Awarded Product of The Year 2009 by The Absolute Sound. Esoteric has introduced a 3 stage tube amplifier that can be used as a direct stereo power amplifier or as an integrated (line level), power amplifier. This new hybrid technology incorporates proprietary circuitry and "cutting edge" tube technology.
The A-100 provides a minimum of 90 watts (Minimim 45 wrms), power output from 4, KT-88's in UL-push/pull operation driven with a direct coupled cathode follower. The cathode follower and voltage amplification stage is directly coupled to form a triple stage combining a variable self-biasing system and a zero voltage control system. The bias system used is an advanced active biasing circuit. This system compensates for fluctuations in bias voltage as supplied to the output stage by detecting cathode current and output level demand. This bias control implementation improves linearity and performance of the output stage by maintaining optimum voltage control. The innovative zero voltage control system stabilizes the cathode follower DC output level to improve operation of directly-coupled circuit components. This occurs in an end to end process from the driver stage to the output stage. Both of these circuits combine to improve the stability and the clarity of the amplifier's output.
The A-100 features a newly designed custom output transformer designed to achieve highly delicate and precise musicality. The amplifier uses specially treated copper foil as the 2nd order coil. This design maintains very tight coupling properties between the 1st order coil. All stages except the KT-88 are powered by fully stabilized power supplies. With this innovative power supply design, the A-100 reproduces an exceptionally deep and finely detailed soundstage.
All tubes except the KT-88 are DC heated. Hum noise is reduced by this heater design. Power supply and output transformers are held by an extremely rigid 'H' structure and circuit components reside in a block configuration surrounding this mainframe design. The massive chassis construction isolates unwanted vibrations and resonance between circuit components and power supplies.
The A-100 is designed for pure power amplification but it also works as an integrated (line level), amplifier by selection from an operating switch on the rear panel designating DIRECT or LINE IN. LINE IN mode activates an input selector (RCA x3 / XLR x1), and also a high quality volume control.
For LINE IN operations an illuminated remote control is included.