QX2015 Matrix Surround Stereo Decoder with Surround Virtualization
Device Specifications
If the stereo recording is not matrix surround
encoded, then no center or surround
channels are decoded; only stereo expansion
of the left and right channels is performed.
Figure 3 shows the functional elements of
the QX2015.
Principles of Operation.
In ordinary stereo systems, the stereo image
is formed between the speakers. QSound
technology allows for placement of sound
images beyond the standard "sound stage".
Matrix encoded recordings encode four
channels of audio into conventional two-
channel stereo; the channels are left, center,
right and surround. The QX2015 processes
each of the channels to create a realistic
surround environment over conventional
stereo playback systems.
Lt, Rt: 4 channel encoded surround
Lv, Rv: QSurround positional audio
Figure 3: QX2015 Simplified Block Diagram
For simple QSurround/Bypass selection, the
QEN/BYP control pin is a TTL-compatible
input.
QEN/BYP
Output
Bypass
QSurround
0
1
Table 1: QSurround/Bypass Mode Selection
Figure 2: QX2015 Pictorial Representation of Effect
Power down output.
§ The center channel is first reduced 3dB
in level, and then added into each stereo
output to create a phantom center
speaker.
§ The front left and right channels are
expanded using QSound’s patented high
quality stereo expansion processor,
QXpander.
§ The mono surround channel is first
processed to synthesize two surround
channels, surround left and surround
right. These two separate channels are
then located on each side of the listener
using QSound’s patented positional
audio technology, Q1.
The voltage of the capacitor at REF1 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 REF1. This
signal may be used to latch a power down
mute function for an output amplifier.
Normally, the QSurround is used in the
preamplifier stage between the stereo source
and the amplifier stages used to drive the
speakers. The QSurround enhancements can
be disabled using the bypass control allowing
the unchanged stereo signal to pass through
to the amplifier stages.
Ref: 2015v099.doc
Rev: 0.99
QX2015 Data Sheet -- Preliminary
QSound Labs, Inc.
Date: 12/15/98
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