Parasound Stereo Amplifier A 23 User Manual

A 23 Amplifier  
Owner’s Guide  
 
TABLE OF CONTENTS  
A 23 Amplifier  
PLACEMENT GUIDELINES FOR YOUR A 23  
1
_________________________________________________________________________________  
2
CONNECTING A PREAMPLIFIER OR SURROUND CONTROLLER  
TO THE BALANCED INPUTS ON THE A 23  
_________________________________________________________________________________  
3
CONNECTING A PREAMPLIFIER OR SURROUND CONTROLLER  
TO THE UNBALANCED INPUTS ON THE A 23  
_________________________________________________________________________________  
4
CONNECTING THE LOOP OUT JACKS ON THE A 23 TO ANOTHER  
POWER AMPLIFIER’S INPUTS  
_________________________________________________________________________________  
5
CONNECTING SPEAKERS TO THE A 23  
_________________________________________________________________________________  
6
CONFIGURING THE A 23 FOR BRIDGED MONO OPERATION  
_________________________________________________________________________________  
7
MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS  
_________________________________________________________________________________  
8
CONNECTING AN EXTERNAL DC SOURCE FOR AUTOMATIC ON-OFF  
_________________________________________________________________________________  
9
CONNECTING THE A 23 TO TRIGGER ANOTHER COMPONENT  
_________________________________________________________________________________  
10  
UNDERSTANDING THE INDICATORS ON THE A 23  
_________________________________________________________________________________  
11  
CONNECTING THE AC POWER CORD  
_________________________________________________________________________________  
12  
MAINTAINING YOUR A 23  
_________________________________________________________________________________  
13  
TROUBLESHOOTING GUIDE  
_________________________________________________________________________________  
14  
SERVICING YOUR A 23  
_________________________________________________________________________________  
15  
TECHNICALLY SPEAKING  
_________________________________________________________________________________  
17  
PARASOUND A 23 DESIGN OVERVIEW  
_________________________________________________________________________________  
19  
PARASOUND A 23 SPECIFICATIONS  
_________________________________________________________________________________  
 
1
PLACEMENT GUIDELINES FOR YOUR A 23  
Power amplifiers are usually heavier and generate more heat than other components. To avoid  
damage to the A 23 or other equipment and to reduce risk of fire, you must follow these guidelines:  
• Place the A 23 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 the top. The bottom clearance can be a little  
less. This helps facilitate heat dissipation.  
• Do not block the front of the A 23 behind closed cabinet doors during use.  
• Do not stack the A 23 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 23  
If you plan to mount the A 23 into a standard 19” wide equipment rack, you will need to purchase  
the optional Parasound HRA 2 Rack Mount Adapter. With its four feet removed, the A 23 chassis  
and front panel height occupies two rack spaces (3-1/2” or 88mm). Please call your Parasound  
dealer or Parasound Technical Services if you need additional advice about rack mounting the A 23.  
A standard single rack space allows 1- 3/4 vertical inches in a 19-inch 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.  
 
CONNECTING A PREAMPLIFIER OR SURROUND CONTROLLER  
TO THE BALANCED INPUTS ON THE A 23  
2
Left and Right Balanced Input Jacks  
Balanced connections will give you the best sound. If your preamplifier or 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  
• One pair of balanced interconnect cables with XLR connectors  
• A preamplifier or surround controller with  
Female  
balanced connectors.  
XLR Connectors  
Before Connecting  
Leave the A 23’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 switch on the rear of the A 23 is in its Balanced  
(up) position.  
To Connect  
1
Plug the male end of the balanced interconnect cable into the Balanced Right Channel  
input jack on the A 23.  
2
Plug the female end of the cable into the balanced right channel output jack on  
your preamplifier (or a channel from your surround controller).  
Repeat steps 1 and 2 above to connect the left channel.  
3&4  
1
3
CAUTION  
2
4
COMPONENTS  
SURROUND  
SOUND  
CONTROLLER  
Right  
Left  
or  
PREAMP  
OUTPUTS  
YOU SHOULD KNOW  
Balanced XLR Jacks and Their Pin Configuration  
The balanced inputs of the A 23 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 screws instead of XLR jacks. These are compatible with the A 23 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.  
Interconnect Cables and Their Color Codes  
Common color codes for input and output jacks are red for right and white for left. Match the  
colors at the outputs from your preamplifier or surround controller to the inputs on your A 23  
so you’ll always hear the channels in their intended position.  
 
