Harman 1210KA manual Headphones, Polarity Phase, Grounding and Shielding

Page 16

Headphones

The PHONES output is a 3-pole ‘A’ gauge jack, wired as a stereo output as shown, ideally for headphones of 150Ω or greater. 8Ω headphones are not recommended.

Polarity (Phase)

You will probably be familiar with the concept of polarity in electrical signals and this is of particular importance to balanced audio signals. Just as a balanced signal is highly effective at cancelling out unwanted interference, so two microphones picking up the same signal can cancel out, or cause serious degradation of the signal if one of the cables has the +ve and -ve wires reversed. This phase reversal can be a real problem when microphones are close together and you should therefore always take care to connect pins correctly when wiring audio cables.

Grounding and Shielding

For optimum performance use balanced connections where possible and ensure that all signals are referenced to a solid, noise-free earthing point and that all signal cables have their screens connected to ground. In some unusual circumstances, to avoid earth or ground ‘loops’ ensure that all cable screens and other signal earths are connected to ground only at their source and not at both ends.

If the use of unbalanced connections is unavoidable, you can minimise noise by follow- ing these wiring guidelines:

•On INPUTS, unbalance at the source and use a twin screened cable as though it were balanced.

•On OUTPUTS, connect the signal to the +ve output pin, and the ground of the output device to -ve. If a twin screened cable is used, connect the screen only at the mixer end.

•Avoid running audio cables or placing audio equipment close to thyristor dimmer units or power cables.

•Noise immunity is improved significantly by the use of low impedance sources,

such as good quality professional microphones or the outputs from most modern audio equipment. Avoid cheaper high impedance microphones, which may suffer from interference over long cable runs, even with well-made cables.

Grounding and shielding is still seen as a black art, and the suggestions above are only guidelines. If your system still hums, an earth/ground loop is the most likely cause. Two examples of how an earth loop can occur are shown below.

Warning!

Under NO circumstances must the AC power mains earth be disconnected from the

mains lead.

14

Soundcraft EFX/EPM User Guide Issue 1210

Page 15 Page 17
Image 16
Page 15 Page 17
Contents
User Guide Soundcraft EFX/EPM User Guide Issue User Guide EPM Models Contents Safety Symbol Guide Important Safety Instructions Neutral Blue US White Live Hot Brown US Black Advice for Those WHO Push the Boundaries IntroductionOverview 60-SECOND Guide EFXPhantom Power Peak LEDMaster Faders Main MetersAUX 1/2 Sends 60-SECOND Guide EPMPFL 22 2-TRACK Inputs Mono OUT ¼ Jack23 2-TRACK Controls Wiring UP Mic InputLine Input Insert PointStereo Inputs Stereo 1/2 and Stereo Mix InsertsMix Outputs Aux & FX Bus OutputsPolarity Phase HeadphonesGrounding and Shielding Products Under Warranty OUT-OF-WARRANTY Products Problem SolvingIf in doubt please contact Soundcraft customer support Block Diagram Soundcraft EFX Block Diagram Soundcraft EPM Mono Input Channel EFX shown GainMID EQ HF EQLF EQ Aux 2 Send EPM only PANMute Input Channel FaderGain control sets the level of the channel signal Inputs Stereo 1/2Gain MF EQFader BalanceChannel Peak LED Soundcraft EFX/EPM User Guide Issue Power Indicator Master Section EFXMIX OUTPUTS, Inserts & Mono Output Bargraph MetersHeadphones Jack AUX 1 PRE/POST Switch and AUX 2 on EPMTrack Track to MIXFootswitch EFX only FX BUS Output EFX only Aux 2 on EPMStereo Return Inputs EFX only Stereo Return Level EFX onlySelect and Load a Program FX OperationSet Audio Levels FX Processor Controls EFX only Reverbs Reverb Controls KaraokeDelays Delay Controls Modulated EffectsPhaser FlangerTremelo/Pan VibratoFactory Reset Effects Data Chart EFX only Microphone Placement Using Your EFX or EPM ConsoleInitial Setup Page Applications Application 3 Places of Worship using EFX Application 4 Recording Soundcraft EFX/EPM User Guide Issue Glossary Distort the signal PhasePeaking BandTypical Connecting Leads Soundcraft EFX/EPM User Guide Issue Soundcraft EFX/EPM User Guide Issue Karaoke MARK-UP Sheets EPM Soundcraft EFX/EPM User Guide Issue Fitting Optional Rackmount Ears Part numbers for the kits areSoundcraft EFX/EPM User Guide Issue EPM/EFX Typical Specifications Soundcraft EFX/EPM User Guide Issue Warranty Benefit of this Warranty may not be assigned by the End UserSoundcraft EFX/EPM User Guide Issue Soundcraft EFX/EPM User Guide Issue Page Soundcraft Soundcraft USA Balboa Boulevard