A 52 Amplifier
Owner’s Guide
TABLE OF CONTENTS
A 52 Amplifier
PLACEMENT GUIDELINES FOR YOUR A 52
2
3
CONNECTING A SURROUND CONTROLLER
TO THE BALANCED INPUTS ON YOUR A 52
CONNECTING A SURROUND CONTROLLER
TO THE UNBALANCED INPUTS ON YOUR A 52
4
5
CONNECTING YOUR SPEAKERS TO THE A 52
MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS
CONNECTING AN EXTERNAL DC SOURCE FOR AUTOMATIC ON-OFF
CONNECTING THE A 52 TO TRIGGER ANOTHER COMPONENT
UNDERSTANDING THE INDICATORS ON THE A 52
CONNECTING THE AC POWER CORD
6
7
8
9
10
11
12
13
14
16
18
MAINTAINING YOUR A 52
TROUBLESHOOTING GUIDE
SERVICING YOUR A 52
TECHNICALLY SPEAKING
PARASOUND A 52 DESIGN OVERVIEW
PARASOUND A 52 SPECIFICATIONS
2
PLACEMENT GUIDELINES FOR YOUR A 52
Power amplifiers are usually heavier and generate more heat than other components. To avoid
damage to the A 52 or other equipment and to reduce risk of fire, you must follow these guidelines:
•
Place the A 52 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 52 behind closed cabinet doors during use.
•
Do not stack the A 52 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 52
To mount the A 52 into a 19" wide equipment rack, you must first attach its HRA 3 rack mount
brackets (not included). With its four feet removed, the A 52 chassis and front panel height occu-
1
pies three rack spaces (5 ⁄4" or 133 mm). When mounting equipment below the A 52, you will
1
also need to allow about ⁄8" below the unit for the bottom chassis screws. A single standard rack
3
space allows 1 ⁄4" vertical height in a 19" wide equipment rack. This measurement standard was
developed by the EIA (Electronic Industries Association) so manufacturers of electronic compo-
nents 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 52.
To attach the rack mount brackets:
•
Remove the two screws from each side of the A 52’s top cover.
•
Line up the two holes on each HRA 3 bracket with these holes on the A 52 and attach
the brackets with the longer screws that are in the bracket kit.
•
Make sure the screws are tight because they will support the entire weight of the A 52
in the equipment rack.
HRA 3 Rack Bracket
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On-Off
HiTemp
CONNECTING A SURROUND CONTROLLER
TO THE BALANCED INPUTS ON YOUR A 52
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.
What You’ll Need:
Male
•
Five balanced interconnect cables with XLR connectors
Female
•
A surround controller with balanced output connectors
XLR Connectors
Before Connecting
❑ Leave the A 52’s AC cord disconnected until you have made all other connections to prevent
any surprise burst of sound.
❑ Make sure that all your cables are long enough so they are not strained or stretched
once they are connected.
❑ Make sure the Balanced - Unbalanced Inputs selector switch on the rear of the A 52 is
in its Balanced (upper) position. The Ground switch should be in its Normal (lower) position.
To Connect
1 Plug the male end of the first balanced interconnect cable into the Balanced Ch 1 input
jack on the A 52.
2 Plug the female end of the cable into the balanced output jack for the channel on your
surround controller that you wish to correspond to Ch 1 on your A 52.
3 – 0 Repeat steps 1 and 2 above to connect Ch 2, Ch 3, Ch 4, and Ch 5.
OUTPUTS
SURROUNDŁ
CONTROLLER
2
4
6
8
10
Inputs Switch,
set to up position
Ground Switch,
set to down position
1
3
5
7
9
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Input
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Unbalanced
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
YOU SHOULD KNOW
Balanced XLR Jacks and Their Pin Configuration
The balanced inputs of the A 52 use XLR jacks that conform to the industry standard of:
Pin 1: Ground, Pin 2: Positive (+), Pin 3: Negative (–).The balanced outputs on some com-
ponents use terminals with 3 screws instead of XLR jacks.These are compatible with the
A 52 as long as you match the bare wires to the corresponding pins on the XLR plug: + to
pin 2, - to pin 3, and Ground to pin 1.
CONNECTING A SURROUND CONTROLLER
TO THE UNBALANCED INPUTS ON YOUR A 52
4
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
RCA Plugs
Before Connecting
❑ Leave the AC cord on the A 52 disconnected until you have made all other connections
to prevent any surprise burst of sound.
