ART and ARTsa Amplifiers
The limited edition ART Amplifier is designed to be a reference amplifier for the use of industry professionals as well as dedicated audiophiles. Like its companion GAT Preamplifier, the ART Amplifier will be offered in an edition of just 250 units (125 pairs) to be sold through selected conrad-johnson dealers and distributors. Those who do not need the prodigious 275 watt power delivered by the mighty ART mono-blocks will want to consider the ARTsa Stereo Amplifier. Nearly identical cosmetically (one more tube in the front), it is exactly an ART amplifier divided into two channels, each producing a solid 140 watts.
At conrad-johnson, our approach to circuit design is predicated on the principle that the surest path to both state-of-the-art musicality and exceptional reliability is simple circuits constructed of the finest available parts. These ART amplifiers exemplify this basic principle. The audio circuit 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. For the ART mono-blocks, four pairs of KT120 output tubes, chosen for their musical accuracy, high power, and reliability, endow this amplifier with a muscular 275 watt output rating. For the ARTsa, two pairs of KT120 output tubes in each channel produce 140 watts of power per channel. A small amount (about 12 dB) of loop negative feedback reduces distortion and achieves a sufficiently high damping factor to control the reactive load typically presented by high-performance loudspeaker systems. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed. Built in LED bias indicators allow the user to make this adjustment using only the supplied screwdriver.
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.