The Audio Research Reference 300 MkII monoblocks are tube power amplification at its most unapologetically grand—massive, glowing, and absolutely regal in the way they command a system. Delivering 300 watts of pure tube authority from banks of 6550s, these amps don’t just drive speakers—they take control of them, with a combination of grip, scale, and tonal beauty that very few tube designs have ever matched.
Sonically, they’re classic ARC at the peak of its Reference-era prowess: huge dynamic swings, a holographic soundstage you can practically step into, and mids that bloom with lifelike presence without ever slipping into syrup. Highs are extended and airy, bass is shockingly tight for tube muscle of this size, and the overall presentation is one of effortless, unforced power.
Visually, the Ref 300 MkIIs radiate that iconic ARC laboratory aesthetic—industrial, purposeful, and glowing with the warm confidence of dozens of tubes ready to make music feel enormous. These monoblocks aren’t just amplifiers; they’re endgame statements for listeners who want the emotional reach of tubes and the scale of a powerhouse.
- Production
- 2001
- Condition
- 9.5/10
- Serial No.
- 31301501 / 31301502
- Orig. MSRP
- $29,990
- Restoration
- Both units have new matched octets of Tung-Sol 6550's
- Both units have 3 new 6AS7 tubes in the power supply
- Installed jumpers to bypass faulty circuit board traces (both)
- Replaced 8 resistors in power supply (both)
- Replaced 2 mosfet power supply regulators (both)
- Replaced 2 zener diodes in power supply (both)
- Replaced 4 film capacitors in power supply (both)
- Adjusted bias (both)
- Factory Specs
Power output
280 watts continuous at 16 ohms from 20Hz to 20kHz with less than 1% total harmonic distortion (typically less than .05% at 1 watt). Actual maximum power available (at the point of clipping) is dependent upon the following: 1) power line voltage. 2) power line condition (ie: regulation, distortion). 3) type and brand of power output tube used. Typical power under average circumstances will be around 290 watts. Maximum power under ideal conditions will be around 300 watts.
Power bandwidth
(-3dB points) 12Hz to 100kHz
Frequency response
(-3dB points at 1 watt) 0.5Hz to 160 kHz
Input sensitivity
1.75V RMS balanced for rated output. (32dB gain into 16 ohms)
Input impedance
200K ohms balanced
Output taps
1, 2, 4, 8, 16 ohms
Output regulation
Approximately 0.8dB 16 ohm load to open circuit
Overall negative feedback
10dB
Damping factor
Approximately 11
Hum & noise
Less than 0.2mV RMS –110dB below rated output (IHF weighted, input shorted, 16 ohm output)
Power supply energy storage
Approximately 448 joules
Power requirements
105–125VAC 60Hz (210–250VAC 50Hz) 900 watts at rated output, 1200 watts maximum, 480 watts at idle, 280 watts standby
Tube complement
(4 matched pairs) 6550C power output, (4) 6H30 triodes, (3) matched 6A57, (2) 6N1P.
Dimensions
19" (48.3 cm) W x 10½" (26.7 cm) H x 23½" (59.7 cm) D. Handles extend 1½" (3.8 cm) forward
Weight
132 lbs. (59.9 kg) Net; Shipped in pairs, 410 lbs. (186 kg) per pair
- Documentation
- https://arcdb.ws/Database/REF300/ARC_REF300MKII_manual.pdf
- The History of Audio Research
- Audio Research Corporation, affectionately known to fans as ARC, was founded by William Z. Johnson, who began designing custom audio electronics in the early 1950’s and who also operated a specialty audio retail store until the mid-1960’s. Johnson’s efforts almost single-handedly revived vacuum-tube designs at a time...
[ Read More ]
- Liner Notes
When introduced a little over two years ago, the REF300 monoblocks created as much of a stir among audiophiles and music lovers as the larger REF600s did when first introduced in late 1995. Well, we're happy to announce that REF300 owners now have good reason to be excited all over again with the introduction of the new and improved REF300MKII.
First, the sonic improvements embodied in the MKII version are nothing short of monumental. The MKII has much more apparent speed than the original, and conveys microdynamics and subtle timbrel details with much higher resolution. Image focus, the sense of body given to notes and voices, and tonal coherence from high frequencies to bass notes are all noticeably better. There is a sense of seamless resolution in the sound stage which, through an appropriate loudspeaker system, is simply mesmerizing with well-recorded material. Finally, the sense of power conveyed by these amplifiers is much more apparent on big dynamic swings -- they have effortless muscle when called for, yet they are capable of amazing delicacy in the next moment. This uncanny ability conveys the same kind of natural intensity and immediacy that listeners have heard from the very successful VTM200 monoblocks.
These sonic improvements are the result of important advances in power supply regulation and driver-stage technology developed over the last year by Audio Research engineers. Incorporating the proven J-FET input for initial gain and low noise, additional gain is accomplished by a 6N1P twin triode, which is direct-coupled to four 6H30 twin triodes used as cathode followers to drive the 6550C output stage. These tubes in the audio gain path are run very conservatively for long service life. On the power supply side, one 6N1P preregulator drives three rugged 6AS7 regulator tubes. With these improved regulators, the power supply and driver circuits are now able to track the incoming signal much more quickly. The result is sonic power combined with delicacy, air and the trademark High Definition® sound.
Control functions, input and output configuration remain unchanged on the MKII, with the exception of the addition of a 12V input /output for remote linkage in custom installations.
- Stock No.
