Marantz 115B Manual

The Marantz 115B is a high-performance stereo amplifier featuring 70 watts per channel RMS, dual power meters, phono inputs for turntables, tape monitoring, loudness contour, bass and treble controls, and speaker selector. Below are key sections for safety, features, installation, setup, operation, and troubleshooting.

1. Features at a Glance 2. Installation 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Connecting Devices 7. Operation Guidelines 8. Maintenance 9. Regulatory Information 10. Troubleshooting

Features at a Glance

Key components: Power amplifier section, preamplifier controls, power meters, input/output terminals, speaker connections.

Feature	Description
Power Output	70 watts per channel RMS into 8 ohms
Power Meters	Dual VU meters for left and right channels
Phono Input	MM/MC phono stage for turntables
Tape Monitor	Tape input/output with monitoring
Tone Controls	Bass and treble adjustment knobs
Loudness Contour	Compensates for low volume listening
Speaker Selector	A/B speaker switching
Headphone Jack	Front panel 1/4" headphone output
Power Switch	Main power on/off with indicator light
Input Selector	Phono, Aux, Tuner, Tape inputs

Installation

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

Connect speakers: Use speaker wire to appropriate terminals (A or B).
Connect audio sources: Phono for turntable, Aux for CD player, Tuner for receiver.
Connect tape deck: Use Tape input/output for recording and playback.
Plug into AC power outlet.

WARNING! Ensure proper ventilation; do not block cooling vents. Use correct speaker impedance.

First-Time Setup

Power on amplifier; check all connections.

Set input selector: Choose appropriate source (Phono, Aux, Tuner).
Adjust volume: Start at minimum, gradually increase to desired level.
Set tone controls: Bass and treble at neutral (12 o'clock) position initially.
Select speakers: Choose A or B speakers using speaker selector.

CAUTION! Always turn volume to minimum before powering on or off.

Specifications

Power Output: 70 watts per channel RMS (8 ohms)
Frequency Response: 10Hz - 50kHz (+0/-1dB)
Total Harmonic Distortion: 0.05% at rated power
Input Sensitivity: Phono: 2.5mV, Aux: 150mV
Signal-to-Noise Ratio: 85dB (Phono), 95dB (Aux)
Tone Controls: Bass: ±10dB at 50Hz, Treble: ±10dB at 10kHz
Power Requirements: 120V AC, 60Hz, 350 watts
Dimensions: 17" W × 5.5" H × 13" D
Weight: 25 lbs

Controls and Settings

Front Panel: Power switch, input selector, volume, balance, bass, treble, loudness, speaker selector, headphone jack.

Rear Panel: AC power cord, phono inputs, aux inputs, tuner inputs, tape inputs/outputs, speaker terminals.

Input Selection: Phono (turntable), Aux (CD player), Tuner (receiver), Tape. Tone Controls: Bass (±10dB), Treble (±10dB). Loudness: Compensates for Fletcher-Munson curve. Balance: Adjusts left/right channel balance. Speaker Selector: A, B, or A+B speakers.

Connecting Devices

Phono: Connect turntable ground wire and RCA cables. Aux: Connect CD player or other line-level source. Speakers: Connect positive and negative terminals correctly.

Turn off amplifier before making connections.
Match cable colors (red-right, white-left).
Ensure secure connections to prevent hum or noise.
Connect ground wire from turntable to ground terminal.

Tip: Use high-quality cables for best audio performance.

Operation Guidelines

Proper operation ensures optimal performance and longevity.

Power sequence: Turn on sources first, then amplifier.
Volume control: Start low, increase gradually to desired level.
Tone adjustments: Make subtle changes to bass and treble.
Meter monitoring: Watch power meters to avoid clipping.
Speaker selection: Use appropriate impedance speakers (4-16 ohms).
Heat management: Ensure adequate ventilation around unit.
Storage: Keep in dry, dust-free environment when not in use.

WARNING! Do not operate with covers removed. Avoid excessive volume levels.

Maintenance

Unplug before cleaning. Use soft, dry cloth for exterior. Compressed air for dust removal.

CAUTION! No internal user serviceable parts. Refer servicing to qualified personnel.

Regulatory Information

Troubleshooting

Symptom	Possible Cause	Corrective Action
No sound	Power/connections	Check power cord; verify input selection; check speaker connections.
Hum or buzz	Grounding/cables	Ensure proper grounding; check cable connections; separate from power cables.
Distorted sound	Overload/damage	Reduce volume; check speaker impedance; inspect for component damage.
One channel silent	Balance/cables	Adjust balance control; check RCA cables; verify speaker connections.
Meters not moving	Signal/meters	Check input signal; verify source is playing; test with different input.

Service: Contact authorized Marantz service center for repairs.