Parasound A 31 manual Parasound a 31 Design Overview, Bare Speaker Wire Ends, Parts Selection

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1. Your Cable TV or Satellite receiver box might require a Cable TV ground isolator.

2. Use balanced input lines with your Parasound A 31. (See Balanced and Unbalanced Lines in this section).

3. When rack mounting, always use the insulated “shoulder” washers. These break the ground loops caused by metal-to-metal contact between the rack, the components, and their rack-mount bolts. Extra washers are available from rack manufacturer Middle Atlantic Products, www.middleatlantic.com.

Bare Speaker Wire Ends

If you plan to use connections with bare wire ends, use a wire stripper to remove just enough insulation to expose a 1⁄2" (13 mm) length of bare wire. You can insert the stripped wire into the hole that goes sideways through the terminal’s metal post. Before inserting the wire, twist its bare strands to prevent any of the strands from making contact across the two speaker terminals. If you have a soldering iron, you can “tin” (apply a small amount of molten solder) to each stripped bare wire to prevent it from unraveling, fraying and oxidizing.

Parasound A 31 Design Overview

Circuit Designed by John Curl

Parasound design consultant John Curl has been a legend among audiophiles and electronic engineers for decades. He pioneered measurements to correlate musical accuracy with the materials used in parts, worked with world-class touring companies, has designed highly coveted audio classics, including the original Mark Levinson JC-2, Denneson JC-80, Vendetta Phono Preamplifier, and CTC Blowtorch preamplifiers; master recorders for Wilson Audio and Mobile Fidelity; and the mixing consoles used in live concerts by The Grateful Dead and the Montreux Jazz Festival in Switzerland.

As our featured amplifier designer since 1990, he has created many products that have earned Parasound worldwide acclaim. John is particularly proud of what he and Parasound have accomplished together: “The circuits I design for Parasound are extremely sophisticated and are typical of products that are far more expensive. I can’t think of any other audio products that offer nearly as much bang for the buck.”

Parts Selection

Every part within the A 31 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 amplifier and an outstanding amplifier.

The Power Supply

The heart of the power supply is a 1.5 kVA toroid power transformer, chosen for its efficiency, low hum field, and high power rating. Encapsulating this massive power transformer in an epoxy-filled steel canister assures ultra-quiet performance.

The A 31 power transformer employs multiple independent secondary windings so that each amplifier channel has its own power supply, assuring more than ample DC voltage at all

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Contents OWNER’S Guide Important Safety Instructions Table of Contents Parasound Staff Keeping Records for Future Reference Important Warranty informationThank You for Choosing Parasound Unpacking Your a Unpacking Your a 31 & Placement GuidelinesAC Mains Voltage Rack Mounting Your Parasound a Audio Connections Audio Input ConnectionsSpeaker Terminals Speaker Wire Length and Gauge thicknessSpeaker Connections Correct Speaker Polarity is ImportantGain Control Settings When to Set the Gain Control Knobs Above or Below NormalAudio Position Automatic on/off Turn On OptionsManual Position 12V Position Automatic on/off12V In Jack AC Power CordVolt Jacks 12V Loop Out JackFront Panel Operation On-Off ButtonGround Loops Eliminating Hum and Buzz Technically SpeakingBalanced and Unbalanced Lines Parasound a 31 Design Overview Bare Speaker Wire EndsPower Supply Circuit Designed by John CurlAudio Circuit Path Topology Complementary ConfigurationRelay-Bypassed Soft Start Circuit Input StageTotal Protection DC Servos Output StageClass A-A/B Operation Total Protection RelaysNo sound from speakers Problems and RemediesUnit will not turn on Background Hum or HissRepair or Service Are You Having Difficulty?Specifications Parasound Products, Inc McKinnon Ave, San Francisco, CA