McIntosh MC275 Vacuum Tube Amplifier Owner’s Manual

McIntosh MC275 Vacuum Tube Amplifier

Thank You

• Your decision to own this Mclnto h MC275 Stereo Power Amplifier ranks you at the very top among discrimi­nating mu ic Ii tener. You now have “The Be t.”
• The  Mclnto h dedication to “Quality,” I a urance that you will receive many years of mu ica1 enjoyment from this unit.
• Please take a short time to read the information in this manual. We want you to be familiar a pos ible with all the features and functions of your new Mclnto h MC275. This will ensure that you receive all the performance ben­efit this equipment can offer you, and that it will become a highly valued part of your home entertainment y tern.

Please Take A Moment

• The serial number, purchase date, and Mclnto h dealer name are important to you for po ible in insurance claims or future services. The serial number I located on the rear panel of the equipment.
• The pace below has been provided for you to record that information:

Safety lntructions

IMPORTANT SAFETY INSTRUCTIONS!

• PLEASE READ THEM BEFORE OPERATING THIS EQUIPMENT.
• WARNING SHOCK HAZARD
• DO NOT OPEN. A AVIS RISQUE DE CHOC NE PAS OUVRIR
• NO USER-SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED PERSONNEL

General

1. Read all the safety and (Fating instructions, contained in this owner’s manual, before this equipment.

2. Retain this owner’s manual for future reference about safety and operating instructions.

3. Adhere to all warnings and operating instructions.

4. Follow all operating and use instructions.

5. Warning: To reduce risk of fire or electrical shock, do not expose this equipment to rain or moisture.

   • This unit is capable of producing high sound pressure levels. Continued to high sound pressure levels can cause permanent hearing impairment or loss. User caution is advised and ear protection is recommended when playing at high volumes.

6. Caution: to prevent electrical shock do not use this (polarized) plug with an extension cord, receptacle or other outlet unless the blades can be fully inserted to prevent blade expusure. To avoid burns, do not physically touch the hot tubes.

   • Attention: pour pevenir Ies chocs elecriques pas utiliser cette fiche polarisee avec un prolongateur, June prise de courant ou unautre sortie de courant, saufsiIes lames peuvent etre inserees afond ans en laisser aucune partie a decouvert.

7. For added protection for this product during a lightning storm, or when it is left unattended and unused for long periods of time, unplug it from the wall outlet and dis- connect the antenna or cable system. This will prevent damage to the product due to lightning or power line surges.

8. Do not use attachments not recommended in this owner’s manual as they may cause hazards.

   • Installation:

9. Locate the equipment for proper ventilation. For ex-ample, the equipment should not be placed on a bed, sofa, rug, or similar surface that may block ventilation openings; or, placed in a built-in installation, such as a bookcase or cabinet, that may impede the flow of air through the ventilation openings.

10. Locate the equipment away from heat sources such as radiators, heat registers, stoves, or other appliance (including amplifiers) that produce heat.
    Mount the equipment in a wall or cabinet only as de- scribed in this owner’s manual

11. Do not use this equipment near water; for example, near a bathtub, washbowl, kitchen sink, laundry tub, in a wet basement or near a swimming pool, etc.

12. Do not place this product on an unstable cart, stand, tripod, bracket, or table. The equipment may fall. causing serious injury to a person, and serious damage to the product.

    • Connection:

13. Connect this equipment only to the type of AC power source as marked on the unit.

14. Route AC power cords so that they are not likely to be walked on or pinched by items placed upon or against them, paying particular attention to cords at plugs, convenience receptacles, and the point where they exit from the instrument.

15. Do not defeat the inherent design features of the polarized plug.

16. Non-polarized line cord adapters will defeat the safety provided by the polarized AC plug. If the plug should fail to fit, contact your electrician to replace your obsolete outlet. Do not defeat the safety purpose of the grounding-type plug.

17. Do not overload wall outlets, extension cords, or integral convenience receptacles as this can result in a risk of fire or electric shock.

    • Care of Equipment:

18. Clean the instrument by dusting it with a dry cloth. Un-plug this equipment from the wall outlet and clean the panel with a cloth moistened with a window cleaner. Do not use liquid cleaners or aerosol cleaners.

19. Do not permit objects of any kind to be pushed and/or fall into the equipment through encloure opening .

    • Never pill liquid into the equipment through encloure opening

20. Unplug the power cord from the AC power outlet when left unused ed for a long period of time.

    • Repair of Equipment:

21. Unplug this equipment from the wall outlet and refer servicing to a qualified service per tunnel under the fol­lowing condition

    • A. The AC power cord or the plug has been damaged,
    • B. Objects have fallen, or liquid has been pilled into the equipment,
    • C. The equipment has been exposed to rain or water,
    • D. The equipment doe not operate normally by follow­ing the operating instructions contained within this owner’ manual. Adju t only tho e controls that are covered by the operating in traction, an im­proper adjustment of other control may re ult in damage and will often require extensive work by a qualified technician to re tore the product to its nor­mal operation,
    • E. The equipment has been dropped or damaged in any way,
    • F. The equipment exhibits a distinct change in perfor­mance -this indicates a need for service.

22. Do not attempt to service beyond that described in the operating instructions. All other services should be re­ferred to qualified service per one.

23. When replacement parts are required ure the er­vice technician ha u ed replacement part specified by McIntosh or have the same characteristics as the origi­nal part? An unauthorized ub situation may result in fire, electric shock, or another hazard.

24. Upon completion of any service or repair to this prod­uct, a k the service technician to perform safety checks to determine that the product is in proper operating con­dition.

Introduction

The patented McIntosh Unity Coupled circuit and output tranformer have e table hed Mclntoh amplifier a the un­challenged leaders in the audio field. Before 1949, low distortion at high power and high efficiency was impossible. In 1961, the ultimate Vacuum Tube Amplifier, the canto h MC275 was introduced. The amplifier utilized the ultimate refinement of the Mclntoh Unity Coupled circuit design and was without question the finest Tereo tube amplifier ever manufactured. The new ver ion of the MC275 adheres closely to the original model. A few changes were made to the original amplifier de ign to reflect technology advances and contemporary y tern requirements.

Performance Features

75 Watts per Channel

• The MC275 Stereo Power Amplifier produce 75 Watt Per Channel using KT88/6550 Output Tube in a Mclntoh
• Unity Coupled circuit.

Bifilar Wound Transformers

• The Mclntoh bifilar wound output transformer provides 4, 8 and 16 ohm output connections to match a wide range of loud speaker impedance.

Balanced Inputs and Level Controls

• Both Balanced and Unbalanced Input and an Input Selec­tor Switch are included. Left and Right (mono) Level Con­trols are provided for the Unbalanced Input

Dual Operating Modes

• A Mode Switch elects either Stereo or Mono Parallel op­eration.

Installation

The MC275 can be placed upright on a table or. helf, standing on it’s four plastic feet. Adequate ventilation ex­tend the trouble free life of any electronic in trument. The uggeted minimum pace for mounting the MC275 in an upright position i 20 inche (50.8cm) wide, 14 inches (35.5cm) deep by 10 inches (25.4cm) high. Always allow for air flow either by ventilation hole or pace next to the bottom of the amplifier and a mean for the warm air to es­cape at the top. The MC275 can be mounted in any position except up ide down. If the amplifier i to be in-tailed on a vertical surface it i recommended that the transformer be on the down ide. Thi mounting position allow the heat
from the tube tori e vertically and not radiate into the transformers. In a y tern tack, the power amplifier should always be at the top o it heat doe not radiate into another component. If all the components are in tailed in a ingle cabinet, one or more quiet running ventilation fan can be a definite help in maintaining all the system component at their cooler possible operating temperature.

