background image

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 weight.

• 

Keep it away from heat sources such as air ducts or radiators.

• 

Avoid placing it on carpeting or another material that might obstruct airflow into the openings 

in the chassis bottom.

• 

Leave at least 3” of space around both sides and 6” of space above the top. The bottom 

clearance can be a little less. 

• 

Do not block the front of the A 21 behind closed cabinet doors during use.

• 

Do not stack the A 21 with other components inside a cabinet unless you use a fan to circulate 

and exhaust the warm air that builds up between them. 

Rack Mounting Your Parasound A 21

To mount the A 21 into a 19” wide equipment rack, you must first attach its rack mount brackets 

(provided). With its four feet removed, the A 21 chassis and front panel height occupies four rack 

spaces (7” or 176 mm). When mounting equipment below the A 21, you will also need to allow 

about 1/8” below the unit for the bottom chassis screws. A single standard rack space allows 

1-3/4” vertical height in a 19" wide equipment rack. This measurement standard was developed 

by the EIA (Electronic Industries Association) so manufacturers of electronic components and 

equipment racks could build products in standardized heights that would fit in a uniform space. 

Please call your Parasound dealer or Parasound Technical Services if you need additional advice 

about rack mounting the A 21.

To attach the rack mount brackets:

• 

Remove the three screws from each side of the A 21.  These are arranged vertically, behind its 

  front panel and in front of its first heatsink fin. 

• 

Line  up  the  three  holes  on  each  bracket  with  the  three  holes  on  the  A  21  and  reinsert 

  the screws. 

• 

Make sure the screws are tight because they will support the entire weight of the A 21 in the 

  equipment rack

1

HRA-4 Rack Adapter Mounted on JC 1

Rack Mount Brackets Attached to A 21

Summary of Contents for Halo A 21

Page 1: ...A 21 Amplifier Owner s Guide...

Page 2: ...u are unpacking your new amplifier inspect it thoroughly for possible shipping damage If you see any contact your Parasound dealer right away Be sure to save and store both the inner and outer cartons...

Page 3: ...NAL DC SOURCE FOR A 21 AUTOMATIC TURN ON OFF _________________________________________________________________________________ CONNECTING THE A 21 TO TRIGGER ANOTHER COMPONENT ________________________...

Page 4: ...rackets provided With its four feet removed the A 21 chassis and front panel height occupies four rack spaces 7 or 176 mm When mounting equipment below the A 21 you will also need to allow about 1 8 b...

Page 5: ...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...

Page 6: ...e Ground switch is in its Normal down position To Connect Plug one end of the cable into the Unbalanced Right Channel Input jack on the A 21 Plug the other end of this cable into the unbalanced right...

Page 7: ...ed or stretched once they are connected To Connect Plug one end of the cable to the right channel Loop Out jack on the A 21 Plug the other end of this cable to the right channel input jack on the othe...

Page 8: ...lack Right negative speaker terminal on the A 21 Insert the other end of the wire with the ridge or other marking into the red right positive terminal on the speaker Insert the wire without the ridge...

Page 9: ...th an impedance of 8 or higher Before Connecting Remove power to all the components in your audio system Set the A 21 Stereo Mono Bridge Switch to its Mono up position To Connect From the Source Plug...

Page 10: ...ou need to first select the Manual On Off option by placing the Auto Turn On switch on the rear panel to its middle Man Manual position Connecting an Active Audio Source for Automatic On Off If you wa...

Page 11: ...utomatically turn on and off the A 21 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...

Page 12: ...matically there is 12 Vdc present at its own DC Trigger Out jack so it can trigger additional amplifiers or other components on and off What You ll Need A cable with a 2 5 mm sub mini plug on each end...

Page 13: ...oblem Please contact Parasound s Technical Service Department Left and Right Channel Status Indicators These are two small round indicators in the center of the recess in the front panel The indicator...

Page 14: ...oltage for your unit is marked on its carton Changing the A 21 s operating voltage involves rewiring internal connections for both its main power transformer and standby power transformer plus changin...

Page 15: ...able 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...

Page 16: ...Mono Bridge switch is in the Mono bridged position Damaged speaker Move to the correct position for the jack in use Balanced Unbalanced Input switch is in the incorrect position Not enough ventilation...

Page 17: ...cept any of the following Units with collect shipping charges Units without a valid RA number Units without a suitable shipping carton Units for which we see or hear evidence of improper packing For a...

Page 18: ...ive signals For example when a 1 Volt signal arrives at a balanced input stage the differential input sees a positive 1 Volt minus a negative 1 Volt or 2 Volts total External hum and noise that someho...

Page 19: ...This separates the A 21 s signal input ground from its chassis ground to isolate unwanted voltage in the ground shield of the unbalanced RCA input cable Be sure your system installation is finished b...

Page 20: ...o drive the MOSFET drivers in the following stage Circuit designed by John Curl Parasound design consultant John Curl has been a legend among audiophiles and electronic engineers for decades He pionee...

Page 21: ...these fuses halt operation to minimize damage to additional parts The Driver Stage The driver stage provides critical amplification for which we employ a complementary matched pair of MOSFETs selected...

Page 22: ...ced 66 k Input Sensitivity for 28 28 V Output into 8 Unbalanced 1 V Balanced 1 V per leg Features and specifications subject to change without notice Loop Output Level Same as input level S N Ratio 11...

Page 23: ...Parasound Products Inc 950 Battery Street San Francisco CA 94111 415 397 7100 Fax 415 397 0144 www parasound com...

Reviews: