Marantz 8B Manual

The Marantz 8B is a classic vacuum tube stereo power amplifier renowned for its exceptional audio quality and vintage design. Featuring 35 watts per channel, EL34 output tubes, high-quality transformers, and premium components, this amplifier delivers warm, detailed sound reproduction. Below are key sections covering specifications, operation, maintenance, and technical details.

Features at a Glance

Key components: EL34 output tubes, 7199 driver tube, high-quality output transformers, gold-plated connectors, walnut wood cabinet.

Feature	Description
Power Output	35 watts per channel (RMS)
Tubes	4x EL34 output, 2x 7199 driver
Inputs	RCA stereo inputs
Outputs	4, 8, 16 ohm speaker taps
Frequency Response	20Hz - 20kHz ±1dB
Total Harmonic Distortion	<0.1% at rated power
Input Sensitivity	1.5V for full output
Damping Factor	14 (8 ohm load)
Power Requirements	117V AC, 60Hz
Dimensions	15" W x 6" H x 10" D

Installation & Setup

Unpack carefully and inspect for shipping damage. Place on stable, ventilated surface.

1. Connect speakers: Use appropriate impedance taps (4, 8, or 16 ohm).
2. Connect preamplifier: Use high-quality RCA cables from preamp outputs.
3. Power connection: Plug into grounded 117V AC outlet.
4. Tube installation: Ensure all tubes are properly seated before power on.

WARNING! Tubes become extremely hot during operation. Allow proper ventilation and keep away from flammable materials.

Technical Specifications

• Power Output: 35 watts per channel continuous
• Tubes: 4x EL34, 2x 7199
• Input Impedance: 100k ohms
• Output Impedance: 4, 8, 16 ohms
• Frequency Response: 20Hz - 20kHz ±1dB
• Hum & Noise: -90dB below rated output
• Damping Factor: 14 (8 ohm load)
• Power Consumption: 200 watts maximum
• Weight: 35 lbs (15.9 kg)
• Finish: Brushed aluminum faceplate, walnut wood cabinet

Controls & Connections

Front Panel: Power switch, power indicator lamp. Rear Panel: RCA input jacks, speaker output terminals, AC power cord, fuse holder.

Inputs: Left and Right channel RCA jacks. Outputs: Multi-tap output transformer with 4, 8, and 16 ohm connections. Power: Rocker switch with neon indicator.

No user-adjustable controls except power on/off. All adjustments require technical expertise.

Operation Guide

Always follow proper startup and shutdown sequence for tube longevity.

1. Turn on connected preamplifier first
2. Switch Marantz 8B power to ON position
3. Allow 30-60 seconds for tubes to warm up
4. Adjust volume from preamplifier
5. For shutdown: Reduce volume to minimum, turn off 8B, then turn off preamp

CAUTION! Never operate without proper speaker load. Always use matched impedance speakers.

Tube Replacement

Tubes typically last 2000-5000 hours. Replace when performance degrades.

1. Power off and unplug amplifier
2. Allow tubes to cool completely (minimum 30 minutes)
3. Remove protective cage if installed
4. Gently rock tubes while pulling straight up
5. Insert new tubes, aligning pins properly
6. Consider professional bias adjustment after tube replacement

Recommended tubes: EL34 power tubes, 7199 driver tubes. Use matched pairs for best performance.

Maintenance & Care

Regular maintenance ensures optimal performance and longevity.

• Clean tubes and sockets annually with contact cleaner
• Dust interior with soft brush every 6 months
• Check and clean speaker terminals periodically
• Inspect capacitors for signs of leakage or bulging
• Store in dry, temperature-stable environment

CAUTION! High voltages present even when powered off. Only qualified technicians should perform internal maintenance.

Safety Precautions

This amplifier contains lethal voltages. Observe all safety guidelines.

1. Always unplug before performing any maintenance
2. Never operate with protective cover removed
3. Ensure proper ventilation around amplifier
4. Use correct fuse rating (specified on rear panel)
5. Keep away from moisture and extreme temperatures
6. Do not block ventilation openings

WARNING! Capacitors can retain dangerous voltages long after power is disconnected.

Troubleshooting

Symptom	Possible Cause	Corrective Action
No sound	Power issue, tube failure	Check power cord, tubes, fuses
Distorted sound	Tube aging, bias issue	Replace tubes, check bias settings
Hum or buzz	Ground loop, tube microphonics	Check grounding, tap tubes gently
One channel dead	Tube failure, connection issue	Swap tubes between channels, check cables
Overheating	Ventilation blocked, bias incorrect	Ensure proper airflow, check bias

Service: Contact qualified tube amplifier technician for internal repairs.

Service Information

The Marantz 8B requires specialized service by technicians familiar with vacuum tube circuitry. Original schematics and service manuals are available from authorized Marantz service centers. For genuine parts and qualified service, contact authorized Marantz dealers.

Support: Consult with professional audio technicians for maintenance and repairs. Original manufacturing date: 1960s. This classic amplifier remains highly sought after by audiophiles worldwide.