Marantz 300DC Manual

The Marantz 300DC is a high-performance stereo power amplifier featuring direct-coupled circuitry, dual power supplies, thermal protection, and advanced heat sink design. With 150 watts per channel into 8 ohms, professional-grade binding posts, balanced and unbalanced inputs, and robust construction, this amplifier delivers exceptional audio performance for demanding audiophile and professional applications. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

Features at a Glance

Key components: Direct-coupled amplifier circuitry, dual mono power supplies, professional binding posts, thermal protection circuit, advanced heat sink design.

Feature	Description
Power Output	150 watts per channel into 8 ohms
Inputs	Balanced XLR and unbalanced RCA inputs
Binding Posts	Professional 5-way speaker terminals
Power Supply	Dual mono transformer design
Protection	Thermal and short-circuit protection
Heat Management	Advanced heat sink with forced air cooling
Frequency Response	10Hz - 100kHz (+0/-3dB)
Signal-to-Noise	110dB (A-weighted)
THD	Less than 0.05% at rated power
Damping Factor	Greater than 200 at 8 ohms

Installation

Unpack and inspect contents. Place on stable, well-ventilated surface.

1. Position amplifier: Allow minimum 6 inches clearance on all sides for proper ventilation.
2. Connect speakers: Use high-quality speaker cable to binding posts.
3. Connect source components: Use balanced XLR or unbalanced RCA cables.
4. Connect power cord: Use provided power cord and appropriate outlet.
5. Ground connection: Ensure proper grounding for balanced operation.

WARNING! Amplifier is heavy; use two people for handling. Ensure adequate ventilation to prevent overheating.

First-Time Setup

Power on amplifier; observe startup sequence.

1. Power sequence: Turn on source components first, then amplifier.
2. Input selection: Choose between balanced (XLR) and unbalanced (RCA) inputs.
3. Gain adjustment: Set appropriate gain level for your system.
4. Speaker connection: Verify proper polarity and secure connections.
5. System check: Test both channels for proper operation.

CAUTION! Always follow proper power sequence to prevent damage to speakers and components.

Specifications

• Power Output: 150 watts per channel (8 ohms, 20Hz-20kHz)
• Dynamic Power: 200 watts (8 ohms), 300 watts (4 ohms)
• THD: Less than 0.05% at rated power
• Frequency Response: 10Hz - 100kHz (+0/-3dB)
• Input Sensitivity: 1.2V (RCA), 2.4V (XLR)
• Input Impedance: 47k ohms (RCA), 20k ohms (XLR)
• Damping Factor: Greater than 200 (8 ohms)
• Signal-to-Noise: 110dB (A-weighted)
• Power Requirements: 120V AC, 60Hz, 600 watts maximum
• Dimensions: 17" W × 6" H × 15" D
• Weight: 45 lbs

Controls and Settings

Front Panel: POWER switch, STATUS indicator, PROTECTION indicator.

Rear Panel: AC power input, balanced XLR inputs, unbalanced RCA inputs, speaker binding posts, ground terminal.

Operation: Power on/off with front switch. Status LED indicates normal operation (green). Protection LED (red) indicates fault condition. Input selection via rear panel input jacks. No user-adjustable gain controls - fixed gain operation.

Connecting Devices

Source Components: Use high-quality interconnects. Speakers: Use appropriate gauge speaker wire.

1. Turn off all components before making connections.
2. Connect sources: Use either XLR (balanced) or RCA (unbalanced) inputs.
3. Connect speakers: Ensure proper polarity (+ to +, - to -).
4. Ground connection: Connect ground terminal if using balanced inputs.
5. Power connection: Use dedicated AC outlet if possible.

Tip: Use high-quality cables and ensure all connections are secure and clean.

Operation Guidelines

Designed for continuous high-performance operation.

1. Power sequence: Sources on first, then amplifier. Reverse for shutdown.
2. Monitoring: Observe status indicators during operation.
3. Temperature: Monitor heat sink temperature during extended use.
4. Load impedance: Ensure speaker impedance is within specified range.
5. Ventilation: Maintain adequate airflow around amplifier.
6. Performance: Allow 30 minutes warm-up for optimal performance.

WARNING! Do not operate with covers removed. Keep away from moisture and extreme temperatures.

Protection Features

Thermal Protection: Automatically reduces output or shuts down if overheating detected. Short-Circuit Protection: Current limiting protects output stages. DC Offset Protection: Monitors DC output and shuts down if excessive.

Care & Maintenance

Unplug before cleaning. Use soft, dry cloth for exterior. Compressed air for ventilation ports.

CAUTION! Do not use liquids or solvents. Keep ventilation ports clear of obstructions.

Regulatory Information

FCC Part 15: Class B digital device; complies with interference limits. UL/CSA certified for safety. Copyright © Marantz; all rights reserved. For support, visit www.marantz.com or contact authorized service centers.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No power	Power cord/outlet	Check power cord connection; verify outlet function; check circuit breaker.
Protection mode active	Overheating/short circuit	Allow cooling; check speaker wires for shorts; verify proper impedance.
No sound	Connections/input	Check input connections; verify source operation; check speaker connections.
Distorted sound	Overload/clipping	Reduce input level; check speaker impedance; verify proper gain structure.
Intermittent operation	Connections/temperature	Check all connections; ensure adequate ventilation; monitor temperature.

Reset: Power cycle amplifier if protection mode activates.

Service: Contact authorized Marantz service center; www.marantz.com