Up for sale is a Audio Research M300 MKII Monoblock Class A Tube High Definition Power Amplifier! This is a very rare, very nice high quality unit and it is fully functional and working. It has minimal cosmetic wear with no damage and has had new tubes installed. These typically come in pairs, I just have the one. These are very rare and sought after. SPECIFICATIONSPower Output - 300 Watts minimum continuous at 8 Ohms from 16Hz to 20kHz with less than 0.8% total harmonic distortion (typically below 0.005%at 1 Watt)Approximate Actual Power Available at Clipping - 330 Watts (1kHz)Power Bandwidth - (-3dB Points) 10Hz to 60kHzInput Sensitivity - 0.9V RMS for rated outputInput Impedance - 60K Ohms, nominalOutput Regulations - Approximately 0.3dB. 8 Ohm load to open circuit (damping factor approximately 30)Negative Feedback - 20dBSlew Rate - 25 volts/microsecondRise Time - 3 microsecondsHum & Noise - Less than 2mV RMS 90dB below rated output (broad-bandwidth unweighted, inputs shorted)Power Supply Energy Storage - Approximately 350 JoulesPower Requirements - 105-125VAC 60Hz (210-250VAC 50Hz), 900 Watts at rated output, 450 Watts at idle - 130 Watts at standbyDimensions - 19 (48 cm) Wide (standard rack panel) x 10.5 (27 cm) High x 16 (41 cm) Deep (front panel back). Handles extend 1 5/8 (4.1 cm) forward of the front panel. Output connectors extend 1 behind rear panel.Weight - 110 lbs, Net 116 lbs shippingTubes Required - 4 - Matched pair 6550 (low gas) Power Output Comes with the ORIGINAL BOX. I dont have the manual, but it can be easily obtained online for free. This is a very large, VERY HEAVY piece of equipment. I will ship via UPS only as theyll have the best prices and are best equipped to handle something like this. Yes, I know that shipping is expensive. I will cover additional insurance and signature confirmation. Local pickup is acceptable and super cool! Any questions just ask, thanks for looking!

I had this pair of Mono Block M300 since 1994 and they are working great and sound radicular powerful and can sound compatible to McIntosh MC275 . The front ends were designed with Solid State operational amplifier to couple 8 pieces of 6550 Power Tube for each Mono Block. The output Transformer was designed with trifilar coils for coupling with plate, gride, and cathode, i.e., that is very similar to the original McIntosh MC275 power amplifier. For modern MC275, the output transformer is designed with only bifilar, one set of coil omitted to save cost. But they did not sound like their original MC275 anymore, very close to Solid State Power Amplifier. You can check with their schematics for the detail of their output transformers. This Audio Research M300 had the sound quality similar to original MC275 from 1960 units with 4 X RMS power output of MC275.The price in the listing is for a pair of mono block Audio Research M300 power amplifier in working condition. You can go Audio Research website to download their service manual with schematic.Because I am planning to move back to my motherland, I have to clear out all fantastic Audio amplifier collections over half a century.

MUST PURCHASE BOTH UNITS TO COMPLET THE SALESOLD AS MONO UNITS. MUST PURCHASE BOTH AS A SET. DUE TO SHIPPING UNITS A RE PRICED SEPARATELY SOLD AS IS UNITS PULLED OUT OF STORAGE MAY WORK OR NOT, MAY NEED NEW 6550 TUBESBOTH UNITS WHERE IN GOOD WORKING ORDER BEFORE BEING PLACED IN STORAGE FOR 18 MONTHS AUDIO RESEARCH M300 Mk II Triode Mode 150 WattsPOWER OUTPUT = TRIODE 150 watts minimum continuous at 8 ohms from 16Hz to 20kHz with less than 0.8% total harmonic distortion (typically below .005% at 1 watt). Approximate actual power available at clipping; 330 watts (1kHz). (Note that actual RMS power output is dependent upon both line voltage and ‘condition’ i. e.: if power line has high distortion, maximum power will be affected adversely, although from a listening standpoint this is not very critical.)POWER TUBES 6550 POWER BANDWITH = (-3dB points) 10Hz to 60kHzINPUT SENSITIVITY = 0.9V RMS for rated outputINPUT IMPEDANCE = 60k ohms, nominalINPUT BALANCED XLROVERALL NEGATIVE FEEDBACK = 20dBPOWER REQUIREMENT = 105-125VAC 60Hz (210-240VAC 50Hz) 900 watts at rated output. 450 watts at idle - 130 watts at standbyDIMENSIONS = 19 (48 cm) W (standard rack panel) x 10½ (27 cm) H x 16 (41 cm) D (front panel back). Handles extend 1 ? (4.1 cm) forward of the front panel. Output connector extends 1 behind rear panel.110 lbs. (50 kg) Net; 128 lbs. (57 kg) ShippingS/N 98236003S/N 98336001SOLD AS MONO UNITS MUST PURCHASE BOTH AS A SET. DUE TO SHIPPING UNITS A RE PRICED SEPARATELY SOLD AS IS NON-RETURNABLE UNITS PULLED OUT OF STORAGE MAY WORK OR NOT, MAY NEED NEW 6550 TUBES