Audio Research I/70 - The New Tube Amplifier

American tube-audio manufacturer Audio Research has introduced the new Audio Research I/70 integrated amplifier. Four 6550 tubes deliver 70 watts per channel, which the company believes is sufficient even for low-sensitivity loudspeakers. The Audio Research I/70 can be expanded by installing two optional modules: a DAC and a phono preamplifier.

The output stages of the Audio Research I/70 are built around four octal beam tetrode 6550 vacuum tubes and deliver 2 × 70 W. The new model features an automatic bias system (auto bias) that keeps the 6550 tubes operating at an optimal point without the need for manual adjustment. In addition to consistent sound quality, this is intended to extend tube life and reduce maintenance.

The external design of the Audio Research I/70 is based on the look of the Reference 330M monoblocks. Clean lines, visible tubes, and a sturdy chassis emphasize the unit’s high-end status. The amplifier is available in a “natural silver” finish or black anodized version. A metal remote control is included, allowing access to all key functions.

The preamplifier stage uses an active tube circuit and is responsible not only for volume control, but also for driving the output stages – an element considered critical for tonal naturalness. Audio Research emphasizes a clear separation of functional sections inside the unit in order to preserve dynamics and transparency.

The most important element of a tube amplifier’s output stage is the output transformer. According to the manufacturer, special attention is paid to these transformers: Audio Research states they are identical to those used in the Reference 75SE amplifier. These components are regarded as key to transient response, frequency response, and bass control, and they are meant to give the I/70 an obvious link to the more expensive Reference series.

The Audio Research I/70 is designed not only for classic loudspeaker systems, but also reflects the growing popularity of high-end headphones. Here, the headphones receive a signal directly from the 6550 output tubes, which – according to the manufacturer – should provide a particularly impressive and dynamic presentation.

For source connections, the unit offers not only unbalanced inputs but also XLR connectors for balanced signal sources. In addition, the new model provides preamp outputs and a dedicated output for an active subwoofer, making it easy to integrate the I/70 into larger stereo systems or subwoofer-based setups.

To meet different listening preferences, the Audio Research I/70 can be enhanced with optional modules. The DAC module adds digital connectivity, including USB-B, coaxial and optical S/PDIF, as well as Bluetooth. For vinyl enthusiasts, an optional MM/MC phono stage module is also available, allowing a turntable to be connected directly to the amplifier. Both modules can be used separately or together, turning the I/70 into the hub of a stereo system for a wide range of sources without the need for external devices.

The Audio Research I/70 is already on sale in Europe with a recommended retail price of €11,990. The version with the built-in phono stage and DAC modules costs €13,790. The optional modules are also sold separately: the phono stage module (for MM and MC cartridges) and the DAC module each cost €1,190. Both expansions together are available as a combined solution for €1,790.