Quote:
Originally Posted by dishe
Its possible your adaptor is defective, but I'm still convinced you're using CELLPHONE adaptors and headphones, and not STEREO ones.
Yes, there's a difference.
Allow me to explain (Again?):
First you need to understand this- 2.5mm stereo connectors existed as a standard component before cellphones starting using them for headsets.
Phones use 2 channels of audio just like stereo headphones do, only phones use the second channel (left) for the microphone input. So, they took the 2.5mm headset connector and used one pin for output and one for input (instead of both being output for stereo).
Then, when cell phone manufacturers (motorola, LG, etc...) starting selling STEREO headsets, they added a third pin, which would be the left audio. This way, you could still use this headset on a non-stereo phone as a mono-headset with the mic.
HTC went the other way around... they used the original STEREO pin layout (Right, Left), and then added a third pin for the mic at the end. That's why older HTC headsets (like the Wizard and Apache ones that used 2.5mm) don't work in standard non-stereo phones (they are trying to use the left speaker as teh mic)!
So, basically, the problem sounds like you are using cellphone-type connectors, which the TREO uses, I beleive. You want standard STEREO connectors, not ones made for a phone (Radio shack sells both I think)!
There's a very simple way to see if I'm correct: TRY PULLING OUT THE 2.5MM ADAPTOR SLIGHTLY AS ITS PLAYING. If the sound becomes stereo as you play with it, YOU KNOW THIS IS YOUR PROBLEM!!
TRY IT!
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Thanks for writing this - it confirms what I had suspected.
It may help to know that I am an audio engineer who regularly uses and builds audio cables and connectors of all types. I am intimately familiar with the routing of audio signals in these devices and many others.
You have some of your signal concepts mixed up. First of all, ALL standard headphones use the "tip" of the plug to carry an audio channel. In a mono headphone, it is the only channel. In a stereo headphone, it is the left channel. That's true in 2.5mm, 3.5mm, and full size quarter-inch plugs.
In stereo headphones, the "ring" is always used to carry the right channel. Again, that's true in all three plug sizes.
When the cellphone industry first introduced the wired mono headset, they used a 2.5mm TRS plug and treated the "ring" (which would normally carry the right channel) instead as a microphone input. This worked fine as long as no one needed stereo, nor tried to use a stereo headset with a cellphone. That's the main reason they selected the 2.5mm plug - so it wouldn't accidentally be used by a 3.5mm stereo headphone.
So there were no problems until someone wanted to support stereo audio from a cellphone. Some clever person figured out that it would be possible to do this by building some simple testing and logic into the phone - so the phone would test the impedance of the "ring" connection, and determine whether it was an earpiece or a microphone. Problem solved, more or less.
But then the next step came along - adding a microphone to a stereo headset. Now they really DID need the extra ring in the 2.5mm TRRS connector, so they added it and put the microphone signal on the second ring. The nice thing about this is that it really didn't add any complexity - the signal routing was exactly the same as with the full stereo headset, so the phone still needed only to test the impedance on the first ring. As far as the phone was concerned, there was no difference between a stereo headset with microphone, and a stereo headset without a microphone. If the headset had a mic signal, it got routed properly. If it didn't, then the microphone input got grounded to the sleeve, which is exactly what you'd want.
I'm not sure what HTC is doing in their adapter, but it's pretty clear that they are doing something non-standard. I base that not on my experience, but on yours. If, indeed, you get stereo by pulling the plug out part way, that strongly indicates that HTC is not routing their signals the way the rest of the industry is. That's a bit of a headache, but it probably provides a lot of benefit to those vendors who are selling Bluetooth alternatives! <g>
So you seem to have some of the basic concepts right, but you've got them all swapped around. And it does appear that we agree that HTC is not following the industry standard. As you put it, "HTC went the other way around".
BTW, my adapters ARE straight standard stereo adapters. They carry the 2.5mm sleeve to the 3.5mm sleeve, the ring to the ring, and the tip to the tip.
You don't have to take my word for any of this - you can test it for yourself. Get a standard mono headset (with mic) and a standard stereo headset (with mic) and a couple of empty plugs (2.5mm and 3.5mm) from Radio Shack. Then interconnect the signals with some small wires and aligator clips. It's easy to verify this (just as I did to confirm my understanding before I wrote this). You can also verify what your adapters are doing with a simple ohmmeter or continuity tester.