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Author Topic: AC hum are easily heard due to the present power adaptor  (Read 766623 times)
yhfung
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« on: March 16, 2011, 07:49:56 am »

For anyone who are have used Linksys SPA ATA can easily distinguish the difference of AC hum generated by the associated power adaptor between OBi110 (with OBi110 power adpaptor) and SPA3102 (with Linksys SPA ATA power adaptor) if you pick up the handset of the phone and press the key '0' for example (you may press other key).

For OBiHai OBi110 an AC hum can be easily heard by a general human ear with the provided power adaptor.

For Linksys SPA3102, a very and extremely low-level AC hum can be heard if you have an extremely sensitive ear with the Linksys provided SPA ATA power adaptor.

The cause of this AC hum in OBi110 is mainly due to the provided power adaptor, which is good for digital device but not for analogue device such as ordinarly telephones.

Please consider to change the present power adaptor to at least the same grade of the Linksys SPA ATA power adaptor. The present AC hum can be significantly reduced.


YH   
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Hong Kong and China OBi Users Group
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PortableTech
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« Reply #1 on: March 16, 2011, 01:23:24 pm »

I have no such hum, in fact it is crystal clear.  One thing, and I am unsure if this is making the difference, I do have them plugged into APC devices, for the battery backup and line filtering.  Perhaps the hum is not only a result of the AC adapter, but perhaps also bad noise on the power lines.
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RonR
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« Reply #2 on: March 16, 2011, 01:31:47 pm »

Plugging the OBi and a cordless phone base unit (and/or the router and/or the PC etc.) raises the potential (no pun intended for the electrical engineers out there) for a ground loop that can result in hum on the phone line.  Plugging everything into a common power source would be a good first step in determining the source of the hum.
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yhfung
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« Reply #3 on: March 16, 2011, 04:36:28 pm »

You are not able to hear the AC hum if you use cordless (including DECT) phone connected to the phone port of the OBi110 since the AC hum will be filtered by the cordless phone. You have to use ordinary phones to carry out this AC hum test.

In this morning, I replaced the 12V power adaptor that came wth my OBi110 box by a Linksys 12V power adaptor (which came with my Linksys WRT54GL router), the AC hum are completely gone! What do you get from this simple experiment? The AC hum comes from the 12V power adaptor. I am sure that if a 12V car battery is connected to the OBi110, you are not able to hear the AC hum too. As a result, please replace the existing 12V power adaptor by another one (good for both analogue and digital device) as proposed in the first post in the future distribution.

The OBi110 body is excellent but the provided 12V power adaptor is TOO bad. I do believe the cost increased, if Linksys-SPA ATA power adaptor is employed, is insignificant but the TOTAL quality (in particular the analogue audio quality) of OBi110 is sgnificantly improved.

I am planning to upload two sound file links such that you are able to distinguish the difference for different type of 12V power adaptors employed.


YH

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« Reply #4 on: March 16, 2011, 04:44:09 pm »

Are you connecting to a 240V AC power supply (outside of the US)?
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yhfung
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« Reply #5 on: March 16, 2011, 09:01:57 pm »

Yes! I used the OBi110 in Hong Kong where AC mains is 230V.

YH
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QBZappy
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« Reply #6 on: March 16, 2011, 09:31:50 pm »

yhfung,

I think the next step is to try a 230 to 120 converter to see if it makes a difference.
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Owner of the 1st OBi110/100 units in service in Canada & South America. 1st OBi202 on my street. 1st OBi1032 in Montreal.
MichiganTelephone
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Posts: 484


« Reply #7 on: March 17, 2011, 12:26:48 am »

Using a corded phone I get absolutely NO hum.  Of course what you get on a 120 volt 60 Hz circuit may be different from what you get on a 230 volt 50 Hz circuit.

It's remotely possible you got a defective power adapter (I'm sure it happens now and then), but considering where you are I'd think you could get a replacement pretty cheap, since it seems like over half the power adapters sold on eBay are shipped from Hong Kong (always amazes me how inexpensively they can ship stuff to the USA but try to ship something back if it's defective and the postage going the other direction is often more expensive than the value of the unit you want to return).
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Inactive, no longer posting or responding to messages.  Goodbye and good luck.  Some of my old Obihai-related blog posts have been moved to http://tech.iprock.com - note this in NOT my blog; I have simply given the owner permission to repost some of my old stuff.
yhfung
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Posts: 205



« Reply #8 on: March 17, 2011, 12:45:50 am »

Please keep in mind that the provided 12V power adaptor is supposed to operate in 110-240V AC, right?

Why does Linksys SPA ATA 5V adaptors operate at either 110V or 240V of AC mains without any problem of AC hum encountered when they came with Linksys ATA?

I believe the engineers in OBiHai can easily check whether there has AC hum when an ordinarly analogue  phone is connected to OBi110 if the input AC votage is 240V.

I am not asking for an replacement, I want to OBi110 to be perfert for applied input AC voltages (110V, 240V) since I am planning to buy OBi110 more in the future. Also many friends of mine are introduced by me to buy many OBi110s for their applications. We have forum (www.telecom-cafe.com) in Chinese and English to discuss how to use OBi110.

