Mark Levinson 27-5 Owners Manual

Operating Manual

Mark Levinson

Nº27.5

Dual Monaural

Power Amplifier

®

Madrigal Audio Laboratories, Inc.

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Important safety instructions

Please read all instructions and precautions carefully and completely before operating your Mark
Levinson® Nº27.5 Dual Monaural Power Amplifier.

1. ALWAYS disconnect your entire system from the AC mains before connecting or disconnecting

any cables, or when cleaning any component.

2. This product is equipped with a three-conductor AC mains power cord which includes an earth-

ground connection. To prevent shock hazard, all three connections must ALWAYS be used.

If your electrical outlets will not accept this type of plug, an adapter may be used. If an adapter
is necessary, be sure it is an approved type and is used properly, supplying an earth ground. If
you are not sure of the integrity of your home electrical system, contact a licensed electrician
for assistance.

3. AC extension cords are not recommended for use with this product. If an extension cord must
be used, be sure it is an approved type and has sufficient current-carrying capacity to power
this product.

4. NEVER use flammable or combustible chemicals for cleaning audio components.

5. NEVER operate this product with any covers removed.

6. NEVER wet the inside of this product with any liquid.

7. NEVER pour or spill liquids directly onto this unit.

8. NEVER block air flow through ventilation slots or heatsinks.

9. NEVER bypass any fuse.

10. NEVER replace any fuse with a value or type other than those specified.

11. NEVER attempt to repair this product. If a problem occurs, contact your Mark Levinson dealer.

12. NEVER expose this product to extremely high or low temperatures.

13. NEVER operate this product in an explosive atmosphere.

14. ALWAYS keep electrical equipment out of the reach of children.

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From all of us at Madrigal Audio Laboratories, thank you for choosing the Mark Levinson® Nº27.5 Dual
Monaural Power Amplifier.

A great deal of effort went into the design and construction of this precision instrument. Used
properly, it will give you many years of enjoyment.

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Table of contents

Unpacking and placement .......................................................................1

Unpacking .............................................................................................. 1

Placement ............................................................................................. 1

Ventilation ..............................................................................................1

Custom installations .............................................................................. 1

Voltage selection ........................................................................................ 2

Figure 1: Rear panel .......................................................................

Signal connections ..................................................................................... 3

Connectors ............................................................................................ 3

Cables .................................................................................................... 3

Connection methods and operating modes .................................... 3

Single-ended normal (non-inverting) operation ............................... 3

Figure 2: Connections for single-ended normal (non-inverting)

operation ..................................................................................

Single-ended inverting operation ...................................................... 4

Figure 3: Female input connector ................................................

Figure 4: Connections for single-ended inverting operation .....

Balanced normal (non-inverting) operation...................................... 5

Figure 5: Connections for balanced normal (non-inverting)

operation ..................................................................................

2

3

4
4

5

Speaker connections .................................................................................6

Lug connection ..................................................................................... 6

Figure 6: Spade and hook lugs .....................................................

Pigtail connection .................................................................................6

Figure 7A: Pigtail connection ........................................................

Figure 7B: Pigtail connection .........................................................

Figure 7C: Pigtail connection ........................................................

Connecting the speakers ..................................................................... 7

Power connection ....................................................................................... 8

Connecting the AC power cord ......................................................... 8

Figure 8: AC power cord polarity .................................................

Performance tips ................................................................................... 8

Protection circuitry ................................................................................ 8

Bridged operation .......................................................................................9

Balanced bridged operation .............................................................. 9

Figure 9: Connections for balanced bridged operation ...........

Figure 10: Balanced bridging cable ...........................................

Single-ended bridged operation ...................................................... 10

Figure 11: Connections for single-ended bridged operation..

Figure 12: Single-ended bridging cable ....................................

Care and maintenance ...........................................................................12

Cleaning ............................................................................................... 12

Fuses...................................................................................................... 12

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10
11

6

6
7
7

8

9

Specifications ............................................................................................13

Dimensions.................................................................................................14

Figure 13A: Dimensions, Nº27.5, top view ..................................

Figure 13B: Dimensions, Nº27.5, side view ..................................

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Unpacking and placement

Unpacking

Placement

Ventilation

Unpack your Mark Levinson® Nº27.5 Dual Monaural Amplifier, and
keep all packing materials (you may need them for future transport).
Because of the Nº27.5's weight, handles are provided front and rear so
two people may lift and carry the amplifier comfortably and without
risk of injury.

Carefully inspect the product for damage and flaws. If you discover
any, see your Mark Levinson dealer immediately.

To get the best performance from the Nº27.5, keep the speaker cables
as short as possible. Locate the Nº27.5 as close to your loudspeakers as
practical.

Locate the Nº27.5 at least three feet away from your turntable and
preamplifier. Otherwise, the Nº27.5 may induce hum in these sensitive
components.

You may place the Nº27.5 in a cabinet or on a shelf, but you must
provide adequate ventilation to prevent overheating. Make sure to
maintain the clearance provided by the Nº27.5's feet, and maintain
adequate clearance above the unit (for unrestricted air flow through
the heatsinks and through the vents in the bottom of the chassis). For
this reason, we recommend against placing the Nº27.5 on deep-pile
carpet.

Custom installations

PRECAUTION

The Nº27.5 has thermal sensors located near each group of output
devices. If the heatsink temperature becomes excessive, these sensors
will shut off the amplifier before damage results. After a brief cooling
period, you can reactivate the amplifier via the front-panel switch. If
this occurs regularly during normal use, ventilation may be
inadequate. If there's adequate ventilation and the problem persists,
see your Mark Levinson dealer immediately.

For custom installations and cabinetry, this information may be helpful.

■ All temperature measurements are made at the top of the

heatsink, 3.5" behind the front plate.

■ Normal heatsink temperature at idle after warm-up, with
unrestricted airflow at 22°C (72°F) ambient temperature: 35°C
(95°F).

■ Maximum permissible heatsink temperature before thermal
protection is activated: 80°C (176°F).

A mechanical drawing is included in this manual (see "Dimensions").

For your protection, review "Important safety instructions" before
you install your Nº27.5.

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