Knoll MX1255 User's Manual
Contents
1. Bous 6 In The Link button is normally set to the in position to give all six stereo inputs individual sources When the Link button is set to the out position that input Left Right is linked or cascaded or paralleled to input 1 without the use of Y cords Any or all combination of linked inputs 2 to inputs 6 are possible When all inputs are linked to input 1 the input impedance is about 4000 Q Caution NEVER connect the MX1255 to impedances less than 4 Q or amplifier damage not covered by the warranty may occur Knoll Systems Point Roberts WA USA amp Delta BC Canada Channel 6 can be mono bridged giving 180 watts into 8 ohms Never connect speaker loads less than 8 ohms to channel 6 in the bridged mode Select the bridge stereo switch to the out position for the bridged mode The bridged input is 6L The 6L gain pot adjusts the bridged gain The speaker is connected to the 6L and 6R in the bridged mode2. Warranty Knoll Systems warrants MX1255 amplifiers sold in the USA and Canada by authorized Knoll dealers to be free of defects in materials and manufacturing This warranty extends for three full years from the date of purchase by the original consumer Any products returned to Knoll Systems and found to be defective by Knoll Systems within the warranty period will be repaired or replaced at Knoll Systems decision at no charge Knoll Systems will not be responsible for the actual cost of installation or removal of the product nor for any incidental or consequential damages Some states do not allow the exclusion or limitation of incidental or consequential damages so the above limitation may not apply to you This warranty gives you specific legal rights You may have additional legal rights that vary from state to state Specifications Inputs Input impedance Outputs Output power Bridged Power channel 6 Peak output power Ideal impedance Frequency response S N ratio THD distortion IMD distortion Trigger control Dimensions Fan Noise Power Weight 12 Gold RCA jacks with adjustable gain 50k Q detachable plug 55 watts RMS per channel 8 2 180 watts RMS 8 Q only 100 watts per channel 8 Q 4 82 10 Hz 40 kHz 1dB iw over 105 dB A weighted 50 watts less than 0 1 20 Hz to 20 kHz less than 0 01 60 Hz 7 kHz 4 1 SMPTE 12 VDC 35mA on 3 5mm mono jack 17 x 3 5 x 11 5 432 x 89 x 292mm quiet 26
3. d service There are no user adjustments on the MX1255 Your installer may make certain gain level adjustments on the rear panel Caution The MX1255 contains no user serviceable parts so do not attempt to open or repair the MX1255 Refer servicing to a qualified technician only or contact the factory for information WARNING To reduce the Made in Canada Link out position risk of electric shock do not Fabrique au Canada 1 Inputs 2 arallels channel 1 expose this apparatus to rain 3 Inputs 4 o channels 2 6 L or moisture L m tadgetiee z Mo Gain speakers 2 sPEAKERS3 Gain The trigger is 12 VDC 35mA per MX1255 via 3 5mm mono jack 5 VDC trigger outputs will not work To connect the trigger to a receiver use a 12 VDC power supply we suggest Knoll PS1202 power supply with an adaptor Plug the power supply into the switched outlet on the rear of the receiver Connect the 12 volt wire toa 3 5mm mono jack Plug the jack into the rear of the MX1255 12 VDC polarity is not important Make sure the MX1255 power switch is off out When the receiver is switched on the MX1255 amplifier is switched on knall aes aia 2 t 4 Gain SPEAKERS4 SPEAKERS 5 Gain o x SPEAKERS 6 l iR O Ooie O O 92 HII we ettin DO NOT OPEN v7 X E Class 2 M X 5 5 12 Channel x 55 Watt Minimum speaker impedance 49 Bridged 8Q2 Bridge 6 Out E POWER RISK OF ELECTRIC SHOCK A Wiring High Current Amplifier
4. dBA 750 watts at 117 VAC or 230 VAC 21 Ibs 9 5 kg Note Specifications subject to change without notice Knoll Systems 145 Tyee Drive Point Roberts WA 98281 14 7163 Vantage Way Delta BC V4G 1N1 Tel 604 940 1689 fax 855 734 3363 Made in Canada Fabrique au Canada lt lt iknoll MX1255 Amplifier 12 Channel Amplifier Installation Instructions v7 3 oll Warning To be installed and or used in accordance with appropriate electrical codes and regulations Description The MX1255 is a member of the long line of Knoll multi channel amplifiers Designed primarily for the custom install industry it is used to power speakers with different or similar sources in multiple rooms With 12 channels rated at 55 watts per channels at 8 Q the MX1255 packs some serious punch Each channel has a gain control The MX1255 can be turned on and off via the front panel power switch or via the 12 VDC trigger MX1255 channels 2 6 can be linked to channel 1 individually using the link switches MX1255 amplifiers designed to meet the amplifier needs of custom installed systems where high quality sound is a specific requirement Key Features 1 Size efficiency The MX1255 consists of a total of 12 power amplifiers in one 3 1 2 high enclosure Each power amplifier channel can deliver 55 watts RMS into an 8 Q load 2 Automatic protection circuitry Each MX1255 channel is individually and fully protected against low impedance overheating
