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ART300 Mono Valve Power Amplifiers (Our in-house review sample)

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Our In-house review sample of a pair of conrad-johnson's flagship mono valve power amplifiers, the ART300.


Limited to 125 pairs worldwide.


ART300 mono-block amplifiers

In celebration of their 40th anniversary, conrad-johnson introduced the ART300 mono-block amplifier.

These amplifiers are designed for our own reference use as well as for industry professionals and dedicated audiophiles. As with previous anniversary products, these amplifiers will be offered as limited editions, with just 125 pairs of the ART300 to be sold through selectedconrad-johnson dealers and distributors.

The ART300 amplifiers embrace cj's firm belief that the surest path to both state-of-the-art musicality and exceptional reliability is to keep the circuits simple and build them with the finest available parts.

The audio circuit of these amplifiers has just three elements, each as simple as possible, and each essential to the operation of the amplifier. A voltage gain amplifier (a single triode) is direct-coupled to a cathode coupled phase inverter (each phase handled by a single triode), which in turn drives the output stage. Power is developed by KT150 output tubes, chosen for their musical accuracy, high power, and reliability. Two pairs are used to produce 300 Watts in the mono ART300. A small amount (about 12 dB) of loop negative feedback reduces distortion and achieves a sufficiently high damping factor to control reactive loudspeaker systems. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed.BuiltinLED bias indicators allow the user to make this adjustment using only the supplied adjustment tool.

Separate, low impedance, discrete dc power supply regulators are provided for the input and phase-inverter stages, thoroughly isolating these stages from the power demands of the output stage. These power supplies are designed to maintain a rock solid supply at all audio frequencies.

The ART300 amplifiers maintain the exacting quality standards for which conrad-johnson is internationally known.

Resistors are precision laser-trimmed metal foil types. CJD Teflon dielectric capacitors are used for coupling the inverter stage to the output stage, and to bypass the large value polypropylene capacitors in the regulated power supplies. Proprietary wide-bandwidth output transformers contribute to excellent high frequency performance. Even the machined gold plated OFC connectors and the internal wiring have been carefully selected for optimal sonic performance. Attention to every detail enable us to extract the full potential from our circuit designs and ensures that our products will perform to this potential for years to come. The ART300 are built without compromise to achieve a new standard in musical performance, and they are built to last.

Power: ART300 Amplifier

300 Watts rms from 30 Hz to 15 KHz at no more than 1.5 % THD into 4 ohms (also available connected for 16 ohm loads)


1.0V rms to rated power

Frequency Response (at 10 watts)

20 Hz to 20 kHz, +/- .25 dB

Hum and Noise

108 dB below rated power 

Input Impedance

100 kOhms

Tube Complement

ART300 – 2 x 6922, 4 x KT150


16.3125D x 19W x 8.75H inches


ART300 73 lbs.