Yamaha A-U671 Integerated Amplifier User Manual

Content

Yamaha A-U671 Integrated Amplifier Manual

Introduction

The Yamaha A-U671 Integrated Amplifier is a compact stereo amplifier designed for listeners who want high-quality two-channel audio with convenient digital connectivity. Its built-in USB DAC allows a computer to connect directly to the amplifier, making it suitable for music libraries, streaming services, and high-resolution audio playback. The amplifier also includes conventional analog inputs for CD players, tuners, network players, and other line-level sources.

With up to 70 watts per channel into 6-ohm speakers, the Yamaha A-U671 Integerated Amplifier can provide powerful, detailed sound in a desktop system, small listening room, or traditional home audio setup. Its compact chassis is easier to position than many full-size amplifiers, while five-way speaker binding posts support secure connections with bare wire, spade connectors, or banana plugs.

This Yamaha stereo amplifier is intended for music enthusiasts, computer-audio users, and anyone building a straightforward hi-fi system without a separate digital-to-analog converter. It supports high-resolution PCM and DSD playback through its USB input, includes a headphone output for private listening, and provides a subwoofer output for extending low-frequency performance.

Use this guide to install the amplifier safely, connect digital and analog equipment, configure speakers, and resolve common operating problems.

Yamaha A-U671 Specifications and Features

Product type: Integrated stereo amplifier with USB DAC functionality.
Maximum output power: 70 W + 70 W at 6 ohms, 1 kHz, and 10% total harmonic distortion.
Frequency response: 10 Hz to 40 kHz within ±3 dB.
Total harmonic distortion: 0.05% for CD input to speaker output at 1 kHz and 6 ohms.
Signal-to-noise ratio: 95 dB for the CD input.
Analog input sensitivity: 230 mV with 47 kΩ input impedance for the CD input.
USB connection: Type-B USB input for computer audio.
USB audio support: PCM music up to 192 kHz/24-bit, DSD playback up to 5.6 MHz, and compatible FLAC, WAV, AIFF, Apple Lossless, MP3, WMA, MPEG-4 AAC, and related formats depending on the playback system.
Speaker connections: Stereo five-way binding posts.
Additional outputs: Headphone output and subwoofer output.
Standby power consumption: Approximately 0.4 W.
Dimensions: Approximately 314 × 70 × 342 mm.
Weight: Approximately 7.3 lb.

How to Set Up the Yamaha A-U671

Place the amplifier on a stable, level surface with open space around the ventilation areas. Do not place it on top of another heat-producing component.
Confirm that the amplifier is switched off and disconnected from AC power before making connections.
Connect the right and left speakers to the matching speaker terminals. Observe polarity by connecting positive to positive and negative to negative.
Connect source equipment to an appropriate analog input using stereo RCA cables. Connect a computer to the USB Type-B input with a suitable USB cable.
Connect an active subwoofer to the subwoofer output if additional bass extension is required. Follow the subwoofer manufacturer’s instructions for crossover and volume settings.
Connect headphones only after reducing the volume. Speaker output may be affected when headphones are connected.
Connect the power cord, switch on the amplifier, select the desired input, and raise the volume gradually.
For computer playback, select the Yamaha USB audio device in the operating system’s sound settings. Use compatible playback software for high-resolution PCM or DSD files.

Never allow speaker-wire strands to touch neighboring terminals, and do not connect the amplifier to speakers with an impedance outside the supported range. If there is no sound, verify the selected input, cable placement, speaker polarity, and computer output device before increasing the volume.

Yamaha A-U671 Troubleshooting Guide

No power

Confirm that the power cord is fully inserted and the AC outlet works with another device. Check that the rear-panel power switch, where fitted, and the front-panel controls are set correctly. If the amplifier repeatedly shuts down, disconnect all equipment and allow it to cool before testing again.

No sound

Check the selected input, source playback status, mute setting, and volume level. Inspect both ends of every RCA, USB, and speaker cable. Make sure speaker wires are firmly secured and that stray strands are not causing a short circuit.

USB audio is unavailable

Reconnect the USB cable directly to the computer, avoid unpowered hubs, and select the amplifier as the computer’s audio output. Restart the playback application after changing the output device. If high-resolution files fail, test a standard PCM file to identify whether the issue is related to software or format compatibility.

Distorted or intermittent audio

Reduce the volume and check for loose connections, damaged cables, excessive bass boost, or speakers that are difficult to drive. Improve ventilation and remove the amplifier from enclosed shelving if it becomes unusually hot.

Support and preventive care

The A-U671 documentation does not identify user-facing numerical error codes for normal operation. Record the symptoms, connected equipment, and input used before contacting an authorized Yamaha service center or the regional Yamaha support department. Keep the owner’s manual and proof of purchase available for warranty assistance. Warranty terms and service availability vary by country, so use Yamaha’s official regional support and manual library for current contact details.

