QSC DSP-3' Manual descarregar pdf (Página 11)

Section 1: Introduction- Technical Overview

This portion of the introduction provides some of the technical details of the DSP-3.

Audio Input Path

There are two audio channels each with two input connectors, a balanced 3-pin ‘euro’ terminal block jack and a pseudo balanced DataPort

input. The inputs are protected with a filter that prevents radio frequency interference. Each input has a selectable input sensitivity of -

10dBV, +4dBu, +12dBu, or +18dBu to properly scale the input signal to the CODEC inputs. The DataPort is scaled to clip with a signal that

is +10dB compared to the ‘euro’ input. Each CODEC input is diode protected to prevent any large signal from destroying its inputs.

Audio Output Path

The first stage the audio passes through after the CODEC is an inverting gain stage that takes advantage of the op amp’s CMRR. The second

stage of the output is a second order Butterworth low pass filter that removes high frequency sampling artifacts. The signal is then sent

out of the DSP-3 through the DataPort or the output ‘euro’ connectors. The output level is selectable from 0dB or -6dB.

Power Supply

No external power supply is needed for use with the CX, DCA and PL2 series amplifiers (or more recent QSC amplifier models released after

printing of this manual). With these models, the DSP-3 is supplied power from the amplifier via the DataPort (HD-15) connection.

When used with the Powerlight series of amplifiers, the DSP-3 requires use of the external supply. The external supply is also used when

connecting to non-QSC amplifiers (or any amplifier that does not have a DataPort). External power is provided by the included power supply

(“wall wart”) via a coaxial power cord jack on the back of the DSP-3.

When using the external power source, we recommend that the DSP-3 be powered-up before the amplifier in order to insure

trouble-free start-up. This will also avoid the possibility of “thumps & bumps” should the DSP-3 be powered

up after the amplifier.

Data Acquisition

The DSP-3 samples the I

MON

and V

MON

lines of QSC amplifiers (via the DataPort) in order to perform dynamics (limiter, compressor, etc.)

processing. The four inputs (I

MON

and V

MON

for both channels) are continuously sampled by a four channel ADC. When used with non-QSC

amplifiers or QSC amplifiers that have no DataPort, dynamics processing is not available. This is because there are no Imon

and Vmon lines for the DSP-3 to sample in the absence of a DataPort connection.

Contact Closure

One contact closure input is provided. It uses pin 9 of the RS-232 DB-9 connector (not normally used for RS-232). Shorting this pin to ground

with a maximum impedance of 1.3 kOhms will cause a general purpose I/O pin of the DSP to be pulled to a logic low. This provides the

user with an event that can be used in software for many purposes.

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QSC DSP-3' Manual Página 11