5. ecting the cable TV feed or contact your cable TV operator to see if they can better isolate your cable feed Suggestion 2 Turn off all components in your system and then disconnect the input cables at the amplifier Turn the amplifier back on to see if the hum is still present If the hum disappears the fault may be in the input cables used Try replacing them with cables that have better shielding and make certain that the input cables are not running on top of any AC power cords Change the cables one at a time to determine if one or all cables are responsive If the hum disappears when the input cables are disconnected but returns after the cables are changed and the system reconnected your source device may be causing the problem Suggestion 3 Poor grounding of the electrical system in your home may also cause ground loop problems particularly when there are multiple components with three prongs grounded power cords Unplug these components one at a time and see if one or all of them is causing the problem The ultimate solution to this type of problem is to rewire your house with an isolated star type grounding configuration Knoll understands that this may be impractical and expensive In some instances the use of an approved AC power isolation transformer of sufficient capacity may solve this problem Warning If you suspect that the grounding system in your home s electrical wiring is causing the hum problem it is importan
6. n all pole MAINS SWITCH is used as the disconnect device the location on the apparatus and the function of the switch shall be described and the switch shall remain readily operable 18 A push button is used to turn the power off and on 19 ALED is used to show when the apparatus is powered on CAUTION These servicing instructions are for use by qualified service personnel only To reduce the risk of electric shock do not perform any servicing other than that contained in the operating instructions unless you are qualified to do so WARNING This product may contain chemicals including lead known to the State of California to cause birth defects or other reproductive harm Wash hands after handling Hum and noise In most cases one of the following suggestions should help you solve a hum noise in your system Please try these steps in the order shown proceeding from one step to the next if the prior suggestion does not eliminate the problem Suggestion 1 To determine if a cable TV connection is responsible for the hum first turn off all the components Disconnect the cable TV feed to your system at the first place where it connects to your components Alternatively disconnect the cable TV wire where it is connected at the wall outlet Turn your system back on and listen if the hum has disappeared If removing the cable TV feed has eliminated the hum you will need to insert a Ground Loop Isolator Knoll model GB634 before reconn
7. overloading over voltage and under voltage The protection circuitry automatically restores the amplifier channel as soon as its parameter returns to the safe operating area 3 Individual input gain adjustment Each channel features an input gain adjustment pot to adjust each channel for gain and speaker sensitivity variations 4 External power on off The MX1255 can be turned off and on by external controllers via its 12 VDC trigger jack 5 Stackable 17 chassis 19 rack ears available 6 Link Feature Certain installations require that some or all of the stereo channels play the same content Instead of using Y cords the Knoll link cascades any or all of channels 2 6 to channel 1 L R 7 Bridgeable Channel 6 can be bridged giving 180 watts RMS into an 8 Q load for use with subwoofers and speakers that need more power Important Safety Instructions 1 Read these instructions 2 Keep these instructions 3 Read all warnings 4 Follow all instructions 5 Do not use this apparatus near water 6 Clean only with dry cloth 7 Do not block any ventilation openings Install in accordance with the manufacturer s instructions 8 Do not install near any heat sources such as radiators heat registers stoves or other apparatus including amplifiers that produce heat 9 Do not defeat the safety purpose of the polarized or grounding type plug A polarized plug has two blades with one wider than the other A grounding t
