ATI P1000-1 User Manual

P1000

STEREO TURNTABLE AMPLIFIER

OPERATING AND MAINTENANCE MANUAL

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GENERAL

A turntable preamplifier is a deceptively simple device and has been the subject of an amazing amount of poor design. The seemingly simple matter of attaching a high capacitance load (in the form of the RIAA feedback network) onto a preamp stage which does not have adequate current drive capacity, guarantees Slew Rate Distortion, Transient Intermodulation Distortion, rising high frequency harmonic distortion and probably a few other distortions we haven’t named as yet. This problem is common to almost all existing preamps.

A second common fault is designing too much gain into the input equalized state to compensate for a mediocre noise figure in the following output stage with the result that the input headroom is severely limited. Since groove stylus velocities of digitally mastered and direct disc recordings exceed 50 cm/sex peaks regularly with even greater dynamic range expected in the future, a high output cartridge can readily strain the typical 80 mV maximum input limit of typical preamps.

ATI has eliminated these two problems by use of a new integrated circuit developed for the European professional audio market and recently made available to the US market through two major manufacturers. This chip incorporates a low noise input stage designed for use with the low source impedances typical of phono cartridges. In addition, this chip has an output stage free of crossover distortion and of sufficient current swing capability to drive 600 ohm loads to full supple voltage. An inherent slew rate capability of 13 volts per microsecond, a 50 KHz gain bandwidth product and 100 db open loop gain make this chip an ideal device for audio applications.

Excellent low noise performance in both input and output stages allows to the MicroAmp to operate at reduced input stage gain yielding an input swing capability of almost 1 V p-p at 1 KHz while preserving excellent noise performance. The high Push Pull output capability allows the first stage to drive the RIAA equalization network with ease and without slew rate limiting to degrade high frequency performance. The high open loop gain provides 46 db loop gain for 200 to 1 distortion reduction even below 50 Hz where the equalized stage is operating at maximum gain.

The high output also allows the output stage to drive the load directly on through a simple 1:1 isolating transformer. ATI proves three models of each MicroAmp; Transformer outputs for high RF field environments. A balanced, differential output stage version (bridge circuit) is also available. It is suitable for low RF environments where balanced output lines are required for hum rejection in long runs and the minor performance degradations of an output transformer are not desired. In addition a simpler, lower cost single ended output model with full 600 ohm drive capability is designed for use for short runs in low RF environments.

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