Krell Industries KAV-250a/3 User's Manual
Contents
1. 250 The Leader in Audio Engineering A Stereo Power Amplifier 250 3 Three Channel Power Amplifier instructions for Use v 99 2 Owner s Reference 250 Stereo Power Amplifier and 250 3 Three Channel Power Amplifier Instructions for Use v 99 2 Cover KAV 250a 3 Three Channel Power Amplifier Krell Industries Inc 45 Connair Road Orange CT 06477 3650 USA TEL 203 799 9954 FAX 203 799 9796 E MAIL krell krellonline com WEBSITE http www krellonline com This product complies with the EMC directive 89 336 EEC and the low voltage directive 73 23 EEC WARNINGS The amplifier must be placed on a firm level surface where it is not exposed to dripping or splashing The ventilation grids on the top of the amplifier and the space underneath the amplifier must be unobstructed at all times during operation Do not place flammable material above or beneath the amplifier Contact your authorized Krell dealer distributor or Krell before using any devices designed to alter or stabilize the AC power for the KAV 250a KAV 250a 3 Before connecting the 250 or KAV 250a 3 make sure the amplifier is off and any output device such as a preamplifier is in mute or stand by mode Make sure all cable terminations are of the highest quality and free from frayed ends short circuits or cold solder joints Use only one set of inputs to the amplifier at a time A2. 1 slow blow 20 amp for 100 120 V or 12 amp for 220 240 V or 250 3 fuses 8 9 amp 1 slow blow 20 amp for 100 120 V or 12 amp for 220 240 V 1 12 VDC output 12 V trigger cable 1 IEC connector power cord 1 T 15 Torx wrench 1 packet containing the owner s reference manual and the warranty registration card Grasp the underside of the foam end caps that encase the amplifier and lift the amplifier straight out of the shipping box Place the amplifier in a safe location and remove the protective plastic wrapping Notes If any of these items are not included in the shipping box please contact your authorized Krell dealer distributor or Krell for assistance Save all packing materials If you ship your amplifier in the future repack the unit in its original packaging to prevent transit damage See Return Authorization Procedure on page 29 for more information 2 KAV 250a and 250 3 Amplifiers Before you integrate the 250 KAV 250a 3 into your system review the following guidelines to choose the location for the component This will facilitate a clean trouble free installation The KAV 250a and KAV 250a 8 require at least two inches 5 cm of clearance on each side and at least two inches 5 cm of clearance above the component to provide adequate ventilation Your amplifier does not require any type of special rack or cabinet for installation For
3. closest to the power supply The cable snaps into place Connect the other end of the ribbon connection cable to jumper pin J6 on the center amplifier channel Option 2 To bridge center and right amplifier channels connect one end of the ribbon connection cable to jumper pin J4 on the center amplifier channel Connect the other end of the ribbon connection cable to jumper pin J6 on the right amplifier channel Replace cover slide the front panel end in first Using the T 15 Torx wrench secure the 12 screws The 250 3 amplifier is now ready for bridged operation Connecting the Bridged 250 3 See Figure 4 on page 11 1 When the left and center amplifier channels are bridged Option 1 connect the output cable from the output device to the center balanced XLR 17 or single ended RCA 20 input Connect the positive loudspeaker lead red to the positive binding post on the center amplifier channel 23 Connect the negative loudspeaker lead black to the positive binding post of the left amplifier channel 24 250 and 250 3 Amplifiers m 21 2 When the center and right amplifier channels are bridged Option 2 connect the output cable from the output device to the right balanced XLR 16 or single ended RCA 19 input Connect the positive loudspeaker lead red to the positive binding post on the right amplifier channel 22 Connect the negative loudspeaker lead black to the p
4. the dimensions of your amplifier see Specifications on pages 30 and 31 Place the amplifier as close to the loudspeakers as possible and keep the speaker cable length to a minimum Speaker cable adds impedance to the load the amplifier must drive regardless of the cable s gauge Krell amplifiers drive the lowest impedances with ease but long speaker cables reduce the maximum power that is delivered to the loudspeakers AC POWER GUIDELINES Krell recommends operating each amplifier from a dedicated 15 amp AC power line For maximum power output operate the 250 or 250 3 amplifier from a dedicated 20 amp AC power line 250 2508 3 Amplifiers LLI lt H Q 18 LO 1 gt lt x LLI T FIGURE 1 1 Power Button 2 Power LED Front Panel Description 250 See Figure 1 on page 4 1 Power Button Use this button to turn the KAV 250a power on and off and also to switch the 12 VDC output 12 V trigger on and off 2 Power LED The blue power LED illuminates when the amplifier is on 250 and KAV 250a 3 Amplifiers 5 FIGURE 2 THE KAV 250a BACK PANEL Balanced Inputs FUSE GATING VALUE 3 Right Input 3 4 Left Input Bridged _ 10 Line Fuse CHA N 5 gt IN 2220 Single ended Inputs Remote Controls 2 5 Right Input 11 12 VDC Remote Power Out 6 Left Input Bridged 12 12 VDC Re
5. J5 on the center amplifier channel 250 and 250 3 Amplifiers m 17 5 Connect one end of the second ribbon connection cable to jumper J4 the center amplifier channel Connect the other end of this ribbon connection cable to jumper pin J5 on the right amplifier channel 6 Replace the cover slide the front panel end in first Using the T 15 Torx wrench secure the 12 screws The 250 3 amplifier is now reconfigured for MAT operation Connecting the 250 3 Reconfigured for See Figure 4 on page 11 1 Connect your output device to a single ended or balanced input on the back panel of the KAV 250a 3 2 Connect each amplifier channel output 22 23 24 to a separate loudspeaker using the positive and negative terminals on the speaker binding posts 18 KAV 250a and 250 3 Amplifiers 2 lt m A 9 a Cc lt gt oc O LL e LO lt 2 18 2 4 m oc D LL 19 PC boards eft iers lt i D D E Te a x mop 5 Qo N 5 lt 282 SIRRA 85584 5 Le 5 0 9 c S32 9599 20520 4 20200 e Of6 8c 2 58 8 008509 6 5 BRIDGED OPERATION The KAV 250a and the 250 3 can be reconfigured for bridged operation When the 250 amplifiers
6. Road Orange CT 06477 3650 USA TEL 203 799 9954 250 3 PAX 203 799 9796 Three Channel Power Amplifier E MAIL krell krellonline com WEBSITE http www krelionline com Stereo Power Amplifier
7. all liability for loss of or damage to this product during ship ment to the Krell factory and prepay all shipping charges Please see the Warranty page in this manual concern ing liability for shipping damage and shipping charges This product may also be hand delivered if arrangemenis with the Service Department have been made in advance Proof of pur chase will be required for warranty valida tion at the time of hand delivery IMPORTANT Use the original packaging to ensure safe transit of this product to the dealer distribu tor or factory Krell may at its discretion return this product in new packaging and bill the owner for such packaging if the product received by Krell was boxed in non stan dard packaging or if the original packaging was so damaged that it was unusable If Krell determines that new packaging is required the owner will be notified before this product is returned To purchase additional packaging please contact your authorized Krell dealer distrib utor or the Krell Service Department 250 and 250 3 Amplifiers Specifications _ KAV 250a Stereo Amplifier FREQUENCY RESPONSE 20 Hzto 20 kHz 0 dB 0 1 dB 0 4 Hzto 170 kHz 0 dB 3 dB SIGNAL TO NOISE RATIO A WEIGHTED 118 dB TOTAL HARMONIC DISTORTION THD 1 kHz lt 0 06 20 kHz lt 0 25 GAIN 26 4 dB INPUT IMPEDANCE 100 kOhms INPUT SENSITIVITY 2 15 Vrms OUTPUT VOLTAGE Peak to Peak 138 V RMS 49 V OUT
8. channels are bridged the amplifiers output power is quadrupled the amplifier delivers 1 000 Watts to an 8 Ohm load The KAV 250a 3 be reconfigured to bridge any two of its three amplifier channels to operate as one combined amplifier channel When using the bridged amplifier channel only the 250 3 delivers 1 000 Watts to an 8 Ohm load Inputs and outputs labeled left and right are on the left and right side of the amplifier respectively when viewing the amplifier from the front panel Reconfiguring the KAV 250a for Bridged Operation See Figure 5 on page 16 Tools needed T 15 Torx wrench and one ribbon connection cable 1 Turn the 250 off by pressing the power button 1 on the front panel The blue power LED 2 extinguishes Unplug the AC power cord from the IEC power connector 13 on the back panel 2 Using the T 15 Torx wrench remove the 12 screws that secure the amplifier cover Carefully remove the cover 3 Locate the small PC board at the rear of each amplifier channel and jumper pins labeled J4 J5 and J6 4 Connect one end of the ribbon connection cable to jumper pin J4 on the left amplifier channel closest to the power supply The cable snaps into place Connect the other end of the ribbon connection cable to jumper pin J6 on the right amplifier channel 5 Replace cover slide front panel end in first Using the T 15 Torx wrench secure the 12 screws The 250 amplifier i
