Audio Research I/70 Integrated Amplifier

The Audio Research I/70 is a 70-watt tube integrated amplifier that brings the performance of Audio Research separates into a single, refined chassis. Four KT120 output tubes paired with the same output transformers used in the Reference 75SE deliver dynamic swing and control that challenge dedicated separates at this price. The I/70 includes an independent tube preamplifier section with preamp outputs, a headphone amplifier driven by the output tubes, and optional AKM DAC and phono cards, making it a complete high-performance system in one box. Built by hand in Minnesota, tested twice, and individually auditioned.

Key Features of the Audio Research I/70

• Reference 75SE Output Transformers: The same output transformers from Audio Research's acclaimed Reference 75SE power amplifier, delivering authority and resolution rarely found in an integrated design.
• 70 Watts from KT120 Tubes: Four KT120 output tubes with three 6922 signal tubes produce 70 watts per channel with the dynamic headroom to drive demanding speakers.
• Independent Preamp Section: Separate tube preamplifier and tube amplifier stages with dedicated preamp outputs for powered subwoofers or external power amplifiers.
• Headphone Output via Output Tubes: The headphone amplifier is driven by the KT120 output tubes, not an afterthought op-amp circuit, delivering a genuine tube headphone experience.
• Optional AKM DAC Card: Velvet Sound DAC chip with USB, Optical, Coax, and Bluetooth inputs, all upsampled for high-resolution digital playback.
• Optional Phono Card: MM and MC phono stage with adjustable MC loading (50 to 1,000 ohms) via remote control.
• Auto-Bias: Automatic bias adjustment keeps output tubes at their optimal operating point daily with no user intervention.
• 75-Step Volume Control: Fine-grained volume adjustment for precise level setting across all source material.
• REF330M-Inspired Design: Visual cues drawn directly from the Reference 330M, including machined aluminum, mesh enclosure, and signature badging.

Reference-Grade Output Stage

The I/70's power amplifier section isn't built around cost-effective compromises. Audio Research fitted it with the same output transformers used in the Reference 75SE, one of the most respected stereo tube amplifiers in the lineup. Combined with four KT120 output tubes and three 6922 signal tubes, the result is 70 watts per channel with a sense of command, control, and resolution that was previously reserved for dedicated separates. The power bandwidth extends from 10Hz to 22kHz, and frequency response reaches from 7Hz to 30kHz at the -3dB points.

Independent Tube Preamplifier

Unlike integrated amplifiers with a simple volume pot ahead of the power stage, the I/70 features a fully independent tube preamplifier section. This active preamp provides a much wider range of gain settings and a 75-step volume control, making it especially effective with recordings cut at low levels for wide dynamic range. Stereo preamplifier outputs let you connect powered subwoofers or, if your system grows, route the signal to an external power amplifier while retaining the I/70's preamp as your system controller.

Headphone Amplifier Driven by Output Tubes

The I/70's headphone output is not a token feature. It's driven by the KT120 output tubes themselves, providing the full benefit of the tube amplifier stage to high-quality headphones. This design approach delivers the same tonal richness, dynamic range, and spatial presentation through headphones that you hear through speakers, making the I/70 equally compelling for late-night listening sessions.

Connectivity and Inputs

The I/70 provides three sets of single-ended (RCA) inputs and one set of balanced (XLR) inputs for analog sources. With the optional DAC card installed, you gain USB, Optical, Coax, and Bluetooth digital inputs, all processed through an AKM Velvet Sound chip with upsampling across all formats. The optional phono card adds both MM and MC capability with adjustable MC loading from 50 to 1,000 ohms, controllable from the remote. Use the Version selector to choose your configuration: I/70 Only for the pure analog integrated, or add DAC, Phono, or both cards.

Auto-Bias and Tube Management

Auto-bias continuously adjusts the KT120 output tube operating points in real time, tracking line voltage changes and tube aging automatically. You never need to measure bias voltage or adjust trim pots. When tubes eventually need replacement, install a matched set and the I/70 handles the rest. This means consistent performance from the first listening session to the last day of tube life.

Design Inspired by the Reference 330M

The I/70's visual design takes direct cues from the Reference 330M monoblock, Audio Research's flagship power amplifier. Black or silver anodized plinths top and bottom, with a fully enclosed transformer array topped by machined aluminum, mesh detailing, and signature REF330M-style badging. A full mesh wrap around the bottom chassis completes the upscale look. This is an integrated amplifier that looks and feels like it belongs alongside Audio Research's statement products.

Audio Research I/70 Integrated Amplifier Video

Explore the Audio Research Integrated and Power Amplifier Range

The I/55 offers a more compact 50-watt integrated with the same optional card architecture in six color options. For dedicated power amplification, the D-80 delivers 70 watts from KT150 tubes in a pure power amp design, while the Reference 80S provides the full Reference circuit. The S-100 and S-200 offer solid-state power amplification to pair with the LS-3 preamplifier.

The Listening Room Difference

We're a third-generation family business with a brick-and-mortar showroom in Chestertown, Maryland, and a reputation built on trust, not hype. Whether you're visiting in person or ordering online, we bring decades of experience, personalized service, and honest guidance to every interaction. We don't just ship boxes. We help build systems, answer your questions like real humans, and make sure every detail of your setup is right, from the cables to the final connection. Our passion is helping you get the most out of your gear, with support that lasts well beyond the sale.

Audio Research I/70 Integrated Amplifier Specifications