Developed as the mate to our award-winning PRE 1 and PRE 1L preamplifiers, the AMP 1 combines a robust, regulated power supply, sophisticated circuit topology, conservative operating parameters and efficient industrial design practices, into one uncompromising, yet affordable, stereo power amplifier product. The sonic result is an amplifier which is both fast, tonally neutral with the real power and control to adequately drive a surprisingly vast array of demanding speakers.

DESIGN FEATURES:

POWER SUPPLY: The heavy duty power transformer is conservatively designed for low temperature rise and moderate flux density, resulting in cool operation, low acoustic noise and long life. In addition, a large power supply reservoir for the high voltage is utilized, along with two solid state voltage regulators which provide electronic filtering, decoupling and voltage regulation for the low level input stages and the phase splitter/driver circuitry. A well filtered unregulated negative supply is also provided for fixed bias of the output stages so as to track any variation or drift in the AC mains voltage, keeping the quiescent current in the output relatively constant.

BIAS CIRCUIT: Individual potentiometers are provided for bias adjustment of each of the 4 output tubes. The use of individual bias controls allows balancing of the operating characteristics of each output tube for optimum performance and compensation for tube aging effects.

OUTPUT STAGE: The heart of a vacuum tube power amplifier, the output transformer, is the key to great performance. Utilizing the best materials (5.25 lbs of M6 grain-oriented silicon steel and soft drawn OHFC copper) and incorporating advanced bobbin winding techniques, we have been able to dramatically improve the performance of this, our latest generation, output transformer. Carefully balanced and interleaved windings insure the widest bandwith, with the lowest phase shift and distortion performance. The output stage consists of a pair of EL34/6CA7 power pentodes biased into class AB1 and configured in an ³Ultra Linear² manner. This "Ultra Linear" connection provides an intermediate operating point between a pentode and a triode, with the power output of a pentode and the low internal output impedance of a triode. Under these operating conditions, the tube functions as a pentode with a small amount of negative feedback applied to the screen grid, resulting in lower distortion products at the higher levels of operation.

OUTPUT TERMINATION: Separate 4 and 8 ohm taps, which are available via convenient rear panel output binding posts, allow the user to optimize the power output of the AMP 1 into any load. An additional 16 ohm tap is provided internally which may be optionally connected in place of the 4 ohm tap. A special compensation network in each output channel maintains constant load impedance at ultrasonic frequencies, making the AMP-1 ultra stable into difficult loads such as electrostatic speakers.

FEEDBACK: A moderate amount of overall negative feedback is use in the AMP 1. The benefits of this design practice include a reduction in the AMP 1ıs output impedance for increased damping factor, reduction of output distortion and increased bandwidth.