❑ Make sure that all your cables are long enough so they are not pulled or stretched
once they are connected.
❑ Make sure the Balanced-Unbalanced Inputs selector switch on the A 52 is in its
Unbalanced (lower) position and the Ground switch is in its Normal (lower) position.
To Connect
1 Plug one end of the cable into the Unbalanced Ch 1 Input jack on the A 52.
2 Plug the other end of the cable into the unbalanced output jack for the channel
on your surround controller that you wish to correspond to Ch 1 on your A 52.
3 – 0 Repeat steps 1 and 2 for Ch 2, Ch 3, Ch 4, and Ch 5.
OUTPUTS
SURROUNDŁ
CONTROLLER
2
4
6
8
10
Inputs Switch,
set to down position
Ground Switch,
set to down position
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
nput
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
1
3
5
7
9
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
YOU SHOULD KNOW
Write Down Your Connections
Make a note of which channel on your surround controller now connects to each channel
of the A 52 so you’ll always hear the channels in their intended position and to facilitate
trouble-shooting in case you encounter a problem later on.
5
CONNECTING YOUR SPEAKERS TO THE A 52
Speaker Terminals
The A 52 speaker terminals accept speaker wires with banana plugs, spade lugs, 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, spade lugs, or bare ends
Dual
Banana Plug
Single
Banana Plug
Spade Lug
Stripped
AWG wire
•
Five loudspeakers
Before Connecting
❑ Remove power to all the components in your audio system.
To Connect
When connecting your speakers you need to keep in mind which channel of the A 52 you
connected to each channel on your surround controller. You can write these down on page 10.
1 Insert one wire with the ridge or other marking into the red Ch 1 + (positive) speaker
terminal on the A 52. Insert the wire without the ridge or other marking into the black
Ch 1 - (negative) speaker terminal.
2 Insert the other end of the wire with the ridge or other marking to the red + (positive)
terminal on the speaker. Insert the other end of the wire without the ridge or other
marking to the adjacent black – (minus) terminal on the speaker.
3 – 0 Repeat steps 1 and 2 for Ch 2, then Ch 3, then Ch 4, and finally Ch 5.
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
1
3
5
7
9
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
SPEAKERS
2
2
4
6
8
10
YOU SHOULD KNOW
Correct Speaker Polarity is Important
Polarity refers to + and – connections. Speaker wires are coded with printing or a ridge on the
insulation on one of the leads so you know which lead was connected to the + and – terminals
at the other end.This coding will help you keep the + and - polarity consistent for all channels.
Speaker Wire Length and Gauge (thickness)
When selecting speaker wire, follow these guidelines:
• Keep the length of your speaker wire as short as possible.
• Use the thickest wire practical. For lengths greater than 50 feet, use speaker wire
with an AWG (gauge) of 14 or lower.The smaller the AWG, the thicker the wire.
• Do not use speaker wire that is thinner than 16 AWG.
• Keep wire lengths for both channels as close to equal as possible.
6
MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS
You can manually turn the A 52 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 52 at any time, you 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.
AutoTurn On Switch, set to middle position
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
Connecting an Active Audio Source for Automatic On-Off
If you want to automatically turn on the A 52 whenever music is playing (an audio signal is present),
choose the audio triggering option by moving the Auto Turn On switch to its Audio (upper) position.
What You’ll Need:
•
An audio source that’s playing
Before Connecting
❑ Remove power to all the components in your audio system.
❑ Make sure the Auto Turn On switch on the A 52 is in its Audio (upper) position.
❑ Set the Audio triggering Sensitivity adjustment knob on the rear panel to the desired level.
Start with the 12 o’clock position.
To Connect
Connect an active audio source to either the Ch 1 Balanced or Unbalanced Input jacks.
(Refer to to pages 2 and 3).
AutoTurn On Switch, set to up position
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
YOU SHOULD KNOW
Turn Off Delay in the Audio Mode
When the music stops, the A 52 will remain on for about five minutes.This delay prevents
unwanted turn-off during silent passages in music or during the pauses between tracks.
CONNECTING AN EXTERNAL DC SOURCE FOR
AUTOMATIC TURN ON-OFF
7
To automatically turn on and off the A 52 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 Auto Turn On switch on the A 52 rear panel is in its 12V (down) position.
