The McIntosh MC1502 is a high-quality Tube Power Amplifier designed to deliver exceptional audio performance. It is part of the McIntosh tradition of excellence, offering a sonically transparent and accurate reproduction of music. The amplifier is capable of driving high-quality loudspeaker systems with its robust power output and advanced circuitry.
Function Description:
The MC1502 serves as a power amplifier, taking a low-level audio signal and amplifying it to drive loudspeakers. It utilizes vacuum tubes for its amplification stages, contributing to its distinctive sound quality. The amplifier is designed for stereo operation, providing two channels of amplification. It incorporates various protection circuits and features to ensure reliable and long-term operation.
Important Technical Specifications:
- Power Output: 150 watts per channel into 2, 4, or 8 ohm loudspeakers.
- Rated Power Band: 20Hz to 20,000Hz.
- Total Harmonic Distortion: 0.5% maximum at any power level from 250 milliwatts to rated power, 20Hz to 20,000Hz.
- Intermodulation Distortion: 0.5% maximum, if the instantaneous peak power output does not exceed twice the rated power output for any combination of frequencies from 20Hz to 20,000Hz.
- Dynamic Headroom: 1.2dB.
- Frequency Response:
- +0, -0.5dB from 20Hz to 20,000Hz
- +0, -3.0dB from 10Hz to 70,000Hz
- Wide Band Damping Factor: Greater than 18.
- Input Sensitivity (for rated output):
- 1.7 Volts Unbalanced
- 3.4 Volts Balanced
- Input Impedance:
- 47,000 ohms Unbalanced
- 20,000 ohms Balanced
- Signal To Noise Ratio (A-Weighted): 112dB below rated output.
- Power Control Input: 5-15VDC, less than 1mA.
- Power Control Output: 12VDC, 25mA (Output is 0.2 seconds from turn On).
- Tube Compliment:
- 4 - 12AX7A Input and Phase Inverter
- 4 - 12AT7 Voltage Amplifier and Driver
- 8 - KT88 Power Output
- Power Requirements: Factory configured for specific AC voltages (e.g., 120V ~ 50/60Hz at 5.5 Amps). Field AC voltage conversion is not possible. Standby power consumption is less than 0.3 watts.
- Overall Dimensions:
- Width: 18 1/4 inches (46.4cm)
- Height: 10 1/4 inches (26cm)
- Depth: 21 inches (53.3cm) including connectors
- Weight: 118 pounds (53.5 kg) net, 135 pounds (61.2 kg) in shipping carton.
- Shipping Carton Dimensions:
- Width: 26 1/2 inches (67.3cm)
- Height: 15 1/2 inches (39.4cm)
- Depth: 28 inches (71.1cm)
Usage Features:
- Unity Coupled Circuitry: This patented McIntosh circuit design ensures low distortion, extended frequency response, and cool operating output tubes, contributing to the amplifier's reliability and sound quality.
- Multifilar Wound Output Transformer: The output transformer windings are part of the Unity Coupled Circuitry, featuring two bifilar wound primaries (one for cathodes, one for plates) and a secondary winding wound together with the primaries. This design provides very close primary to secondary coupling, resulting in flat frequency response and wide power bandwidth.
- Balanced and Unbalanced Input: The MC1502 offers both balanced (XLR) and unbalanced (RCA) input connections. Balanced connections help guard against induced noise and allow for longer cable runs without compromising sound quality. An INPUT MODE switch on the rear panel allows selection between these input types.
- Sentry Monitor Tube Protection: McIntosh Sentry Monitor Tube Protection Circuits are integrated to ensure a long and trouble-free operating life for the MC1502. This circuitry protects the power amplifier in case of an impedance mismatch with loudspeakers, a short circuit at the output terminals, or a power output tube failure. In such events, the small signal vacuum tube illumination for the affected channel changes from green to red.
- Vacuum Tube Sockets: Small signal vacuum tube sockets feature ceramic base construction with gold-plated contacts to protect against atmospheric contamination. Output tube sockets include air-pipe cooling at their bases for long-term operation.
- Amplifier Gold Plated Connectors: Input jacks and output binding posts are gold-plated for trouble-free connections.
- Special Power Supply: A large core power transformer and large capacitors ensure stable, noise-free operation even with variations in the power line.
- LED Tube Illumination: Tri-color LEDs illuminate the small signal processing tubes, indicating different operational modes: amber for warm-up (audio muted), green for normal operation (selected by Tube Light Control), and red (flashing) for Sentry Monitor activation (protection circuitry activated). A TUBE LIGHTS control on the front panel allows users to turn the tube lights ON or OFF.
- Power Control: The POWER CONTROL on the front panel can be set to REMOTE for integration with other McIntosh components, allowing the amplifier to turn ON/OFF with the preamplifier. Alternatively, it can be set to ON for manual operation.
- Auto Off Power Save Feature: The MC1502 includes an Auto Off Power Save Feature that automatically places the amplifier into standby mode after approximately 30 minutes of no audio input signal. This feature can be enabled or disabled via a switch on the rear panel. If a Power Control Connection is established with a preamplifier, the Auto Off Switch is bypassed.
- Loudspeaker Connections: The amplifier provides output terminals for 2, 4, and 8 ohm loudspeakers. It is crucial to match the loudspeaker impedance to the amplifier connections for optimal performance and safety. The manual provides a Loudspeaker Cable Distance vs Wire Gauge Guide to ensure adequate cable sizing for minimal power loss.
Maintenance Features:
- User Serviceability: The MC1502 has no user-serviceable parts, including the vacuum tubes. Any repairs must be performed by an authorized McIntosh Service Agency.
- Ventilation: Adequate ventilation is essential for extending the trouble-free life of the MC1502. It requires at least 19 inches (48.3cm) above the top, 6 inches (15.2cm) for the front, rear, and sides, and 1/2 inch (1.3cm) below for unobstructed airflow.
- Shipping and Packing Instructions: Detailed instructions are provided for repacking the equipment for shipment, emphasizing the importance of attaching the four feet to the bottom and re-inserting the foam insert over the vacuum tubes to prevent shipping damage. The use of original shipping carton and interior parts in good serviceable condition is recommended.
- Foam Insert Removal: Prior to connecting the AC power supply cord, a special foam insert surrounding the vacuum tubes must be removed. Failure to do so can result in a fire hazard and damage to the unit. The Tube Shield Metal Cover must be temporarily removed to access and remove the foam, and then re-installed for proper and safe operation.
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