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A 51 Amplifier
Owner’s Guide
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THANK YOU! Congratulations and Thank You for Choosing Parasound Your new Parasound Halo Series A 51 power amplifier presents the latest advancements in amplifier technology. The A 51 is built to the strict quality and performance standards set by Parasound. We’re proud to offer you this exceptional audio component that will bring you many years of enjoyment and dependability. Here at Parasound, we design our products to perform at a higher level of flexibility and sonic performance than you may
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TABLE OF CONTENTS A 51 Amplifier PLACEMENT GUIDELINES FOR YOUR A 51 2 CONNECTING A SURROUND CONTROLLER TO THE BALANCED INPUTS ON YOUR A 51 3 CONNECTING A SURROUND CONTROLLER TO THE UNBALANCED INPUTS ON YOUR A 51 4 CONNECTING YOUR SPEAKERS TO THE A 51 5 MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS 6 CONNECTING AN EXTERNAL DC SOURCE FOR AUTOMATIC ON-OFF 7 UNDERSTANDING THE INDICATORS ON THE A 51 8 CONNECTING THE AC POWER CORD 9 MAINTAINING YOUR A 51 10 TROUBLESHOOTING GUIDE 11 SERVICING YOUR A 51 12
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2 PLACEMENT GUIDELINES FOR YOUR A 51 Power amplifiers are usually heavier and generate more heat than other components. To avoid damage to the A 51 or other equipment and to reduce risk of fire, you must follow these guidelines: • A cable with a 2.5 mm sub-mini plug on each end (provided). • Place the A 51 on a separate shelf that will adequately support its weight. • Keep it away from heat sources such as air ducts or radiators. • Avoid placing it on carpeting or another material that might obs
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CONNECTING A SURROUND CONTROLLER 3 TO THE BALANCED INPUTS ON YOUR A 51 Left and Right Balanced Input Jacks Balanced connections will give you the best sound. If your surround controller has balanced XLR output jacks, we recommend that you connect them to these inputs. Refer to the Balanced and Unbalanced Lines in the Technically Speaking section for additional information about why we recommend using balanced lines. What You’ll Need: Male • Five balanced interconnect cables with XLR connect
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RCA Plugs CONNECTING A SURROUND CONTROLLER 4 TO THE UNBALANCED INPUTS ON YOUR A 51 Ch 1-5 Unbalanced Inputs Use these inputs if your surround controller doesn’t have balanced output connectors or if you simply prefer to use unbalanced connections. What You’ll Need: • Five shielded interconnect cables with RCA plugs • A surround controller with five RCA output jacks Before Connecting ❑ Leave the AC cord on the A 51 disconnected until you have made all other connections to prevent any surprise
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5 CONNECTING YOUR SPEAKERS TO THE A 51 Speaker Terminals The A 51 speaker terminals accept speaker wires with banana plugs or bare ends. Refer to Bare Wire Speaker Termination in the Technically Speaking section for information about bare wire termination. Common Speaker Connectors What You’ll Need: • Five lengths of AWG 16 or thicker speaker wire with banana plugs or bare ends • Five loudspeakers Dual Single Stripped Banana Plug Banana Plug AWG wire Before Connecting ❑ Remove power to all the
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6 MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS You can manually turn the A 51 on and off with its front panel On-Off button. It can also be triggered to turn on and off automatically when your preamplifier, surround controller, or system controller is turned on and off. Manual On-Off from the Front Panel If you want to manually turn on and off the A 51 at any time, you need to first select the Manual On- Off option by placing the Auto T urn On switch (on the rear panel) to its middle Man (Manual) p
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CONNECTING AN EXTERNAL DC SOURCE FOR 7 AUTOMATIC TURN ON-OFF To automatically turn on and off the A 51 with an external DC voltage, choose the DC Triggering option by moving the Auto Turn On switch on the rear panel to its lower 12V position. What You’ll Need: • A cable with a 2.5 mm sub-mini plug on each end (provided) • A “control” component with +9Vdc to +12Vdc trigger voltage 2.5 mm sub-mini plug Before Connecting ❑ Remove Power to all the components in your audio system. ❑ Make sure the A
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8 UNDERSTANDING THE INDICATORS ON THE A 51 a AC Present Indication When the A 51 is plugged into a live AC outlet, a soft blue halo glows behind its On-Off button and its red “P” Badge glows faintly. These indicate that the unit is plugged into a live AC outlet, even when it is turned off. b On, Off and Fault/Protection Status Indicators Whenever the A 51 is turned on, the soft blue glow behind its On-Off button will change to red for about five seconds as its internal circuits stabilize. The
