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Audio Research VS55 Amplifier - 50 Glorious Tube Watts Per Channel

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Pickup currently unavailable at SkyFi 479

Audio Research Vs55 Amplifier - 50 Glorious Tube Watts Per Channel

Audio Research VS55 Amplifier - 50 Glorious Tube Watts Per Channel

SkyFi 479

Pickup currently unavailable

479 South Broad Street
Glen Rock NJ 07452
United States


Perfect for driving efficient bookshelf speakers or large vintage floorstanding speakers.

Tested and working perfectly in our lab. The output tubes are pulling strong and appear to have little use. This piece was biased to perfection and is producing full power without any drama. 

Features 8 and 4 ohm taps to get the most out of your speakers.  12V triggers will allow you to manage power from a preamp with the same connection. 

Condition is very good with no significant signs of use. 

From a review via SoundStage! written by John Potis:

"These days there are more manufacturers of high-end electronics than any reviewer can shake a stick at. But none is more time-honored than Audio Research Corporation.

...The VS55's treble grabbed my attention next. It was as honest and extended as any I’ve heard. It seemed to go on out forever and with absolutely no editorializing whatsoever, which could be a mixed bag. Good recordings sounded spectacular, offering a great measure of air and space and giving instruments occupying the highest octaves real presence.

...The VS55 does some things, such as bass and dynamics, like much more expensive amps, and better than most amplifiers I’ve heard. And it wraps it all up with such a remarkably clean and transparent treble that it’s no wonder Audio Research has maintained such an enviable reputation for all these years.


Power output 50 watts per channel continuous from 20Hz to 20kHz. Approximate actual power available at "clipping" 52 watts (1kHz)
Power bandwidth (-3dB points) 12Hz to 50kHz
Frequency response (-3dB points at 1 watt) 1.0 Hz to 60 kHz
Input sensitivity 1.1V RMS Single-ended for rated output. (25 dB gain into 8 ohms)
Input impedance 100K ohms Single-ended
Output taps 8 ohms, 4 ohms
Output regulation Approximately 1.0 dB 8 ohm load to open circuit
Overall negative feedback 12.5 dB
Damping factor 10
Distortion 1kHz total harmonic distortion typically 1% at 50 watts, below .05% at 1 watt
Slew rate 5 volts/microsecond
Rise time 5 microseconds
Hum & noise Less than 0.2mV RMS - 100dB below rated output (IHF weighted, input shorted)
Power supply energy storage 166 joules
Power requirements 105-125VAC 60Hz (210-250VAC 50Hz) 320 watts at rated output, 500 watts maximum, 200 watts at "idle"
Tube complement (2 matched pairs) 6550EH power output, (3) 6N1P input and driver
Other Tube locations and types are screened next to each opening in the top plate, along with bias-adjustments for the two pair of 6550 Electro-Harmonix output tubes.
The rear has 12 V in/out triggers for remote installation and L / R channel access points for a voltmeter (used when setting bias).
The amp rests on four elastometer feet and use detachable 12 gauge power cord with IEC socket.
Dimensions 14" (35.6 cm) W x 7" (17.8 cm) H x 14" (35.6 cm) D. Rear connectors extend .88" beyond chassis
Weight 32 lbs. (14.5 kg) Net; 38 lbs. (17.3 kg) Shipping.


The SkyFi Testing Process for Tube Amplifiers:

We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and tubes are inspected for signs of stress overheating or cracking.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If it all looks clean we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier the remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will also be tested.

We also test all tubes for output gain and leakage on our calibrated B&K 747 tester against the original manufacturers specifications. If needed, the tubes will be replaced from our vast NOS (New Old Stock) vintage or modern inventory.

Final testing involves pushing actual music thorough the amplifier. We've learned over time that some issues are only noticeable to a trained ear while listening to familiar source material. Our test bench has reference vintage KEF speakers that we're very familiar with which quickly reveal any discrepancies. Some amplifiers will then move into our listening room where they are tested with our in-house reference speakers of choice.

Please click here for detailed specifics regarding our specialized packing process that separates us from the rest.



Original Box







Yes - Power Cord

Physical Condition


Working Condition


SKU: 100365