9. left amplifier channel closest to the power supply The ribbon snaps into place Connect the other end of the ribbon connection cable to jumper pin J5 on the right amplifier channel 5 Replace the cover slide the front panel end in first Using the T 15 Torx wrench secure the 12 screws The KAV 250a amplifier is now reconfigured for MAT operation Connecting the KAV 250a Reconfigured for MAT See Figure 2 on page 6 1 Connect your output device to a single ended or balanced input on the back panel of the KAV 250a 2 Connect each amplifier channel output 7 8 to a loudspeaker using the positive and negative terminals on the speaker binding posts Reconfiguring the KAV 250a 3 for MAT See Figure 6 on page 19 Tools needed T 15 Torx wrench and two ribbon connection cables 1 Turn the 250 3 off by pressing the power button 14 on the front panel The blue power LED 15 extinguishes Unplug the AC power cord from the IEC power connector 29 on the back panel 2 Using the T 15 Torx wrench remove the 12 screws that secure the amplifier cover Carefully remove the cover 3 Locate the small PC board at the rear of each amplifier channel and jumper pins labeled J4 J5 and J6 4 Connect one end of the first ribbon connection sabie to jumper pin J4 on the left amplifier channel closest to the power supply The ribbon snaps into place Connect the other end of this ribbon connection cable to jumper pin
10. other devices that incorporate a 12 V trigger This allows you to turn the KAV 250a 3 on and off using a Krell or other component in a custom installation Notes 12 VDC Outin 12 V trigger remote power is limited to 30 ma Consult the owner s manual of each component used in a custom installation to take full advantage of the 250 3 remote capability Power Supply 29 1 Power Connector The 250 3 is equipped with a standard female IEC power connector for use with the provided AC power cord 250 and 250 3 Amplifiers 13 Connecting the 250 250 3 Amplifier to Your System INPUT AND OUTPUT CONNECTIONS The following steps describe how to connect cables to the 250 or 250 3 amplifier 1 Neatly arrange and organize the wiring to and from the amplifier and all components Separate AC wires from audio cables to prevent hum or other unwanted noise from being introduced into the system 2 Connect the loudspeaker cables to the 250 amplifier channel output speaker binding posts 7 8 or the KAV 250a 3 amplifier channel output speaker binding posts 22 23 24 located on their respective back panels The amplifier channel outputs for the 250 and KAV 250a 8 use five way loudspeaker binding posts The loudspeaker binding post terminals accept spade lugs bare wire banana plugs or pins Use the red terminal for the positive conn
11. sales slip provided by an authorized Krell dealer or distributor or on the warranty registration card sent to Krell In the event adequate proof of purchase date is unavailable the warranty period will begin on the date the unit was originally shipped from the factory Krell can determine the original ship date from the serial number Transfer of warranty to a second owner occurs auto matically Please contact Krell to have the registration on the warranty changed When the warranty is transferred any successive owner assumes the remainder of the original warranty period The warranty for Krell products is valid only in the country to which they were originally shipped through the authorized Krell distributor for that country and at the factory There may be restrictions on or changes to Krell s warranty because of regulations within a specific country Please check with your distributor for a complete understanding of the warranty in your country unit is serviced by a distributor who did not import the unit there may be a charge for service even if the product is within the warranty period Freight to the factory is your responsibility Return freight within the United States U S A is included in the warranty If you have purchased your Krell product outside the U S A and wish to have it serviced at the factory all freight and associated charges to the factory are your responsibility 28 Krell will pay return f
12. secured may void your warranty MULTI AMP THROUGHPUT Multi Amp Throughput MAT an internal connection option for either the KAV 250a or the 250 3 lets you send the same music signal to all amplifier channels using one balanced or single ended connection MAT reduces installation complexity and cabling requirements in systems containing multiple amplifiers Inputs and outputs labeled left and right are on the left and right side of the amplifier respectively when viewing the amplifier from the front panel KAV 250a and KAV 250a 3 Amplifiers 15 FIGURE 5 RECONFIGURING THE KAV 250a FOR OR BRIDGED OPERATION PC boards showing MAT jumper configuration PC boards showing bridged jumper configuration Power supply 16 PC boards 250 KAV 250 a 3 Amplifiers Reconfiguring the 250 for See Figure 5 on page 16 Tools needed T 15 Torx wrench and one ribbon connection cable 1 Turn the 250 off by pressing the power button 1 on the front panel The blue power LED 2 extinguishes Unplug the AC power cord from the IEC power connector 13 on the back panel 2 Using the T 15 Torx wrench remove the 12 screws that secure the amplifier cover Carefully remove the cover 3 Locate the small PC board at the rear of each amplifier channel and jumper pins labeled J5 and J6 4 Connect one end of the ribbon connection cable to jumper pin J4 on the
