What is A-BUS?
A-BUS is a patented technology that allows for the distribution of audio,
electrical power and data over ordinary 8-conductor twisted-pair
wires, typically Cat-5 cable.* Products that incorporate A-BUS technology
are used to create multi-room audio systems. A-BUS products were
first developed in Australia and continue to be manufactured there
as well as in Asia. In the US and elsewhere, A-BUS technology is
licensed to leading manufacturers who incorporate the technology
into their own audio products.
Who is behind A-BUS?
A-BUS was invented by Len Andrews and Andrew Goldfinch of LeisureTech
Electronics. LTE has been a leader in custom home installation in
the Australian market as a manufacturer and distributor of CI products
for many years.
What comprises an A-BUS system?
A-BUS products use different nomenclature depending on the manufacturer.
We will use generic terms here.
A-BUS consists of two basic components: A “HUB” and a “POWER
In an A-BUS-based multi-room audio system, sound sources such as a
CD player and AM-FM tuner connect to the hub and are distributed via
Cat-5 cable to amplifier modules in outlying rooms. The hub also supplies
the electricity that powers the power modules. The amplifier modules
connect directly to the speakers using conventional speaker wire.
A simple power module is a single-gang wallplate (like a light switch)
that contains amplifier circuitry as well as a volume knob for adjusting
speaker volume. A power module wallplate may also contain a keypad
and an IR receiver that allows for direct control of the sound sources.
In this case, commands issued on the keypad or via an IR remote travel
back to the sound sources via the same Cat-5 cable.
I’ve seen the technology name “A-BUS/READY” on
the front of Harman Kardon and Onkyo Integra receivers. What does
“A-BUS/READY” on the front of a receiver or amplifier means
there is an A-BUS RJ-45 jack on the back that streamlines connection
via Cat 5 wire to an A-BUS multi-room audio system. An A-BUS/READY
AV receiver may be the centerpiece of a home theater while at the same
time functioning as the hub for a multi-room audio system.
I have also heard about “A-BUS/DIRECT” as a new loudspeaker
technology. What is “A-BUS/DIRECT”?
A-BUS/DIRECT is an application of A-BUS technology where the power
module is mounted directly on the back of the in-ceiling or in-wall
speaker. An Infra-red eye built into the speaker relays control commands
sent via the included remote control. This application of A-BUS removes
the necessity for a wall-mounted control. (If still desired, the wall-mounted
control may be installed as well.)
How is an A-BUS system installed?
Because they involve inside-the-wall wiring and (typically) in-wall
or in-ceiling speakers, A-BUS systems are usually installed by professional
AV contractors or electricians or other trained professionals.
A-BUS/CUSTOM – an A-BUS system typically installed by Custom
A basic 4-room A-BUS system would have the sound sources and the hub
located in a central area, with Cat-5 cables running directly to A-BUS
power modules in each room. Then each power module is wired directly
to the room’s speakers.
A-BUS/STRUCTURED – an A-BUS system installed with a structured
wiring system. A basic 4-room A-BUS system would have the sound sources connect an
interface hub and from there to the structured wiring panel via a simple
Cat-5 cable. In the structured wiring panel, the A-BUS hub would then
connect to Cat-5 cable running directly to A-BUS power modules in each
room. Then each power module is wired directly to the room’s
How many rooms can an A-BUS system have?
The short answer is – as many as you need! It can support one room but a typical hub supports
4 rooms. For more rooms, simply connect additional hubs (in a “daisy
chain” fashion) and a power module for each new room or zone.
One additional power supply is needed for every four rooms.
Can you add a “local” source to an
Yes – quite easily. The A-BUS power module contains an auxiliary
input that connects to a wall-mounted Local Input Module or LIM. The
LIM – usually positioned along a baseboard near an AC outlet – has
RCA-type input jacks that allow you to simply connect an audio source
for use just in that room. For example, the audio output of a TV set
or MP3 player would automatically play over the in-room speakers whenever
turned on. The LIM contains a special circuit that automatically switches
to the local audio source when it senses signal.
What type of speakers does an A-BUS system require?
A single A-BUS power module can easily drive two pairs of 8-ohm in-wall
speakers to satisfyingly loud levels. In fact, any speaker with an
efficiency rating of around 90 dB or greater is suitable.
Isn’t A-BUS a Russound technology?
Russound was the first licensee of A-BUS technology starting in 2000.
They also handled the licensing in the US for a while but that reverted
back to LeisureTech Electronics in the Spring of 2002. Russound has
their own line of A-BUS products as do several other manufacturers.
Who else is involved with A-BUS technology?
Many Harman Kardon receivers have A-BUS/READY RJ-45 jacks on the back and they offer A-BUS products to enable simple A-BUS systems. Additionally, the structured wiring industry has recognized A-BUS to be a terrific solution for multi-room audio. A-BUS is the audio solution of choice for Honeywell, Eaton, Home Director, Channel Vision, UStec and AMP/tyco. Phase Technology is the newest A-BUS partner. In the United Kingdom, Audio Partnership has their OPUS line that is part of the A-BUS family of providers.
