Stereo?
 

I was trying to use my Mogul today to drive my car stereo's aux input. I had to connect the supplied adapter to the USB port, then a 2.5mm to 3.5mm headphone adapter to that, then a 3.5mm patch cable to the car stereo input. Kludgy, but all the connections worked.

Nonetheless, only the right channel was activated. I thought that maybe I had a bad connection, but I did some testing and found that the problem goes all the way back to the HTC-supplied adapter (USB to 2.5mm). If I plugged in my HTC headphones directly into the USB port, I got full stereo. But if I used the HTC supplied adapter to a pair of headphones with a 2.5mm plug, only the right channel came through.

So there are two possibilities: 1) The HTC-supplied adapter is defective, or 2) there is something in the hardware, software, or connection that deliberately sends just one channel through that connection.

Anyone know? Is there a setting somewhere to fix this?

You're probably using the headset connection.

--James

I suppose the obvious response is: Of course I'm using the headset connection - there IS no other connection on the Mogul. So feel free to elaborate.

A quick look through the manual suggests that this adapter is supposed to transfer a stereo signal, so it appears that the most likely scenario is that the supplied adapter is defective.

What device did you have before? I think it may be your 2.5mm to 3.5mm adapter that dose not work with the supplied adapter for the Mogul. :(

it is the adapter but its not defective and it is stereo. im not sure how to explain it but it has some thing to do wit how the contacts are lined up in the adapter,

you can tell what i mean if you use a stereo headset that was made for a cell phone with a 2.5mm plug with the contact for a mic you will hear stereo sound,

but if you use (most if not all) 2.5mm to 3.5mm adapter with out a mic contact you will only receive mono sound,
{do to the lining up of the contacts in the adapter}

I'm guessing your 2.5mm to 3.5mm adapter is bunk. Either that or it doesn't want to play right with the HTC cabling.

Buy this. It's nice and small, and it offers not only a standard 3.5mm plug (and yes, I've plugged in headsets into it and it outputs stereo), but your standard USB plug too.

Works great on the Mogul, and you can't go wrong with the price.

http://www.semsons.com/2miusband3st.html

There is a KNOWN INCOMPATIBILITY with many 2.5 -> 3.5 adapters- I find it funny that it didn't even occur to you to consider THAT part of your connection!
This was the same way on the HTC Wizard and Tornado, and afaik all HTC phones that had a 2.5mm plug. It only worked with "True" 2.5mm stereo adaptors, and not 2.5mm adaptors made for phones, since phones usually made the first pin channel the mic instead (real stereo uses the first 2 channels for L+R, phones use Mic+Right, and stereo phones use Mic+Right+Left).

What you can do is pull the adaptor out just slightly, essentially skipping the first contact inside, and you'll hear full stereo sound! Problem is that this is a flimsy connection and will probably not stay connected.

Pick up a regular stereo (non-phone type) 2.5 -> 3.5 adapter from Radio Shack for $5, or get a Sony BT2500 a2dp stereo head unit like I did for truly wireless music... Bluetooth stereo is a lot cheaper than it used to be, and I can keep my phone in my pocket while the music comes out of the car speakers!

Since all of you have raised this issue, let me make it clear that I DID, in fact, explore the entire signal path. I took a normal pair of 2.5mm cellphone headphones and plugged them into the HTC-supplied adapter. The result was that only the right channel worked. So here's the score:

Mogul to HTCadapter to adapter to cable to car stereo - right channel only
Mogul to HTCadapter to adapter to 3.5mm headphones - right channel only
Mogul to HTCadapter to Seidio 2.5mm headphones - right channel only
Mogul to HTC-supplied headphones - full stereo.

That's why I conclude that the HTC-supplied adapter is defective.

To answer Budney's question, my 2.5 to 3.5 adapter worked fine with my Treo, and to answer Dishe's remark, it DID come from Radio Shack. I also have one from TreoCentral, which I'd try if I could just find the darn thing. <g>

Destructor, thanks for the product pointer. It would be nice to have an adapter that goes straight to the 3.5mm socket. I'll still bug Sprint about replacing the HTC one.

Edit: I just found my TreoCentral 2.5 to 3.5 adapter and tested it. Same result, right channel only.

the reason both of your adapters don't work are because the Treo has a slightly different plug. both of my adapters that work on my treo will not work with my 6700and mogul while my adapter that I had for my 6700 works perfectly with my mogul.

Then why don't my 2.5mm Seidio headphones work? The only adapter they go through is the HTC-supplied USB adapter. The Treo adapters aren't even in the picture.

If your Treo adapters don't work, then it sounds like your adapter is broken as well. That is a possibility that I've considered - the HTC adapter may be broken by design. If that's the case, then swapping it won't do me a whole lot of good. It sounds like HTC may have done something decidedly non-standard with respect to normal 2.5mm cellphone headphones.

I promise you that HTC did not do something non-standard by design. It works great for me, I've used it a few times (prefer bluetooth stereo audio tho).

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!

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.

Two quick added thoughts:

1) This scenario.....

