audio research

Tube stereo power amplifier.

From the ARC website

The least expensive of the latest- generation "VT" series of vacuum-tube power amplifiers from Audio Research, the VT50 is compact in its physical dimensions, but has sufficient output (with hefty distributed power supplies) at 50 watts per channel to effectively drive and control just about any moderately efficient loudspeaker available today. It suffers not by sonic comparison or in musical resolution, but only in loudness cabability in a given music system. Even so, comfortably realistic levels with surprising musical dynamics are easily within the VT50's grasp.
Based on the same circuit design as the VT100 and VT200, the VT50 features a dual-mono circuit layout reaching back to the large power transformer. Two matched pair of 6550-C tubes provide the output (one pair each channel), while four 6922 twin triodes serve as input and driver tubes (two each channel). Constant-current source technology (as used in the Reference Series) help maintain output stage balance and headroom under dynamic music conditions. Distributed power supplies yield a total energy storage of 354 joules (compared to 183 joules in the CA50), giving the VT50 remarkable dynamic snap in addition to its inherent sweetness and delicacy. And, like its more powerful siblings, the VT50 provides the convenience of both balanced and single-ended inputs for easy connection to any quality preamplifer.

Chassis design and size are identical to the CA50/REF1 mechanical package, but of course without front-panel control knobs. A simple oversized rocker switch provides power on/off. Output terminals offering 4-8-16 ohm impedance options are of the heavy gold-plated type used on larger Audio Research amplifiers. Power cord is a detachable 14 gauge with IEC connector.

For moderate or high-efficiency high- resolution loudspeaker systems, the VT50 is a natural mate. Paired with dynamics or electrostatics, the VT50 makes music come alive, with surprising dynamics when called for, vivid midrange transparency and image focus, and delightfully non-fatiguing upper-frequency extension and air. This is a power amplifier sure to become a favorite of music lovers who appreciate accuracy and nuance without the bombast.





MSRP (US new retail)
$3,495. Increased to $3,995 on Feb 5 2001.


Power output 45 watts per channel continuous from 30Hz to 15kHz. Approximate actual power available at "clipping" 50 watts (1kHz)
Power bandwidth (-3dB points) 12Hz to 45kHz
Frequency response (-3dB points at 1 watt) 1.5Hz to 50 kHz
Input sensitivity 1.95V RMS (Bal or SE) for rated output. (22.8 dB gain into 16 ohms.)
Input impedance 200K ohms Balanced, 100K ohms Single-ended
Output taps  
Output regulation Approximately 1.3dB 16 ohm load to open circuit
Overall negative feedback 8.5 dB
Damping factor 6
Distortion 1kHz total harmonic distortion typically 1% at 45 watts, below .05% at 1 watt.
Slew rate 10 volts/microsecond
Rise time 7 microseconds
Hum & noise Less than 0.25mV RMS < 100dB below rated output (IHF weighted, input shorted)
Power supply energy storage 354 joules
Power requirements 105-125VAC 60Hz (210-250VAC 50Hz) 275 watts at rated output, 330 watts maximum, 200 watts at "idle"
Tube complement (2 matched pairs) 6550C, (2) 6922 driver; (2) 6922 input.
Dimensions 19" (48.3 cm) W x 7" (17.8 cm) H x 15" (38.1 cm) D. Handles extend 1.5" (3.8 cm) forward
Weight 41 lbs. (18.6 kg) Net; 54 lbs. (24.5 kg) Shipping.