CONNECTING A PREAMPLIFIER OR SURROUND CONTROLLER  
TO THE UNBALANCED INPUTS ON THE A 23  
3
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:  
Left  
• One standard pair of shielded interconnect cables with  
Right  
RCA plugs  
• A source component with RCA output jacks  
RCA Plugs  
Before Connecting  
Leave the AC cord on the A 23 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 switch on the A 23 is in its Unbalanced (down) position.  
To Connect  
Plug one end of the cable into the Unbalanced Right Channel Input jack on the A 23.  
1
2
Plug the other end of this cable into the unbalanced right channel output jack on your  
preamplifier (or a channel from your surround controller).  
3&4  
Repeat steps 1 and 2 for the left channel.  
3
1
CAUTION  
2
4
COMPONENTS  
SURROUND  
SOUND  
CONTROLLER  
Right  
Left  
or  
PREAMP  
OUTPUTS  
 
CONNECTING THE LOOP OUT JACKS ON THE A 23 TO  
ANOTHER POWER AMPLIFIER’S INPUTS  
4
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:  
Left  
• One standard pair of shielded interconnect cables with  
Right  
RCA plugs  
• An additional amplifier  
RCA Plugs  
Before Connecting  
Leave the AC cord on the A 23 disconnected from the wall until you have made all of  
the connections in the system to prevent any surprise burst of sound.  
Make sure that your interconnect cables are long enough so they are not strained or  
stretched once they are connected.  
To Connect  
1
Plug one end of the cable to the right channel Loop Out jack on the A 23.  
Plug the other end of this cable to the right channel input jack on the other power amplifier.  
Repeat steps 1 and 2 for the left channel.  
2
3&4  
3
1
CAUTION  
2
4
COMPONENTS  
Right  
Left  
INPUTS  
POWER AMP  
YOU SHOULD KNOW  
These jacks eliminate the need for two “Y” connector cables to split the outputs from the two  
source channels between your A 23 and another amplifier. The A 23 Loop Out jacks provide  
the same signals that are received at either the balanced or the unbalanced inputs. Refer to  
Loop Out Jacks in the Technically Speaking section for more information about when to use  
the loop out jacks.  
 
