PARASOUND P 3 DESIGN OVERVIEW

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Parts Selection

Every part within the P 3 is carefully chosen for its accuracy and reliability. Metal film resistors with 1% tolerance are selected for their precision and because their values don’t drift as they heat up during operation. Polypropylene and mica capacitors are used extensively for their superior linearity and low dielectric absorption. Semiconductors are selected for superior performance in their specific roles in the circuit. Gold has the best conductivity of any metal, so we use high quality gold-plated input connectors and speaker terminals. The double-sided circuit boards are FR4 glass epoxy for long-term durability. The chassis is made of heavy gauge steel to safely house the internal circuitry. This attention to detail when selecting parts makes the difference between a very good preamplifier and an outstanding one.

The Power Supply

The P 3 power supply begins with a large toroidal power transformer that is chosen for its high efficiency, low radiated hum, and high current rating. Encapsulating the power transformer in an epoxy- filled steel canister assures ultra-quiet performance. The audio signal path circuits and the switching/control circuits have independent closely regulated power supplies. This preserves the purity of the audio signal by preventing interference between the circuits. We also use a hand-made detachable audiophile-grade AC cord to deliver the AC voltage to the power transformer.

To create the DC voltage, we use high-speed rectifier diodes and large-capacity Nichicon electrolytic filter capacitors that are famous for low dielectric absorption and Effective Series Resistance (ESR). Two precision 6,800 uF filter capacitors are used for the audio signal path B+ and B- rails, plus two 2,200 uF capacitors for the control/switching circuitry. In addition, these filter capacitors are bypassed with polypropylene capacitors to help reduce AC ripple and to eliminate noise and interference that is generated in AC power lines from computers and other appliances in the home.

Audio Circuit Path Topology

Direct Inputs 1 and 2 of the Parasound P 3 preamplifier are selected by hermetically sealed relays with gold contacts. The other inputs are switched by a precision CMOS IC with outstanding characteristics for signal overload, low distortion and crosstalk, and wide frequency response. This provides longer-term reliability than the mechanical rotary selector switches used in most preamplifiers. The P 3 also employs the newest Burr-Brown OPA 2134 integrated circuits with FET input stages for audio gain functions in the audio signal path. They are laser-trimmed for precision and boast incredibly low noise and distortion specifications. We run the OPA 2134s at very high current to assure pure class A for linear performance and musical characteristics, without fatigue and harshness. The P 3 volume and balance controls are high-precision analog volume control ICs which provide very close level matching between channels, far closer than is possible with a manual or motor-driven mechanical potentiometer.

Functionality

The P 3’s elegant front panel control and status display make it easy to use. Its remote handset provides convenient control over both the P 3 and the matching Parasound T 3 Tuner. Separate On and Off remote commands permit system programming for unambiguous on/off status. Features that facilitate P 3 system integration include its RS232 interface for more robust control than IR, wired external IR input and loop out, and DC trigger input and output. These make the P 3 as functional as it is great sounding.