Audio Research PH3

The PH3 is a phono preamplification stage intended for use with an active line-level stereo preamp. Fully single-ended from input to output, the PH3 uses a combination of J-FET input stage technology (for low inherent circuit noise) and class A operation vacuum-tube gain via three 6922 twin triodes. Total gain of the PH3 is 54 dB (non-adjustable). Used with typical line preamplifiers having 12 to 18 dB of gain, the PH3 is suitable for phono cartridges having .25 mV output or higher. Input impedance is factory-set at 47K ohms, and input capacitance at 90 pF. On the rear panel, the PH3 provides one pair of gold-plated, audiophile-grade single-ended connectors for L & R inputs, and one pair for outputs. Specifications: Frequency response: ±.15dB of RIAA, 10Hz to 60kHz; 3dB points below 0.5Hz and above 400kHz Distortion (THD): Less than .005% at .50V RMS 1kHz output Noise & hum: 0.1µV equivalent input noise, IHF weighted, shorted input (80 dB below 1mV 1kHz input) Gain: 54dB at 1kHz (MC & MM compatible) Input impedance: 47K ohms and 90pF Unbalanced. (Provisions for any value below 47K ohms or added input capacitance for matching certain magnetic cartridges.) Output impedance: 200 ohms Unbalanced. Recommended load 50K-100K ohms and 100pF. (10K ohms minimum and 2000pF maximum.) Maximum inputs: 60mV RMS at 1kHz (240 mV RMS at 10kHz) Rated outputs: .50V RMS 10Hz to 60kHz, 100K ohm load (output capability is 30V RMS output at 1/2% THD at 1kHz). Power supplies: Electronically-regulated low and high voltage supplies. Line regulation better than .01% Tube complement: (3) 6922/E88cc dual triodes Power requirements: 100-135VAC 60Hz (200-270VAC 50/60Hz) 28 watts maximum. Line fuse 0.6A SLO BLO (0.3A SLO BLO 230V) Dimensions: 19" (48 cm) W x 5.25" (13.4 cm) H (standard rack panel) x 10.25" (26 cm) D. Handles extend 1.50" (3.8 cm) forward of front panel. Rear chassis fittings extend .75" (2.2 cm) Weight: 10 lbs. Net; 21 lbs.