Electrohome VistaGRAPHX 10K Guía de instalación descargar pdf (Pagina 17)

EXTRONEWS JAN/FEB 1999

Crosstalk is specified in dB, the level of

the signal leakage. Crosstalk should be

specified in relation to a particular

frequency. Since crosstalk results from

inductive and capacitive coupling, the

degree of crosstalk will vary according to

frequency. Therefore, crosstalk specifica-

tions should be compared at similar

frequencies.

Total Harmonic Distortion (THD)

Total Harmonic Distortion is determined

by measuring the amplitude of a series of

harmonics. The actual calculation is made

by adding the sum of the squares of the

individual values, then taking the square

root of this value. So what does this tell

the user? It's simply the measure of the

amount of distortion generated by the

amplifier. This specification requires

rather unusual equipment to measure,

and Total Harmonic Distortion + Noise

(THD + N) is usually listed instead of

THD.

Total Harmonic Distortion

plus Noise (THD+N)

This measurement is more common than

straight THD. In fact, in discussions,

people often mean THD+N although they

refer to the measurement as "THD".

THD+N is just what it says, the THD

value and the noise value combined.

Figure 2 shows the setup used to measure

THD+N.

To determine THD+N, a signal of specific

frequency is fed to the amplifier.

Following the output of the amplifier, a

notch filter is used to filter out the initial

test frequency, leaving only the harmonics

generated by the amplifier and the noise.

A band pass filter is used to limit the

range of frequencies/harmonics that will

be measured as noise. Finally, the noise

level is measured as voltage. This

measurement is one of the most realistic

in that it measures the harmonics and

other noise while an actual signal is being

processed by the amplifier.

FIGURE 2: THE FILTERS ALLOW ONLY THE HARMONICS AND NOISE TO PASS, AND THE LEVEL IS

MEASURED AT THE OUTPUT.

Get Ready to Rock at

“Battle of the Bands”

at INFOCOMM ‘99

Once again Extron will hold the

“Battle of the Bands” at its INFOCOMM party.

The “Battle of the Bands” is one of the most memorable

highlights of Extron’s annual bash—musicians and

audience members alike have a rollicking good time.

Previous contestants have included the following groups:

the Barco Band, the Electrohome Blues Band, NEC’s

Maximum Bandwidth and the Ceiling Mounts, and Stewart

Filmscreen’s The Rocs. This battle is open to all

companies, so Extron encourages both veterans and

newcomers to put a band together and start practicing!

If you would like more information about the “Battle of

the Bands” at Extron’s INFOCOMM ’99 party, please call

Humphrey den Dekker at 714.491.1500, ext. 6228.

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Electrohome VistaGRAPHX 10K Guía de instalación Pagina 17

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