Audio Research I/70 Integrated Amplifier

Open Box Baby! 70-Watt Vacuum Tube Integrated Amplifier | The Grid HiFi

The Soul of Audio Research. One Beautifully Complete Amplifier.

The Audio Research I/70 brings the company's vacuum tube amplification heritage into a single, elegantly engineered component. Delivering 70 watts per channel, it combines a dedicated tube preamplifier, a tube power amplifier, digital connectivity, and thoughtful system flexibility without requiring a separate stack of electronics.

Four KT120 output tubes and the same output transformer design used in the Reference 75 amplifier form the foundation of the I/70. Automatic tube bias makes everyday ownership easier, while its substantial power and 4- and 8-ohm speaker connections make it a compelling centerpiece for a serious two-channel system.

The result is an integrated amplifier designed for listeners who want the experience of Audio Research separates in a more streamlined package.

Reference-Inspired Tube Amplification

The I/70 is more than a preamplifier and power amplifier sharing a chassis. Its independent tube preamplifier and power amplifier sections preserve a flexible architecture while delivering 70 watts of continuous power per channel from 20 Hz to 20 kHz.

The amplifier employs four KT120 output tubes alongside three 6922 tubes—one for the input stage and two for the driver stage. Its output transformers draw directly from Audio Research's Reference 75 design.

Automatic bias eliminates the need for routine manual bias adjustments, allowing owners to enjoy the amplifier without making tube maintenance part of every listening session.

Analog Sources, Digital Music, and Vinyl

The I/70 accommodates traditional analog components with three single-ended RCA input pairs and one balanced XLR input pair.

For digital playback, Audio Research describes a DAC card featuring an AKM Velvet Sound converter with USB, optical, coaxial, and Bluetooth connectivity. Incoming digital signals are upsampled.

Vinyl enthusiasts can specify an optional phono card supporting both moving-magnet and moving-coil cartridges. Its gain settings are selectable using the I/70 remote, and moving-coil loading is adjustable from 50 to 1,000 ohms.

This combination allows the I/70 to anchor a system built around a turntable, digital source, or both.

A Tube-Driven Headphone Experience

The I/70's headphone output is driven by its KT120 output tubes rather than being presented simply as an incidental convenience.

That makes personal listening part of the amplifier's core design. Enjoy your favorite headphones without abandoning the tube amplification that defines the rest of the system.

Room to Grow

A dedicated stereo preamplifier output gives the I/70 flexibility beyond a conventional integrated amplifier. It can feed an external power amplifier or powered subwoofers equipped with line-level inputs.

The active tube preamplifier also incorporates a 75-step volume control and a wide range of gain settings, providing precise adjustment across different recordings and listening levels.

For listeners building a system over time, these connections help the I/70 remain useful as the rest of the system evolves.

A Modern Expression of Audio Research Design

The I/70 takes visual inspiration from the Reference 330M monoblock amplifier. Black or silver anodized plinths frame an enclosed transformer assembly finished with machined aluminum, mesh, and distinctive badging.

A mesh wrap around the lower chassis completes the design, giving the amplifier a contemporary appearance while retaining the unmistakable character of Audio Research.

Each I/70 is built by hand at the company's Minnesota facility, tested twice, and individually auditioned in its reference system.

Key Features

• 70 watts per channel of vacuum tube amplification

• Four KT120 output tubes and three 6922 tubes

• Reference 75-derived output transformers

• Automatic tube bias

• Independent tube preamplifier and power amplifier sections

• 75-step volume control

• Three RCA inputs and one balanced XLR input

• DAC card with USB, optical, coaxial, and Bluetooth connectivity

• Optional MM/MC phono card with adjustable MC loading

• Tube-driven headphone output

• Stereo preamplifier outputs for external amplification or powered subwoofers

• 4-ohm and 8-ohm speaker output taps

• Available in black or silver finishes

• Hand-built in Minnesota, USA

Technical Specifications

The following figures are taken directly from Audio Research's published I/70 product specifications.

Experience Audio Research at The Grid HiFi

An integrated amplifier should do more than simplify your equipment rack. It should bring your music system together.

At The Grid HiFi in Houston, we can help pair the Audio Research I/70 with appropriate loudspeakers, a turntable, digital sources, and headphones. We'll also help determine whether the optional phono card or additional subwoofer integration makes sense for your system.

Whether you're moving into your first serious tube amplifier or simplifying an established two-channel setup, the I/70 offers a distinctive way to experience Audio Research.

Contact The Grid HiFi to explore the Audio Research I/70 and build your ideal listening system.