QSC Audio DSP-3 - Manual (Page 17)

Section 1:
Introduction-
Technical Overview
17
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 I
MON
and V
MON
(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 (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, 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.
This portion of the introduction provides some of the technical details of the DSP-3.