13. shorting pins for the 250 KAV 250a 3 are inserted into the XLR inputs the unit is shipped with the pins in place When using the single ended inputs these shorting pins must be inserted between pins 1 and 3 to keep external noise from corrupting the signal For more information see the 250 KAV 250a 3 Amplifier to Your System page 14 250 and 250 3 Amplifiers 27 Warranty The KAV 250a and KAV 250a 3 amplifiers have a limited and transferable warranty of five years for parts and labor on Circuitry Should this product fail to perform at any time during the warranty Krell will repair it at no cost to the owner except as set forth in this warranty This warranty does not apply to damage caused by acts of God or nature The warranty described on this page shail be in lieu of any other warranty expressed or implied including but not lim ited to any implied warranty of merchantability or fitness for a particular purpose There are no warranties which exceed beyond those described in this document If this product does not perform as warranted herein the owner s sole remedy shall be repair In no event will Krell be liable for inci dental or consequentia damages arising from purchase use or inability to use this product even if Krell has been advised of the possibility of such damages The warranty period begins on the date of retail purchase as noted on the retail
14. single ended RCA connectors Amplifier Channel Outputs 22 23 24 Outputs These are the right 22 center 23 and left 24 KAV 250a 3 amplifier channel outputs with five way loudspeaker binding posts The loudspeaker binding post terminals accept spade lugs bare wire banana plugs or pins Use the red terminal for the positive connection and the black terminal for the negative connection For information about loudspeaker connections for bridged operation see Reconfiguring the 250 3 for Bridged Operation on page 21 Fuses 25 AGC 12 Fuses The AGC 12 Vott loudspeaker fuses protect the 2504 3 against short circuits in loudspeaker output 26 Line Fuse The line fuse protects the KAV 250a 3 against short circuits in internal power supplies 12 KAV 250a and 250 3 Amplifiers B 5 ES dl s FA E amp 1 SE TS ARNOT SONIC aa 222 mimm ge ens 225 Back Panel Description continued Note Fuses must be replaced with the fuse value specified the 250 3 back panel Use 20 slow blow line fuse for 100 120 V systems or a 12 amp slow blow line fuse for 220 240 V systems Remote Controls 27 12 VDC Remote Power Out 28 12 VDC Remote Power In _ The 250 3 is equipped with an output that sends 12 VDC power on off 12 V trigger signals to other Krell components and
15. AGC 12 Fuses AGC 12 Volt loudspeaker fuses protect the 250 against anole circuits in loudspeaker output 10 Line Fuse The line fuse protects the 250 against short circuits in internal power supplies Note Fuses must be replaced with the fuse value specified on the KAV 250a back panel Use a 20 amp slow blow line fuse for 100 120 V eu ora 12 amp slow blow line fuse for 220 240 V systems 250 and 250 3 Amplifiers BE Back Panel Description continued Remote Controls 11 12 VDC Remote Power Out 12 12 VDC Remote Power In 250 is equipped with an output that sends 12 VDC power on off 12 V trigger signals to other Krell components and other devices that incorporate a 12 V trigger This allows you to turn the 250 on and off using a Krell or other component in a custom installation Notes 12 VDC Out in 12 V trigger remote power is limited to 30 ma Consult the owner s manual of any component used a custom installation to take full advantage of the 250 remote capability Power Supply 13 IEC Connector The 250 is equipped with a standard female IEC power connector for use with the provided AC power cord 8 250 and KAV 250a 8 Amplifiers rin eee FIGURE 3 THE 250 3 FRONT PANEL 14 Power Button 15 Power LED aaa anne Pata oh See SN Front Panel Description KAV 250a 3 See Fi
16. N PROCEDURE 29 SPECIFICATIONS 30 250 and 250 3 Amplifiers iii Illustrations FIGURE 1 The 250 Front Panel FIGURE 2 250 Back Panel FIGURE The KAV 250a 3 Front Panel FIGURE 4 The 250 3 Back Panel FIGURE 5 Reconfiguring the 250 for MAT or Bridged Operation FIGURE 6 Reconfiguring the KAV 250a 3 for MAT or Bridged Operation Page 11 16 19 250 and 250 3 Amplifiers See oi cee eet Introduction Thank you for your of the Krell 250 Stereo Power Amplifier or 250 3 Three Channel Power Amplifier The 250 and 250 3 amplifiers provide substantial two and three channel output power that delivers realistic music production at an exceptional value These amplifiers can be customized with a variety of optional system configurations Multi Amp Throughput MAT bridged operation and high power mono operation These options provide a wider range of power outputs and connection options Both the 250a 250 3 amplifiers provide balanced and single ended inputs for complete compatibility with other components 250 250 3 amplifiers can be operated using the 12 VDC trigger for other components Either amplifier integrates seamlessly home theater or whole house systems This reference manual contains important informa
