poe injector


I've bought this poe :


The bomebox works, but turn itself off after some times. Also, there was a little ringing noise in the bomebox I've never heard before. I had the feeling that this poe met the specs, doesn't it ?

Is it ok if I insist or there is a risk damaging the bomebox ?

Thank you very much !


This POE provides for 500ma of power according to the web site. The BomeBox draws 150ma so if you have any downstream BomeBoxes or USB, that leaves an additional 350ma of power for those devices. Typically the USB2 spec I believe is for up to 50ma per attached USB port so you can have 7 USB devices attached to your BomeBox (assuming they are all in spec) or you can have up to 2 additional BomeBoxes (with no USB ports attached).

The key is to calculate the total current requirements needed for your configuration by adding them up and ensuring your POE is providing enough current.

I’m assuming, of course that the POE you purchased is not faulty itself. If you are getting some noise, perhaps it is. To troubleshoot, I would disconnect all downstream devices from the power chain to see if it still has a problem. If it does, the POE is likely faulty. If not, add one device at a time until you hear the noise. The newly added device could be a problem or at that point you could be exceeding the current your POE can provide.


Finally, make sure the POE is connected to the ethernet port on the left (POE In).


Steve Caldwell
Bome Q and A Moderator and
Independent Bome Consultant/Specialist

Hi Steve,

Thank you very much for your answer.

I had trouble to identify this as something related with power because when there was trouble with the bomebox powered over usb, the connected device did not work, and with poe it’s the bomebox that stop working.

I have 2 devices that take some power :

– 2 roli seaboard block : 10 watt

– an android phone with Lemur and Midi over usb. I don’t know the power consumption of the phone

My keyboad (Roli) needs 10 watts of power over usb (5v) so -> 2 amps.

I didn’t find the information for the phone, but my charger is 1 amps, so I assume my phone is 5watts.

So we’ve got a total of 15 watts, plus the bomebox itself 7.2 watt (350ma/48V) = 22.2 watt. And my poe is 24 watt. So maybe my phone is a little bit more.

Did I understand the math correctly ? If I buy a POE with 30watt, will it be enough ?

If it’s not enough, I found this one, with 60watts :


But is there a risk to damage the bomebox with too much power ?

Thank you very much !

Hi, I can’t really recommend/endorse any given power adapter. Just make sure when you do he wattage calculations that you multiply the volts times the amps so 1 amp at 5 volts is 5 watts. 350 ma (.35) at 48 volts comes to 16.8 watts which seems really high to me. I don’t think it actually takes nearly that much.

I think BomeBox is actually 350 ma at 5v so it is really just 1.75 watts. When using 48 volts, I’m pretty sure BomeBox steps down the voltage to 5v before using it. I’ll ask Florian to clarify the specification

USB provides 5 volts so if powered by USB use the amperage multiplied by 5 to get to the wattage.

For POE, anything that BomeBox uses (or attached USB devices) should be subtracted from the power supply to get to the remaining power out of the POE out connection.

Steve Caldwell
Bome Q and A Moderator and
Independent Bome Consultant/Specialist

the ringing noise is not a good sign, and I’ve never heard that.
I don’t know this type of PoE injector, maybe it has bad quality, or outputs more or less than 48V?
Would you have the possibility to try a different 48V PoE source?
Of course, it’s also possible that your BomeBox is faulty… but it would be great to find out before sending it back.

And to clarify some things:

  1. the BomeBox uses max. 150mA at 5V. That’s 0.75W, so at 48V it uses roughly 15mA.
  2. I’m not sure how you power your other devices, but in any case, the BomeBox will output a max.1A on the USB host connector. If you use a USB hub, we generally recommend using a powered USB hub.
  3. 3) there is no risk of damaging the BomeBox by using a higher rated PoE injector, but it also doesn’t help (except for cascading BomeBoxes via “Ethernet Out”). In your setup, I mainly see the problem of the quality of the PoE injector.

Best regards,

Thanks for the clarification, Florian!

thinking about it… are you powering 2 Roli blocks and your cell phone via the USB connector at the BomeBox? That’s definitely out of specification…

Edit : Sorry I’ve read the doc once more and it answered my one question : with poe, it is also limited to 1A, but it is more stable (not more powerfull). Sorry.
Yes I was overpowering it because I thought with poe there was not the limitation of 1A on the usb output. So the limitation 1A anyway, either with the unit powered by poe or usb ?
I’m using non-powered usb hub, because I’ve tried with 3 powered usb-hub and it never worked (but they were all from the trademark Anker, so I think it had to do with that).
If I use a power usb hub, I imagine that I have no limitations by the bomebox (just by the usb hub).
The ringing noise appeared when I was asking too much power on the usb hub (for example when plugging a roli), and it did that on another bomebox too.
Many thanks again for all those informations.