To Connect
1 Plug one end of the trigger wire into the 12V Input jack on the A 52.
2 Plug the other end of this wire into the external DC source.
CONTROL
COMPONENT
2
Output
AudioTurn On Switch,
set to down position
1
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
YOU SHOULD KNOW
If the device you want to use to control your A 52 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 the lead without the stripe is negative.
8
CONNECTING THE A 52 TO TRIGGER ANOTHER COMPONENT
Whenever the A 52 is turned on either manually or automatically, 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 wire with a 2.5 mm sub-mini plug on each end (in addition
to the wire provided with the A 52)
•
A component that can be triggered with an external +9 Vdc to +12 Vdc
2.5 mm sub-mini plug
source. The A 52 DC trigger output provides up to 150 mA of current
Before Connecting
❑ Remove power to all the components in your audio system.
To Connect
1 Plug one end of the trigger wire into the 12V Output jack on the A 52.
2 Plug the other end of this wire into the component that you want the A 52 to trigger.
CONTROLLED
COMPONENT
2
Input
AutoTurn On Switch,
set to down position
1
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
YOU SHOULD KNOW
If the device you want your A 52 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 stripe is negative.
9
UNDERSTANDING THE INDICATORS ON THE A 52
a AC Present Indication
When the A 52 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 52 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. Then the red glow is replaced
by a brighter blue glow to indicate normal operation. If the glow remains red after turn on
or while the amp is playing, it indicates activation of the A 52’s protection circuits and no
sound will be heard from the speakers.
The A 52 protects itself from external conditions such as excessive heat, load impedance
that is too low, or a short-circuited speaker connection or wire. After you correct the fault,
the A 52 will resume operation. If the A 52 remains “in protection” after it has cooled down
and you’ve confirmed there are no external faults, it could indicate an internal problem.
Please contact Parasound’s Technical Service Department.
c – g Channel Status Indicators
These are the five small round indicators in the center of the recess in the front panel.
The indicator on the left displays the status of channel one and the subsequent indicators
display the status of channels two through five.
c – g All Indicators Illuminated
When all five channels are operating normally, these will all glow blue.
c – g No Illumination:
When the A 52 is turned off, these indicators are off. An indicator that does not glow when
the A 52 is turned on represents a fault in that channel.
h High-Temp Indicator
This indicator is near the right side of the panel recess. It will glow red if any channel overheats.
The On-Off button will also glow red if the A 52 overheats and shuts down to protect itself.
Refer to the Troubleshooting Guide on page 12.
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On-Off
HiTemp
10
CONNECTING THE A 52 AC POWER CORD
AC Power Connections
We recommend that you plug your A 52 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 52 requires AC power that is continuous rather than switched on and off.
110 V - 120 V or 220 V - 240 V Operation
The A 52 can operate on either 110 V - 120 V or 220 V - 240 V. The correct line (or “AC mains”)
voltage for your unit is marked on its carton. Changing the A 52’s operating voltage involves
rewiring internal connections for both its main power transformer and standby power trans-
former, plus changing fuse values. Since there is a risk of electric shock, voltage changes
must be referred to a qualified technician.
What You’ll Need:
•
An IEC 65 AC Cord (provided)
•
An AC outlet or high quality AC power strip within reach of the AC cord
Before Connecting
❑ Remove power to all the components in your audio system.
To Connect
1 Plug the female end of the AC cord to the AC receptacle on the rear of the A 52.
2 Plug the male end of the AC cord to an AC outlet or power strip.
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
12
V
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
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Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
1
2
11
MAINTAINING YOUR A 52
Your Parasound A 52 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 fewdrops of water or glass cleaner.
Main Power Fuse
If this fuse blows, please contact Parasound Technical Service for further advice.
Notes:
12
TROUBLESHOOTING GUIDE
TROUBLE
PROBABLE CAUSE
REMEDY
Power cord is disconnected
Connect power cord to a live AC outlet
No power
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
DC trigger source wired in
reverse or voltage too low
Check polarity of DC source with a voltmeter.
