Audio research high definition stereo power amplifier classic 60

Description

The Audio Research Classic 60 is a revered stereo power amplifier known for its ability to deliver a musically natural and dynamic sound with surprising authority for its 60-watt-per-channel rating. Introduced in the late 1980s, this amplifier embodies Audio Research's commitment to high-definition audio through a hybrid design, utilizing solid-state input stages coupled with a vacuum tube output stage. This combination aims to provide the strengths of both technologies: the low noise and wide bandwidth of solid-state with the harmonic richness and engaging musicality of tubes.  

The Classic 60 employs four matched pairs of 6550 output tubes, operating in a triode configuration with partial cathode coupling, a design choice that contributes to its smooth and detailed sonic character. The input stage typically features JFETs and 6FQ7/6CG7 driver tubes. This hybrid approach also enhances reliability and tube life. Operationally, the Classic 60 is relatively straightforward. It typically features a front-mounted power switch and indicator LEDs. The rear panel provides single-ended RCA inputs and robust binding posts for 4, 8, and 16-ohm speaker taps, offering flexibility with various loudspeaker designs. Some models also include cooling fans for the output tubes, contributing to their longevity. Sonically, the Classic 60 is often praised for its exceptional midrange clarity, detailed resolution, and a wide, deep soundstage. Despite its moderate power rating, it exhibits impressive dynamic capability and control, capable of driving a wide range of loudspeakers to satisfying levels in most listening environments. Its ability to resolve fine musical nuances and present a coherent and engaging sonic picture makes it a highly sought-after amplifier among audiophiles.  

Key Features:

• Hybrid Design: Solid-state input stage with vacuum tube (6550) output stage.
• Triode Output Stage with Partial Cathode Coupling: For a richer and more lifelike sound.
• 60 Watts per Channel: Into 4, 8, and 16-ohm loads.  
• Automatic Bias Adjustment: Continuously adjusts to changes in line voltage for optimal performance.
• DC Balance Servo: Maintains DC balance in each pair of output tubes.
• Fan Cooling: Enhances tube and component life.
• High-Quality Components: Built with audiophile-grade parts and meticulous hand assembly in the USA.
• Multiple Speaker Taps: Offers flexibility with different speaker impedances.

Specifications (Based on available information):

• Output Power: 60 watts minimum continuous per channel into 4, 8, and 16 ohms from 15Hz to 20kHz with less than 1% total harmonic distortion. Typically 62 watts at 1kHz into 16 ohms at clipping.  
• Power Bandwidth (-3dB points): 12Hz to 40kHz.  
• Frequency Response: Typically 1Hz to 70kHz (-3dB at 1 watt).
• Input Sensitivity: 0.55V RMS for rated output.
• Input Impedance: 100k ohms (nominal).  
• Output Taps: 4, 8, and 16 ohms.
• Output Regulation: Approximately 0.3dB, 16 ohm load to open circuit (equivalent to an output impedance of 0.56 ohms).  
• Overall Negative Feedback: 20dB.
• Damping Factor: Approximately 30.  
• Slew Rate: 20V/µs.
• Rise Time: 2µs.
• Hum & Noise: Less than 2.0mV RMS – 84dB below rated output (20kHz bandwidth, unweighted, inputs shorted).
• Power Supply Energy Storage: Approximately 280 joules.  
• Power Requirements: 105-125VAC 60Hz (210-250VAC 50Hz), 500W at rated output, 700W maximum, 370W at idle.
• Tube Complement: (8 matched pairs) 6550, (4) 6FQ7/6CG7.  
• Dimensions (W x H x D): 19" (48 cm) x 7" (18 cm) x 15.75" (40 cm) (Handles extend 1 5/8" ( 4.1 cm) forward of the front panel, output connectors extend 1" behind rear panel).  
• Weight: 63 lbs (28.64 kg) net, 76 lbs (34.55 kg) shipping.