4
One trial is not enough; even flipping a coin to decide which amp is X would yield the right result about half the
time. No, it takes repeated trials, with X randomly selected each time, to get a statistically significant test. If
the listening judge answers correctly in only about 50% of the trials, he or she didn’t hear any audible difference
between the amps. But if far more than 50% of the answers are correct, the listener clearly discerned some audible
difference.
Notice that the decision made in each trial isn’t “which amp sounds better?” Instead, the goal is to identify whether
the amps sound totally alike or different; deciding which is better sounding is a job best left for later. You can’t
judge whether one amp sounds better than another unless you determine that they actually sound different!
The ABX Comparator not only automatically and randomly selects the amplifiers, but also tracks the choices the
listening judge makes in each trial. After a sequence of trials, the ABX will report how many trials and how many
correct answers the judge made.
A B X C O M P A R A T O R
C A L I B R AT E
T R I A L
R E V I E W
S C R O L L
P O W E R
O N
R C
ABX1
D ATA
U N I T A
X
U N I T B
E N T E R
II. DESCRIPTION
THE ABX COMPARATOR
Power switch
The rear panel has input and output connectors, a 9-pin RS-232 port for connecting to an optional computer,
and an additional RS-232 port for slaving one or more additional ABX units.
Calibration
voltmeter display
LCD display
UNIT A
button
UNIT X
button
UNIT B
button
ENTER
button
CALIBRATE
button
TRIAL
button
REVIEW
button
SCROLL
button
Infrared sensor
(for remote)
CH2—LINE OUT—CH1
CH2—LINE IN—CH1
CH2—LINE OUT—CH1
INPUT
OUTPUT
INPUT
RS232
B
B
A
M
P
CH1
CH2
CH1
CH2
A
A
A
M
P
P 1=G
P 2=+
P 3=-
B
A
SLAVE
QSC AUDIO
PRODUCTS INC.
REPLACE
FUSE WITH
SAME TYPE.
SEE USER'S
MANUAL FOR
RATING.
MADE IN
U.S.A.
Binding post signal terminals
“Combo”signal connectors
RS232 output
to slave ABX
AC power
connection
RS232 to optional
computer
Front panel
Rear panel
The front panel features a power switch, a digital voltmeter display (for calibration), an alphanumeric LCD display,
eight input and control buttons, and a female 8-pin DIN connector. During operation, menus, instructions, and
data appear on the LCD display.
Summary of Contents for ABX Comparator
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