Yamaha A-U671 Pros and Cons

Advantages

Integrated USB DAC: A computer can connect directly without requiring a separate external DAC.
High-resolution playback: Support for DSD and high-resolution PCM suits computer-audio libraries and compatible music software.
Strong compact performance: The rated 70-watt-per-channel output is suitable for many bookshelf and medium-sized room systems.
Flexible connections: Analog inputs, USB, speaker binding posts, headphone output, and subwoofer output cover common stereo configurations.
Space-efficient design: Its relatively shallow, low-profile chassis works well on a desk or compact equipment shelf.

Limitations

Two-channel focus: It is designed for stereo listening rather than surround sound or home-theater processing.
No built-in wireless streaming: Bluetooth, Wi-Fi, and network streaming require separate source equipment.
Computer-dependent USB playback: The USB input is intended for a computer connection, not direct playback from a USB storage drive.
Limited expansion compared with modern network amplifiers: Users wanting streaming apps, multiroom audio, or HDMI switching may need a different product category.
Best suited to careful system matching: Select speakers within the amplifier’s supported impedance range and match the power capability to the listening room.

The Yamaha A-U671 Integerated Amplifier is a practical choice for compact hi-fi systems, desktop listening, and users who value USB high-resolution audio. A network amplifier or AV receiver may be more appropriate for wireless streaming, television integration, or surround sound.

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Faqs

How do I set up the Yamaha A-U671 Integrated Amplifier for the first time?

Place the Yamaha A-U671 Integrated Amplifier on a stable, well-ventilated surface. With the power unplugged, connect the left and right speakers to the matching SPEAKERS terminals, carefully observing positive and negative polarity. Connect a CD player or other source to the RCA LINE inputs, or connect a computer to the rear USB Type-B port. Turn on the source and amplifier, then select LINE or USB with the INPUT control.

What speaker impedance is compatible with the Yamaha A-U671 Integrated Amplifier?

Use speakers rated at 6 ohms or higher with the Yamaha A-U671 Integrated Amplifier. Speakers with lower impedance can activate the amplifier’s protection circuitry or place excessive stress on its output stage. Before powering on, ensure that no loose speaker strands touch another terminal or the amplifier chassis. Keep the left and right channels connected correctly, and avoid connecting multiple speaker pairs unless their combined load remains safe.

Why is there no sound from my Yamaha A-U671 Integrated Amplifier?

First, check that the amplifier is powered on and that the correct input, LINE or USB, is selected. Confirm the source component is playing and its output is enabled. Make sure the RCA or USB cable is firmly connected, and verify that the speaker wires are attached to the correct terminals. Cancel mute if active, and disconnect headphones because headphone insertion can disable sound from the speakers and subwoofer.

How can I connect a computer to the Yamaha A-U671 Integrated Amplifier using USB?

Connect the computer to the Yamaha A-U671 Integrated Amplifier’s USB Type-B input with a suitable USB cable. After the connection is recognized, select the Yamaha A-U671 or A-U670/A-U671 audio device as the computer’s sound output. Choose USB on the amplifier, then start playback from your music application. If there is no sound, check the operating system’s volume, application output setting, and whether another program is controlling the audio device.

What high-resolution audio formats does the Yamaha A-U671 Integrated Amplifier support?

The Yamaha A-U671 Integrated Amplifier includes a USB DAC for computer audio and supports PCM sampling rates up to 384 kHz with word lengths up to 32 bits. It also supports DSD playback at 2.8224 and 5.6448 MHz. Actual playback depends on the computer, operating system, driver, music software, and file format. If a file will not play, try a compatible PCM version or update the computer’s audio configuration.

Why does the Yamaha A-U671 Integrated Amplifier shut down or enter protection mode?

Protection mode commonly results from a speaker-wire short circuit, a low-impedance speaker load, overheating, or an internal fault. Turn off the Yamaha A-U671 Integrated Amplifier and unplug it before inspecting the speaker connections. Separate loose strands and ensure the positive and negative terminals cannot touch. Allow the unit to cool, then reconnect it securely. If protection returns with correct wiring and suitable speakers, disconnect power and contact an authorized service center.

How do I connect a subwoofer to the Yamaha A-U671 Integrated Amplifier?

Connect the subwoofer’s line-level input to the Yamaha A-U671 Integrated Amplifier’s SUBWOOFER jack using an appropriate audio cable. Set the subwoofer’s volume and crossover controls gradually, starting with moderate levels. If bass is weak or absent, check that the cable is connected to the subwoofer input rather than an output, confirm the subwoofer is powered on, and inspect speaker polarity. Disconnect headphones when using the speakers and subwoofer.

How should I clean and maintain the Yamaha A-U671 Integrated Amplifier?

Turn off and unplug the Yamaha A-U671 Integrated Amplifier before cleaning. Wipe the exterior with a soft, dry cloth; avoid liquids, aerosol cleaners, and abrasive materials. Keep ventilation openings clear and do not stack heat-producing equipment directly on top. Periodically inspect speaker and RCA cables for damage and check that connections remain tight. Avoid operating the amplifier in damp, dusty, or excessively hot locations, and seek professional service for internal problems.