Audio Research i/55 Integrated Vacuum Tube Amplifier

$15,200.00

Please contact us to order

Colour: Black

Black

White

Silver

Extra input: None

None

DAC Card

Phono Card

Product variants

The I/55 takes advantages of new features and advancements from the 1/70 to create a worthy successor to the I/50.
I/55 imports all of the functionality of the 1/70 into a chassis that maintains the look and power output of the I/50.

Availability

Ask a question

Specifications

Power Output: 50 watts continuous from 20Hz to 20kHz. 1kHz total harmonic distortion typically 1% per channel, below 0.1% at 1 watt

Power Bandwidth: (-3dB points) 10Hz to 22kHz

Frequency Response: (-3dB points at 1 watt) 7Hz to 30kHz

Input Sensitivity: 1.25V RMS for rated output.

Input Impedance: 100K ohms Balanced, 48K ohms Single Ended

Output Polarity: Non-inverting. Balanced input pin 2+ (IEC-268)

Output Taps: 8 ohms, 4 ohms

Power Requirements: 105-130VAC 60Hz (210-250VAC 50Hz) 252 watts at rated output.

Tubes Required: 2 matched pair 6550WE; 3-6922 (1 input, 2 driver).

Dimensions: Width 16.5” (42 cm) Height 7.25” (18 cm) Depth 13.5” (34 cm)

Weight: 40 lbs (18.1 kg); 51 lbs (23.1kg) shipping weight.

I was a little surprised at how well the amp managed to keep a grip on the dynamics when playing loud.

Stereonet

The foundation is an all-tube amplification circuit using two matched sets of 6550 power tubes, fed by 6922 input tubes. The traditional combination of power and grace for which Audio Research is renowned is instantly recognizable even in this compact model. Challenge the I/55 and be surprised by its depth of bass and dynamic expression. Two Lexie Tubes® provide display information for input selection and volume.
Chief among the improvements from I/50 to I/55 is the addition of auto-bias.
This keeps the output tubes in their optimal operating range for the life of the tubes.

The I/55 integrated amp has independent tube preamplifier and tube amplifier sections, providing flexibility with a set of stereo preamplifier outputs. While we suspect very few listeners will pair it with an external power amp, many will need this feature to feed powered subwoofers that offer only low-level inputs.
The active preamplifier also offers a much wider range of gain setting compared to the passive preamp on board the I/50. This is especially helpful with recordings that are cut at a low gain setting for wide dynamic range. Despite its identical power rating to the I/50, the I/55 will offer additional output due to both additional gain and higher headroom in its preamplifier section.
The headphone output is driven by the 6550 output tubes. It was designed for high quality headphones, able to provide the best possible personal listening experience.

The DAC card's AKM Velvet Sound DAC chip provides high resolution formats over USB, Optical, Coax, and Bluetooth. All are upsampled. The result is fine resolution, great transparency, and tonal purity that is rarely heard outside of the finest separate DACs.
There are three sets of single-ended inputs and one set of Balanced XLR inputs.
The optional phono card has both MC and MM gain settings, controlled via the 1/55 remote. MC loading is also adjustable, from 50 to 1k ohms.

Who is this for?

The i/55 is designed for the discerning listener who values musicality above all else and refuses to compromise on authentic tube sound. If you've graduated beyond mass-market receivers and recognize that your speakers deserve better, this integrated amplifier delivers the warmth, dimensionality, and emotional truth that only Audio Research's vacuum tube topology can provide. This is for someone who listens to complete albums, who hears the difference between good and transcendent, and who understands that fifty watts of pure Class A tube power reveals more music than 200 watts of solid-state ever could.

Your listening room is likely a dedicated space or your primary living area, somewhere between 10 to 40 square metres, where music matters. The i/55 pairs beautifully with speakers of moderate to high sensitivity—anything from 87dB and up—allowing those carefully matched KT150 output tubes to work their magic without strain. Whether you're driving stand-mount monitors or medium-sized floorstanders, this amplifier delivers the control and finesse that transforms your speakers into conduits of pure musical expression rather than mere transducers.

This integrated amplifier serves as the heart of a refined two-channel system where simplicity meets sophistication. Connect your turntable through the built-in phono stage, add a quality digital source, and you have everything you need. The i/55 eliminates the complexity of separates while preserving Audio Research's legendary performance, making it ideal for the listener who wants reference-grade sound without filling an equipment rack. This is the amplifier you've been working toward.

Audio Research has a winner on its hands with the new I/50 integrated amplifier. If you've ever wondered about the sonic capability of classic thermionic power, here's a fantastic opportunity to test the tubes.

If you match it with the right speakers and also ensure quality in the rest of the signal path, the Audio Research I/50 could be one of the most successful amp buys in this price range.

I enjoyed my time with the Audio Research I/50. It is the perfect amplifier for use in a relatively small room with a high-quality source and speakers.