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Parasound A 52 User's Manual
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1. ponent receiving the signal they are equal but 180 degrees out of phase with each other with respect to ground lo send and receive balanced signals requires special differential circuitry 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 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 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 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 m
2. 20 kHz 8w 225 watts RMS x 5 continuous 20 Hz 20 kHz 4w Current Capacity 30 amperes peak per channel Slew Rate gt 130 volts per microsecond Frequency Response 5 Hz 100 kHz 0 3 dB at 1 watt Total Harmonic Distortion lt 0 2 at Tull power lt 0 03 at typical listening levels IM Distortion lt 0 04 TIM Unmeasureable Dynamic Headroom 1o dB Interchannel Crosstalk gt 8 dB at 1 kHz gt 63 dB at 20 kHz Input Impedance Unbalanced 47k w Balanced 94k w V 1 0 Features and specifications subject to change without notice Input Sensitivity for 28 28 V Output into 8 vi Unbalanced 1 V Balanced 1 V per leg S N Ratio 113 dB input shorted IHF A weighted 104 dB input shorted unweighted Damping Factor 1000 at 20 Hz DC Trigger Requirements 9 Vdc to 12 Vdc 2 mA Audio Trigger Requirements 50 mV AC 250 mV AC DC Trigger Output Capacity Requirements 12 Vdc 150 mA Dimensions Width 174 437 mm Panel height 5 133 mm Height with feet 5 150 mm Depth 19 501 mm Power Requirement otandby 25 Watts Full Power into 8w 1200 Watts Net Weight 50 Ib 22 8 kg Shipping Weight 64 Ib 29 kg Parasound Products Inc 2002 PARASOUND Parasound Products Inc 950 Battery Street San Francisco CA 941 I 415 397 7100 Fax 415 397 0144 www parasound com
3. 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 e An IEC 65 AC Cord provided e An AC outlet or high quality AC power strip within reach of the AC cord Before Connecting Q Remove power to all the components in your audio system To Connect Plug the female end of the AC cord to the AC receptacle on the rear of the A 52 Plug the male end of the AC cord to an AC outlet or power strip PARASOUND A52 Amplifier Parasound Products Inc San Francisco CA USA 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 amplifiers 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 TROUBLESHOOTING GUIDE TROUBLE No power Auto turn on doesn t function with a trigger voltage Auto turn on doesn t function with an audio input signal Power on but no sound A52 will not turn off when audio signal is removed On Off button glows red and channel indicator s off Distorted sound Hum and or buzz through speakers A 52 is overheating PROBABLE CAUSE Power cord is disconnected
4. Audio triggering Sensitivity adjustment knob on the rear panel to the desired level otart 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 Auto Turn On Switch set to up position PARASOUND 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 To automaticallv turn on and off the A 52 with an external DC voltage choose the DC Triggering option bv moving the Auto Turn On switch on the rear panel to its lower 12V position What You ll Need Ll A cable with a 2 5 mm sub mini plug on each end provided e A control component with 9vdc to 12vdc trigger voltage 2 5 mm sub mini plug Before Gonnecting Q Remove Power to all the components in your audio system Q Make sure the Auto Turn On switch on the A 52 rear panel is in its 12v down position To Connect Plug one end of the trigger wire into the 12v Input jack on the A 52 Plug the other end of this wire into the external DC source Audio Turn On Switch set to down position Balanced PARASOUND Normal mus PF around Balanced it Input Unbalanced ff Unbalanced ff Unbalanced ff Unbalanced f
5. that there is adequate ventilation around the A 52 Be sure the load impedance of each channel is no less than 4 ohms 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 Switch the input cables If distortion moves to another channel the problem is with a component other than the A 52 Move to the correct position for the jacks In use 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 Move the Ground switch to its Lift position Install a cable isolation device such as the Xantech 634 Ground Breaker www xantech com Contact Parasound Technical Service Make sure the speaker or speaker selector load is 4 ohms or higher Make sure the A 52 has adequate ventilation 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 VVe 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 th
6. the length of your speaker wire as short as possible e 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 e Do not use speaker wire that is thinner than 16 AWG e Keep wire lengths for both channels as close to equal as possible 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 Tum On switch on the rear panel to its middle Man Manual position Auto Turn On Switch set to middle position PARASOUND 9 A52 Amplifier Parasound Products Inc ft A 9 A AN Connecting an Active Audio Source for Automatic On Off If you want to automatically turn on the A 52 whenever music is plaving 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 e An audio source that s playing Before Connecting Q Remove power to all the components in your audio system Q Make sure the Auto Turn On switch on the A 52 is In its Audio upper position Q Set the