5
CONNECTING SPEAKERS TO THE A 23  
Speaker Terminals  
The five-way binding post speaker terminals on the A 23 accept most speaker wire  
terminations including single or dual banana plugs, 1/4” spade lugs, or bare wire.  
Refer to Bare Wire Speaker Termination in the Technically Speaking section for  
information about bare wire termination.  
Common Speaker Connectors  
What You’ll Need:  
The GND notch  
signifies ground  
or speaker left  
Red ususally  
designates right  
Two lengths of speaker wire  
AWG 16 or thicker with banana  
plugs, spade lugs, or bare wire  
• Loudspeakers or a speaker  
selector box  
Dual  
Banana Plug  
Single  
Banana Plug  
Spade Lug  
Stripped  
AWG wire  
Before Connecting  
Remove power to all the components in your audio system.  
To Connect  
1
Insert one wire with the ridge or other marking into the red Right + (positive) speaker  
terminal on the A 23. Insert the wire without the ridge or other marking into the black  
Right - (negative) speaker terminal on the A 23.  
2
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 or other marking  
into the black right - (negative) terminal on the speaker.  
3&4  
Repeat steps 1 and 2 for the left channel  
CAUTION  
3
1
2
4
Speakers  
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 both 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
CONFIGURING THE A 23 FOR BRIDGED MONO OPERATION  
In certain applications, you may require your A 23 to power a single 8 speaker by using  
its bridged mono feature. In most instances, you won’t use the A 23 this way and you can  
skip this section.  
What You’ll Need:  
• One length of speaker wire with banana plugs, spade lugs, or bare wires  
• One shielded balanced or unbalanced interconnect cable for each A 23 used in  
bridged mono  
• One loudspeaker with an impedance of 8 or higher  
Before Connecting  
Remove power to all the components in your audio system.  
Set the A 23 Stereo - Mono Switch to its Mono (up) position.  
To Connect: From the Source  
1
2
3
Plug one end of the interconnect cable into the Balanced or Unbalanced Right  
Channel & Mono Input jack on the A 23  
Plug the other end of this cable into the desired output channel on the preamplifier  
or surround controller.  
Do not make any connection to either Left Channel Input jack on the A 23.  
To Connect: To the Speaker  
4
Insert the wire with the ridge or other marking into the red Right + (positive) speaker  
terminal on the A 23. (This is the positive speaker terminal in bridged mono.)  
5
Insert the wire without the ridge or other marking into the Left + (positive) speaker  
terminal on the A 23. (This is the negative speaker terminal in bridged mono.)  
6
7
Insert the wire with the ridge or other marking into the red + (positive) terminal on the speaker.  
Insert the wire without the ridge or  
6
7
other marking into the black --  
(negative) terminal on the speaker.  
Speaker  
8
Do not make connections to either  
of the A 23's black speaker terminals.  
4
5
3
1
C A U T I O N  
8
Common speaker connectors  
Components  
The GND notch  
signifies ground  
or speaker left  
Red ususally  
designates right  
Surround  
2
Sound  
Controller  
OUTPUTS  
Preamp  
Dual  
Banana Plug  
Single  
Banana Plug  
Spade Lug Stripped  
AWG wire  
YOU SHOULD KNOW  
IMPORTANT! - Before Trying Bridged Mono  
You should not connect a speaker with an impedance of less than 8 to the A 23 when it is  
configured for bridged mono operation. Refer to Bridged Mono Operation in the Technically  
Speaking section for additional information about. Use the right channel Gain control to  
adjust level in the bridged mode.  
 
7
MANUAL AND AUTOMATIC TURN ON-OFF OPTIONS  
You can manually turn the A 23 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 23 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.  
Connecting an Active Audio Source for Automatic On-Off  
If you want to automatically turn on the A 23 whenever music is playing (an audio  
signal is present), choose the audio triggering option by moving the Auto Turn On  
switch to its upper Audio position.  
What You’ll Need:  
An active audio source connected to the left or right Input jack on the A 23  
Before Connecting  
Remove power to all the components in your audio system.  
Make sure the Auto Turn On switch on the A 23 is in its Audio (up) 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 Left or Right Balanced or Unbalanced  
Input jacks. (Refer to to pages 2 and 3).  
Switch in up position  
Start Sensitivity at 12 o'clock  
CAUT IO N  
YOU SHOULD KNOW  
Turn Off Delay in the Audio Mode  
When the music (audio signal) stops, the A 23 will remain turned on for about five minutes. This  
delay prevents unwanted turn-off during silent passages in music or pauses between tracks.  
 
CONNECTING AN EXTERNAL DC SOURCE FOR  
AUTOMATIC ON-OFF  
8
If you want to automatically turn on and off the A 23 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 AutoTurn On switch on the a 23 rear panel is in it 12V (down) position.  
To Connect  
1
2
Plug one end of the trigger wire into the 12V Input jack on the A 23.  
Plug the other end of this wire into the external DC source  
1
CA UT IO N  
CONTROL  
2
COMPONENT  
Output  
YOU SHOULD KNOW  
If the device you want to use to control your A 23 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.  
 
9
CONNECTING THE A 23 TO TRIGGER ANOTHER COMPONENT  
Whenever the A 23 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 cable with a 2.5 mm sub-mini plug on each end (in  
addition to the one provided with the A 23)  
• A component that can be triggered with an external  
2.5 mm sub-mini plug  
+9 Vdc to +12 Vdc source. The A 23 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
2
Plug one end of the trigger wire into the 12V Out jack on the A 23.  
Plug the other end of this wire into the component that you want the A 23 to trigger.  
1
CA UTI ON  
CONTROL  
2
COMPONENT  
Input  
YOU SHOULD KNOW  
If the device you want to use to control your A 23 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 white stripe is negative.  
 
