QSC Audio DSP-3 manual Audio Output Path, Power Supply, Data Acquisition, Contact Closure

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 an electronically balanced DataPort input. The inputs are protected with a filter that prevents radio frequency interference. The inputs have software- selectable full scale input level sensitivity; this is the level at which the analog to digital converters reach their full scale digital value. Refer to the Specifications section for full details. The DataPort is scaled to clip with a full scale digital input if the DSP-3 does not change gain structure. 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 is an inverting gain stage. The second stage 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’ connec- tors. The output level is selectable in software.

Power Supply

No external power supply is needed for use with the CX, DCA and PL2 two-channel, 2 RU series amplifiers produced with date-codes of August, 1999 or later. With these models, the DSP-3 is supplied power from the amplifier via the DataPort (HD-15) connection. CX,

DCA, and PL2 amps made prior to August 1999 DO NOT provide adequate power supply voltage to the module, requiring the use of the same type of external DC supply as used with Powerlight amplifiers. The amps in question will have a serial number PRIOR to 0899XXXXX, where the first four digits of the serial number are the MMYY datecode. Again, the modules WILL work with these amps just fine, but will require the use of our external power supply. External power is not required for all other directly-mounted-to-amplifier situations.

When used with the Powerlight series of amplifiers (or 3 RU & 4- channel amps), the DSP-3 requires use of the accessory external supply. The accessory 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 accessory 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 pow- ered up after the amplifier.

Data Acquisition

The DSP-3 samples the IMON and VMON (current and voltage monitor- ing from the amplifier) lines of QSC amplifiers (via the DataPort) in

order to perform dynamics (limiter, compressor, etc.) processing. The four inputs (IMON and VMON for both channels) are continuously sampled by a four channel ADC. When used with non-QSC amplifiers or QSC amplifiers that have no DataPort, the power limiter DSP “object” is not available as this function relies upon amplifier current and voltage feedback. The DSP-3 will also not be able to monitor the protect or power status of the amplifier as these features require amplifier data via 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. The current release of Signal Manager software uses this input to allow switched gain functions. Each of the Switched Gain blocks will be switched simultaneously by the single contact closure (switch). Each Switched Gain block has a two gain settings; one for open and one for closed switch conditions.

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