Page 2 - Congratulations and Thank You for Choosing Parasound; Technically Speaking; The Parasound Staff; YOU SHOULD KNOW
1 THANK YOU! Congratulations and Thank You for Choosing Parasound Your new Parasound Halo Series A 21 power amplifier presents the latest advancements in amplifier technology. The A 21 is built to the strict quality and performance standards set by Parasound. We’re proud to offer you this exceptiona...
Page 3 - TABLE OF CONTENTS; A 21 Amplifier
PLACEMENT GUIDELINES FOR YOUR A 21 _________________________________________________________________________________ CONNECTING A STEREO PREAMPLIFIER OR A SURROUND CONTROLLER TO THE BALANCED INPUTS ON YOUR A 21 _________________________________________________________________________________ CONNECT...
Page 4 - PLACEMENT GUIDELINES FOR YOUR A 21; Rack Mounting Your Parasound A 21
PLACEMENT GUIDELINES FOR YOUR A 21 Power amplifiers are usually heavier and generate more heat than other components. To avoid damage to the A 21 or other equipment and to reduce risk of fire, you must follow these guidelines: • Place the A 21 on a separate shelf that will adequately support its wei...
Page 5 - CONNECTING A STEREO PREAMPLIFIER OR A SURROUND; Left and Right Balanced Input Jacks; Balanced and Unbalanced Lines; Before Connecting
XLR Connectors Male Female YOU SHOULD KNOWBalanced XLR Jacks and Their Pin Configuration The balanced inputs of the A 21 use XLR jacks that conform to the industry standard of: Pin 1: Ground, Pin 2: Positive (+), Pin 3: Negative (--). The balanced outputs on some components use terminals with 3 scre...
Page 6 - Inputs; To Connect; Unbalanced Right Channel Input
Left and Right Unbalanced Inputs Use these inputs if your preamplifier or surround controller doesn’t have balanced output connectors or if you simply prefer to use unbalanced connections. What You’ll Need: • A pair of shielded interconnect cables with RCA plugs • A source component with RCA output ...
Page 7 - Loop Out; CONNECTING THE A 21 LOOP OUT JACKS
Loop Out Connector The Right and Left Loop Out jacks provide connections to route the same input signals from your preamplifier or surround controller to an additional power amplifier. In most instances, you won't use the loop out feature so you can skip this section. What You’ll Need: • One pair of...
Page 8 - Speaker Terminals; Technically Speaking; CONNECTING SPEAKERS TO YOUR A 21
Stripped AWG wire Dual Banana Plug Common Speaker Connectors Single Banana Plug Spade Lug Red usually designates right The GND notch signifies ground or speaker left Speaker Terminals The five-way binding post speaker terminals on the A 21 accept most speaker wire terminations including single or du...
Page 9 - CONFIGURING THE A 21 FOR BRIDGED MONO OPERATION; sp
CONFIGURING THE A 21 FOR BRIDGED MONO OPERATION 6 YOU SHOULD KNOW IMPORTANT! - Before Trying Bridged Mono You should not connect a speaker with an impedance of less than 8 Ω to the A 21 when it is configured for bridged mono operation. Refer to Bridged Mono Operation in the Technically Speaking sect...
Page 10 - MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS; system controller is turned on and off.; Manual On-Off from the Front Panel
MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS 7 YOU SHOULD KNOWTurn Off Delay in the Audio Mode When the music (audio signal) stops, the A 21 will remain turned on for about five minutes. This delay prevents unwanted turn-off during silent passages in music or pauses between 1 Switch in up position Start...
Page 11 - Remove Power to all the components in your audio system.; Plug one end of the trigger wire into the
CONNECTING AN EXTERNAL DC SOURCE FOR A 21 AUTOMATIC TURN ON-OFF 8 1 2 YOU SHOULD KNOW If the device you want to use to control your A 21 doesn’t have a 2.5 mm trigger output connector, you can cut one plug off the cable and terminate the end as required. The lead with the red stripe is positive and ...