10  
UNDERSTANDING THE INDICATORS ON THE A 23  
A
AC Present Indication  
When the A 23 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
C
On and Off Indications for Both Manual and Automatic Modes  
When the A 23 is first turned on, the soft blue glow behind the On-Off button turns red for about  
five seconds and then becomes a brighter blue.  
Channel Status Indicators  
These are two small round indicators in the center of the recess in the front panel. The indicator  
on the left displays the status of the left channel and the indicator on the right displays the status  
of the right channel.  
D
E
No Illumination:  
When the A 23 is turned off, these indicators are off.  
Blue Illumination of Channel Status Indicator:  
When both channels are operating normally, these both glow blue.  
F
No Illumination of Channel Status Indicators:  
A blue channel indicator will stop glowing if there is a fault in its corresponding amplifier  
channel. If this occurs for either channel, the halo glow behind the On-Off button will also  
change from blue to red.  
G
H
High-Temp Indicator  
This indicator is near the right side of the panel recess. It will glow red if either channel overheats.  
Level Controls  
We recommend that you rotate the Left and Right Level controls to their maximum clockwise  
positions, marked THX Reference. Refer to Level Controls in Technically Speaking for more  
information about setting level controls.  
I
Ground Switch  
The Ground switch can assist in reducing audible hum caused by ground loops in your system.  
Leave this switch in its Normal (down) position unless you hear hum through your speakers (you’ll  
only be able to hear this hum after your entire system is installed and operating). You can try the  
Lift (up) position to eliminate it. Please refer to the Technically Speaking section for detailed  
technical information about the causes of ground loops and what you can do about them.  
A
B
G
C
D
E
F
H
I
H
50  
3
C A U T I O N  
 
11  
CONNECTING THE AC POWER CORD  
AC Power Connections  
We recommend that you plug your A 23 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 23 requires AC power that is continuous,  
rather than switched on and off.  
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
2
Plug the female end of the AC cord to the AC receptacle on the rear of the A 23.  
Plug the male end of the AC cord to an AC outlet or power strip.  
AC Voltage Selection Switch  
The A 23 can operate on either 110-120 Vac or 220-240 Vac operation. When you  
purchased your A 23, its rear panel Voltage Selector switch was already set for the  
proper voltage in your area. Nevertheless, it’s wise to double-check it before plugging  
into an AC outlet.  
If you move to a location with a different line voltage, you can easily convert the A 23.  
For 110-120 Vac Operation: Remove the lock-out bracket with a phillips screwdriver.  
Next, slide the switch sideways toward the left until the indent on the switch lines up  
with the 115/60Hz label on the rear panel. The main fuse value should be 6.3 A for  
110-120 Vac operation  
For 220-240 Vac Operation: Remove the lock-out bracket with a phillips screwdriver.  
Next, slide the switch sideways toward the left until the indent on the switch lines up  
with the 230V/50Hz label on the rear panel. The main fuse value should be 3.15 A for  
220-240 Vac operation  
If you’re unsure about the correct setting for your region, please consult your Parasound  
dealer or a qualified service technician.  
1
2
 