Try connecting a 9V battery to the 12V DC input
Auto turn on doesn’t
function with a trigger
voltage
Auto Turn On selector switch
Make sure Auto Turn On selector switch is
is in wrong position
in its 12V position
Auto Turn On selector switch
is in wrong position
Make sure Auto Turn On selector switch is
in its Audio position
Auto turn on doesn’t
function with an audio
input signal
Sensitivity incorrectly adjusted
Turn the Audio trigger Sensitivity knob
counterclockwise
Sensitivity level too high
Turn Sensitivity knob clockwise toward 250 mV
A52 will not turn off when
audio signal is removed
Bad connection from surround
controller
Check input connections or try a different
set of cables
Power on, but no sound
Over-current protection circuitry
has been activated- one or more
blue channel LEDs not illuminated
Check speaker load impedance. Check speaker
wires and connections
On-Off button glows red
and channel indicator(s)
off
A 52 has overheated - red Hi
Temp indicator is on
Allow A 52 to cool. Check that there is adequate
ventilation around the A 52. Be sure the load
impedance of each channel is no less than 4 ohms
Damaged speaker
Connect each speaker to another channel on the
A 52. If the same speaker remains distorted, the
speaker or its wire is damaged. If the other speak-
er distorts, the problem may be with the A 52, the
surround controller, or a source component
Distorted sound
Problem with surround controller
or source component
Switch the input cables. If distortion moves
to another channel, the problem is with a
component other than the A 52
Balanced-Unbalanced Input
switch is in the incorrect position
Move to the correct position for the jacks
in use
Ground loop between surround
controller and A 52 or at the
equipment rack
Move the Ground switch to its Lift position.
Install nylon shoulder washers on both sides
of the panels of all equipment to insulate metal
from touching the rack
Hum and / or buzz
through speakers
Ground loop from cable TV
Move the Ground switch to its Lift position.
Install a cable isolation device such as the
Xantech 634 Ground Breaker.
Other ground loop
Contact Parasound Technical Service
Load impedance at speaker
terminals is too low
Make sure the speaker or speaker selector
load is 4 ohms or higher
A 52 is overheating
Not enough ventilation
Make sure the A 52 has adequate ventilation
13
SERVICING YOUR A 52
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 52 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 Returning Your A 52 to Parasound for Service
If Parasound determines that you should send your A 52 to Parasound, you will be given a Return
Authorization (RA) number. This RA number must be clearly marked on the outer carton only.
IMPORTANT: Enclose a copy of your original purchase receipt. A unit is eligible for warranty
repair ONLY when the purchase receipt shows that the unit was purchased from an
Authorized Parasound Dealer. A unit obtained through unauthorized channels is not eligible
for warranty repair. Parasound is not responsible for any sellers’ misrepresentations about our
warranties or other service policies.
We do not accept 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 non-warranty repair, contact us for an estimate of the repair charges before you ship
the unit to us. The same packing and Return Authorization number procedures apply.
Important Notice - Shipping the A 52
Before shipping the unit to Parasound, you MUST re-pack the unit into its fitted molded foam
insert sandwich and its original carton. If you do not have the original packing cartons and foam
inserts, call us for new packing materials that we can provide to you for a nominal charge. Use
of any other carton and packing materials will probably result in shipping damage, and
refusal of the unit. Common carriers such as UPS seldom pay claims for damage incurred
during shipment when a product is surrounded only with Styrofoam “peanuts” or otherwise
improperly packed.
We cannot stress enough the importance of properly packing your A 52. Shipping damage
resulting from inadequate packing can cost you a lot of money and significantly increase the
time required for repair.
Ship the unit with adequate insurance. After repair under warranty, the unit will be returned
to you via prepaid UPS within the continental United States.
14
TECHNICALLY SPEAKING
A differential input circuit amplifies only the difference
between the positive and negative signals. For exam-
ple, 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 somehow gets into a balanced line is
common to both its positive and negative conductors
with respect to ground. Therefore, it is canceled or
rejected by the differential input circuit.
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 52 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. If you set this
control to 250 mV, the A 52 might not turn on during
quiet musical passages. The detented position (click
stop) at 12 o’clock corresponds to 100 mV. It’s a good
starting point and will be suitable for most systems.
This phenomenon of rejecting noise signals common
to both positive and negative conductors is called
common mode rejection. Differential inputs are speci-
fied according to how well they reject signals com-
mon to both conductors. This is measured in dB and
is called the common mode rejection ratio or CMRR.
Balanced and Unbalanced Lines
Recording and broadcast studios use balanced con-
nections exclusively because of their inherent ability
to reject noise and hum, thus assuring the best
sound. Certain high quality preamplifiers and surround
controllers built for residential use utilize balanced
connections with XLR jacks for the same reasons.
