User manual MCINTOSH MC275 MK4

[. . . ] Unplug this apparatus during lightning storms or when unused for long periods of time. Servicing is required when the apparatus has been damaged in any way, such as power-supply cord or plug is damaged, liquid has been spilled or objects have fallen into the apparatus, the apparatus has been exposed to rain or moisture, does not operate normally, or has been dropped. Do not expose this equipment to dripping or splashing and ensure that no objects filled with liquids, such as vases, are placed on the equipment. The mains plug of the power supply cord shall remain readily operable. Thank You Your decision to own this McIntosh MC275 Stereo Power Amplifier ranks you at the very top among discriminating music listeners. [. . . ] The McIntosh Sound is "The Sound of the Music Itself. " Performance Features · Power Output The MC275 consists of two separate power amplifier channels, each capable of 75 watts into 4, 8 or 16 ohm Loudspeakers in stereo. It may also be operated in mono at 150 watts into 2, 4, or 8 ohm Loudspeakers. Bifilar Wound Transformers and Output Circuit The Power Output Sections utilize the famous McIntosh Patented Unity Coupled Circuit with a Bifilar Wound Output Transformer for low distortion, extended frequency response and cool operating output tubes. Balanced and Unbalanced Inputs Balanced connections guard against induced noise and allow long cable runs without compromising sound quality. Gold Plated Connectors and Tube Socket Contacts Gold Plated Input Jacks and Output Binding Posts provide trouble free connections. Ceramic tube sockets with gold plated contacts provide protection from atmospheric contamination. Super Mirror Chassis Finish The famous McIntosh Stainless Steel Chassis with Super Mirror Finish ensures the pristine beauty of the MC275 will be retained for many years. · Connector Information XLR Connectors Below is the Pin configuration for the XLR Balanced Input Connectors on the MC275. Refer to the diagram for connection: Pin 2 PIN 1: Shield/Ground PIN 2: + Input Pin 1 PIN 3: - Input Pin 3 · · · 4 MC275 Dimensions MC275 Dimensions The following dimensions can assist in determining the best location for your MC275. There is additional information on page 7 pertaining to installing the MC275 into cabinets. 16-1/2" 41. 91cm 7-7/8" 20. 00cm 8-1/4" 20. 96cm Front View of the MC275 1-3/4" 4. 45cm 13-5/8" 34. 61cm Top View of the MC275 12" 30. 48cm Left Side View of the MC275 5-9/16" 14. 13cm Right Side View of the MC275 1-3/4" 4. 45cm 4-3/8" 11. 11cm 1-1/4" 3. 18cm 5 Installation of Tubes and Tube Cover Caution: To prevent electrical shock make sure that the AC POWER CORD IS NOT CONNECTED TO THE MC275 when inserting or removing Tubes, as there are hazardous voltages present at the pins of the Tube Sockets. Your MC275 has gone through an extensive series of performance tests during the manufacturing process. The MC275 is supplied with the actual Tubes that were used to test and confirm the performance of this amplifier. To protect the Vacuum Tubes from possible shipping damage, they are packed in four layers of foam and placed into the Tube Cover. It is secured to the MC275 Chassis. Note: Gloves or a soft cloth will prevent "fingerprinting" of the Tubes during their installation. Tinnerman Clip Fasteners Tube Cover Figure 1 Figure 1 1. Remove the Tube Cover from the MC275 Chassis by lifting up on both sides. Orient the Tube Cover to the wide opening along one side of its longer dimension. Carefully remove the Tubes from the remaining pieces of foam and temporarily place them in a safe location. Remove the remaining foam from the Tube Cover and retain all four pieces for possible future use. The MC275 Chassis has nomenclature screened on it to specify both the circuit location and Tube Type for each channel. Refer to figure 4. Note: It is extremely important to insert the Tubes in the correct location. Tube Cover with Layers of Foam and Tubes Figure 2 Power Output Tubes Small Signal Tubes Power Output Tubes: 1. On the top left side of the amplifier, locate the Tube Socket that has the nomenclature V8 KT88/6550 next to it on the chassis. Orient the Tube so the key on the base of the Tube is aligned with the corresponding key on the Tube Socket. Carefully insert the Tube into the socket until the base of the Tube is fully seated in the Tube Socket. There are two different types of Small Signal Tubes (12AX7A and 12AT7) used in each channel. [. . . ] Refer to figure 10. Figure 10 13 Specifications Specifications Power Output Stereo Minimum sine wave continuous average power output per channel, both channels operating is: 75 watts into 4, 8 or 16 ohm load Power Output Mono (Parallel) Minimum sine wave continuous average power output is: 150 watts into 2 ohm, 4 ohm or 8 ohm load Output Load Impedance 4, 8, or 16 ohm (Stereo Mode) 2, 4, or 8 ohm (Mono Mode) Rated Power Band 20Hz to 20, 000Hz Total Harmonic Distortion Maximum Total Harmonic Distortion at any power level from 250 milliwatts to rated power output is 0. 5% Intermodulation Distortion Maximum Intermodulation Distortion if instantaneous peak output per channel does not exceed twice the rated output, for any combination of frequencies from 20Hz to 20, 000Hz, with both channels operating is 0. 5% A-Weighted Signal To Noise Ratio 100dB Frequency Response +0, -0. 25dB from 20Hz to 20, 000Hz +0, -3dB from 10Hz to 70, 000Hz Sensitivity 1. 2 Volt unbalanced inputs 2. 5 Volt balanced inputs Wide Band Damping Factor Greater than 14 Tube Compliment 3 - 12AX7A Inputs and Phase Inverters 4 - 12AT7 Voltage Amplifier and Drivers 4 - KT88/6550 Power Output Power Requirements 100 Volts, 50/60Hz at 3. 6 amps 110 Volts, 50/60Hz at 3. 6 amps 120 Volts, 50/60Hz at 3. 6 amps 220 Volts, 50/60Hz at 1. 8 amps 230 Volts, 50/60Hz at 1. 8 amps 240 Volts, 50/60Hz at 1. 8 amps Note: Refer to the right side panel of the MC275 for the correct voltage. Overall Dimensions Width is 16-1/2 inches (41. 91cm) Height is 8-1/4 inches (20. 96cm) including feet Depth is 12 inches (30. 48cm) Weight 67 pounds (30. 5kg) net, 75 pounds (34. lkg) in shipping carton 14 Packing Instructions Packing Instructions In the event it is necessary to repack the equipment for shipment, the equipment must be packed exactly as described and shown below. The MC275 Vacuum Tubes must be removed from the Amplifier Tube Sockets and placed into the inside openings of the four layer foam packing material. The foam with the tubes located inside are placed into the Amplifier Tube Cover and secured to the Chassis. Failure to do this will result in damage to the Vacuum Tubes and possibly the MC275. [. . . ]