12  
MAINTAINING YOUR A 23  
Your Parasound A 23 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:  
 
13  
TROUBLESHOOTING GUIDE  
PROBABLE CAUSE  
REMEDY  
TROUBLE  
Power cord is disconnected  
Connect power cord  
No power  
Auto On selector switch is in wrong  
position  
Check for correct position of the Auto On switch  
Make sure the switch is in the  
correct position for your region  
AC Voltage selector switch is in the  
wrong position  
Replace with same value fuse  
AC fuse blown  
DC trigger source wired in reverse  
or voltage too low  
A 23 will not turn on  
with DC voltage  
Check polarity of DC source with a voltmeter  
Try connecting a 9 V battery to the 12V DC input  
Auto On selector switch in wrong  
Make sure Auto On selector switch  
position  
is in its 12V position  
Make sure Auto On selector switch  
is in its Audio position  
Auto On selector switch in wrong  
position  
A 23 will not turn on with  
audio source  
Sensitivity incorrectly adjusted  
Turn the Audio trigger Sensitivity  
knob counterclockwise  
A 23 will not turn off when Sensitivity level too high  
audio signal is removed  
Turn Sensitivity knob clockwise toward 200mV  
Level controls turned too low  
Power on, but no sound  
Turn level controls clockwise  
Bad connection from preamplifier or Check input connections or try a  
different set of cables  
controller  
Over-current protection circuitry has  
been activated- one or both blue  
channel LEDs not illuminated  
Check speaker load impedance. Check speaker  
wires and connections  
A 23 has overheated - red Hi Temp  
indicator is on  
Allow A 23 to cool. Check that there is adequate  
ventilation around the A 23. Be sure the load  
impedance of each channel is no less than 4  
Distorted sound  
Damaged speaker  
Connect each speaker to the opposite channel  
on the A 23. If the same speaker remains distorted,  
the speaker or its wire is damaged. If the other  
speaker distorts, the problem may be with the  
A 23, the preamp, or a source component  
Problem with preamplifier or source Switch the left and right input cables. If  
distortion moves to the other channel, the  
problem is with a component other than the A 23  
component  
Move to the correct position for the  
jack in use  
Balanced-Unbalanced switch is in  
the incorrect position  
Mono Bridge switch is in the Mono Move switch to its Stereo position  
bridged position  
Hum and / or buzz  
through speakers  
Move the Ground Lift switch to its Lift position  
Ground loop between preamplifier  
and A 23 or at the equipment rack  
Install nylon shoulder washers on both sides of  
the panels of all equipment to insulate metal  
from touching the rack  
Move the Ground Lift switch to its Lift position.  
Install cable isolation device such as the  
Xantech 634 Ground Breaker  
Ground loop from cable TV  
Other ground loop  
Contact Parasound Technical Service  
Load impedance at speaker terminals Make sure the speaker or speaker  
is too low  
A 23 is overheating  
selector load is 4 ohms or higher  
Not enough ventilation  
Make sure the A 23 has adequate ventilation  
 
14  
SERVICING YOUR A 23  
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 23 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 23 to Parasound for Service  
If Parasound determines that you should send your A 23 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 23  
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 23. 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.  
 
15  
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 200 mV  
(fully clockwise). If you set this control to 50 mV, the A 23  
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 200 mV, the A 23 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.  
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.  
This phenomenon of rejecting noise signals common  
to both positive and negative conductors is called  
common mode rejection. Differential inputs are  
specified according to how well they reject signals  
common to both conductors. This is measured in dB  
and is called the common mode rejection ratio or CMRR.  
Bare Speaker Wire Ends  
If you plan to use connections with bare wire ends,  
use a wire stripper to remove just enough insulation  
to expose a 1/2” (13mm) length of bare wire. You can  
insert the stripped wire into the hole that goes  
sideways through the terminal's metal post. Before  
inserting 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.  
Balanced and Unbalanced Lines  
Recording and broadcast studios use balanced  
connections 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.  
Bridged Mono Operation  
Unbalanced connections with RCA jacks are found on  
all home audio equipment. RCA jacks and two-  
conductor wires are less costly than the additional  
circuitry, higher priced XLR connectors and three-  
conductor wiring required for balanced connections.  
In normal operation, the left and right amplifier  
channels each amplify both the positive and negative  
halves of the musical signal. In bridged mono  
operation, the A 23’s entire left channel drives only  
the positive half of the musical signal and its entire  
right channel drives only the negative half of the  
musical signal. This doubles its voltage swing.  
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.  
This doubled voltage swing enables the A 23 to  
deliver double its 150 watts per channel 4 power, or  
300 watts, into a single 8 speaker.  
The audible benefit of this higher power is increased  
dynamic range, or headroom, so that musical peaks  
can be reproduced with less distortion. Considering  
that musical peaks and crescendos require 10-100  
times as much power as average listening levels, this  
added headroom is a substantial advantage for  
unrestrained, undistorted listening, even if your  
average listening level is moderate.  
Balanced lines are superior because they utilize  
separate 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  
component 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.  
Bridging allows an amplifier to deliver more power into  
a single speaker because in this mode, the load appears  
to the amplifier as only half of its rated impedance.  
Thus, the single 8 speaker appears as a 4 load and  
a 4 speaker appears as only a 2 load.  
The A 23 is not capable of driving 2 for extended  
periods because it will draw more current and  
generate more heat than it can dissipate. We strongly  
recommend against using speakers rated at less than  
8 when bridging.  
A
differential input circuit amplifies only the  
difference between the positive and negative 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 somehow gets into a  
Remember that mono bridging requires a separate A 23  
for each speaker. You can’t simultaneously drive two  
speakers in stereo and one speaker mono bridged.  
 