- 9225372336349
The Audio Research Reference 300 MkII monoblocks are tube power amplification at its most unapologetically grand—massive, glowing, and absolutely regal in the way they command a system. Delivering 300 watts of pure tube authority from banks of 6550s, these amps don’t just drive speakers—they take control of them, with a combination of grip, scale, and tonal beauty that very few tube designs have ever matched.
Sonically, they’re classic ARC at the peak of its Reference-era prowess: huge dynamic swings, a holographic soundstage you can practically step into, and mids that bloom with lifelike presence without ever slipping into syrup. Highs are extended and airy, bass is shockingly tight for tube muscle of this size, and the overall presentation is one of effortless, unforced power.
Visually, the Ref 300 MkIIs radiate that iconic ARC laboratory aesthetic—industrial, purposeful, and glowing with the warm confidence of dozens of tubes ready to make music feel enormous. These monoblocks aren’t just amplifiers; they’re endgame statements for listeners who want the emotional reach of tubes and the scale of a powerhouse.
Production
2001
Condition
9.5/10
Serial No.
31301501 / 31301502
Orig. MSRP
$29,990
Restoration
- Both units have new matched octets of Tung-Sol 6550's
- Both units have 3 new 6AS7 tubes in the power supply
- Installed jumpers to bypass faulty circuit board traces (both)
- Replaced 8 resistors in power supply (both)
- Replaced 2 mosfet power supply regulators (both)
- Replaced 2 zener diodes in power supply (both)
- Replaced 4 film capacitors in power supply (both)
- Adjusted bias (both)
Factory Specs
Power output
280 watts continuous at 16 ohms from 20Hz to 20kHz with less than 1% total harmonic distortion (typically less than .05% at 1 watt). Actual maximum power available (at the point of clipping) is dependent upon the following: 1) power line voltage. 2) power line condition (ie: regulation, distortion). 3) type and brand of power output tube used. Typical power under average circumstances will be around 290 watts. Maximum power under ideal conditions will be around 300 watts.
Power bandwidth
(-3dB points) 12Hz to 100kHz
Frequency response
(-3dB points at 1 watt) 0.5Hz to 160 kHz
Input sensitivity
1.75V RMS balanced for rated output. (32dB gain into 16 ohms)
Input impedance
200K ohms balanced
Output taps
1, 2, 4, 8, 16 ohms
Output regulation
Approximately 0.8dB 16 ohm load to open circuit
Overall negative feedback
10dB
Damping factor
Approximately 11
Hum & noise
Less than 0.2mV RMS –110dB below rated output (IHF weighted, input shorted, 16 ohm output)
Power supply energy storage
Approximately 448 joules
Power requirements
105–125VAC 60Hz (210–250VAC 50Hz) 900 watts at rated output, 1200 watts maximum, 480 watts at idle, 280 watts standby
Tube complement
(4 matched pairs) 6550C power output, (4) 6H30 triodes, (3) matched 6A57, (2) 6N1P.
Dimensions
19" (48.3 cm) W x 10½" (26.7 cm) H x 23½" (59.7 cm) D. Handles extend 1½" (3.8 cm) forward
Weight
132 lbs. (59.9 kg) Net; Shipped in pairs, 410 lbs. (186 kg) per pair
Documentation
https://arcdb.ws/Database/REF300/ARC_REF300MKII_manual.pdf
The History of Audio Research
Audio Research Corporation, affectionately known to fans as ARC, was founded by William Z. Johnson, who began designing custom audio electronics in the early 1950’s and who also operated a specialty audio retail store until the mid-1960’s. Johnson’s efforts almost single-handedly revived vacuum-tube designs at a time...
[ Read More ]
Liner Notes
When introduced a little over two years ago, the REF300 monoblocks created as much of a stir among audiophiles and music lovers as the larger REF600s did when first introduced in late 1995. Well, we're happy to announce that REF300 owners now have good reason to be excited all over again with the introduction of the new and improved REF300MKII.
First, the sonic improvements embodied in the MKII version are nothing short of monumental. The MKII has much more apparent speed than the original, and conveys microdynamics and subtle timbrel details with much higher resolution. Image focus, the sense of body given to notes and voices, and tonal coherence from high frequencies to bass notes are all noticeably better. There is a sense of seamless resolution in the sound stage which, through an appropriate loudspeaker system, is simply mesmerizing with well-recorded material. Finally, the sense of power conveyed by these amplifiers is much more apparent on big dynamic swings -- they have effortless muscle when called for, yet they are capable of amazing delicacy in the next moment. This uncanny ability conveys the same kind of natural intensity and immediacy that listeners have heard from the very successful VTM200 monoblocks.
These sonic improvements are the result of important advances in power supply regulation and driver-stage technology developed over the last year by Audio Research engineers. Incorporating the proven J-FET input for initial gain and low noise, additional gain is accomplished by a 6N1P twin triode, which is direct-coupled to four 6H30 twin triodes used as cathode followers to drive the 6550C output stage. These tubes in the audio gain path are run very conservatively for long service life. On the power supply side, one 6N1P preregulator drives three rugged 6AS7 regulator tubes. With these improved regulators, the power supply and driver circuits are now able to track the incoming signal much more quickly. The result is sonic power combined with delicacy, air and the trademark High Definition® sound.
Control functions, input and output configuration remain unchanged on the MKII, with the exception of the addition of a 12V input /output for remote linkage in custom installations.
Stock No.
9225372336349
