QSC Audio owner manual I.Description, SPA-3STEREO PRECISION ATTENUATOR

SPA-3 STEREO PRECISION ATTENUATOR

I.DESCRIPTION

The SPA-3 is a stereo preci-
					SPA-3 SPECIFICATIONS
sion	attenuator		accessory
					GENERAL INFORMATION
for use with DataPort-
equipped QSC amplifiers. It					Operating temperature	0–70° C
mounts directly to the back					Input type, each channel	Differential balanced (transformer balancing optional)
of two-channel CX, DCA, and					Input impedance	28.4 kΩ balanced, 14.7 kΩ unbalanced
PL2 models, but it can be					Output impedance	95 Ω, quasi-balanced
used	with	the		others
					Maximum RMS output voltage	+18 dBu
(PowerLight, ISA, and four-
					Equivalent input noise (ref. to max. output level)	less than -100 dBr
channel CX			or	DCA
					Dynamic range	116 dB
amplifers)		by	using a
					THD @ 1 volt	< 0.03%
DataPort cable and a re-
					Frequency response	20 Hz–20 kHz, ±0.2 dB
mote mounting rack. Ampli-
fiers from the ISA series					Common-mode rejection	>50 dB minimum; >60 dB typical
cannot power the SPA-3, so					Power requirements	+15V @ <300 mA via ext. power jack, or from amplifier via pin 9 of DataPort
it requires a 15-volt exter-
					CONTROLS
nal DC power supply when					Programming	Pushbutton switches for incremental adjustment: Shift, Up, and Down
used with one of them.
					INDICATORS
					Attenuation (each channel)	2-digit 7-segment LED display
					Signal presence (each channel)	Green LED
					0.5 dB indicator (each channel)	Decimal point
					CONNECTORS
					Input	Two 3-pin "Euro-style" detachable terminal blocks
					DataPort	HD15 male (to amplifier)
					External power	2.5 mm coaxial jack; center pin positive
					PROGRAMMABLE OPERATING PARAMETERS
					Attenuation	0 to 32 dB in 0.5- or 1.0-dB increments
					Bypass	Either channel

Signal

LED

Up

Down

Shift

Input

Stage

½Micro- controller

Digital
Potentio-
meter
		To amplifier,
		via DataPort
		Output
		Stage
8.8.	2-Digit
	7-Segment	Block diagram of one channel of the SPA-3
	Display

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