All Parasound Halo series power amplifiers have
balanced inputs with XLR jacks so you can take full
advantage of their inherent noise reduction capability
and superior sound quality.
Bare Speaker Wire Ends
If you plan to use connections with bare wire ends,
use a wire stripper to remove just enough insulation
1
to expose a ⁄2” (13 mm) length of bare wire. You can
insert the stripped wire into the hole that goes side-
ways through the terminal’s metal post. Before insert-
ing 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.
Unbalanced connections with RCA jacks are found on
all home audio equipment. RCA jacks and two-conduc-
tor wires are less costly than the additional circuitry,
higher priced XLR connectors and three-conductor
wiring required for balanced connections.
Choosing Interconnect Cables and Speaker Wires
We are often asked to recommend specific brands
of interconnect cables and speaker wires. It’s true
that with some amplifiers, sound quality will vary
greatly according to interconnect cables and speaker
wires. However, Parasound amplifiers use robust
circuitry that sounds superb regardless of intercon-
nects and speaker wires. Therefore, we feel that
choosing a brand of cable for Parasound amplifiers
is purely a matter of personal taste.
In an unbalanced line, the positive audio signal appears
at the center pin of the RCA jack and the negative
signal on the outer shield wire, which also functions as
the ground connection. Unbalanced interconnect cables
are vulnerable to hum from an AC line, or other noise,
such as RF (Radio Frequency), which can be reproduced
through your loudspeakers. Since the unbalanced line’s
ground also carries the audio signal, there is no way
for the connected amplifier or preamplifier to distinguish
between the audio signals you want and unwanted
noise emanating from external sources.
Ground Loops - Eliminating Hum and Buzz
Audible hum and buzzing noises in a system are usu-
ally related to issues with the component grounds.
Ground (sometimes called common) is a point of
reference for voltages in virtually all audio and video
components. Ground is supposed to remain at zero
volts while the audio signal swings positive (voltage
above ground) and negative (voltage below ground).
If ground isn’t at zero, there can be an audible 60 Hz
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 addi-
tion to the hum.
Balanced lines are superior because they utilize sepa-
rate conductors for audio and ground: two inner
conductors carry the positive and negative audio
signal, and a third outer wire connects the grounds
and also shields the two signal conductors. When
the positive and negative signals appear at the com-
ponent receiving the signal they are equal, but 180
degrees out of phase with each other with respect to
ground. To send and receive balanced signals requires
special differential circuitry.
15
TECHNICALLY SPEAKING continued
The ideal of zero voltage ground for all the compo-
nents in a system is practically impossible, because
some resistance between the ground points of differ-
ent components is inevitable. By keeping components
close together with their power cords plugged into a
common AC outlet or power strip, you’ll avoid the
problems created by resistance in the house’s wiring.
2. When rack mounting, always use insulated “shoul-
der” washers. These break the ground loops caused
by metal-to-metal contact between the rack, the
components, and their rack-mount bolts. Extra wash-
ers are available from rack manufacturer Middle
3. Use the Ground switch on the A 52 to eliminate
most ground loops. This separates the A 52’s sig-
nal 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 before you try moving the
Ground switch from its Normal to its Lift position.
Hum and buzz is also caused when unwanted voltage
flows through multiple component ground points
called ground loops. Here are three tips to avoid
ground loops:
1. Use balanced input lines with your Parasound A 52.
(See Balanced and Unbalanced Lines in this section)
Ground Switch, set to up position
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Balanced
Audio
12 V
Sensitivity
Lift
50 mV 250
Man
Unbalanced Output
Inputs
Input
Normal
Ground
Parasound Products, Inc.
San Francisco, CA USA
AutoTurn On
WARNING
To Prevent Fire Or Shock Hazard,
Do Not ExposeThis UnitTo Rain
Or Moisture.
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
Balanced
Unbalanced
L
U
C
A
S
F
I
L
M
Input
Input
Input
Input
Input
Fuse
T15A/250V1-115V Area
T8A/250V-230V Area
Manufactured under
license from Lucasfilm
Ltd. Lucasfilm andTHX
are registeredTrademarks
of Lucasfilm Ltd.
