no pretty pictures in this manual because everything is so
clearly labelled on the chassis and that epoxy paint Elias uses on the silk-screen is nearly
impossible to get off and so we didn't think you would mind having to just look directly at
the amplifiers to understand what we are talking about in these pages.

All the strange and extraneous remarks you have noticed so far in this Owner's Manual have
been put here on purpose because we know you will keep reading so you don't miss the next
quip. In the rare case that you find a mispelling or an error in grammer in this Owners
Manuel, please consider that it was put there for a porpoise as their are allways some peeple
looking for missteaks and they might as well find them hear.

15

SPECIFICATIONS

Input Impedance: 110 Kohm
Input Sensitivity: TRIODE UL

FB MIN: 175mV 155mV
FB STD: 312mV 340mV

FB MAX: 480mV 566mV
Gain: 29dB
Negative Feedback: MIN= 3dB; STD=6dB; MAX=10dB of global NFB
Max. Output Power defined as power output reaching 1.5% THD @ 1KHz
into 5 ohms: TRIODE UL

FB MIN: 18W 20W

FB STD: 27W 42W

FB MAX: 28W 46W
into 8 ohms: TRIODE UL

FB MIN: 14W 24W

FB STD: 24W 40W

FB MAX: 25W 41W
Signal to Noise Ratio Ref. 1W: Typically 82 dB A-WGT 20-20K
Noise Floor: Typically 150µV = -74dBu A-WGT

Typically 650µV = -62dBu unweighted
Dynamic Range: 83dB
THD+noise @ 5W less than 0.15%
Frequency Response at full power UL mode w/MAX NFB: 20 Hz to 20 kHz FLAT
Frequency Response at 5W into 5 ohms: 10 Hz to 30 kHz FLAT, -3.75dB @ 100KHz

Recommended Speaker Load: Optimized for 5 ohms
Actual Output Impedance: TRIODE UL

FB MIN: 2.83 ohms 3.57 ohms
FB STD: 1.87 ohms 2.16 ohms
FB MAX: 1.28 ohms 1.36 ohms

Power Consumption (idle): 102 Watts (0.85A @ 120VAC)
Power Consumption (at Rated Full Power): 168 Watts (1.4A @ 120VAC)
Vacuum Tubes: 1 x 12AT7WA Ei, 1 x 6414 JAN NOS, 4 x EL84 Output per monoblock
Output Tube Quiescent Standing Current: 25mA
Set Bias for 250mVDC measured across each 10 ohm cathode resistor
Fuse types for 120VAC operation: MDL or MDA 3 AMP / 250 Volt SLO-BLO

240VAC operation: MDL or MDA 2 AMP / 250 Volt SLO-BLO

B+ FUSE: MDA 4/10th AMP, 250 Volt SLO-BLO
Dimensions: 11" deep x 10" wide x 5" tall
Shipping weight each: 18 pounds

Specifications subject to change because they just might.

16

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 transferrable warranty is available 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, or registration can be made online in the Tech Support section of
www.manleylabs.com.

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. Tubes are warranted for six months provided the
warranty registration is completed as outlined in paragraph 1.

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 can be supplied 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.

MANLEY LABORATORIES, INC.

13880 MAGNOLIA AVE.

CHINO, CA. 91710 USA

TEL: [phone]
FAX: [phone]

for Tech Support email: [e-mail]

website: www.manleylabs.com

17

WARRANTY REGISTRATION

We ask, grovel and beg that you please fill out this registration form and send the bottom half to:

MANLEY LABORATORIES
REGISTRATION DEPARTMENT
13880 MAGNOLIA AVE.

CHINO CA, 91710 USA
Or you may FAX this form in to: [phone] or you may fill in the online warranty registration
form found in the Tech Support section of our website www.manleylabs.com or you can be really
diligent and register your warranty three times to see if we get confused!

Registration entitles you to product support, full warranty benefits, and notice of product enhancements
and upgrades, even though it doesn't necessarily mean that you will get them (Just kidding!) You
MUST complete and return the following to validate your warranty and registration. Thank you again
for choosing Manley gear and reading all the way through The Owner's Manual. (We really mean that
sincerely, the bit about thanking you for choosing our gear. THANK YOU!!!)

MODEL MAHI SERIAL #'s__________________

PURCHASE DATE ______________ SUPPLIER ______________________

--------------------------------------------------------------------------------------------------------

PLEASE DETACH THIS PORTION AND SEND IT TO MANLEY LABORATORIES

MODEL MAHI SERIAL #'s___________________

PURCHASE DATE ______________ SUPPLIER _______________________

NAME OF OWNER _______________________________________________

ADDRESS ______________________________________________________

CITY, STATE, ZIP ________________________________________________

EMAIL: ________________________________________________________

TELEPHONE NUMBER___________________________________________

COMMENTS OR SUGGESTIONS?__________________________________

________________________________________________________________

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