ABX Switch
Rev 2
01-29-14
www.avahifi.com
The rev 2 ABX Switch allows seamless switching between two sources, two power amps, and three sets of
speakers. Some of its features are:
1) Precise volume level matching, in 0.1 db increments.
2) Infrared remote control.
3) Blind test mode.
4) Line level subwoofer support with built in selectable subwoofer filter.
5) Programmable power up state and persistent volume settings
A common ground
is used throughout the switch.
Extreme care should be used to ensure correct cable
polarity, as a dual banana plug flipped around between the ABX switch and the amplifier output will
connect ground to the positive amp output that could result in catastrophic amplifier damage.
All line
level signals connect through RCA jacks and all speaker level signals connect through dual banana plugs. A
line level signal is around 1 to 2 volts AC. It is the typical signal level that comes out of a high level source
like a CD player or tuner. It is also the typical signal level used to connect a pre-amp to a power amp.
When a line level signal approaches its maximum 1-2 vac, the audio system approaches its maximum
output. The ABX Switch was
not
designed to connect to maximum line level signals, it was designed to
“drop in” to a system set at
normal
listening levels (or slightly louder) and then attenuate those levels
slightly
to achieve equal volume settings for all components. There are 96 different volume settings
maintained in the ABX Switch, a sub volume and a mains volume left / right pair for every possible
combination of source, amp, and speaker. These volume settings persist through power cycling. This ABX
Switch has a programmable power up state. When the record, “rec”, button is pressed twice on the remote,
the current ABX switch state is written to memory and is then used to set the state after power up.
The “Y” RCA jacks form a simple splitter. Connect a line level signal to the center jack and you get two
duplicate signals on the jacks to the left and right. This is useful when testing two preamps or DAC’s…Not
really needed for testing power amps and speakers. There is a 10k ohm resistor between center jack and left
/ right jacks so isolation exists between the duplicate signals.
