NAD 118 Owner's Manual

Also see for 118: Specifications

Contents

NAD 118 Owner's Manual Manual pdf 18 page image

NA D18GB7. GLOSSARYABSOLUTE PHASESee “Polarity”ADCAnalogue to Digital converter. Refer also to chapter“Introduction”DACDigital to Analogue converter. Refer also to chapter“Introduction”DSPDigital Signal ProcessingGAINAmplification factor; for the Model 118 the input sen-sitivity (and therefore the amplification factor) for theanalogue sources can be changed to prevent overload-ing of the ADC (signal too loud) or not exploiting theADC to its full potential (signal too low).Infrasonic filter Filter to remove the lowest frequen-cies. Most loudspeakers cannot reproduce these fre-quencies yet the presence of these frequencies can puta significant strain on both power amplifiers and loud-speakers, in which case it is best filtered out.PEAKSudden burst in the signal which can cause distortionif it overloads the ADC and/or DAC, indicated by thePeak LED (23). Setting the input gains, high gain andsystem sensitivity controls and switches correctlyavoids overload.POLARITYThe sound shock wave created by hitting e.g. a drumstarts with an increase of the air pressure, (representednormally as a positive electrical signal), then as thesound progresses in time, air pressure will rapidlydecrease, represented as a negative signal. All thishappens very fast, the slowest audible change (verylow frequencies) from positive to negative and viceversa is approximately 40 times per second.An analogue audio signal will change continuously invalue from negative to positive and vice versa, a directrepresentation of sound. A good loudspeaker will trans-form this electrical signal exactly as changes in airpressure (sound) by rapidly moving the cone(s) in andout.Please refer to graphs opposite; the signal in figureB is identical to that of figure A, but with reversed polar-ity (the length of time of the shown signal is extremelyshort, a fraction of a second). The peaks and troughswhich are on the positive side at figure A are now at thenegative side in figure B.Analogue representation of an audio signalB. Normal same signal, polarity reversedSAMPLING FREQUENCYThe frequency with which an ADC or DAC calculatesthe digital signal. Three different sampling frequenciesare commonly used: 32kHz for radio and televisionbroadcasts, 44.1kHz for CD and 48kHz for DAT.timesame signal, polarity reversedlevel+–Btimelevel+–normalA