7. 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 pies three rack spaces 54 or 133 mm When mounting equipment below the A 52 you will also need to allow about below the unit for the bottom chassis screws A single standard rack space allows 1 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 e Remove the two screws from each side of the A 52 s top cover e 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 CONNECTING A SURROUND CONTROLLER TO THE BALANCED INPUTS ON YOUR A 52 Left and Right Balanced Input Jacks Balanced connections will give you the best soun
8. Auto Turn On selector switch is in wrong position AC fuse blown DC trigger source wired in reverse or voltage too low Auto Turn On selector switch is in wrong position Auto Turn On selector switch is in wrong position REMEDV Connect power cord to a live AC outlet Check for correct position of the Auto Turn On switch Replace with same value fuse Check polaritv of DC source with a voltmeter Try connecting a 9V battery to the 12V DC input Make sure Auto Turn On selector switch is in its 12V position Make sure Auto Turn On selector switch is in its Audio position Sensitivitv incorrectiv adjusted Turn the Audio trigger Sensitivitv knob counterclockwise Sensitivitv level too high Bad connection from surround controller Over current protection circuitry has been activated one or more blue channel LEDs not illuminated A 52 has overheated red Hi Temp indicator is on Damaged speaker Problem with surround controller or source component Balanced Unbalanced Input switch is in the incorrect position Ground loop between surround controller and A 52 or atthe equipment rack Ground loop from cable TV Other ground loop Load impedance at speaker terminals is too low Not enough ventilation Turn Sensitivity knob clockwise toward 250 mV Check input connections or try a different set of cables Check speaker load impedance Check speaker wires and connections Allow A 52 to cool Check
9. HALO PARASOUND A 52 Amplifier Owners Guide THANK YOU Congratulations and Thank You for Choosing Parasound Your new Parasound Halo Series A 52 power amplifier presents the latest advancements in amplifier technology The A 52 is built to the strict quality and performance standards set by Parasound VVe re proud to offer you this exceptional audio component that will bring you many years of enjoyment and dependabilitv Here at Parasound we design our products to perform at a higher level of flexibility and sonic performance than you may have expected We encourage you to read this entire manual to learn all the features and capabilities of your new Halo Series A 52 Amplifier If you re eager to get up and running right away simply follow the basic step by step instruc tions to connect and operate the A 52 If you want to learn about some of the technical and design aspects of your A 52 refer to the Technically Speaking and Parasound A 52 Design Overview sections in the back of the manual If you run into difficulties the Troubleshooting Guide should help you quickly remedy the problem We appreciate you taking the time to read these instructions and thank you for selecting Parasound for your listening pleasure The Parasound Staff Unpacking Your A 52 Unpack your A 52 from the shipping carton remove the AC power cord and the control wire with a 2 5 mm sub mini plug on each end This is the trigger connection wire Whil
10. 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 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 design for Parasound are extremely sophisti cated and are typical of products that are far more expensive 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
11. cess 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 All Indicators Illuminated When all five channels are operating normally these will all glow blue 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 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 cu PARASOUND CONNECTING THE A 52 AC POWER CORD AC Power Gonnections 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 circult 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