17. PUT POWER EACH CHANNEL 8 Ohms 250 W DRIVEN 4 Ohms 500 W BRIDGED 8 Ohms 1 000 W POWER CONSUMPTION Idle 210 W 1 850 INPUTS 1 pair single ended RCA connectors 1 pair balanced via XLR connectors OUTPUTS 1 pair amplifier channels via five way speaker binding posts DIMENSIONS 19w 6 3h 15 34 in 48 3w x 16h x 38 9d cm WEIGHT Shipping 50 Ib 22 7 kg Unit only 43 ib 19 5 kg 30 p KAV 250a and KAV 250a 3 Amplifiers 250 3 Three Channel Amplifier FREQUENCY RESPONSE SIGNAL TO NOISE RATIO A WEIGHTED TOTAL HARMONIC DISTORTION THD GAIN INPUT IMPEDANCE INPUT SENSITIVITY OUTPUT VOLTAGE OUTPUT POWER EACH CHANNEL DRIVEN BRIDGED POWER CONSUMPTION INPUTS OUTPUTS DIMENSIONS WEIGHT 20 Hz to 20 kHz 0 dB 0 2 dB 0 4 Hz to 112 kHz 0 dB 3 dB 118 dB 1 kHz lt 0 06 20 kHz lt 0 25 26 4 dB 100 kOhms 2 15 Vrms Peak to Peak 138 V RMS 49 V 8 Ohms 250W 4 Ohms 500 W 8 Ohms 1 000 W Idle 235 W 1 930 W 3 single ended RCA connectors 3 balanced via XLR connectors 3 amplifier channels via five way speaker binding posts 19w x 6 3h x 15 8d in 48 3w 16h 40 14 cm _ 60 27 2 kg 52 Ib 23 5 kg Shipping Unit only All operational features functions specifications and policies are subject to change without notification 250 and 250 3 Amplifiers 31 Krell Industries Inc 250 45 Connair
18. duct will be void The prod uct will be returned to original factory layout specifications at the owner s expense before it is repaired All repairs required after the product has been returned to original fac tory specifications will be charged to the customer at cur rent parts and labor rates All operational features functions and specifications and policies are subject to change without notification To register your product for warranty benefits complete and return the Warranty Registration Card enclosed in the shipping box within 15 days of purchase Thank you KAV 250a and KAV 250a 3 Amplifiers Procedure If you believe there is a problem with your component please contact your dealer dis tributor or the Krell factory to discuss the problem before you return the component for repair To expedite service you may wish to complete and e mail the Service Request Form in the Service Section of our website at http Awww krellonline com To contact the Krell Service Department TEL 203 799 9954 Monday Friday 9 00 AM to 5 00 PM EST FAX 203 799 9796 E MAIL service krellonline com WEBSITE http www krelloniine com PRODUCT NAME SERIAL NUMBER 29 To return this product to Krell please follow this procedure so that we may serve you better 1 Obtain a Return Authorization Number R A number and shipping address from the Krell Service Department 2 Insure and accept
19. ection and the black terminal for the negative connection 3 Connect the interconnect cables from your output device to the amplifier inputs The 250 is equipped with balanced 3 4 or single ended 5 6 inputs and the _ 250 3 is equipped with balanced 16 17 18 or single ended 19 20 21 inputs located on their respective back panels The balanced inputs use three pin XLR connectors the single ended inputs use RCA connectors 4 Insert the end of the AC power cord into the IEC power connector on the KAV 250a 13 or 250 3 29 back panel Insert the other end into the AC outlet The amplifier is now ready for operation See Amplifier Operation on page 25 The 250 KAV 250a 3 amplifier is shipped with shorting pins in the XLR inputs These pins should remain in the XLR inputs if the amplifier is operating in the single ended mode When the shorting pin is inserted pins 1 and 3 are shorted together Remove the shorting pins to connect the amplifier for balanced operation The XLR pin configuration is described below Pin 1 Ground Pin 2 Non inverting 0 Pin 3 Inverting 180 Krell recommends using balanced interconnect cables Balanced interconnect cables not only can minimize sonic loss but are also immune to induced noise especially with installations using long cables Balanced connections have 6 dB more gain than single ended connections When level matching is critical keep t