CAUTION
To Prevent Electric Shock, Do Not
Remove Cover. No User-Serviceable
Parts Inside, Refer Servicing To
Qualified Service Personnel.
AC 115V
AC 230V
60Hz
50Hz
Power Consumption: 1350W
16
PARASOUND A 52 DESIGN OVERVIEW
electrolytic filter capacitors, chosen for their low
Circuit Designed by John Curl
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 generated
in AC power lines from computers and other appli-
ances in the home.
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.
Relay-Bypassed Soft Start Circuit
When the A 52 is first turned on, there is a significant
amount of in-rush current required to charge the enor-
mous power supply capacitors. In order to suppress
this in-rush current and to prevent nuisance tripping
of circuit breakers, we employ NTC (negative tempera-
ture coefficient) resistors. These resistors cut the
in-rush current by approximately 50%. Once they heat
up, they essentially become a jumper with zero ohms
resistance. However, the A 52 goes one step further for
this circuit. After the NTC resistors have done their job
of suppressing in-rush current a gold contact relay auto-
matically is activated to jump across the NTC resistors
to completely bypass them. This extra step insures that
the resistors do not restrict any current whatsoever to
the power supply once the A 52 is in full operation.
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 sophisti-
cated 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 52 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 opera-
tion. Polypropylene and mica capacitors are used
extensively for their superior linearity and low dielec-
tric 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.
Audio Circuit Path Topology
Parasound’s circuit topology is a hybrid of carefully
chosen discrete transistors that result in superior per-
formance at each stage. We use JFETs (Junction Field
Effect Transistors) for the input stage; MOSFETs
(Metal Oxide Field Effect Transistors) for the driver
stage and bipolar transistors for the output stage.
Discrete transistors are more sonically accurate than
integrated circuits commonly used by other brands.
Complementary Configuration
Each stage of amplification has transistors fed by the
positive DC power supply and complementary transis-
tors fed by the negative DC power supply. Thus, half
of the devices amplify the positive half of the musical
waveform while the other half of the devices amplify
the negative half. This complementary topology is
inherently linear, which reduces distortion and
improves sonic accuracy.
The Power Supply
The heart of the power supply is a 1.4 kVA toroidal
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 Input Stage
The A 52’s input stage uses matched pairs of discrete
JFETs arranged in a differential configuration. JFETs
are ideal for the input stage because their inherently
high impedance is unaffected by the impedance of
source components. Differential configuration provides
superior noise reduction. These precision input JFETs
are also cascoded to produce the current necessary
to drive the MOSFET drivers in the following stage.
The A 52 power transformer employs multiple inde-
pendent secondary windings so that each amplifier
channel has its own power supply, assuring more than
ample DC voltage at all times and under all conditions.
It also reduces inter-channel crosstalk that can blur
the sound and impair the correct sense of where
instruments, dialogue and effect are positioned.
Each channel’s +/- 60 Vdc B+ and B- supply rails use
high-speed rectifier diodes and two large 10,000uF
17
PARASOUND A 52 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. This is important
because odd-order distortion sounds unnatural and
fatiguing to the human ear, whereas even-order dis-
tortion is less offensive because it is consonant,
rather than dissonant. Our MOSFET driver stage pre-
vents the harshness and brittle sound so often found
in other amplifiers.
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 offset or capacitors to block DC.
Unfortunately, trim controls can allow DC offset to
increase over time, and even the most expensive
capacitors in the audio signal path will “veil” sonic
clarity and attenuate bass response.
Parasound power amplifiers incorporate ingenious and
fast-acting DC servo circuits, completely eliminating
the need for coupling and blocking capacitors. The
The Output Stage
The amplifier’s sonic characteristics are established by A 52 is direct-coupled from its input jacks to its speak-
its input and driver stages. Now, the sole job of its
output stage is to deliver the enormous current and
er terminals. This advanced circuitry never needs
adjustment or maintenance. It operates outside the
voltage from its power supply to the speakers. Bipolar audio signal path to keep the DC offset at the output
output transistors are better than MOSFETS in the
output stage because of their higher safe operating
area (SOA) and inherent ruggedness. Each channel’s
output stage employs two pairs of high current (15-
ampere) bipolar transistors to insure long-term reliabil-
ity, even with continuous high power operation and
challenging speaker loads. Lightning-fast (60 MHz)
transistors respond instantly to complex demands in
the musical signal, virtually eliminating distortions that
occur with slower transistors. Slew rate limiting and
Transient Intermodulation Distortion (TIM) are simply
not an issue in the A 52.
of the A 52 at a constant 0.00 Vdc. The results are
startling clarity, freedom from listening fatigue, and
formidable bass response.
