On Tuesday September 6th the forum will be down for maintenance from 9:30 PM to 11:59 PM PDT

Main Menu

Using OBi100(US) in HongKong, got humming background noise

Started by stanley.siu, September 19, 2013, 05:00:30 PM

Previous topic - Next topic


The Obi100 was working fine in US, my brother took it back to HongKong.  Installed and working except humming noise in the background on both sides when he called/received call to US.  Hong Kong AC power is 50HZ while US AC power is 60HZ.  Any suggestion, please! 


The power supply spec is:

QuotePower Supply Type Universal Switching with Fixed US, EU, UK Style Plug Prongs (Model Dependent)
Input Power AC Input: 100 to 240 Volts 0.3A 50-60Hz (26-34 VA)
Output Power DC: +12V 1.0 Amp Max

I have two OBi110's here in the UK where the power frequency is 50Hz and I have no hum.

Having said that, it does sound like a power or noise induction problem. Your brother might try a different power socket or a different power supply, if he has a compatible one. Also, noise can be induced into to telephone wiring if it runs near to power wiring.

Do a search on this forum for "noise", there's been quite a few posts about it.

Good luck.


My brother in Hong Kong has cancelled his landline phone line service yesterday.  He connected Obi100 to his existing landline phone jack.  The humming noise disappeared.  He also pleased that he has multiple phones connected to one Obi100 around his house thru existing landline wiring. :)


It's good to hear that your brother is now hum free. I hope that he completely disconnected the incoming telephone company wiring from his internal house wiring.


The hum might come from the AC-to-12VDC adaptor using power switching technology. You may reduce the hum to minimal if a linear AC-to-12VDC is used.

Hong Kong and China OBi Users Group


The noise is coming through the power supply but it is only an issue when the Obi is connected to the house phone wires and those wires cross the power lines. A linear power supply should solve the problem but make sure its output is regulated.

I had posted what the problem is at;wap2. Only the last post of that thread is important and answers the question.