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Cambridge Audio Control Bus; Anyone know how to use it?



I submitted these questions to CA customer care almost 3 months ago; and haven't as yet had a response. Thought I'd ask here in case anyone has encountered similar issues, or can answer any of these questions.

Here's my setup:
851E pre-amplifier
851W power amplifier
851C cd player
651T tuner
Stream Magic 6

All of these components feature control bus. I have them connected, using single RCA cables, as follows;

preamp out > power amp in.
power amp out > cd player in
cd player out > tuner in
tuner out > sm6 in
SM6 out> preamp in (effectively creating a loop)

My questions:

1. Is it safe to create a control bus loop? will this cause any damage?

2. I have enabled 'azur mode' in the stream magic 6's iPhone app, and changed the mode to "amp". However, the volume controls in the app will not change the volume on my preamp. How can I get this to work? Running latests SM6 firmware with latest amp. Control doesn't work in either amp or AVR mode.

3. I understand that control bus is supposed to allow me to power on all components with the press of a button. Currently, When I turn on my preamp, the cd player and power amp both come to life - however, the rest of the components (the 651t and stream magic 6) must be powered as normal using the controls on the front. However, when I enter the 851e setup menu, the option to power sync these devices is lit. Any ideas?

4. Is it possible to set the system up so that, for example, when I press input button number 1 the CD player powers on; and then, if I were to press input number 2 the CD player would power off and the stream magic would come on, and so on?

5. Is there a way I can turn on my preamp and not have any of the other components power on, without having to disconnect any cables or change any settings? For example, the one-off occasion when I want to use headphones, it seems silly to have the power amp start up only to have to turn it off again.

Sorry for so many questions; all of this should be covered in a user manual somewhere. however the user manuals for these components are vague to say the least.

If anyone has any ideas, I'd love to hear them; if not, I'll leave the control bus disconnected. If not; I guess it'll be yet another trip to Richer Sounds.


New member
Sep 1, 2009
Same problems for me. I don't understand anything although I suspect that it should make my life much easier especially for power on and off.

Is there a good instruction file somewhere?




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