SparkFun Forums

[lordsteve]

When I insert a plug into the jack, it shorts the input and my project goes dead. (This project uses a MAX4410 stereo headphone Driver.) In the datasheet for this jack, one can see how the tip of the plug could possible touch both Left and Right contacts, at least I think so. What can be done about that?

Thanks.

[leon_heller]

You probably have it wired wrong.

[lordsteve]

I don't think so, but I was, however, wrong to say that by looking at the datasheet one could see how left and right could be connected. What I was looking at was the schematic diagram, not a mechanical drawing. My bad.

[leon_heller]

Check the pins with a meter if you aren't sure.

[riden]

I've never seen a 3.5mm stereo audio jack short the input when the plug is inserted. I have seen the opposite (remove the plug and the input gets shorted to ground), but most are pretty vanilla. Are you using a stereo plug? Can you give us a link to the datasheet for your jack?

[esklar81]

If you're actually getting a short when you insert a plug, i.e., two of the three leads to the jack are being connected together with zero resistance, I suggest you check the impedances on the plug. As riden pointed out, make sure you're using a stereo plug. If you're using a mono plug, it's supposed to connect both the left and right signals to the same plug lead.

Happy Hunting,
Eric

[lordsteve]

Datasheet:
http://www.sparkfun.com/commerce/produc ... ts_id=8032

[riden]

I have used these connectors from Sparkfun and they don't short when the plug is inserted. Check your wiring or try another plug.

[lordsteve]

Could someone tell me what the term "shunt" means in the context of this product? (See the schematic.)

http://www.sparkfun.com/commerce/produc ... ts_id=8827

[lordsteve]

Using my multimeter in Ohm-meter mode to check continuity, I found that inserting a (stereo) plug into this jack shorts the left side to the right side during insertion. That shorting causes a brown out. I tested pins 2 and 5 (the outer pins) for continuity and pins 3 and 4 (the inner pins). I suppose that's just normal for audio jacks or do I look for an alternative made to specifically not short the left side to the right?

Thanks for any help.

[tetsujin]

If you're actually getting a short when you insert a plug, i.e., two of the three leads to the jack are being connected together with zero resistance, I suggest you check the impedances on the plug. As riden pointed out, make sure you're using a stereo plug. If you're using a mono plug, it's supposed to connect both the left and right signals to the same plug lead.

No it's not...

On a mono plug, the tip carries the signal and the sleeve is ground. A stereo plug has a "ring" to carry right-channel (or other purposes) - the location of the ring coincides with the sleeve on a mono plug... So plugging a mono plug into a stereo jack shorts the right channel to ground.

[JonChandler]

The tip and ring of the plug probably get shorted together by the sleeve on the jack when the plug is inserted. As the plug is pushed in, the ring and sleeve may also short together briefly.

This will be especially true where the sleeve is long, which is the case for a panel-mount jack with a long threaded neck. Here's an example:

http://media.digikey.com/photos/CUI%20P ... 1-3513.JPG

[lordsteve]

I tried to add a 10uF cap to the amplifier chip (MAX4410) to see if it was just a brief spike, but to no avail. How do other devices deal with this?

Thanks.

[esklar81]

@ tetsujin,
Well, perhaps I should restrict myself to posting educated guesses. ;o} Thanks for the correction!

@lordsteve,
What are you calling "left side" and "right side"? Specifically, are you referring to the right and left audio channels or the right and left sides of the jack assembly?

It would be helpful to us if you told us what you have connected to where and which pins (by name/number) have continuity to each other with the jack empty and with the jack filled by a stereo plug. Also, when you do the test, you need to have the stereo plug not wired to anything. If the plug is wired to anything, that "anything" may well change the results.

For example, if you have nothing connected to the jack and nothing connected to the plug, then the Ground, Ring, and Tip connections of the jack should be shorted to the sleeve, ring, and tip of the plug, respectively. However, the Ground/sleeve, ring, and tip should be isolated from each other.

Conversely, if you have the plug wired to a set of speakers/headphones with each side of the speakers having an resistance of R ohms, then the resistances, measured from the jack connections, should be:
Ground <> Ring: R + r
Ground <> Tip: R + r
Ring <> Tip: 2R + r
(r is the resistance of the jack's internal connections to itself and the plug. It may be too small for you to measure.)

My understanding of the "shunt" connections is that they are connected to the corresponding signal inputs when there is no plug in the jack and disconnected when a plug is inserted. That behavior allows using them to connect a speaker that is muted by the insertion of a plug.

Please let us know what, if anything, you had wired to the plug when you did your testing and how much resistance you had that you are calling "shorted". Also, if there is something wired to the plug, what are the resistances between the pairs of contact areas on the plug?

TIA,
Eric

[lordsteve]

The jack was not wired to anything and there was no plug inserted. The resistance I deemed a short was 1 (one) ohm. When I say left is shorted to right, I mean that the left audio signal is shorted to the right audio signal. This happens momentarily when a plug is inserted. When the short occurs...brown out. When I manually short the left audio channel to the right audio channel, same thing...brown out.

I'm assuming this is a common problem and must happen frequently. There has to be some way to handle it.