ABX Comparator USER MANUAL ON POWER D ATA UNIT A X UNIT B ENTER C A L I B R AT E TRIAL REVIEW SCROLL ABX1 ABX COMPARATOR RC ▼ ABX Comparator Double-blind listening test switcher 1
ABX Listening Test Comparator I. INTRODUCTION The ABX Comparator is a signal routing and measuring device that permits simple and accurate comparative listening tests of two or more power amplifiers or even line-level audio components. Using advanced microcontrollers, the ABX Comparator’s features and functions allow you to quickly set up and conduct sessions of critical listening test trials for performance evaluations.
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.
To route the audio signals, the ABX Comparator uses passive circuitry comprising relay switches controlled by the internal microcontroller. To avoid any possible coloration of the audio and to allow bidirectional signal flow (because testing of line-level devices uses a different hookup configuration than testing amplifiers does), no active circuitry is used in the test signal path. THE REMOTE CONTROL The handheld remote control, shown at left, communicates with the ABX via encoded infrared light.
Speakers Speakers CD PLAYER CH1 B A M P B INPUT CH1 OUTPUT CH2 CH2 CH2—LINE OUT—CH1 A M P A CH2—LINE IN—CH1 B A INPUT CH2—LINE OUT—CH1 A RS232 QSC AUDIO PRODUCTS INC. SLAVE P 1=G P 2=+ P 3=- REPLACE FUSE WITH SAME TYPE. SEE USER'S MANUAL FOR RATING. MADE IN U.S.A.
CONNECTING TO “COMBO” CONNECTORS The six Neutrik “Combo™” connectors accept either 3-pin male XLR or ¼-inch (6.3 mm) male TRS connectors. Pin 2 and tip are +; pin 3 and ring are -; pin 1 and sleeve are shield. CONNECTING TO BINDING POST TERMINALS When setting up the ABX for amp testing, it is vitally important for safety reasons that you connect the cabling between the amplifier outputs, the ABX, and the speakers correctly. Use only fully insulated stranded wire. 1.
In the calibration mode, the ABX Comparator will produce a 1 volt RMS, 1 kHz tone and send it to both channels of both amplifiers in place of the audio signal input. At the same time, the digital voltmeter display will show the output level from each amplifier channel, starting with Channel 1 of Amplifier A. In Calibration Mode, however, the loudspeakers are muted, so you won’t hear the test signal. 1. Turn off the audio source—the CD player, DAT, et al—until you complete the calibration process. 2.
THE TEST SESSION BEGINS NOTE: To preserve objectivity in the test, don’t tell the listening judge before or during the trials which amplifier is A and which is B. Otherwise, if he or she has even a slight prejudice toward or against one amp, they may try to pay attention to “does Amp X sound like Brand Z” instead of to whether the amps sound alike or different. Instruct the listening judge: 1. Each trial starts with the X, or unknown, amplifier, which could be either Amp A or Amp B.
but over an increasing number of trials will almost certainly tend to approach 50%. For example, the chances of a coin coming up heads on two successive tosses is 1 in 4; on three successive tosses, 1 in 8; on four successive tosses, 1 in 16. Getting tosses of heads ten times in a row is likely only one time in 1024. In other words, large samples tend to smooth out the aberrations of randomness that occur.
CH1 B A M P B INPUT CH1 OUTPUT CH2 CH2—LINE OUT—CH1 B A INPUT CH2 A M P A CH2—LINE IN—CH1 CH2—LINE OUT—CH1 A P 1=G P 2=+ P 3=- RS232 QSC AUDIO PRODUCTS INC. SLAVE REPLACE FUSE WITH SAME TYPE. SEE USER'S MANUAL FOR RATING. MADE IN U.S.A. CONNECTORS AND DESCRIPTIONS LINE IN A two-channel source of high-quality audio, such as a CD player, DAT etc., connects to the audio inputs of the ABX Comparator. These inputs use “Combo” jacks which accept both XLR and ¼" TRS connectors.
Speakers LINE-LEVEL EQUIPMENT COMPARISONS The ABX Comparator is useful for comparing line-level Speakers equipment such as CD players, preamplifiers, and other equipment, too. The setup is a little different and varied with CH1 out CH2 out CH 2 in CH 1 in this form of testing.
SPECIFICATIONS SPECIFICATIONS Functionality: Calibration Mode Amplifier A selectable; Channels 1 and 2 individually selectable Amplifier B selectable; Channels 1 and 2 individually selectable Calibrating Signal selected automatically Trim control: 100 mV per step. Up to 2 Vrms max. Calibrating Signal Display Range: 00.0 to 99.9 Vrms ±0.1 Vrms tolerance Trial Mode Audio signal “X” in each trial is selected randomly and automatically. Trials will begin with number “01” and go up to “25,” maximum.
Connectors Line-level audio inputs and outputs: Neutrik “Combo” XLR female and ¼” TRS connectors Speaker-level audio inputs and outputs: “Touchproof” binding posts Control port for slave unit: HD15 female RS-232 RS-232 port for remote computer control: HD15 male Power Requirements Voltage line: 80-260 VAC (autosensing), 50–60Hz Power consumption: 40 W Physical Dimensions: 19" (48.26 cm) W × 1.75" (4.44 cm) H × 12" (30.48 cm) D © Copyright 1998 QSC Audio Products, Inc. All rights reserved.
