Reference 300MKII Vacuum Tube Monaural Power Amplifier

REFERENCE 300MKII Power Amplifier

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.

Factory upgrades are available. New regulation and driver tubes are included in the cost of the upgrade, as is a two-year Limited Warranty extension (90 days on vacuum tubes). Please contact our Customer Service Department to preschedule units for the MKII upgrade to avoid unnecessary delays. Improved sonic performance, a warranty extension and enhanced resale value: that's product support as only Audio Research offers.

Happy listening!

Model Reference 300MKII Specifications
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 (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.
TUBES REQUIRED: 4 Matched pair 6550C Power Output; (4) 6H30 triodes; (3) matched 6A57; (2) 6N1P.

The REFERENCE 300 has sufficient bias adjustment range to allow the use of any of the following output tube types: 6550, 6550B, 6550C, KT88, KT90, KT91, KT100.

The REFERENCE 300 as supplied from Audio Research is equipped with the Russian 6550C, which is our current choice for reliability and long service.

DIMENSIONS: 19" (48.3 cm) W x 10.5" (26.7 cm) H x (23.5" (59.7 cm) D. Handles extend 1.5" (3.8 cm) forward.

WEIGHT: 132 lbs. (59.9 kg) Net; Shipped in pairs, 410 lbs. (186 kg) per pair.

Specifications subject to change without notice.

Audio Research Corporation
3900 Annapolis Lane North
Plymouth, Minnesota USA 55447-5447
Phone: 763-577-9700 Fax: 763-577-0323
©2003 Audio Research