12. d 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 a m What You ll Need e Five balanced interconnect cables with XLR connectors 44 On onae A surround controller with balanced output connectors XLR Connectors Before Gonnecting Q Leave the A 52 s AC cord disconnected until you have made all other connections to prevent any surprise burst of sound Q Make sure that all your cables are long enough so they are not strained or stretched once they are connected Q 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 Plug the male end of the first balanced interconnect cable into the Balanced Ch 1 input Jack on the A 52 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 C Repeat steps 1 and 2 above to connect Ch 2 Ch 3 Ch 4 and Ch 5 OUTPUTS SURROUNDE 08 00 0000 O Ta 7 z Inputs Switch set to up position Ground Switch set to down position Balanced mi f o e 0 6 PARASOUND Man A 52 Amplifie
13. e 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 a
14. e lugs or bare ends Dual Single Spade Lug Salen Banana Plug Banana Plug AWG wire Five loudspeakers Before Connecting Q 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 MB 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 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 Repeat steps 1 and 2 for Ch 2 then Ch 3 then Ch 4 and finally Ch 5 Inpu 6 Ch 3 SPEAKERS es 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 e Keep
15. e that all your cables are long enough so they are not pulled or stretched once they are connected Q 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 Plug one end of the cable into the Unbalanced Ch 1 Input jack on the A 52 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 C Repeat steps 1 and 2 for Ch 2 Ch 3 Ch 4 and Ch 5 OUTPUTS SURROUND e CONTROLLER Inputs Switch set to down position Ground Switch set to down position r Moisture 250V1 II5V Area T8A 250V 230V 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 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 EP ES M What You ll Need ff 4 f Five lengths of AWG 16 or thicker speaker wire 4 with banana plugs spad
16. e you are unpacking your new amplifier inspect it thoroughiv for possible shipping damage If you see any contact your Parasound dealer right away Be sure to save and store both the inner and outer cartons and the packing inserts for possible future transport lo save room for storage you can cut the seams on the bottom of the cartons and flatten them Keeping Records for Future Reference Record the serial number located on the bottom of your A 52 In the space below Also note your Parasound Dealers name and phone number VVe recommend that you keep your purchase receipt with this manual and store them both in a safe place You may need to refer to this information sometime in the future Parasound A 52 Amplifier Serial Parasound Dealer Phone Number Date of Purchase YOU SHOULD KNOW There is no Parasound warranty for this unit if it was not purchased from an Authorized Parasound Dealer Investigate any warranty claims made by unauthorized dealers very carefully as you will need to depend entirely upon the dealer and NOT upon Parasound Unauthorized dealers may lack the capability to arrange repairs of Parasound equipment Authorized Parasound Dealers are listed at www parasound com or you can call 415 397 7100 between 8 30 am and 4 30 pm Pacific time A missing or tampered serial number could indicate that this unit was stolen or sold by an unauthorized dealer If this unit is missing its serial number you should return it to you
17. f Unbalanced Or Moisture T8A 250V 230V Area 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 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 e A wire with a 2 5 mm sub mini plug on each end in addition fm to the wire provided with the A 52 AG mem li e A component that can be triggered with an external 9 Vdc to 12 Vdc source he A 52 DC trigger output provides up to 150 mA of current Before Gonnecting Q Remove power to all the components in your audio system To Gonnect Plug one end of the trigger wire into the 12V Output jack on the A 52 Plug the other end of this wire into the component that you want the A 52 to trigger Auto Turn On Switch set to down position Balanced Normal Inputs Balanced f j MZ Balanced j NEY Balanced ff MZ Balanced MU Balanced Unbalanced Unbalanced Unbalanced Unbalanced Manufactured under R K OF ELECTRIC SHOCK BOT OFE O O YOU SHOULD KNOW If the device you want your A 52 to contr
18. gether 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 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 PARASOUND A52 Amplifier 2 Ground Switch set to up position 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 Atlantic Products www middleatlantic com 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 To Prevent Fire Or Shock Hazard Do Not Expose This Unit To Rain Or Moisture Fuse TI5A 250VI 1I5V Area T8A 250V 230V Area C AC 15V 60Hz DI AC 230V 50Hz EJ Power Consum ption 1350W PARASOUND A 52 DESIGN OVERVIEW Circuit Designed by John Curl Parasound design consultant John Curl has been a legend
19. igh 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 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 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 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
