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