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Curious buzzing from DAC when next to telephone - anyone explain?

post #1 of 8
2/27/10 at 9:21am
Thread Starter 
I experienced a curious hum / buzz the other day, and narrowed it down to the DAC.

It turned out to be caused by my telephone which was sitting next to it - move it away a few inches, and it faded out.

The really curious part is that while the phone was there and hence causing the buzz, it would also disappear as I moved my hand closer to the chassis of the DAC - no need to touch it! Very perplexing...

Anyone educate me? I am clearly missing some electronic edumacation...
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post #2 of 8
2/27/10 at 12:18pm
EMI.

You need a better phone. I highly recommend a Western Electric model 500...
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post #3 of 8
2/27/10 at 1:04pm
Thread Starter 
The phone is wireless but was not in use; the handset was positioned on the charger. It is a fairly modern Panasonic unit.

A vague idea of EMI is nice, but why would moving my hand close disrupt the effect?
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post #4 of 8
2/27/10 at 6:32pm
Quote:
Originally Posted by badmonkey View Post
The phone is wireless but was not in use; the handset was positioned on the charger. It is a fairly modern Panasonic unit.

A vague idea of EMI is nice, but why would moving my hand close disrupt the effect?
The phone is a radio transmitter. It could still be "talking to" the base even while sitting on it. It's more likely the base is just the charger and it doesn't interrupt transmissions when used.

Your hand absorbs radio waves. Just like microwaving a piece of meat. It actually does cause internal heating - nothing you'll notice and you won't be harmed. But you're absorbing the radio signal and keeping it out of your DAC.

Solution? Get a real phone:



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post #5 of 8
2/27/10 at 6:41pm
Build a Faraday cage and put your DAC in it.

Or move the phone.

Or get a wired phone.

Or move your gear.
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post #6 of 8
3/1/10 at 2:35am
That phone Uncle Erik suggests is a thing of beauty. It'll probably also outlive you. The cockroaches will be using them after World War III.

A beautiful, restored one is not cheap either. (I will get myself one after I get the VOIP system here working. The idea of a phone from 1940 connected to VOIP system amuses me.

Of course the bluetooth Model 500 from Sparkfun amuses me too... =)
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post #7 of 8
3/1/10 at 3:34am
The worse are those new DECT 6.0 phones. They release a microwave burst every second or so that I've had interfere with my gear. I recently changed my phone next to my pc for exactly that reason.
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post #8 of 8
3/1/10 at 4:07am
Quote:
Originally Posted by Lou Erickson View Post
A beautiful, restored one is not cheap either. (I will get myself one after I get the VOIP system here working. The idea of a phone from 1940 connected to VOIP system amuses me.
Been there, done that. Works beautifully, so long as none of your dial plans requires a # or *.

All of my landline phones are rotary - two (black) WE 500s, and a (beige) 554.

I have a spare WE 500, in Moss Green, that I'm not using... has a four-pin cable, but I don't recall if it's modular or not.
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