Original owner! Exceptionally low hours. Recently tested by a local audio specialist. Sounds fabulous and in great condition. Stored in temperature and humidity-controlled home for decades. Operated within clean, no-smoking, no pet, adult-only environment.Even though Audio Research significantly over-builds their products, we used a Variac (a variable transformer) to gently recharge all capacitors in the amp. Link below.This is a transistor (solid state) amplifier. No maintenance required. Minor faceplate imperfection as shown in photosOne of The Absolute Sounds favorite solid-state amps back in the day. Sounds great! $1295 when new. Adjusted for inflation, this amp would sell for $5300 today. $695 or Best Offer...Includes original double box and users manual Audio Research Corporation is one of the oldest continually operating manufacturers in American audio. The company was founded in 1970 in Minneapolis by William Z. Johnson. Audio Research has been synonymous with the state-of-the-art in music reproduction since its beginning. Currently they have ~50 technical, assembly and support staff. https://iseinc.com/_shop/variabletransformers/variac-portable-units/variacportable120vacinput0-140voutput/3pn1010bvariabletransformer120vacsinglephaseinput0-140vacoutput10acasedmodelwithcordplugreceptaclelightedswitchandfuse.html Users Manual: https://www.arcdb.ws/Database/D52/ARC_D52_D52B_manual.pdf From the Audio Research website POWER OUTPUT 50 watts per channel minimum RMS (both channels operating) at 8 ohms from 1 Hz to 20 kHz with less than .25% total harmonic distortion. Typically less than .02% at rated power in midband. Approximate actual power available per channel at clipping (both ch. op.): 80 (4 ohms), 60 (8 ohms), 35 (16 ohms) FREQUENCY RESPONSE 0.05 Hz to 100 Khz (-3 db) INPUT SENSITIVITY 1.1 Volts RMS for rated power and load INPUT IMPEDANCE 30 Kohms (nominal) DAMPING FACTOR More than 500 at rated power and load (20 Hz to 20 kHz). (Effective internal impedance approximately .012 ohms.) DISTORTION Intermodulation distortion: Less than .1% at rated output (56.56 V p to p) and load (SMPTE method). THD and IMD both decrease with decreasing output. HUM and NOISE Wide-band, unweighted, more than 90 dB below 50 watts at 8 ohms - power line components (hum) more than 80 dB below 50 watts at 8 ohms. POWER REQUIREMENTS 105-120/210-240 VAC, 50/60 Hz, 600 watts maximum. 120 watts at idle. 300 watts at rated power. DIMENSIONS 19 (48 cm) W x 5 ¼ (13 cm) H (standard rack mount panel size) x 10 ½ (26.7 cm) D (front panel back). Handles extend 1 ½ (3.8 cm) forward of the front panel. WEIGHT 39 lbs. (17.7 kg) Net, 45 lbs. (20.5 kg) Shipping