Page 12 - CONNECTING THE A 21 TO TRIGGER ANOTHER COMPONENT
B CONNECTING THE A 21 TO TRIGGER ANOTHER COMPONENT 9 1 2 YOU SHOULD KNOW If the device you want your A 21 to control doesn’t have a 2.5 mm trigger output connector, you can cut one plug off the cable and terminate the end as required. The lead with the stripe is positive and the lead without the str...
Page 13 - UNDERSTANDING THE INDICATORS ON THE A 21; Technical Service Department.
UNDERSTANDING THE INDICATORS ON THE A 21 AC Present Indication When the A 21 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. On, Off and F...
Page 14 - AC Power Connections; switched on and off.; Plug the male end of the AC cord to an AC outlet or power strip.; CONNECTING THE A 21 AC POWER CORD
AC Power Connections We recommend that you plug your A 21 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...
Page 15 - MAINTAINING YOUR A 21; with a few drops of water or glass cleaner.; Main Power Fuse
MAINTAINING YOUR A 21 Your Parasound A 21 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 ...
Page 16 - TROUBLESHOOTING GUIDE; PROBABLE CAUSE; TROUBLE
TROUBLESHOOTING GUIDE 13 A 21 will not turn off when audio signal is removed PROBABLE CAUSE Power cord is disconnected REMEDY Hum and / or buzz through speakers Ground loop between preamplifier and A 21 or at the equipment rack Move the Ground switch to its Lift position Install nylon shoulder washe...
Page 17 - SERVICING YOUR A 21; If All Else Fails –Call Us for Help; a) Refer you to an authorized Parasound repair center near you, or; Procedure for Returning Your A 21 to Parasound for Service; outer; IMPORTANT: Enclose a copy of your original purchase receipt.; We do not accept any of the following:; Units with collect shipping charges; Important Notice - Shipping the A 21
SERVICING YOUR A 21 14 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 21 will need further...
Page 18 - TECHNICALLY SPEAKING; common mode rejection.; Bare Speaker Wire Ends
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 200 mV (fully clockwise). If you set this control to 50 mV, the A 21 m...
Page 19 - TECHNICALLY SPEAKING continued; Choosing Interconnect Cables and Speaker Wire
TECHNICALLY SPEAKING continued 16 Choosing Interconnect Cables and Speaker Wire We are often asked to recommend specific interconnect cables and speaker wire. It’s true that with some amplifiers, sound quality will vary greatly according to interconnect cables and speaker wires. However, Parasound a...
Page 20 - PARASOUND A 21 DESIGN OVERVIEW; Relay-Bypassed Soft Start Circuit
PARASOUND A 21 DESIGN OVERVIEW 17 chosen for their low Equivalent Series Resistance (ESR) and dielectric absorption. In addition, these filter capacitors are bypassed with smaller polypropylene capacitors to reduce AC ripple in the DC supply and to further eliminate noise and interference that is ge...
Page 21 - PARASOUND A 21 DESIGN OVERVIEW continued; DC Servos
PARASOUND A 21 DESIGN OVERVIEW continued 18 Total Protection - DC Servos Direct Current (DC) burns out speakers. Every power amplifier must have some way to insure that DC from its power supply never reaches its + or - speaker terminals. Most amplifiers simply use trim controls to reduce their DC of...
Page 22 - PARASOUND A 21 SPECIFICATIONS
Power Output - Both Channels Driven 250 watts RMS x 2, continuous, 20 Hz - 20 kHz, 8 Ω 400 watts RMS x 2, continuous, 20 Hz - 20 kHz, 4 Ω Power Output - Mono 750 watts RMS, 20 Hz - 20 kHz, 8 Ω Current Capacity 60 amperes peak per channel Slew Rate > 130 volts per microsecond Frequency Response 5 ...
