audio research

Tube mono power amplifier.

From the ARC website

In late 1995, Audio Research introduced the REFERENCE 600 Monoblock Power Amplifiers and the companion Stereo Line Preamplifier, the REFERENCE ONE. Worldwide recognition of the sonic supremacy of these models was quickly forthcoming, with both models winning the hearts of many, many purchasers as well as audio reviewers.

But technology doesn't stand still -- especially at Audio Research! A number of ardent music lovers have asked for a REFERENCE power amplifier with slightly less output and more room-friendly dimensions. This amplifier is now available as the REFERENCE 300. Suggested U.S. retail price is $11,995 each or $23,990 the pair.

With almost 300 watts of vacuum-tube output power and vacuum-tube power supply regulation, the REF300 monoblocks incorporate a number of refinements over the original REF600 model. Among the many improvements are output-stage constant current bias regulation and redesigned power-supply voltage regulators. Although the REF300 is smaller, quieter and cooler-running (fewer output tubes and two internal cooling fans instead of four), many owners will never notice the reduction in output power compared to the REF600. Together, these changes result in an astonishing level of sonic improvement over the original REF600 design. Bass notes are defined with more body and accuracy; highs are better focused and more extended; and musical dynamics are more vividly portrayed against a backdrop of natural recorded ambience. The sense of "hearing through" the equipment is the best ever, in our opinion. One listen, and you will know that a new, higher standard for accurate music reproduction has once again been established.

At the same time, the convenience and flexibility of the original REF600 has been preserved. Front-panel controls and large, illuminated analog meters allow easy output-tube biasing, A.C. line voltage monitoring, and power-output observation. In addition, a 20-amp three-pin A.C. connector with detachable heavy-gauge line cord are now standard.




From the ARC website

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). Improved sonic performance, a warranty extension and enhanced resale value: that's product support as only Audio Research offers.


MSRP (US new retail)
$25,990/pair. Later increased to $29,990/pair.


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). 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 10 dB
Damping factor 11
Slew rate  
Rise time  
Hum & noise Less than 0.2mV RMS –110dB below rated output (IHF weighted, input shorted, 16 ohm output)
Power supply energy storage 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 REFERENCE 300: (4 matched pairs) 6550C power output, (4) 6550C regulators, (1) 6922 regulator rmplifier, (4) 6922 driver, (4) 6922 input.
  REFERENCE 300 MKII: (4 matched pairs) 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.
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


Issue 128 (REFERENCE 300)