In fact, I have used many Linksys ATAs such as SPA1001, SPA PAP2T, SPA 3000, SPA941 such that I am able to tell you the differences very easily if the AC input voltage is 240V.

Only 1US dollar increased in 12V power adaptor, the performance of OBi110 operates at 240V can be improved significantly. Please consider for the next production.


YH


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QBZappy
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« Reply #9 on: March 17, 2011, 05:36:11 am »

yhfung,

OBI discussion in HK. Way cool.
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Owner of the 1st OBi110/100 units in service in Canada & South America. 1st OBi202 on my street. 1st OBi1032 in Montreal.
yhfung
OBi110 Beta Testers
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Posts: 205



« Reply #10 on: March 18, 2011, 10:14:08 pm »

Are you connecting to a 240V AC power supply (outside of the US)?

Do you have the same problem when the input AC voltage increased to 240V?

YH
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plugger2
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« Reply #11 on: March 19, 2011, 11:13:46 am »

FWIW, I am using a standard North American adapter with 240VAC/50Hz power without noise problems. It is plugged into a UPS, however, so the power is very clean. But I think it indicates that the problem is not that these are electrically noisy with 240VAC power per se.
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yhfung
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Posts: 205



« Reply #12 on: March 20, 2011, 04:26:25 am »

I do not know how many ATA or ATA with routers that you have ever used before. For me I have used them at least 20+.

As I mentioned in the previous posts, if the power adpator is replaced by the BIG 12V power adaptor for Linksys WRT54GL router, the AC hum, with input AC voltage 230V, is completely gone!


YH

« Last Edit: March 22, 2011, 02:16:41 am by yhfung » Logged

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kba1
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« Reply #13 on: March 21, 2011, 08:08:31 pm »

I'm having similar issues with the power adapter.  In my case, I'm in the U.S., and running the Obi110 into a two-line AT&T cordless phone system.   I have my regular POTS line running into "Line 1" of the phone Obi running into "Line 2."

With the Obi plugged into the included power adapter, I had problems with the AT&T phone.  There was a ground hum on both lines and caller ID information did not display. 

After reading this thread, I tested the Obi with another 12V power adapter that I happened to have in the house.  (It was rated lower than the included Obi adapter -- 400mA instead of 1.0 Amps.)   With the new adapter, all the problems cleared up.   No more hum, and caller ID worked properly.  I'm sure that part of the issue is poor isolation between the two lines in the AT&T phone, but the included Obi110 power supply apparently has some issues as well.

I'd like to see Obi switch to better power adapters and make them available to those of us who are having issues with the included one.   Does anybody know if it will harm the Obi110 to continue to power it with a 12V, 400mA power supply?
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MichiganTelephone
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Posts: 484


« Reply #14 on: March 22, 2011, 06:12:10 am »

I'd like to see Obi switch to better power adapters and make them available to those of us who are having issues with the included one.   Does anybody know if it will harm the Obi110 to continue to power it with a 12V, 400mA power supply?

I can't say whether it would actually harm the OBi but one thing I'd be afraid of is that eventually the power supply itself would overheat and fail.  Another thing you might discover is that you not be able to connect as many ringers to the line as you could if you had full power available.
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Inactive, no longer posting or responding to messages.  Goodbye and good luck.  Some of my old Obihai-related blog posts have been moved to http://tech.iprock.com - note this in NOT my blog; I have simply given the owner permission to repost some of my old stuff.
Jeff205
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Posts: 41


« Reply #15 on: March 22, 2011, 08:16:02 am »

I am in the US, replaced my power adapter and my hum went away.  My only concern now is will it hurt to use a different adapter.  It is Input: 120VAC 60Hz 11w Output: 12VDC 500mA.  It just the first one I put my hands on (I have several to choose from), so I mainly want to make sure I do not break anything.
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MichiganTelephone
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Posts: 484


« Reply #16 on: March 22, 2011, 08:31:07 am »

It would be better if it were 12 volts, 1 Amp (1000 mA) to exactly replace the original adapter, but be sure the plug polarity is correct (shell is negative, center is positive). I'd definitely watch for signs that the power supply may be overheating if using one with a significantly lower mA rating.
« Last Edit: March 22, 2011, 08:32:38 am by MichiganTelephone » Logged

Inactive, no longer posting or responding to messages.  Goodbye and good luck.  Some of my old Obihai-related blog posts have been moved to http://tech.iprock.com - note this in NOT my blog; I have simply given the owner permission to repost some of my old stuff.
Jeff205
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Posts: 41


« Reply #17 on: March 22, 2011, 08:39:38 am »

Okay.  It may be worthwhile to order one with exact specs if I don't have one already.

Sorry, but how would I determine the polarity?

FYI: I did switch to one with 750mA with the same success.
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kba1
Newbie
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Posts: 3


« Reply #18 on: March 22, 2011, 09:07:17 am »

Does anybody know what the power supply plug size is on the Obi 110?   I'm guessing it's 5.5 x 2.5mm, but I don't have calipers to measure it.   Also, if anybody has tested a specific power supply that has the right specifications and doesn't cause hum on a two-line phone, it would be helpful if you could share that information.
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Jeff205
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« Reply #19 on: March 22, 2011, 09:09:34 am »

Got the polarity issue.  I overlooked it on the plug. 
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