.... is the reason for my original question. In some phones, there are settings that determine how the headphone connections are handled. I thought that it might be possible that HTC had included some setting in the 6800 that might affect how it responded to a set of headphones.

2) I bought the adapter that Destructor recommended earlier. It seems like the simplest solution to the problem. It's already been shipped, and should arrive by about Friday.

Other way around vs. other cell phone makers.
Truth is, I'm using an adaptor that dates back to before the music phones came out. Before the cell phones decided to add a third connection for the other ear, there were already devices using the 2.5mm jack with regular L+R pin layout instead of mono+mic like phones do.
Examples are the ipaq 1900 series ppcs, some (very few) mini-disc players, portable audio recorders with line-in stereo, and some weird Chinese pen-sized mp3 players.
Then cell phones added the third pin and everything has been incompatible ever since. When this first happened, people were buying the stereo adaptors from places like Radio Shack, and returning them because their Motorola's and Samsungs and LG's were only outputting one ear at a time unless they pulled it out a tiny bit. So, all these companies started making "stereo cell phone 2.5mm adaptors" and hence all this confusion.

I don't think this is true, since I've never seen or heard of anyone who didn't have a problem using the wrong adaptor. I'd like what you're saying to be true... It sounds like a simple solution to a complicated problem, but what phones have you seen that do that? All the ones I've seen needed to be pulled out a bit to make them stereo when using my adaptors from my old 2.5mm equipment. HTC is the only manufacturer that uses the same pre-cell phone standards for 2.5mm as the older equipment that I've had (which I'm thankful for since I have all this junk already).
There is no real standard I suppose, but I consider the first and oldest layout the proper one if only because it came first.

Anyway, it makes no difference really. Bottom line- it works with the right stuff, and no, it does not need to be HTC specific.

Even the simplest $10 ohmmeter will easily let you test it yourself. Get a normal stereo patch cable with a 3.5mm plug on each end. Plug one end into your adapter. Then use the ohmmeter to see which part of each plug is connected through the adapter. I've done this with both of my adapters, and both pass the signals straight through - tip to tip, ring to ring, sleeve to sleeve. If yours does the same thing (and works correctly with your 6800), then I just need to get Sprint to give me a working adapter. If yours does something different, then obviously HTC is doing something weird - and a new adapter won't change anything.

Come to think of it, you don't really even need to test it. All you have to do is look at it. If the 2.5mm plug on your adapter has a tip and TWO rings, then you might want to test it to see what's going where. If it only has one ring, then there really isn't much room for doubt. So take a look - is it a TRS plug or a TRRS plug?

Obviously, I don't expect you to run out and buy an ohmmeter just to answer my question, but if you have one handy it might help to clear this up. Either way, thanks for all the consultation.

Does the Titan definitely support A2DP? http://en.wikipedia.org/wiki/A2DP#Ad...ile_.28A2DP.29

I figured I better ask before plunking down some $$$ ;-)

yes it does i use it on mine

that sony stereo I mentioned sounds BEAUTIFUL with the titan!

i said this already in another thread but i cant find it now so here i go again ..

i was piecing together a little custom dash-board dock to charge the phone and send audio to my car stereo's aux inputs just by sliding the phone into it ... even did a little handsfree mic and answer button ...

i had the same problem with normal 2.5 stereo adapters ... gold plated straight outta radio shack and best buy ... had to pull them out slightly to get all the rings and pins to line up correctly ...

i tried a few cellphone headsets too ... even an old custom adapter i made for a SE P910 and was also working with a HTC Wizard ... none of them worked right either ...

anyway i ended up hacking up the wired stereo headset that came with the phone and playin around to find out which wires did what ... i know, not the most delicate approach but ill never use a wired headset and i wasnt about to stop working on my little dashboard dock project :P gotta love streaming shoutcast and hearing kit from knight-rider (TomTom6 voice) in the background telling you which way to turn in 300 yards ... all through the truck speakers :)

so i dont know if this will be any help to anyone but heres the message i sent to the one guy that asked about it in the other thread


> i dont know the actual pinout since i didnt try to open up the plug but i know the color codes of the wires and dont mind sharing at all :)
>
> solid red = right +
> striped red = right -
> solid green = left +
> striped green = left -
> white insulated = mic +
> copper (unpainted) = mic - (common ground)
> blue = call/answer/reject/redial button signal wire
>
> now im pretty sure thats it but it couldnt hurt to play around with the wires once you chop it up ... i sat there with a small mic and a pair of headphones trying different combinations when i figured it all out ...
>
> im not sure of the signifigance considering im a novice but ... the mic - lead will work as ground for the speakers also .... i didnt wire my adapter this way just cause i thought using the correct channel grounds might be safer but i figured i would mention it anyway
>
>also ... not to insult ... incase you know as much as or more than me but if you want to equip whatever you're doing with the call button you can use any simple momentary contact SPST switch to trip the signal wire to the ground ...
>
> anyway, glad i could help

Thanks for posting this. I had considered cutting the end off of the supplied adapter and wiring it correctly. It's a pain to solder those tiny wires, though. I've got a workable adapter coming in the mail, so that should meet my needs for now. But it's good to know that I have another option if I want to go that route.