Obi110 and corded phone results in ground loop hum, how to get rid of it?
Diana:
There are a couple of things you should try before going out a purchasing extraneous devices:
(1) Check the box where your old telephone cables enter your house and check to see if it is grounded to say the water pipe and/or a ground rod. Is it the same grounding source as your electrical system? Is the receptacle serving the OBi properly grounded?
(2) If you have additional/extra pairs of telephone cables running from jacks, try switching to another pair throughout. There might be an "offending" pair between two jacks that is giving rise to this hum. You could test one at a time to isolate which jack is the source of the hum by starting with one jack and testing the phone, while adding additional jacks.
(3) Since you have a Cordless Phone System, why worry about the corded phone......
sailing:
I used a Lynksys adapter before the Obi. There was no hum with the same setup. Of course someone else's wiring could be a problem accentuating the problem but I believe the problem is the Obi.
Myself and others have focused on the power adapter because that is the only part that we can change or adjust but I believe the issue has to do with the way the audio is driven over the telephone wires. The original telephone systems used a transformer to couple the audio. This technique produced balanced lines which rejected noise that was injected into the line. With the latest electronics, a transformer was replaced with opamps that would try to mimic the noise reduction capability of a transformer. It is possible to achieve good noise reduction with electronics but the circuitry must be designed with this in mind. Since I have not taken apart an Obi, and I don't intend to, and without a circuit schematic, I am speculating that this is the case. Below are to reference links on the topic. The first one is very technical. They both sum up the issue very well.
http://sound.westhost.com/articles/balanced-2.htm#s1
http://yarchive.net/phone/60hz_hum.html
Navigation
[0] Message Index
[*] Previous page