20. fter reconfiguring for MAT do not use more than one input at the same time After bridging do not use both inputs at the same time THERE ARE NO USER SERVICEABLE PARTS INSIDE ANY KRELL PRODUCT Please contact your authorized Krell dealer distributor or Krell if you have any questions not addressed in this reference manual This product is manufactured in the United States of America Krell is a registered trademark of Krell Industries Inc and is restricted for use by Krell Industries Inc its subsidiaries and authorized agents Multi Amp Throughput is a trademark of Krell industries Inc All other trademarks and tradenames are registered to their respective companies 1999 by industries Inc All rights reserved P N 1960101710688 Contents INTRODUCTION i 1 DEFINITION OF TERMS 1 UNPACKING m 2 PLACEMENT 3 AC Power Guidelines 3 FRONT PANEL DESCRIPTION 250 5 BACK PANEL DESCRIPTION 250 7 FRONT PANEL DESCRIPTION 250 3 10 BACK PANEL DESCRIPTION KAV 250a 3 12 CONNECTING THE KAV 250a KAV 250a 3 AMPLIFIER YOUR SYSTEM 14 Input and Output Connections 14 OPTIONAL SYSTEM CONFIGURATIONS 15 Multi Amp Throughput 15 Bridged Operation 20 Examples of Connection Scenarios 22 AMPLIFIER OPERATION 20025 On Off and Operation _ 25 AMPLIFIER TROUBLESHOOTING 26 How to Troubleshoot System Noise 26 QUESTION AND ANSWER oT WARRANTY 28 RETURN AUTHORIZATIO
21. gure 3 on page 9 14 Power Button Use this button to turn the KAV 250a 3 power and off and also to switch the 12 VDC output 12 V trigger on and off 15 Power LED The blue power LED illuminates when the amplifier is powered on 10 250 and 250 3 Amplifiers FIGURE 4 THE KAV 250a 3 BACK PANEL 29 22 25 23 25 24 21 28 26 29 Balanced Inputs Fuses 16 Right Input 25 AGC 8 Fuses 2 TUDE CATING YRLAG 17 Center Input 26 Line Fuse l CHANG cD O AG C8 18 Left Input Remote Controls 2000 Single ended Inputs 27 12 VDC Remote Power Out 19 Right Input 28 12 VDC Remote Power 20 Center Input 21 Left Input Power 29 IEC Power Connector Amplifier Channel Outputs 22 Right Output 23 Center Output 24 Left Output Back Panel Description 250 3 See Figure 4 page 11 The 250 3 back panel provides connections for all inputs and outputs remote control input and output links and AC power supply Inputs and outputs labeled left and right are on the left and right side of the amplifier respectively when viewing the amplifier from the front panel Balanced Inputs 16 17 18 Inputs These are the right 16 center 17 and left 18 250 3 channel inputs for output devices with balanced XLR connectors Single ended Inputs 19 20 21 Inputs These are the right 19 center 20 and left 21 KAV 250a 3 channel inputs for output devices with
22. his gain value in mind 14 250 and 250 3 Amplifiers Optional System Configurations The 250 and 250 3 can be reconfigured for either Multi Amp Throughput MAT or bridged operation IMPORTANT Removing the cover to reconfigure for MAT or for bridged operation is the ONLY instance you are authorized to remove the cover of ANY Krell component without voiding your Warranty For more information on product limitations and restrictions see Warranty on page 28 Before Reconfiguring for MAT or Bridged Operation Read the following important safety instructions before you attempt to reconfigure your amplifier for either MAT or bridged operation 1 Unplug the power cord Unplug the AC power cord from both the IEC power connector of the 250 119 250 3 29 on the back panel and from the AC outlet 2 Avoid the power supply After removing the screws see instructions below and the cover locate and stay aware of the location of the power supply Avoid making contact with that area of the amplifier 3 Remove jewelry Rings necklaces bracelets and other pieces of metal jewelry can conduct an electrical charge Consider removing them before attempting any reconfiguration 4 Always replace cover Make sure the amplifiers cover is properly replaced and secured by the 12 screws before resuming operation IMPORTANT Operating the amplifier without the cover properly replaced and
23. is now safe to turn off the rest of the system IMPORTANT Always turn off the amplifier before changing input connections and mute or fully attenuate the preamplifier level when switching sources These amplifiers have tremendous reserves of power and safely drive loudspeakers to extremely high sound pressure levels However use care when setting high playback levels and lower the volume level at any sign of loudspeaker distress 250 and KAV 250a 3 Amplifiers E 25 Amplifier Troubleshooting HOW TROUBLESHOOT SYSTEM NOISE When you mix and match audio components each with its own ground potential a low frequency hum may occur in one or both loudspeakers This often occurs when introducing a new component into a system If a low frequency hum emanates from the loudspeakers when you place the 250a stereo 250 3 three channel amplifier into your system follow these simple troubleshooting steps 1 Check all input and output connections making sure they are of sound construction 2 With the amplifier off remove the interconnect cables then press the KAV 250a power button 1 or 250 3 power button 14 to turn the amplifier on 3 If the hum disappears press the power button again to turn the amplifier off and reinsert one of the interconnect cables 4 Turn the amplifier back on If the hum reappears with one or both interconnect cables inserted there may be a defective cab