16  
TECHNICALLY SPEAKING continued  
Choosing Brands of Interconnect Cables and Loop Out Jacks  
Speaker Wire  
The Right and Left Loop Out jacks are convenient  
connections to route the same input signals from  
your preamplifier or surround controller to an  
additional power amplifier. These jacks eliminate the  
need for “Y” connectors to split the source signal  
between your A 23 and another amplifier. The Loop  
Out jacks work with either the Balanced or the  
Unbalanced Input jacks. Here are some examples of  
where you could use the Loop Out jacks:  
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 amplifiers use robust circuitry  
that sounds superb regardless of interconnects and  
speaker wires. Therefore, we feel that choosing a  
brand of cable for Parasound amplifiers is purely a  
matter of personal taste.  
1. When multiple speakers and amplifiers are to be  
played simultaneously, you can route the output of your  
preamplifier or controller to the first A 23 then connect  
Eliminating Hum and Buzz - Ground Loops and the  
A 23 Ground Lift Switch  
Audible hum and buzzing noises in a system are  
usually related to issues with the component its Loop Out jacks to a second A 23 (or other amplifier)  
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 addition to the hum.  
to power additional speakers for the same channel.  
2. Some high-end speaker manufacturers recommend  
bi-amplifying or “bi-amping” without using an  
electronic crossover. When bi-amping this way, one A 23  
drives only the woofers and another A 23 drives only  
the tweeters. For example, you could connect the left  
and right channel outputs of the preamplifier to the  
inputs of the first A 23 to power the woofers, and then  
connect its Loop Out jacks to the second A 23 to  
power the tweeters.  
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. 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.  
Level Controls  
When the Level knobs are turned fully clockwise, the  
actual level controls are essentially out of the circuit.  
The left and right channels are perfectly matched, and  
your A 23 can reach its fullest sonic potential.  
In some cases, you’ll need to reduce the level  
settings. For example, if you find it difficult to make  
precise volume adjustments at low listening levels,  
your preamplifier or surround controller probably has  
a very high output (or gain) that you can match by  
reducing the A 23’s level. Conversely, if you need to  
advance your preamplifier or surround controller’s  
volume to nearly the top of its range for average  
listening levels, you should increase the level settings  
on the A 23. The A 23 Level adjustment that optimizes  
the range of motion on the preamplifier’s volume  
control is sometimes called “gain staging”.  
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 23.  
(See Balanced and Unbalanced Lines in this section).  
2. When rack mounting, always use insulated  
“shoulder” washers. These break the ground loops  
caused by metal-to-metal contact between the rack,  
the units, and their rack-mount bolts. Washers are  
included in Parasound rack mount kits. Extras are  
available from rack manufacturer Middle Atlantic  
3. Use the Ground Lift switch on the A 23 to eliminate  
most ground loops. This separates the A 23’s signal  
input ground from its chassis ground to isolate  
unwanted voltage in the ground shields of the  
unbalanced (RCA) interconnect cables. Be sure your  
system installation is finished before you try moving the  
Ground Lift switch from its "Normal" to its "Lift" position.  
 
