Alesis 12R manual ① to Eliminate HUM if the Above has Failed

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Operating Instructions

①TO ELIMINATE HUM IF THE ABOVE HAS FAILED:

A)Disconnect the power from all outboard devices and tape machines except for the mixer and control room monitor power amp.

B)Plug in each tape machine and outboard effect device one at a time. If possible, flip the polarity of the plug of each device (turn it around in the socket) until the quietest position is found.

C)Make sure that all of the audio cables are in good working order. Cables with a detached ground wire will cause a very loud hum!!

D)Keep all cables as short as possible, especially in unbalanced circuits.

If these basic experiments don’t uncover the source of the problem, consult your dealer or a technician trained in proper studio grounding techniques. In some cases, a “star grounding” scheme must be used, with the mixer at the center of the star providing the shield ground on telescoping shields, which do NOT connect to the chassis ground of other equipment in the system.

Note that the Multimix 12R is grounded through its AC cable. Signal ground is connected to chassis ground, which in turn may be grounded again by the rack rails. But since almost all of the inputs and outputs of the Multimix 12R are balanced, the ground does not have to be made part of the signal path unless you are connecting to unbalanced equipment. If the Multimix 12R is mounted in a metal rack, the mixer shares a common ground with the other equipment in the same rack. In some cases (such as a star ground scheme), you may need to use nonconductive rack rails or rack isolators to avoid ground loops.

To avoid the possibility of electric shock, never defeat the safety ground found on other equipment in the system. When in doubt about proper electrical grounding schemes or the power to your system, consult a qualified, licensed electrician.

Telescoping shield: In fixed installations using balanced outputs where the amplifier is more than 20' from the mixer and on a different AC power panel, it may be advisable to disconnect (or "float") the shield at the amplifier end. This keeps the ground potential of the amp

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Contents Reference Manual Page Important Safety Instructions Page Page Page Page Page CE Declaration Of Conformity Front Panel Table of Contents Dimensional Drawing ApplicationsUsing this manual IntroductionAlesis Multimix 12R Microphone Preamplifier/Mixer ConventionsGrounding Instructions Unpacking InstallationAC power Mounting Use clean powerPower switch Cable common sense ConnectionsInputs Microphone Inputs Phantom power Line-level devices synthesizers, CD players, video Phantom Power will not be Used Tape in jacks Phonograph turntables About stereo effect devices How to connect effect devices and signal processorsEffects via Aux Send and Aux Return Using Aux 1 as an effects send Connecting an in-line processor Connections Outputs To a stereo PA system or instrument amplifierTo a mono system To a stage monitor foldback systemTo another mixer To a stereo tape recorderTo an Adat multitrack recorder In-line Adat recordingUsing two Multimix 12Rs for more flexibility Connections Phones Monitor OutConnections Operating Instructions Before turning the mixer on, zero out the controlsSetting input trim levels Peak LED methodMetering/Unity Gain method Typical Fader and Control Levels Unity gain pointsTrim gain ranges Aux Send levelsProper gain staging of other equipment How to Set Aux Send and Return Levels AUX System Effects Send/ReceivePage Using the meter Output distortionAvoiding noise System noise ground loops, hum, induced noise① to Eliminate HUM if the Above has Failed Page Operating Instructions Tracking/Overdubbing ApplicationsMultitrack recording Mixdown Using the High and LOW EQ controls Monitoring AUX 1 in the Phones jack Troubleshooting Troubleshooting IndexPage Refer All Servicing to Qualified Technicians Maintenance/ServiceExterior cleaning Frequency Response SpecificationsConnectors Levels ImpedanceDistortion THD+N PowerNoise performance typical Dimensional Drawing Block Diagram Level diagram Index TapeWarranty / Contact Alesis Contact Information
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