How to connect the Cambridge Audio CXN100 to the CXA81 Mk II and Q Acoustics 3050c

What you need

Already have

Control bus cablein both Cambridge boxes, the orange one in the CXA81 Mk II

Need to buy

Balanced XLR interconnecta pair, CXN100 to A1

Speaker cablesone pair, equal lengths

An XLR interconnect is a pair of leads rather than a single moulded cable, one per channel, so buy them as a stereo pair at the length you need. Cambridge Audio give the wiring standard for anybody checking a lead: pin 1 ground, pin 2 hot and in phase, pin 3 cold and phase inverted. The unbalanced RCA output is still on the back of the CXN100 if you would rather use it, and the same A1 button covers both, which is what the light is distinguishing.

The 3050c is a floorstander and needs assembling before it needs cabling. The support base is best attached during unpacking rather than after it, two rear stabilisers come in the carton, and the spikes thread into the base with locking nuts. Get the speaker upright, then adjust each spike with the Allen key until it is level and stable. On a wood or stone floor, push a spike cover over each spike before you turn the speaker up the right way.

Q Acoustics want the 3050c at least 0.2m from the back wall, 0.5m from the side walls, 2.0 to 4.0m apart and equidistant from where you sit. Turning them slightly inwards will sharpen the stereo image at the cost of a narrower sound stage, which is a trade rather than an improvement, and worth trying both ways. Settle the positions, then measure the cable route around the edge of the room, take the longer side, allow slack, and buy an equal-length pair.

Connecting it

1. Assemble the speakers first. They are heavy, so get help lifting them, hold the cabinet rather than the drive units or the bags, and never drag a speaker across the floor once the spikes are on.
2. Fit the support base and the two rear stabilisers, thread the spikes with their locking nuts half way in, stand the speaker up, then level it with the Allen key from the top of each spike.
3. Switch everything in the system off at the mains before making any speaker connection. Q Acoustics ask for that, and it costs nothing.
4. Prepare the speaker cable as Q Acoustics describe: split it back about 40mm, bare 10mm, twist each end to gather the strands, then crop back to 7mm of bare wire. Unscrew each terminal anticlockwise, insert the bare end into the hole in the terminal column, and retighten fully hand tight.
5. Red to red and black to black, right speaker to the right channel, left to left. The red terminal on the CXA81 Mk II is the positive one.
6. Run the balanced pair from the CXN100's XLR output to the A1 input on the amplifier, keeping left to left and right to right.
7. Connect the control bus lead between the two boxes, using the orange RCA cable that came with the amplifier.
8. Power up, then press A1 on the front panel until the light is ORANGE, and check that speaker set A is selected. Bring the volume up from low.

What the control bus is for

There is a cable in both of these boxes that is not an audio cable, and most people never work out what it does. The control bus is a pair of RCA sockets on the back of each CX Series product, and it sends power and volume commands between them.

Wired up, the two boxes behave as one: standby and volume travel down it, so a single remote handles the pair and neither box gets left awake on its own. It carries no audio at all, so it can be routed anywhere and it cannot degrade anything, and since Cambridge Audio supply the lead with both products you will have a spare.

Where the volume lives

The CXN100 has a volume control of its own, which only does anything when its pre-amp mode is enabled. In this system it should not be. The amplifier is the box with the volume control, and the streamer's analogue output should be left fixed so that one dial governs the system.

Pre-amp mode exists for a different shape of system, where a CXN100 feeds a power amplifier directly and there is no integrated amplifier in the middle to do the job. Turning it on here gives you two controls in series, and a quiet system with both of them half way up.