Total Protection - Relays
Each channel of the A 52 has a high-quality protection
relay with gold-plated contacts for long-term reliability.
These relays function to protect either the amplifier,
the speakers, or both. When the A 52 is first powered
on, these relays remain open for three seconds as the
positive and negative power supplies stabilize and
reach equilibrium. This prevents annoying popping or
other transient noises. Relay protection also prevents
damage to your speakers in case of a catastrophic
amplifier failure. Any amplifier that doesn’t use relay
protection for its speaker outputs compromises the
safety of the amplifier and your speakers.
Class A-A/B Operation
Pure class A operation provides the purest sound.
However, an amplifier operating entirely in class A
operation would be enormous, highly inefficient, and
generate too much heat. Class A/B combines some of
the advantages of Class A with the efficiency of Class
B operation. It is a compromise that reduces the heat
generated in pure class A operation and the odd-order
harmonic distortion created in class B. In class AB,
the driver and output stages are always partially
turned on, which provides a nominal amount of pure
class A operation. At higher power levels, when the
musical waveform swings from positive to negative
and vice versa, each bank of transistors is allowed
to rest momentarily. This resting, or quiescent time,
makes it possible to deliver high amounts of power
without overheating. It also makes it possible to use
passive cooling and avoid fans, whose noise can be
heard over the music. The A 52 input and driver
stages employ pure Class A while its output stage
operates with higher pure Class A power than many
amplifiers selling for twice or three times its price.
The result is less fatiguing, more natural sound.
Total Protection - Current Overload
Specialized current-sensing transistors are connected
to the output stages of the A 52 to constantly monitor
the current flow through the output transistors. If the
current drawn by this stage exceeds a predetermined
safe level due to a load impedance below 1 ohm or a
short circuit at the speaker terminals, the output relay
will open immediately to prevent any of the output
transistors or other parts from failing.
Total Protection - Fuses
Each channel of the amplifier has a separate fuse for
its positive and negative DC voltage rails. These fuses
provide backup protection in case the over-current
protection does not work in time, or if an internal part
fails. In the event of a part failure, these fuses halt
operation to minimize damage to additional parts.
18
PARASOUND A 52 SPECIFICATIONS
Power Output - All Channels Driven
125 watts RMS x 5, continuous,
20 Hz - 20 kHz, 8W
Input Sensitivity for 28.28 V Output into 8 W
Unbalanced: 1 V
Balanced: 1 V per leg
225 watts RMS x 5, continuous,
20 Hz - 20 kHz, 4W
S/N Ratio
> 113 dB, input shorted, IHF A-weighted
> 104 dB, input shorted, unweighted
Current Capacity
30 amperes peak per channel
Damping Factor
> 1000 at 20 Hz
Slew Rate
> 130 volts per microsecond
DC Trigger Requirements
+9 Vdc to +12 Vdc, 2 mA
Frequency Response
5 Hz - 100 kHz, +0/-3 dB at 1 watt
Audio Trigger Requirements
50 mV AC - 250 mV AC
Total Harmonic Distortion
< 0.2 % at full power
DC Trigger Output Capacity Requirements
< 0.03 % at typical listening levels
+12 Vdc, 150 mA
IM Distortion
Dimensions
1
< 0.04 %
Width: 17 ⁄4" (437 mm)
1
Panel height: 5 ⁄4" (133 mm)
TIM
7
Unmeasureable
Height with feet: 5 ⁄8" (150 mm)
3
Depth: 19 ⁄4" (501 mm)
Dynamic Headroom
> 1.5 dB
Power Requirement
Standby: 25 Watts
Interchannel Crosstalk
> 78 dB at 1 kHz
Full Power into 8W : 1200 Watts
> 63 dB at 20 kHz
Net Weight
1
50 ⁄4 lb. (22.8 kg)
Input Impedance
Unbalanced: 47k W
Balanced: 94k W
Shipping Weight
64 lb. (29 kg)
V 1.0 Features and specifications subject to change without notice.
© Parasound Products, Inc. 2002.
Parasound Products, Inc. 950 Battery Street, San Francisco, CA 94111
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