17  
PARASOUND A 23 DESIGN OVERVIEW  
Circuit designed by John Curl  
Parasound design consultant John Curl has been a To create the +/- 55 Vdc B+ and B- supply rails for each  
legend among audiophiles and electronic engineers channel, we use high-speed rectifier diodes and four  
for decades. He pioneered measurements to correlate enormous 12,000 uF Elna electrolytic filter capacitors,  
musical accuracy with the materials used in parts, chosen for their low Equivalent Series Resistance  
worked with world-class touring companies, has (ESR) and dielectric absorption. In addition, these  
designed highly coveted audio classics, including the filter capacitors are bypassed with smaller  
original Mark Levinson JC-2, Denneson JC-80, polypropylene capacitors to reduce AC ripple in the  
Vendetta Phono Preamplifier, and CTC Blowtorch DC supply and to further eliminate noise and  
preamplifiers; master recorders for Wilson Audio and interference that is generated in AC power lines from  
Mobile Fidelity; and the mixing consoles used in live computers and other appliances in the home.  
concerts by The Grateful Dead and the Montreux Jazz  
Festival in Switzerland.  
Audio Circuit Path Topology  
Parasound’s circuit topology is a hybrid of carefully  
As our featured amplifier designer since 1990, he has chosen discrete transistors that result in superior  
created many products that have earned Parasound performance at each stage. We use JFETs (Junction  
worldwide acclaim. John is particularly proud of what Field Effect Transistors) for the input stage; MOSFETs  
he and Parasound have accomplished together: “The (Metal Oxide Field Effect Transistors) for the driver  
circuits I design for Parasound are extremely stage and bipolar transistors for the output stage.  
sophisticated and are typical of products that are far Discrete transistors are more sonically accurate than  
more expensive. I can’t think of any other audio integrated circuits commonly used by other brands.  
products that offer nearly as much bang for the buck.”  
Complementary Configuration  
Each stage of amplification has transistors fed by the  
Parts Selection  
Every part within the A 23 is carefully chosen for its positive DC power supply and complementary  
accuracy and reliability. Metal film resistors with 1% transistors fed by the negative DC power supply.  
tolerance are selected for their precision and because Thus, half of the devices amplify the positive half of  
their values don’t drift as they heat up during the musical waveform while the other half of the  
operation. Polypropylene and mica capacitors are devices  
amplify  
the  
negative  
half.  
This  
used extensively for their superior linearity and low complementary topology is inherently linear, which  
dielectric absorption. Semiconductors are selected for reduces distortion and improves sonic accuracy.  
superior performance in their specific roles in the  
circuit. Gold has the best conductivity of any metal, so The Input Stage  
we use high quality gold-plated input connectors and The A 23’s input stage uses matched pairs of discrete  
speaker terminals. The double-sided circuit boards JFETs arranged in a differential configuration. JFETs  
are FR4 glass epoxy for long-term durability. The are ideal for the input stage because their inherently  
chassis is made of heavy gauge steel to safely house high impedance is unaffected by the impedance of  
the internal circuitry. This attention to detail when selecting source components. Differential configuration  
parts makes the difference between a very good amplifier provides superior noise reduction. These precision  
and an outstanding amplifier.  
input JFETs are also cascoded to produce the current  
necessary to drive the MOSFET drivers in the  
following stage.  
The Power Supply  
The heart of the power supply is a 1 kVA toroidal  
power transformer, chosen for its efficiency, low hum The Driver Stage  
field, and high power rating. Encapsulating this The driver stage provides critical amplification for  
massive power transformer in an epoxy-filled steel which we employ a complementary matched pair of  
canister assures ultra-quiet performance.  
MOSFETs selected for their tube-like sonic qualities.  
MOSFETs tend to generate less odd-order harmonic  
The A 23 power transformer employs multiple distortion than bipolar transistors. This is important  
independent secondary windings so that each because odd-order distortion sounds unnatural and  
amplifier channel has its own power supply, assuring fatiguing to the human ear, whereas even-order  
more than ample DC voltage at all times and under all distortion is less offensive because it is consonant,  
conditions. It also reduces inter-channel crosstalk that rather than dissonant. Our MOSFET driver stage  
can blur the sound and impair the correct sense of prevents the harshness and brittle sound so often  
where instruments are positioned.  
found in other amplifiers.  
 