Is it patented?
LeisureTech holds patents for its distributed stereo system under which audio, status, power and data are carried down a Cat-5 cable. A-BUS products may be covered by one or more of the following patents US 7,181,023 , 7,668,318, 6,389,139; AU739808; NZ502982; CA 2301062; MX241196. LeisureTech has further patent applications pending in the US and elsewhere.
Does A-BUS compete with traditional centrally powered distributed
audio system design?
Yes – and with good reason.
A-BUS provides a sensible alternative to the traditional approach of
using a big expensive multi-channel amp and sending speaker level signal
over expensive speaker wire. A-BUS is easier to install, simple for
consumers to use, great-sounding and flexible enough to accommodate
a wide variety of consumer applications.
A-BUS uses Cat 5 cable (one) and distributes power, audio signal,
and data from a hub located either behind the equipment or in the home’s
structured wiring panel. The A-BUS combination of power, audio signal
and data is sent from the A-BUS hub to an A-BUS power module located
in each room. The power module is either integrated into a wall-mounted
keypad that includes system control for that room, or the power module
is integrated right into the speakers and control is accomplished via
Why should I use A-BUS rather than centrally powered systems?
There are many reasons – here is a partial list.
• A-BUS simplicity means less training for installers to
• A-BUS requires less cabling – a single Cat-5 cable
from equipment area or structured wiring panel to each room and then
short runs of speaker wire from keypad to speakers. If A-BUS/DIRECT
or A-BUS/ACTIVE speakers are used, then the Cat-5 cable goes directly
to the speaker locations.
• A-BUS is truly plug and play – no expensive programming.
• A-BUS is very flexible – it connects as easily to a stack
of entertainment gear as it does to a structured wiring panel. It’s
superb for new home installations and it is a great way to add multi-room
entertainment to an existing home. It easily accepts local inputs
like MP3 players, computer sound output, musical keyboards, etc.
in any room and it can easily accommodate audio distribution from
one room to a hundred.
• A-BUS has been proven to be dependable – around the
Why isn’t it appropriate to compare the
power rating of A-BUS to that of centrally powered systems?
Let’s state the key point right up front – one of the most
powerful benefits of A-BUS is that it takes the age-old problem of
delivering power over a long distance right out of the equation.
Well – how much power does A-BUS have?
That’s a good question to ask - but for A-BUS it’s
the wrong question – here’s why. You see – the
patented A-BUS system was designed specifically to solve the problem
of sending music over long lengths of speaker wire around the home.
When Category 5 cable was introduced about 10 years ago, it opened
the door to a new way of sending high quality sound around the home.
This patented system design is called A-BUS.
A-BUS does not send speaker-level signal all that way down the wire
so there is no need for large amounts of wattage to make up for the
losses that occur when you send speaker level signal over speaker wire.
A-BUS sends line-level signal so that it arrives in the local room
or zone ready for local amplification by the A-BUS power module in
How does A-BUS sound in comparison to other distributed sound system
A-BUS sounds cleaner, and more musical. That’s because
A-BUS is delivering a cleaner, line-level signal all the way into the
individual room. There it is amplified and then the amplified signal
is sent just a short distance to the speakers.
That’s why the A-BUS slogan is, “Have you heard it?”
Here’s another way of dealing with the question of power when
comparing centrally powered systems with A-BUS.
When it comes to discussing the power output of distributed audio
systems, it is important to understand what is being discussed and
why. Is that the right question to ask to get the answer they are looking
For example: The Mini Cooper is a popular new vehicle, as is the new
Ford F-150 pick-up. Have you ever heard the topic of payload
mentioned when discussing the Mini?
Of course not.
Conversely, have you ever heard of the topic of handling being discussed
when talking about the Ford?
And it would be very wrong to compare them simply by quoting the
power output of their motors.
When the topic of power and distributed audio comes up we need to
look at this one specification and ask how relevant it is? E.g.
- “If you were asking about a traditional distributed audio system
that is centrally powered, then that would be an appropriate question
because those systems have to overcome the problem of power over distance.
The only way to try to overcome the great loss of power and quality
over distance is with larger amounts of power.
A-BUS solved the problem by patenting a different approach. A-BUS
delivers cleaner, un-amplified signal with no losses, all the way into
the individual room and amplifies it there. The right question to ask
is, “Which approach delivers a cleaner signal?
How do you turn an A-BUS system on or off?
Automatic Signal Sensing.
Most A-BUS hubs include a sensing circuit to power the A-BUS system
up automatically when audio signal is sensed. This is indicated by
a red indicator on the power module When power is off the power amplifiers
in each module go to standby.
The system may also be switched on with the use of a 12 Volt power
pack connected to the switched power output of the main amplifier.
When plugged into the status socket the audio sensing circuit is
Manual Switching. On some hubs there is a manual override switch which
permanently powers up the A-BUS system.