20. nd 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 TECHNICALLY SPEAKING Audio Trigger Sensitivity Adjustment The Audio Sensitivity Control sets the threshold of the audio trigger signal You can adjust this level from a maximum sensitivity of 50 mV fully counterclockwise to a minimum sensitivity of 250 mV fully clockwise If you set this control to 50 mV the A 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 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 h
21. nd 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 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 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 lt 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 p
22. ol 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 UNDERSTANDING THE INDICATORS ON THE A 52 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 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 Channel Status Indicators These are the five small round indicators in the center of the re
23. olten solder to each stripped bare wire to prevent it from unraveling fraying and oxidizing 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 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 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 to
24. ower 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 DC Servos Direct Current DC burns out speakers Every power amplifier must have some way to insure that DC from its power supply never reaches its or speaker terminals Most amplifiers simply use trim controls to reduce their DC 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 A 52 is direct coupled from its input jacks to its speak er 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 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 con
25. 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 The Power Supply The heart of the power supply s 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 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 electrolytic filter capacitors chosen for their low Equivalent Series Resistance ESR and dielectric absorption In addition these filter capacitors are bypassed with smaller polypropylene capacitors to reduce AC ripple in the DC supply and to further eliminate noise and interference that is generated in AC power lines from computers and other appli ances in the home Relay Bypassed Sof
26. r Unbalanced Output Input 12v NV Normal Parasound Products Inc Inputs Po Ground San Francisco CA USA Auto Turn On Omer Oa oa gt A O LUCASFILM Input EN Input awm f input To Prevent Fire Or Shock Hazard X Unbalanced Unbalanced Unbalanced fs Unbalanced Unbalanced Do Not Expose This Unit To Rain H S U e Or Moisture Try o Fuse a d under fil fil sz RZ O O O i M i E 1 1 1 i O O 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 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 e Five shielded interconnect cables with RCA plugs e A surround controller with five RCA output jacks RCA Plugs Before Connecting Q Leave the AC cord on the A 52 disconnected until you have made all other connections to prevent any surprise burst of sound Q Make sur
27. r dealer immediately for a full refund TABLE OF CONTENTS A 52 Amplifier PLACEMENT GUIDELINES FOR YOUR A 52 CONNECTING A SURROUND CONTROLLER TO THE BALANCED INPUTS ON YOUR A 52 CONNECTING A SURROUND CONTROLLER TO THE UNBALANCED INPUTS ON YOUR A 52 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 MAINTAINING YOUR A 52 TROUBLESHOOTING GUIDE SERVICING YOUR A 52 TECHNICALLY SPEAKING PARASOUND A 52 DESIGN OVERVIEW PARASOUND A 52 SPECIFICATIONS 10 11 12 13 14 16 18 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 e Place the A 52 on a separate shelf that will adequately support its weight e Keep it away from heat sources such as air ducts or radiators e Avoid placing it on carpeting or another material that might obstruct airflow into the openings in the chassis bottom e Leave at least 3 of space around both sides and 6 of space above the top The bottom clearance can be a little less e Do not block the front of the A 52 behind closed cabinet doors during use e Do not stack the A 52 with other components inside a cabinet
28. t 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 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 suppl
29. tacts 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 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 overcurrent 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 PARASOUND A 52 SPECIFICATIONS Power Output All Channels Driven 125 watts RMS x 5 continuous 20 Hz
30. y Thus halt 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 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 PARASOUND A 52 DESIGN OVERVIEW continued The Driver Stage 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 The Output Stage The amplifiers sonic characteristics are established by its input and driver stages Now the sole job of Its output stage is to deliver the enormous current a
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