You need to note a couple of things.
First is the power rating of the SB. Somewhere in the docs or even on the box you should find the correct voltage and power consumption and of course the connector polarity. Any third-party PSU you try should have 5V out, the correct connector and polarization, and AT LEAST the current-providing capability that the SB demands, and preferably 150% of it - presumably 2A is good.
If you were originally having problems with the supplied SB PSU, this suggests one of two things:
a) the smoothing in the PSU had partially failed. You can check this by trying the PSU from the SB downstairs which presumably works fine. You do not say you've tried that. If that makes no difference, then we can assume:
b) some aspect of any smoothing of the analog supplies inside the SB had failed. You can check this by swapping the two SBs which you have apparently done and didn't fix it, which again points at (a).
In fact, I do not know whether or not (b) is actually valid, as I don't know what goes on in the SB for supply smoothing to the analog stages. The fact that a different PSU fixes the problem suggests that this is NOT due to hum loops or interactions between the SB and the speakers.
Providing a fully-smoothed audio-quality PSU of the right current and voltage will probably solve /either/ problem, even if it is the result of a smoothing failure in the SB. You want to locate a third-party supply that is designed for audio devices such as boomboxes, portable CD players, etc. The best supplies for this purpose are generally, but today not always, linear (heavy transformer inside and fixed AC input voltage) types rather than switch-mode (small, light and universal input voltage); however it can be quite hard to find linear power units with current delivery in excess of 1A, so by all means try a switch-mode if the supplier tells you it is designed to drive audio devices.
Certainly you should not get the hum if you use the digital outs, but you may well get signal degradation of other kinds if there is excess ripple on the clocking and digital output circuit supplies, so this is worth fixing at source.
Hope this helps, --Richard E
Robert Boltman wrote:The set-up in the bedroom is producing a really annoying hum - especially as the speakers are 6 inches from my ear!!
I have tried: - alternate speakers - alternate squeezebox - plugging in to headphone jack / phono sockets - pluggng squeezebox in to separate mains spurs/rings (a downstairs one and the cooker one in the kitchen) - a ground loop isolator - an alternate power supply (from a Ipaq, same rating, 5v 2A as the supplied one)
None of the above made any discernable difference.
I finally tried a third power supply (this time from an Iomega external zip drive) which was only rated 5v 1A. This worked! But only for 3 months... this weekend the SB started rebooting a lot (esp when selecting max brightness), then the display started flickering, then it simply would boot at all. Swapped back for the other power supply - works fine, but the hum is back.
Arghhhhhhhhhhhhhhhhhhhhhhhhhhh! :-(
I assume that the SB draws more than an amp and so has knackered the p/s.
What do I do now? I love the SB, and it makes a great bedside alarm clock, but I just can't sleep with the hum.
The hum isn't affected by the volume on the speakers, gets a lot worse if only one channel is connected (using the phonos)?!? and is really quite audible - it can be heard the other side of the room, not just when I'm lying next to it.
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