OBi 交流声问题

角色

之前都在OBi forum也提及过，而他们说他们只能用Switching power supply。因为我之前有很多Linksys的Linear Transformer，所以在香港和大陆用换上Linksys 12V 1A的Transformer火牛！整个交流声都没有。

现在一个问题是能否switching牛做东linear牛的效果呢？这个问题，可能要用到Spectrum Analyzer才能有答案。

为什么Linksys的SPA （SPA3102，SPA941）都是用Switching power supply就可以做到没有交流声， 而OBi就不可以呢?

因为我也是一名专业Electrical Engineer，可以说主要是成本问题。

角色

daibaan

this may not be a power supply problem at all!

When I first got my OBi, I have the following connections: LINE, PHONE, ETHERNET, POWER.
- a phone is connected to the PHONE port directly.
- LINE port is connected the red/green paire of wire from the outside phone panel
I play with it for a week, make sure I have all the basics figured out. No AC hum problem.

Then I connect the PHONE port to the second pair (yellow/black) of my house wire, basically route the OBi phone port back to the phone connect panel outside of my house, which is connected to my 4 other locations in my house. that is when I start hearing the AC hum.  Only one of these 4 locations actually has a phone connection to the yellow/black pair of wire, at the other 3 locations the phones are still connected to the red/green pair and the yellow/back pair is left dangling, which I assume acts as antennae packing AC hum.  As soon as I disconnected the 3 yellow/black pairs from my connection panel, the AC hum is gone.

So, before blaming AC hum on the power supply, check to see if the problem exist when
- phone is directly connected to the phone company line (i.e w/o OBi in place)
- phone is directly connected to the OBi phone port

角色

Thank you for your advice and suggestion.

In fact, this issue has been confirmed by Obihai Technology that AC hum generated by the switching AC power adaptor is heard with ordinarly corded phones. If cordless phone is used, AC hum is filtered out.

I believe that we may reduce the AC hum by adjusting the impedance and gains to match or fit the corded phone.

YH

daibaan

Yes, I have seen the power-supply related AC hum problem mention in obitalk forum, and suggestion on using other un-certified power supply.

I am just sharing my experience of non-power-supply related AC hum problem in case someone encounter the same situation