8. pper wire is recommended with 14 gauge minimum for runs over 30 10m Note Ideally the MX1255 likes 6 8 Q loads Connecting to 4 Q loads won t hurt the MX1255 but those channels connected to 4 Q loads may occasionally shutdown due to overloading Never connect to speaker loads less than 4 Q Channel 6 bridged mode minimum 8 Q speaker 7 Individually adjust the channel gains as required Ideally all gains are fully on fully clockwise 8 Make sure the speakers in each room are connected in phase with the amplifier going to the speaker Out of phase speakers give unstable imaging and poor bass response 9 Connect trigger if being used to a 12 VDC source about 35mA using a 3 5mm mono jack 5 VDC triggers will not work 10 Connect the AC power into an outlet that supplies at least EIGHT amps 1000 watts dedicated to each MX1255 11 If more power is needed channel 6 can be mono bridged to give 180 watts into an 8 Q load Minimum impedance for channel 6 in the bridged mode is 8 Q The bridged switch needs to be in the out position The bridged input is 6L and the 6L gain pot adjusts the bridged gain The speaker is connected to the 6L and 6R in the bridged mode Caution Never listen to sound that is distorted If distorted sound is heard turn the volume down immediately or speaker and or amplifier damage could occur that is not covered by the warranty If this problem persists contact your dealer User adjustments an
9. t that you do not make any changes to the wiring Only a licensed electrician should make any changes to household wiring and they must be made in full compliance with all local building safety and electrical codes Knoll Systems service information The MX1255 amplifier does not contain any user serviceable parts inside If you suspect a problem that may require servicing contact us at www knollsystems com contact html or by phone at 800 566 5579 Troubleshooting If a problem is encountered with the MX1255 the most expedient procedure is to locate the problem and if possible repair it before requesting service Be sure to carefully check other system components such as controllers CD players volume controls wiring speakers etc that may be at fault Problem Action Power LED does 1 Check that the MX1255 is plugged in not light no sound 2 Test the AC outlet with a lamp 3 If remote on off is used check that the trigger voltage is at 12 VDC 4 Check MX1255 power button on in Sound cuts out 1 Verify speaker impedance is 4 16 Q Changing speakers may be required 2 Check if the MX1255 feels hot If it s hot increase cooling see Installation Turn the volume down Check speakers for damage Check inputs for proper levels MX1255 gain and source output level may have to be adjusted 4 Speakers may be less than 4 Q Sound is distorted WUN MX1255 does 1 Push MX1255 power switch off out not
10. turn off 2 If trigger is being used power switch needs to be set to off out position or amp is on all the time 3 Try disconnecting trigger jack Trigger does not 1 Measure the trigger voltage with a volt work meter It needs to be 11 15 volts DC to work current is about 35mA total per amp See page 5 for details Speaker pops when 1 Speaker may need resistor placed amp turned on or off across terminal Suggest 2k0 1 4 w Discharges speaker internal capacitor Installation Installing the MX1255 should be relatively easy With a bit of planning it will give trouble free service for years 1 The most important consideration when installing the MX1255 is cooling The MX1255 has a lot of power packed into a small chassis size When installing it in an equipment stack it should be the top component It needs at least 3 5 of space above the amplifier to allow for adequate convection cooling 2 Amplifiers should always be the top components in the system 3 If MX1255 channels frequently shutdown due to overheating install a fan directed up from the MX1255 bottom center 4 Never operate the MX1255 on its side as the cooling potential drops significantly when operated this way 5 Connect the MX1255 inputs to the source component outputs with good quality short as possible RCA jack cables Connect each channel individually 6 Connect the MX1255 speaker outputs to speakers using good quality speaker wire Minimum 16 gauge co
11. ype plug has two blades and a third grounding prong The wide blade or the third prongs are provided for your safety If the provided plug does not fit into your outlet consult an electrician for replacement of the obsolete outlet 10 Protect the power cord from being walked on or pinched particularly at plugs convenience receptacles and the point where they exit from the apparatus 11 Only use attachments accessories specified by the manufacturer 12 Use only with the cart stand tripod bracket or table specified by the manufacturer or sold with the apparatus When a cart is used exercise caution when moving the cart apparatus combination to avoid injury from tip over 13 Unplug this apparatus during lightning storms or when not used for long periods of time 14 Refer all servicing to qualified service personnel Servicing is required when the apparatus has been damaged in any way such as power supply cord or plug is damaged liquid has been spilled or objects have fallen into the apparatus the apparatus has been exposed to rain or moisture does not operate normally or has been dropped 15 Under no circumstances should the output terminals of the amplifier be short circuited 16 Be sure that the loudspeakers connected can handle the output power of the amplifier at the loudspeakers rated impedance The warranty on the amplifier does not cover damage to loudspeakers that have inadequate power handling capabilities 17 Where a
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