How do I vanquish the hum monster?

[William Rossiter]

I've installed a 1/4" phono jack that cuts out the 3" TV speaker when I plug
in the phones. But I get a whole lot of hum in the phones. I am guessing
that because the phones are more sensitive than the speaker, I have to turn
the TV volume control down quite a bit, making the hum more audible than the
program sound. I am further guessing that I could put some kind of
attenuater into the circuit that goes into the phones, but not into the
speaker, and thus could turn the volume up to outshout the hum without
busting my eardrums. But I don't know where to go from there: do I just
wire a resistor into the hot side of the signal? Or what?

 

[James Sweet]

"William Rossiter" <ctn41205@centurytel.net> wrote in message
news:l7ydnQr2eLfSy1-iRVn-tw@centurytel.net...

I've installed a 1/4" phono jack that cuts out the 3" TV speaker when I
plug
in the phones. But I get a whole lot of hum in the phones. I am
guessing
that because the phones are more sensitive than the speaker, I have to
turn
the TV volume control down quite a bit, making the hum more audible than
the
program sound. I am further guessing that I could put some kind of
attenuater into the circuit that goes into the phones, but not into the
speaker, and thus could turn the volume up to outshout the hum without
busting my eardrums. But I don't know where to go from there: do I just
wire a resistor into the hot side of the signal? Or what?

You want a resistor in series with the headphone jack. Something you should
check though, if this is a hot chassis set as a great many are, then
installing a headphone jack is *very* dangerous since the jack will be
floating more than 120v above ground and is a serious shock hazzard. You
need to isolate it with a transformer.

 

[Jerry G.]

On a standard headphone you need a resistor in series with each side of the
headphones, one for left, and one for right. The value used is usually
around 120 to 150 ohm at 1 watt for each resistor.

If your set is not isolated from the mains this can be a very dangerous
ordeal, and present a safety hazard. A headphone should only be connected
to a unit that is isolated from the AC mains. Most consumer equipment is HOT
to the AC mains on its speaker drive.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
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WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
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"William Rossiter" <ctn41205@centurytel.net> wrote in message
news:l7ydnQr2eLfSy1-iRVn-tw@centurytel.net...
I've installed a 1/4" phono jack that cuts out the 3" TV speaker when I plug
in the phones. But I get a whole lot of hum in the phones. I am guessing
that because the phones are more sensitive than the speaker, I have to turn
the TV volume control down quite a bit, making the hum more audible than the
program sound. I am further guessing that I could put some kind of
attenuater into the circuit that goes into the phones, but not into the
speaker, and thus could turn the volume up to outshout the hum without
busting my eardrums. But I don't know where to go from there: do I just
wire a resistor into the hot side of the signal? Or what?