Audio Research I/50
Audio Research valve integrated amplifier, 2x50 watts RMS, fitted with XLR and single-ended inputs, designed to drive a wide variety of speakers.
Description
The I/50 is a valve integrated amplifier from Audio Research, designed to bring together preamplification and power stage in a single chassis. It delivers 2x50 watts RMS per channel and is aimed at those wishing to connect their speakers directly without a separate power amplifier, whilst enjoying the sound characteristic of tube electronics.
The output stage relies on two matched pairs of Sovtek 6550WE tubes and three 6922 tubes, one at the input and two at the output. Total harmonic distortion stays below 0.1% at 1 watt, with a bandwidth of 10 Hz to 22 kHz (-3 dB) and an extended frequency response of 7 Hz to 30 kHz (-3 dB at 1 watt). The input sensitivity of 1.25 V RMS at rated power and the input impedances of 48 kOhms single-ended and 100 kOhms balanced allow good compatibility with most sources. Speaker outputs available at 4 and 8 ohms allow the use of speakers with varying impedances.
Connectivity includes three single-ended inputs and one XLR input, one of which can be configured as pass-through to integrate into an existing home cinema setup. The top panel is limited to three controls: power, input selection and volume, complemented by two LexieTubes® displays indicating the active input and the volume level. A headphone jack allows individual listening, and a metal remote control is supplied with the unit.
This type of amplifier suits a classic stereo system where the user is seeking the sonic texture characteristic of tubes, without adding further components to the chain. The presence of a pass-through input also makes it an option for home cinema systems wishing to retain a valve-driven front channel.
Technical specifications
| Power | 2x50 watts RMS |
| Total harmonic distortion | below 0.1% at 1 watt |
| Bandwidth | 10 Hz – 22 kHz (-3 dB) |
| Frequency response | 7 Hz – 30 kHz (-3 dB at 1 watt) |
| Input sensitivity | 1.25 V RMS at rated power |
| Input impedance (single ended) | 48 kOhms |
| Input impedance (balanced) | 100 kOhms |
| Output polarity | non-inverting, balanced input pin 2+ (IEC-268) |
| Output impedance | 8 ohms, 4 ohms |
| Dimensions (W x H x D) | 42 x 18 x 34 cm |
| Weight | 18.1 kg |
What to check before buying used
On a valve amplifier of this generation, the condition of the tubes governs everything: the two pairs of 6550WE and the three 6922 wear and become mismatched with hours of use, leading to loss of gain or distortion on one channel. The bias of the power tubes deserves to be checked and readjusted after any replacement. Also inspect the power supply capacitors, which are sensitive to ageing, and test the volume potentiometer for crackling or track wear characteristic of this type of electronics.
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