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[Tesla]

For headphones that have 3 contact points on the (1/8"-3.5mm) plug, compatibility is good and all that I have tried seem to work fine.

For headphones that have 4 contact points, like both of these below ... they don't work properly because they cause an echo and one or more channels play too low.

http://www.newegg.com/Product/Product.aspx?Item=N82E16826193054&Tpk=rh-bud168

Notes on these:
1. They sound really good on everything else I've plugged them into. No compatility problems.

I also tried these:

http://www.newegg.com/Product/Product.aspx?Item=N82E16826265223

Notes on these:
1. These also sound really good on everything else I've plugged them into. No compatility problems (even with phones the mic works).
2. Thinking the 4th contact is for the mic, thought the external mic might work on the AirPad (since it could be a phone if it had a 3g or 4g radio inside) but no, I couldn't get the mic to work either.

Ideally, if you connect headphones like the Plantronics, they should work for sound. Then, it would be nice if the external mic worked (since there is no BlueTooth and the internal mic quality is only fair). If you connect some like the Rosewill, they should work for sound. If there is a software option that we need to check to make it ignore the 4th contact (so they will work, so be it). The way it is now, neither work and these are industry standard. That is why I posted it as a Compatibility Problem.

I understand this might be a lack of features in the Android OS (the missing Audio Mixer or Audio config. is a sign of that) but the hardware still needs to work properly.

[Brian H]

Thank you for the information.
I also think the fourth band is a microphone and when inserted into a stereo headphone jack. The bands don't align correctly in the jack and caused problems.

[YB]

you are correct Brian H. The Microphone band is still a "standard", but in the case of our AirPad, it accepts only standard headphone 1/8" stereo plugs.

[Tesla]

Thank you for the information.
I also think the fourth band is a microphone and when inserted into a stereo headphone jack. The bands don't align correctly in the jack and caused problems.

You are welcome and thanks for confirming the 4th contact band is for the Mic. However, it's not really an alignment problem. I'm pretty sure we are understanding each other, but I'm going to go ahead and clairify more.

Like I said ... every 3 or 4 contact band headsets I have (with or without a Mic) work in every other MP3 player, computer, laptop, BlackBerry, iPhone, etc. I have . The AirPad is the only exception.

The other devices accomplish this "universal compatibility" in the socket jack itself.
- For devices that only play in stereo, there are 3 little tabs that reach down to to touch the contact bands on the plug. If the plug happens to have a 4th contact band, it doesn't matter because nothing is touching it.

- For devices that play in stereo and also have the ability to "record", there are 4 little tabs that reach down to to touch the contact bands on the plug. If the plug happens to have a 4th contact band, it records from the Mic (if present).

For the AirPad to neither record nor play properly with industry standard headphones doesn't seem right.

[Tesla]

you are correct Brian H. The Microphone band is still a "standard", but in the case of our AirPad, it accepts only standard headphone 1/8" stereo plugs.

Both the headphone sets linked to in my original post use standard 1/8" stereo plugs. If the Plantronics set is throwing you off because it includes the Mic, just focus on the Rosewill set.

[Brian H]

The Rosewill shows four connections even if the mic is not connected.
My guess is the bands still are shorting between the stereo connections in the AirPad.

I could not find the exact pinout for the Roswill ,but did find a generic pinout for the iphone. That Rosewill indicated it works on.
Tip is Left Audio
First ring Right Audio
Next ring Common
Sleve Microphone.
If the common ring is not making connection to the Airpads common it may not work.
If the Rosewill has the unused mic shorted to the common ring. It should work.
No actual data on how the AirPad is configured.
So I guess we are still woundering.

[Tesla]

Brian,

Thanks for showing an interest. This is important because while the supplied headphones are adequate and provide basic sound functionality, the audio circuit and amp in this tablet is actually pretty good. With a good pair of headphones or earbuds, it can sound much better. Like all consumer electronics these days, the provided heaphones are basic in-expensive models (to keep the package price down). Companies like Plantronics and Skull-Candy (and even Rosewill at the low end) are providing nice aftermarket devices to people who care about sound quality.

So, here is the basic 3-pin pinout. Yes, you are right about the schematic. Between Sleeve(GND) and either L or R I get about 32 ohms which is correct. This is also confirmed here:

http://pinouts.ru/Home/Tele35s_pinout.shtml

And here is the 4 band: http://pinoutsguide.com/HeadsetsHeadphones/samsung_i9100_headset_pinout.shtml

It should be noted that the Rosewill ring bands are exactly the same size as the supplied headphones, except the last one or Sleeve/GND is divided into 2 rings. This makes the 3rd ring band Sleeve(GND) and the 4th or lower one is not connected to anything according to the ohm meter.

The industry standard (inside the jacks or the machines themselves) is to touch the plug high on the sleeve ring to get the ground for the tiny "speakers". This is the problem area. It could be that whoever built the AirPad hardware used a non-industry-standard jack and it's touching the plug too low and not making contact. I'm not sure what a completely missing ground sounds like.

Alternatively, (since this hardware is likely based an a "reference design" that sometimes includes a phone) it would have a proper 4 contact band headset jack that also supports a mic. When the phone part was ripped out or not implimented, if the audio mixer was not reprogrammed to make the external mic work for other things (we know it doesn't now) and left in limbo, it could be the cause.

So, I think it could be firmware, hardware or software at this point. You would think x10 would know.

[Brian H]

Thanks for your insight and data.
Your findings look similar to what I was seeing on some web sites.