18  
PARASOUND A 23 DESIGN OVERVIEW continued  
The Output Stage  
Parasound power amplifiers incorporate ingenious  
The amplifier’s sonic characteristics are established  
by its input and driver stages. Now, the sole job of its  
output stage is to deliver the enormous current and  
voltage from its power supply to the speakers. Bipolar  
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 three pairs of high current (15-  
ampere) bipolar transistors to insure long-term  
reliability, 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 23.  
and fast-acting DC servo circuits, completely  
eliminating the need for coupling and blocking  
capacitors. The A 23 is direct-coupled from its input  
jacks to its speaker terminals. This advanced circuitry  
never needs adjustment or maintenance. It operates  
outside the audio signal path to keep the DC offset at  
the output of the A 23 at a constant 0.00 Vdc. The  
results are startling clarity, freedom from listening  
fatigue, and formidable bass response.  
Relay Protection  
Each channel of the A 23 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 23 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 23 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.  
Over-Current Protection  
Specialized current-sensing transistors are connected  
to the output stages of the A 23 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.  
Fuse Protection  
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.  
Total Protection  
DC Servo  
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.  
 
19  
PARASOUND A 23 SPECIFICATIONS  
Continuous Power Output - Stereo  
125 watts RMS x 2, 20 Hz-20 kHz, 8 ,  
both channels driven  
Loop Output Level  
Same as input level  
200 watts RMS x 2, 20 Hz-20 kHz, 4 ,  
both channels driven  
S/N Ratio  
> 112 dB, input shorted, IHF A-weighted  
Continuous Power Output - Mono  
Damping Factor  
400 watts RMS, 20 Hz-20 kHz, 8 Ω  
> 800 at 20 Hz  
Current Capacity  
DC Trigger Requirements  
45 amperes peak per channel  
+9 Vdc to +12 Vdc, 2 mA  
Slew Rate  
Audio Trigger Requirements  
> 130 volts per microsecond  
50 mV AC - 200 mV AC  
Frequency Response  
DC Trigger Output Capacity Requirements  
5 Hz-100 kHz, +0/-3 dB at 1 watt  
+12 Vdc, 150 mA  
Total Harmonic Distortion  
Dimensions  
< 0.06 % at full power  
Width: 17-1/2” (437 mm)  
< 0.03 % at typical listening levels  
Panel Height: 3-1/2” (88 mm)  
Total Height with feet: 4-1/8” (105 mm)  
Total Height with rack adapter attached: 3-5/8”  
Depth: 13-3/4” (350 mm)  
IM Distortion  
< 0.04 %  
TIM  
Power Requirement  
Unmeasureable  
Standby: 25 Watts  
Full Power into 4 : 700 Watts  
Dynamic Headroom  
> 1.5 dB  
Net Weight  
28 lb.(12.7 kg)  
Interchannel Crosstalk  
> 80 dB at 1 kHz  
> 63 dB at 20 kHz  
Shipping Weight  
35 lb.(15.9 kg)  
Input Impedance  
33 k Ω  
Input Sensitivity  
Balanced-1 V for 28.28 V output into 8 Ω  
Unbalanced-1 V per leg for 28.28 V output  
into 8 Ω  
Features and specifications subject to  
change without notice.  
© Parasound Products, Inc. 2002. V 1.0  
 
Parasound Products, Inc. 950 Battery Street, San Francisco, CA 94111  
415-397-7100 / Fax 415-397-0144 www.parasound.com  
 

Milwaukee Handheld TV SM806 User Manual
MTD Lawn Mower 050 thru 062 User Manual
Multi Tech Systems Network Card MT5634ZBA VV90 User Manual
Nilfisk ALTO Vacuum Cleaner 40 User Manual
Oki Printer 8 8N User Manual
Onkyo Home Theater System PHC 5 User Manual
Onkyo Network Hardware T 4070 User Manual
Optoma Technology Headphones HD8600 User Manual
Panasonic Cassette Player CQ VX777EUC User Manual
Panasonic Smoke Alarm 6362 User Manual