MC275 Side Panel Connections

1. Connect Balanced XLR cables from the Balanced Out- puts of a Preamplifier to the BALANCED INPUTS or connect Unbalanced cables from the Unbalanced Out- puts of a Preamplifier to the UNBALANCED INPUTS.
2. Connect a cable from the Common or Negative termisnal of each loudspeaker to the appropriate LEFT or RIGHT COM terminal.
3. Connect a cable from the Positive terminal of each loudspeaker to the appropriate LEFT or RIGHT 4, 8 or 16 (+) terminal. Use the impedance terminals that are closest to the impedance of your loudspeakers. If your loudspeaker impedance is between 4, 8 or 16 ohms, use the next lowest terminal. For example, if your loud- speakers are 6 ohms impedance, connect them to the COM and 4 terminals. If you are uncertain of your loudspeaker’s impedance, use the COM and 4 termisnals.
4. Connect the MC275 Power Cord to a live 50/60Hz AC outlet. Refer to the information on the connecting panel of your MC275 to determine the correct voltage for your unit,

NOTES:

1. The Auriliary AC Outlet will become live whenever the MC275 AC power is ON. Connect source or accessory component power cords to this outlet. This outlet is fused.
2. The MC275 uses a Slo-Blo type fuse, refer to the information on the MC275 to determine the correct fuse rating for your unit.

How to Connect the MC275 for Mono Operation

NOTE: Always set the mode switch to the MONO position before connectioning and operating the MC275 in MONO. In Mono Parallel Output configuration, the 4, 8 or 16 Ohm outputs will be connected in parallel which causes their original impedances to drop in half to 2. 4, and 8 ohms. Either Left or Right terminals can be used since the jumper wires have connected them in parallel.

1. Connect a Balanced XLR cable from the Balanced mono output of a Preamplifier to the R (MONO) BaIanced input or connect an unbalanced cable from the Unbalanced mono output of a Preamplifier to the R (MONO) Unbalanced Input.
   • Mono 2 Ohm Loudspeaker(s)
   • A. Connect one jumper wire from the LEFT 4 terminal to the RIGHT 4 terminal and a second jumper wire from the LEFT COM terminal to the RIGHT COM terminal.
   • B. Connect a cable from the Common or Negative ter- minal of a loudspeaker to the LEFT or RIGHT OUTPUT COM (-) terminal and from the Positive loudspeaker terminal to either of the 4 OUTPUT terminals.
   • Mono 4 Ohm Loudspeaker(s)
   • A. Connect a jumper wire from the LEFT 8 terminal to the RIGHT 8 terminal and a second jumper wire from the LEFT COM terminal to the RIGHT COM tenninal.
   • B. Connect a cable from the Common or Negative ter- minal of a loudspeaker to the LEFT or RIGHT
   • OUTPUT COM terminal and from the Positive loudspeaker terminal to either of the 8 OUTPUT terminals.
   • Mono 8 Ohm or higher loudspeaker(s)
   • A. Connect a jumper cable from the LEFT 1 6 terminal to the RIGHT 1 6 terminal and a second jumper wire from the LEFT COM terminal to the RIGHT COM terminal.
   • B. Connect a cable from the Common or Negative ter- minal of a loudspeaker to the LEFT or RIGHT OUTPUT COM (-) terminal and from the Positive loudspeaker terminal to either of the 16 OUTPUT terminals.

NOTES:

1. The Auxiliary AC Outlet will become live vvhenerer the MC275 A C power is ON. Connect soume or accessory component power cords 10 rhis outlet. This outlet is nor fu sed.
2. The MC275 uses a Slo-BIO type fuse. Rifer to the information on the MC275 ‘o determine the correct fuse raring for your unit.

How to Operate the MC275

• Before turning the MC275 on, check all connections and plugs to see that they are firmly and correctly connected.
• Check to make sure that the tubes are firmly seated.

Mode Switch

• With the MODE switch in the Stereo position, the input signals are to be fed to either the L and R unbalanced jacks or to the balanced XLR, L and R connectors. With the switch in the Mono position, the input signal is to be fed to either the R (MOM)) unbalanced jack or to the balanced XLR, R (MONO) connector.

Input Switch

• Place this switch in the Unbalanced position to use the Unbalanced inputs or in the Balanced position to use the Balanced inputs.

