Safety issue using (mono) jack plugs

Johnix · 8th August 2004, 02:29 PM

Hi,

1st of all, i'd like to know the exact connections inside a jack plug :

For a stereo jack :

the extremity is the left signal
the middle is the right one
then it's ground (the bigger one)

Is this correct ?

For a mono jack :
the extremity is the hot point
then the bigger part is the ground ?

Correct as well ?

If so, when you connect a mono (male) plug inside a stereo (female) one, is there a risk to short-circuit the right channel of the female plug (through the common ground of the male plug) ?

I am designing a headphone amp so this has to be taken into account

Netlist · 8th August 2004, 02:42 PM

Hi Johnix
Stereo: correct
Mono: correct
Yes, you will ground your right signal. This is not correct but not harmful to the headphones or amp.

Edit: It's harmless at line level, which isn't your case. You will short your amps right output and that's not good.

/Hugo

Johnix · 9th August 2004, 06:40 AM

So I suppose my amp need to work even with it's output grounded

Not easy....

Netlist · 9th August 2004, 07:03 AM

Grounding amp inputs is harmless, grounding outputs is harmfull.
Maybe I wasn't clear enough.
So you should use both male and female stereo jacks.

/Hugo

Johnix · 9th August 2004, 09:41 AM

Well, I personnaly won't plug a mono jack in my female stereo socket

I was just thinking of what could happen if somebody not aware of that problem accidentaly plugged a mono jack

What about inserting a resistor between the output of the headphone amp and the socket ?

8th August 2004, 02:29 PM	#1
Johnix diyAudio Member Join Date: Jul 2004 Location: Lyon (France)	Safety issue using (mono) jack plugs Hi, 1st of all, i'd like to know the exact connections inside a jack plug : For a stereo jack : the extremity is the left signal the middle is the right one then it's ground (the bigger one) Is this correct ? For a mono jack : the extremity is the hot point then the bigger part is the ground ? Correct as well ? If so, when you connect a mono (male) plug inside a stereo (female) one, is there a risk to short-circuit the right channel of the female plug (through the common ground of the male plug) ? I am designing a headphone amp so this has to be taken into account

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8th August 2004, 02:42 PM	#2
Netlist diyAudio Moderator Emeritus Join Date: Jan 2003	Hi Johnix Stereo: correct Mono: correct Yes, you will ground your right signal. This is not correct but not harmful to the headphones or amp. Edit: It's harmless at line level, which isn't your case. You will short your amps right output and that's not good. /Hugo

9th August 2004, 06:40 AM	#3
Johnix diyAudio Member Join Date: Jul 2004 Location: Lyon (France)	So I suppose my amp need to work even with it's output grounded Not easy....

9th August 2004, 07:03 AM	#4
Netlist diyAudio Moderator Emeritus Join Date: Jan 2003	Grounding amp inputs is harmless, grounding outputs is harmfull. Maybe I wasn't clear enough. So you should use both male and female stereo jacks. /Hugo

9th August 2004, 09:41 AM	#5
Johnix diyAudio Member Join Date: Jul 2004 Location: Lyon (France)	Well, I personnaly won't plug a mono jack in my female stereo socket I was just thinking of what could happen if somebody not aware of that problem accidentaly plugged a mono jack What about inserting a resistor between the output of the headphone amp and the socket ?