A 51 Amplifier Owner’s Guide
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.
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
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.
CONNECTING A SURROUND CONTROLLER TO THE BALANCED INPUTS ON YOUR A 51 3 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.
4 CONNECTING A SURROUND CONTROLLER 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.
CONNECTING YOUR SPEAKERS TO THE A 51 5 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.
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 OnOff option by placing the Auto Turn On switch (on the rear panel) to its middle Man (Manual) position.
CONNECTING AN EXTERNAL DC SOURCE FOR AUTOMATIC TURN ON-OFF 7 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 12 V 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.
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.
CONNECTING THE A 51 AC POWER CORD 9 AC Power Connections We recommend that you plug your A 51 into the same AC wall outlet or power strip that powers 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.
10 MAINTAINING YOUR A 51 Your Parasound A 51 power amplifier requires no periodic maintenance and has no userserviceable 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.
TROUBLESHOOTING GUIDE 11 TROUBLE PROBABLE CAUSE REMEDY No power Power cord is disconnected Connect power cord Auto Turn On selector switch is in wrong position Check for correct position of the Auto Turn On switch AC fuse blown Replace with same value fuse Auto turn on doesn’t function with a trigger voltage DC trigger source wired in reverse or voltage too low Check polarity of DC source with a voltmeter.
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 perform 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.
TECHNICALLY SPEAKING Audio Trigger Sensitivity Adjustment The Audio Sensitivity Control sets the threshold of the audio trigger signal. You can adjust this level from a maximum sensitivity of 50 mV (fully counterclockwise) to a minimum sensitivity of 250 mV (fully clockwise). If you set this control to 50 mV, the A 51 might be falsely triggered on by non-musical or noisy signals that can appear in the system, such as when you switch preamp inputs at high volume levels.
14 TECHNICALLY SPEAKING continued hum (or 50 Hz hum in regions with 50 Hz AC). The harmonics of these frequencies (120 Hz, 240 Hz, 480 Hz or 100 Hz, 200 Hz, 400 Hz) may add buzz in addition to the hum. The ideal of zero voltage ground for all the components in a system is practically impossible, because some resistance between the ground points of different components is inevitable.
PARASOUND A 51 DESIGN OVERVIEW Circuit Designed by John Curl Parasound design consultant John Curl has been a legend among audiophiles and electronic engineers for decades.
16 PARASOUND A 51 DESIGN OVERVIEW continued The Driver Stage Total Protection - DC Servos The driver stage provides critical amplification for which we employ a complementary matched pair of MOSFETs selected for their tube-like sonic qualities. MOSFETs tend to generate less odd-order harmonic distortion than bipolar transistors.
PARASOUND A 51 SPECIFICATIONS Power Output - All Channels Driven Input Sensitivity for 28.
Parasound Products, Inc. 950 Battery Street, San Francisco, CA 94111 415-397-7100 / Fax 415-397-0144 www.parasound.