24. le Have the interconnect cables checked before proceeding If the interconnect cables are sound you may be experiencing a ground loop This can often be easily eliminated Please contact your authorized Krell dealer distributor or Krell for suggestions on how to solve this problem 26 KAV 250a and 250 3 Amplifiers Question and Answer Q Should leave the 250 or 250 3 amplifier on at all times A No These amplifiers do not have a stand by mode Leaving them on at all times would result in considerable heat output and power consumption For best results turn the amplifier off when not in use and allow a five minute warm up after it is turned on See Amplifier Operation on page 25 When turn the amplifier on there is a loud hum the loudspeakers What should do A When a new component is introduced a low frequency hum may occur in one or both loudspeakers Check all input and output connections and cables making sure they are of sound construction See How to Troubleshoot System Noise on page 26 If the connections and cables are sound you be experiencing a ground loop This can often be easily eliminated Please contact your authorized Krell dealer distributor or Krell for suggestions on how to solve this problem Q When connect the amplifier to my system using the single ended inputs a loud buzz comes from my loudspeakers Is the amplifier broken A Check that the
25. mote Power In Amplifier Channel Outputs Power 7 Right Output Bridged 13 IEC Power Connector 8 Left Output Bridged Back Panel Description 250 See Figure 2 on page 6 KAV 250a back panel provides connections for all inputs and outputs remote control input and output links and AC power supply Inputs and outputs labeled left and right are on the Jeft and right side of the amplifier respectively when viewing the amplifier from the front panel Balanced Inputs 3 4 Inputs These are the right 8 and the left 4 250 channel inputs for output devices with balanced XLR connectors Single ended Inputs 5 6 Inputs These are the right 5 and the left 6 250 channel inputs for output devices with single ended RCA connectors The left balanced or single ended inputs are used for bridged operation Reconfiguring the KAV 250a for Bridged Operation page 20 Amplifier Channel Outputs 7 Output Bridged 8 Output Bridged These are the right 7 and left 8 250 amplifier channel outputs with five way loudspeaker binding posts The loudspeaker binding post terminals accept spade lugs bare wire banana plugs or pins Use the red terminal for the positive connection and the black terminal for the negative connection For information on loudspeaker connections for bridged operation see Reconfiguring the 250 for Bridged Operation on page 20 Fuses 9
26. ositive binding post of the center amplifier channel 23 The remaining channel may be connected for normal operation IMPORTANT When operating the amplifier bridged mode and using an output device with single ended RCA cable be sure to remove the shorting from the balanced input EXAMPLES OF CONNECTION SCENARIOS High Power Mono Operation High power mono operation uses two 250 bridged amplifiers one amplifier is dedicated to the left loudspeaker and one amplifier is dedicated to the right loudspeaker Additional loudspeakers in a home theater system may be connected in this way by using additional KAV 250a amplifiers The diagram below illustrates connecting a system for high power mono operation 22 250 250 3 Amplifiers Examples of Connection Scenarios continued Power Biamplification Stereo 2 channel Power biamplification uses the MAT feature of the 250 to send the same music signal to all amplifier channels using one balanced or single ended input connection When the KAV 250a is reconfigured for one channel of the amplifier powers the loudspeaker s high frequency end and the other channel powers the loudspeaker s low frequency end This connection scenario is used only with loudspeakers that feature two sets of binding posts For more information consult the owner s reference for your loudspeakers The diagram below illustrates connecting a