Unbalanced Gain

• For stereo operation, position the L and R gain controls for desired sensitivity. When using McIntosh preamplifi- ers, we suggest setting the gain controls to the 2.5V posi- tion. For mono operation, use the R MONO control.

Operating in Mono

With the Unbalanced Inputs

1. Set the MODE Switch to MONO.
2. Set the INPUTS Switch to UNBALanced.
3. Turn the R (MONO) UNBALANCED GAIN Control to the 2.5V position when using a McIntosh Preamplifier or Control Center. If more amplifier gain is needed, the control can be increased to the I V position.

With the Balanced Inputs

1. Set the MODE Switch to STEREO.
2. Set the INPUTS Switch to BALanced.
3. The amplifier sensitivity at the Balanced Inputs is fixed at 2.0 Volts.

Operating in Stereo With the Unbalanced Inputs

1. Set the MODE Switch to STEREO.
2. Set the INPUTS Switch to UNBALanced.
3. Turn the L and R UNBALANCED GAIN controls to the 2.5V position when using a McIntosh Preamplifier or Control Center. If more amplifier gain is needed, the controls may be in- creased to the 1 V position.

With the Balanced Inputs

1. Set the MODE Switch to STE- REO.
2. Set the INPUTS Switch to BALanced.
3. The amplifier sensitivity at the Balanced Inputs is fixed at 2.0 Volts.

Tube Type and Location

Specifications

Power Output Stereo

• 75 watts into 4, 8, or 16-ohm loads is the minimum sine wave continuous average power output per channel from 20Hz to 20,000Hz

The output RMS voltage is:

• 17.3 volts across 4 ohms
  • 24.5 volts across 8 ohms
• 34.6 volts across 16 ohms

Mono

• 150 watts into 2, 4, or 8 ohm loads is the minimum sine wave continuous average power output from 20Hz to 20,000Hz

The output RMS voltage is:

• 17.3 volts across 2 ohms
• 24.5 volts across 4 ohms
• 34.6 volts across 8 ohms

Output Load Impedance

• Stereo 4. 8 or 16 ohms
• Mono 2, 4, or 8 ohms

Rated Power Band

• 20Hz to 20,Hz

Total Harmonic Distortion

• 0.5% maximum harmonic distortion at any power level from 250 milliwatts to rated power from 20Hz to 20,000Hz

Intermodulation Distortion

• 0.5% maximum if instantaneous peak power output does not exceed twice the output rating for any combination of frequencies from 20Hz to 20,000Hz.

Frequency Response

• 20Hz to 20,OOOHz +0 -O.2dB, IOHz to IOO.MHz +0 -3dB (at I watt output)

Noise and Hum

• 100dB below-rated output (A-Weighted)

IHF Dynamic Headroom

• 1.1 db

Input Sensitivity

• Unbalanced, 1.0 volt to 30 volts through gain control
• Balanced, 2.0 volts fixed

Power Requirements

• 100 volts, 50/60Hz, from 240 watts to 400 watts
• 110 volts, 50/60Hz, from 240 watts to 400 watts
• 120 volts, 50/6()Hz, from 240 watts to 4(X) watts
• 220 volts, 50/60Hz, from 240 watts to 4()() watts
• 230 volts, 50/60Hz, from 240 watts to 400 watts
• 240 volts, 50/6()Hz, from 240 watts to 4(Å) watts
• NOTE: Refer to the side panel of the MC275 for the correct voltage

Dimensions

• 161, wide (40.6cm) by 7-1/21, high (19.0cm) by 121, deep (30.5cm)

Weight

• 67 pounds (30.5kg) net, 75 pounds (34.1kg) in shipping carton
• McIntosh Laboratory, Inc.
• 2 Chambers Street
• Binghamton, NY 13903
• Serial Number:———————————————–
• Purchase Date:———————————————–
• Dealer Name:————————————————

Customer Service

• If at any time you have questions about your MC275 Stereo Power Amplifier, please contact:
• McIntosh Laboratory, Inc.
• 2 Chambers Street
• Binghamton, New York 13903
• Phone: 607-723-3512
• FAX: 607-724-0549
• Copyright 1997 C by McIntosh Laboratory, Inc.

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