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9 CONNECTING THE A 51 AC POWER CORD AC Power Connections We recommend that you plug your A 51 into the same AC wall outlet or power strip that pow- ers your other audio components, especially the preamplifier or system controller. Having all the audio components on the same power circuit helps prevent hum caused by possible ground loops. The A 51 requires AC power that is continuous rather than switched on and off. 110 V - 120 V or 220 V - 240 V Operation The A 51 can operate on either 110 V -
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10 MAINTAINING YOUR A 51 Your Parasound A 51 power amplifier requires no periodic maintenance and has no user- serviceable parts inside. To avoid the risk of electric shock, do not remove its top cover. The amplifier’s exterior can easily be cleaned with a soft cloth pre-moistened only with a few drops of water or glass cleaner. Main Power Fuse If this fuse blows, please contact Parasound Technical Service for further advice. Notes:
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11 TROUBLESHOOTING GUIDE TROUBLE PROBABLE CAUSE REMEDY Power cord is disconnected Connect power cord No power Auto Turn On selector switch Check for correct position of the Auto is in wrong position Turn On switch AC fuse blown Replace with same value fuse DC trigger source wired in Check polarity of DC source with a voltmeter. Auto turn on doesn’t reverse or voltage too low Try connecting a 9V battery to the 12V DC input function with a trigger voltage Auto Turn On selector switch Make sure A
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12 SERVICING YOUR A 51 If All Else Fails –Call Us for Help Call your Parasound dealer or Parasound’s Technical Service Department toll free at 1-866-770-TECH (8324). We can often solve the problem with simple diagnostic tests you can per- form yourself. If we determine that your A 51 will need further inspection or servicing, we will: a) Refer you to an authorized Parasound repair center near you, or b) Authorize return of the unit to us and advise you of the correct procedure. Procedure for R
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13 TECHNICALLY SPEAKING minus a negative 1 Volt, or 2 Volts total. External hum Audio Trigger Sensitivity Adjustment and noise that somehow gets into a balanced line is The Audio Sensitivity Control sets the threshold of the common to both its positive and negative conductors audio trigger signal. You can adjust this level from a with respect to ground. Therefore, it is canceled or maximum sensitivity of 50 mV (fully counterclockwise) rejected by the differential input circuit. to a minimum sens
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14 TECHNICALLY SPEAKING continued hum (or 50 Hz hum in regions with 50 Hz AC). The 1. Use balanced input lines with your Parasound A 51. harmonics of these frequencies (120 Hz, 240 Hz, 480 (See Balanced and Unbalanced Lines in this section). Hz or 100 Hz, 200 Hz, 400 Hz) may add buzz in addi- 2. When rack mounting, always use the insulated tion to the hum. “shoulder” washers. These break the ground loops The ideal of zero voltage ground for all the compo- caused by metal-to-metal contact betwe
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15 PARASOUND A 51 DESIGN OVERVIEW Circuit Designed by John Curl Each channel’s +/- 80 Vdc B+ and B- supply rails use Parasound design consultant John Curl has been a high-speed rectifier diodes and four enormous 8,200 uF legend among audiophiles and electronic engineers electrolytic filter capacitors, chosen for their low for decades. He pioneered measurements to corre- Equivalent Series Resistance (ESR) and dielectric absorp- late musical accuracy with the materials used in parts, tion. In addi
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16 PARASOUND A 51 DESIGN OVERVIEW continued The Driver Stage Total Protection - DC Servos The driver stage provides critical amplification for Direct Current (DC) burns out speakers. Every power which we employ a complementary matched pair of amplifier must have some way to insure that DC from MOSFETs selected for their tube-like sonic qualities. its power supply never reaches its + or - speaker ter- MOSFETs tend to generate less odd-order harmonic minals. Most amplifiers simply use trim control
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17 PARASOUND A 51 SPECIFICATIONS Power Output - All Channels Driven Input Sensitivity for 28.28 V Output into 8 Ω 250 watts RMS x 5, continuous, Unbalanced: 1 V 20 Hz - 20 kHz, 8Ω Balanced: 1 V per leg 400 watts RMS x 5, continuous, S/N Ratio 20 Hz - 20 kHz, 4Ω > 112 dB, input shorted, IHF A-weighted > 102 dB, input shorted, unweigh Current Capacity 60 amperes peak per channel Damping Factor > 1100 at 20 Hz Slew Rate > 130 volts per microsecond DC Trigger Requirements +9 Vdc to +12 Vdc, 2 mA F
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Parasound Products, Inc. 950 Battery Street, San Francisco, CA 94111 415-397-7100 / Fax 415-397-0144 www.parasound.com