27. reight to the U S A based freight for warder of your choice Freight and other charges to ship the unit from the freight forwarder to you are also your respon sibility Krell is not responsible for any damage incurred in transit Krell will file claims for damages as necessary for units dam aged in transit to the factory You are responsible for filing claims for shipping damages during the return shipment Krell does not supply replacement parts and or products to the owner of the unit Replacement parts and or products will be fumished only to the distribtuor performing service on this unit on an exchange basis only any parts and or prod ucts retumed to Krell for exchange become the property of Krell No expressed or implied warranty is made for any Krell product damaged by accident abuse misuse natural or personal disaster or unauthorized modification Any unauthorized voltage conversion disassembly component replacement perforation of chassis updates or modifications performed to the unit will void the warranty The operating voltage of this unit is determined by the fac tory and can only be changed by an authorized Krell distrib utor or at the factory The voltage for this product in the U S A cannot be changed until six months from the original purchase date In the event that Krell receives a product for warranty ser vice that has been modified in any way without Krell autho rization all warranties on that pro
28. s now ready for bridged operation Connecting the Bridged KAV 250a See Figure 2 on page 6 1 Connect the output cable from the output device to the balanced XLR 4 or the single ended RCA 6 inputs connectors marked BRIDGED INPUT 2 Connect the positive loudspeaker lead red to the positive binding post on the left amplifier channel output 8 marked BRIDGED Connect the negative loudspeaker lead black to the positive binding post on the right amplifier channel 7 marked BRIDGED 20 250 and KAV 250a 3 Amplifiers IMPORTANT When operating the amplifier in bridged mode and using an output device with single ended RCA cables be sure to remove the shorting pin from the left balanced XLR input 4 Reconfiguring the KAV 250a 3 for Bridged Operation See Figure 6 on page 19 Tools needed T 15 Torx wrench and two ribbon connection cables 1 9 Turn the KAV 250a 3 off by pressing the power button 14 on the front panel The blue power LED 15 extinguishes Unplug the AC power cord from the IEC power connector 29 on the back panel Using the T 15 Torx wrench remove the 12 screws that secure the amplifier cover Carefully remove the cover Locate the small PC board at the rear of each amplifier channel and jumper pins labeled J4 J5 and J6 Option 1 To bridge left and center amplifier channels connect one end of the ribbon connection cable to jumper pin J4 on the left amplifier channel
29. system for power biamplification 250 and KAV 250a 3 Amplifiers A 23 Examples of Connection Scenarios continued Multi Power Mode Multi power mode uses the KAV 250a 3 s MAT feature to independently power multiple pairs of stereo loudspeakers to extend the listening environment throughout your home When the 250 3 is reconfigured for MAT each channel powers an individual loudspeaker with one 250 3 dedicated to driving outputs to the left loudspeakers and one KAV 250a 3 driving outputs to the right loudspeakers The diagram below illustrates connecting a system for multi power mode 24 250 and 2504 3 Amplifiers Amplifier Operation ON OFF AND OPERATION When powering up your system turn amplifiers on last When powering down your system turn amplifiers off first The procedures for amplifier operation follow 1 Press the 250 power button 1 250 3 power button 14 on the amplifiers front panel Wait until the blue power LED 2 on the 250 or 15 on the 250 3 illuminates and you hear a click The amplifier is now ready for operation 2 With the output device muted or volume control fully lowered select an output device Decrease or increase the volume control to the desired listening level 3 Before turning the system off mute or lower the output device volume Press the front panel power button to turn the amplifier off It
30. tion on placement installation and operation of the 250 and 250 3 amplifiers Please read this information carefully A thorough understanding of these details helps ensure satisfactory operation and long life for your KAV 250a or 250 3 amplifier and related system components Definition of Terms Multi Amp Throughput An internal connection option that sends the same music signal to all amplifier channels using one balanced or single ended connection MAT reduces installation complexity and cabling requirements in systems containing multiple amplifiers MAT also allows a variety of connection scenarios including powering loudspeakers that have two sets of binding posts and independently powering multiple pairs of stereo loudspeakers to extend the listening environment throughout your home Bridging An internal connection option that links two amplifier channels to operate as one combined amplifier channel greatly increasing the channel s power output On When the power button on the front panel is pressed and the blue power LED illuminates the amplifier is on and ready to play music Off When the power button on the front panel is pressed and the blue power LED turns off the amplifier is off KAV 250a and 250 3 Amplifiers 1 Unpacking Open the shipping box which contains 1 amplifier unit packed in foam end caps 2 ribbon connection cables 250 fuses 2 AGC 8 9
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