Tube Preamp Reviews

Reference 1 preamplifier: Tubed line stage with remote control. Inputs: Tape, Tuner, Phono, CD, Video, Aux 1, Aux 2, Aux 3 (XLR and RCA connections). Outputs: 2 main, 1 tape (XLR and RCA connections). Tube complement: eight 6922/E88CC dual-triode (vacuum tube audio circuit, solid-state power supply). Frequency response: 1Hz–200kHz, ±0.5dB. Distortion: <0.015% @ 4V RMS, balanced output. Gain: 12.3dB balanced, 6.3dB single-ended at main output; 0dB at tape output. Input impedance: 220k ohms balanced, 110k ohms single-ended. Maximum input: 7.0V RMS balanced, 3.5V RMS single-ended. Output impedance: 400 ohms balanced, 200 ohms single-ended, 20k ohms minimum load recommended, 200pF maximum capacitance. Rated outputs: 4V RMS, 2V RMS single-ended into 100k ohm balanced load. (Maximum balanced capability is 30V RMS @ <0.5% THD @ 1kHz.) Noise: 13µV RMS residual noise (IHF-weighted), balanced output with gain minimum (110dB below 4V RMS output, 93dB below 2V RMS single-ended output). Power requirements: 100-135VAC, 60Hz (200–270VAC, 50/60Hz); 90W maximum.
Dimensions: 19" (480mm) W by 7" (178mm) H by 15.5" (394mm) D. Handles extend 1.5" (38mm) forward of front panel. Weight: 30 lbs (13.6kg).
Serial number of unit reviewed: 08289001.
Price: $8495 (1998).

VT200 power amplifier: dual-mono tubed power amplifier with ultralinear output stage. Tube complement: eight 6550C in matched pairs, ten 6922 (six driver, four input). Output power: 200Wpc continuous into 8 ohms (23dBW), 20Hz-20kHz. THD @ 1kHz: typically 1% @ 200W, <0.01% @ 1W. Power bandwidth: 12Hz–120kHz, -3dB. Frequency response: 0.5Hz–200kHz, -3dB @ 1W. Input sensitivity: 2.5V RMS, balanced or single-ended (27dB gain into 16 ohms). Input impedance: 200k ohms balanced, 100k ohms single-ended. Output taps: 1, 2, 4, 8, 16 ohms. Output regulation: approximately 0.8dB with 16 ohm load to open circuit (damping factor approximately 11). Overall negative feedback: 10dB. Slew rate: 25V/µs. Rise time: 1.5µs. Hum & noise: <0.2mV RMS, 109dB below rated output (IHF weighted, input shorted, 16 ohm output). Power-supply energy storage: approximately 674 joules. Power requirements: 105–125VAC, 60Hz (210–250VAC, 50Hz); 990W at rated output; 1200W maximum; 680W at idle.
Dimensions: 19" (483mm) W by 10.5" (267mm) H by 23.6" (600mm) D. Handles extend 1.5" (38mm) forward of front panel. Weight: 118 lbs (46.5kg).
Serial number of unit reviewed: 68097002.
Price: $8995 (1998).

Both: Approximate number of dealers: 65.
Manufacturer: Audio Research High Definition, 5740 Green Circle Drive, Minnetonka, MN 55343-4424. Tel: (612) 939-0600. Fax: (612) 939-0604. Web: www.audioresearch.com