QX2014 QXpander Processor
Device Specifications
For simple QXpander/Bypass selection, the
B/Q control pin is a TTL-compatible input.
Principles of Operation.
In ordinary stereo systems, the stereo image
is formed between the left and right
speakers, and is confined by the speaker
positions (i.e., the "sound stage" is located
between the two speakers). The QXpander is
designed to form the stereo image beyond
the speakers, thus enlarging the "sound
stage".
B/Q
0
Output
Bypass
1
QXpander
Table 2: QXpander/Bypass Mode Selection
Power down output.
The voltage of the capacitor at VREF is
approximately half of supply voltage and is
compared with the internal Vcc supply. The
comparator output goes high when the
internal Vcc supply drops below the voltage
maintained at the capacitor at VREF. This
signal may be used to latch a power down
mute function for an output amplifier.
If the center channel is defined as the
monaural or common component of the left
and right channels, then Figure 2 represents
the spatial response of the QXpander at a
typical setting of the spread control, vs the
normal image width of stereo in bypass
mode.
Normally, the QXpander is used in the
preamplifier stage between the stereo source
and the amplifier stages used to drive the
speakers. The QXpander enhancements can
be disabled using the bypass control allowing
the unchanged stereo signal to pass through
to the amplifier stages. Figure shows the
functional elements of the QX2014.
Figure 3: QXpander Spatial Response
Stereo
L
L
QXpander
Spatial
Enhancement
The degree of QXpander enhancement can
be controlled via the SPC and QIN pins,
most conveniently by connecting a single-
gang 50k linear pot between SPC and
ground, with the wiper AC coupled to QIN
through a 2.2µF electrolytic capacitor. (See
typical application schematic.)
Stereo In
R
Stereo Out
R
Switch
SPREAD
QEN/BYP
Figure 4: QXpander™ Simplified Block Diagram
QIN Coupling Capacitor
Spread
Min
Max
GND
SPC
Table 1: Spread Control
Ref: 2014v100.doc
Rev: 1.00
QX2014 Data Sheet -- Preliminary
QSound Labs, Inc.
Date:
99.04.2107
Page 2 of 6
