Audio Research I/55 – Tube Integrated Amplifier with DAC and Phono Stage

The American tube audio manufacturer Audio Research has introduced the integrated amplifier Audio Research I/55, which combines proven engineering solutions with modern functionality. The new model borrows key design elements from the flagship Audio Research I/70 and adapts them to a more compact chassis. As a result, the Audio Research I/55 integrated amplifier is aimed at listeners who value the characteristic tube sound but do not want to compromise on flexible connectivity and ease of use. As the successor to the Audio Research I/50, the new model incorporates important technical improvements from the larger Audio Research I/70 and brings them into a format suitable for compact High End systems.

The Audio Research I/55 features a fully tube-based amplification path. The output stage uses two matched pairs of 6550 tubes, while the input and driver stages are built around 6922 tubes. This classic circuit topology forms the foundation of the signature Audio Research sound, focused on high transparency, dynamic expression, and controlled bass performance.

Compared to the I/50, a key innovation is the integrated Auto-Bias circuit, which continuously monitors the idle current of the output tubes and adjusts it automatically. For the user, this means stable operation throughout the entire tube lifespan without the need for manual bias adjustments.

A significant step forward has also been made in the preamplifier stage. The Audio Research I/55 features a tube preamp section with a noticeably wider gain range than its predecessor. This simplifies playback of quietly recorded material and provides greater dynamic headroom in everyday use. Despite the same nominal power rating of 50 watts per channel, the Audio Research I/55 subjectively delivers greater drive and control, particularly with more demanding loudspeakers. In addition, preamplifier outputs (Pre-Out) are provided for connecting external power amplifiers or active subwoofers.

Beyond the analog tube section, Audio Research also offers a modern digital stage for the I/55. The optional DAC module is based on an AKM Velvet Sound chipset capable of processing high-resolution audio via USB-B, S/PDIF (optical), S/PDIF (coaxial), and Bluetooth. All digital signals within the unit are upsampled to ensure enhanced detail and clarity. The amplifier’s connectivity includes multiple analog inputs, including unbalanced RCA and balanced XLR inputs, allowing the Audio Research I/55 to integrate easily into a wide range of audio systems.

Optionally, the Audio Research I/55 can also be equipped with a phono stage module supporting both MM (Moving Magnet) and MC (Moving Coil) cartridges. MC input impedance can be adjusted directly from the remote control within a range from 50 ohms to 1 kΩ.

For personal listening, a high-quality headphone output is provided, powered directly by the 6550 output tubes. This makes the amplifier equally appealing to owners of high-end headphones who want to enjoy tube sound not only through loudspeakers.

The Audio Research I/55 integrated amplifier is now available in Europe. The recommended retail price for the base version without optional modules is €8,990. The version equipped with both DAC and Phono modules is priced at €10,790. Both modules can also be installed separately at a later time: the phono board costs €1,190, and the DAC module is priced the same. The two modules can also be purchased together for €1,790.