2.5mm or 3.5mm

Msquared announce.lists.openmoko at msquared.id.au
Tue Jun 17 09:31:31 CEST 2008

First, my preference.  Then some thought-provoking discussion....

(I know it's late - I've been finishing off a project of my own!)

On Fri, May 30, 2008 at 08:18:16AM +0200, Joerg Reisenweber wrote:

> B) classic 3.5mm headphones "Walkman(R)" connector, where you have to
> DIY an adapter for any standard cellphone headset? (or does anybody know
> of 3.5mm headSET standards or adapters?) 

I think on the whole, a 4-conductor one of these is best (which, it seems,
is the same conclusion you came to).

However, I have some other things to say regarding the hardware,
standards, and reliability.  Read on...

On Fri, May 30, 2008 at 10:21:35PM +0200, Kim Alvefur wrote:

> ipod shuffle does usb over 4 pol 3.5mm TRS, could be similar?

This is a very bad idea.  If this is true, then I just can't fathom what
Apple were thinking at the time.  I'm sick and tired of companies changing
standards, and changing connectors from one hardware generation to the

One of the reasons I'm giving up Palm-based devices and switching to
OpenMoko is that Palm seem to have a new connector every new generation of
hardware, which renders all previous peripherals useless.

Also, their connectors are flimsy and poorly designed, as are the
connectors on virtually every phone in the market.  USB provides power and
data, I think it's time all phones used it.

On Fri, May 30, 2008 at 03:36:40PM +0200, Joerg Reisenweber wrote:

> > Agree about the extra battery issue, but I have to agree with Thomas
> > wired headsets no longer seem to be a fashion accessory in wide use,
> > whereas BT cyborgs are all over the shop like a bad episode of Dr Who.
> Just a big bunch of nerds trying to look important. None of them is
> listening to music, while still able to take a call without panically
> removing the earpieces to listen to the phone-earspeaker ;-)

Not so.  I have one each of these, and they are fantastic:


They both function as stereo headphones and as phone headsets.

On Fri, May 30, 2008 at 10:02:27AM +0200, Sander van Grieken wrote:

> External adapters are a bad idea since it could put extra force on the
> jack socket.

I can attest to this; I've had about three Palm Treo 650 where the headset
socket eventually died.  However, I attribute this to poor design of the
socket mechanism itself.

Spefically, the very same solder joints that provide signal are the same
solder joints that mechanically anchor the socket housing to the board.
Over time, normal wear and tear causes the electrical connections to
become intermittent and fail.

Unless wiggling the plug in the socket does not stress the electrical
connections between the socket and the board, then it will eventually

On Fri, May 30, 2008 at 11:21:46AM +0200, Erland Lewin wrote:

> But of course it would be nice if the audio out was less sensitive to
> impedance issues than people have said the Freerunner probably will be.

I heard about this, and I must admit I'm a bit concerned.  I hope it will
not be a problem.

> I don't think computer headsets with 3.5 mm plugs are normally very
> portable.

This is probably true, and is a good case for 2.5mm + adapter being
supplied on the next Neo.

On Fri, May 30, 2008 at 11:38:06AM +0200, Pawel Kowalak wrote:

> There's one issue though... Someone may like to listen mp3s and be able
> to answer phones without pulling Neo out of his pocket or changing to BT
> headset...

Check out the BT headsets I list above.  Nice solution!  I believe that
Philips have released newer models, too...

On Fri, May 30, 2008 at 02:42:45PM +0200, Thomas Franck wrote:

> I vote for B (3.5mm) as well.. even if just headphone.. IMHO, the 2.5
> ones are just too fragile...

I agree: I once had a headset cord catch on a door; the cord was yanked
out of the socket, and while the socket survived, the end of the plug was
bent beyond repair.

On Sat, May 31, 2008 at 12:18:01PM +0200, Kim Alvefur wrote:

> > http://discussions.apple.com/message.jspa?messageID=5262651
> > 
> > says that the iPhone plug uses: tip=R, ring1=L, ring2=Common,
> > sleeve=Mic (which is not what I would have guessed)
> God damn it, Apple. Ground is supposed to be closest to the cable! WHY?

In my experience, it seems that all manufacturers are guilty of violating
common practise, written standards, and just common sense.  More of them
need to read books by Donald Norman...

On Sat, May 31, 2008 at 05:00:25AM +0200, Flemming Richter Mikkelsen wrote:

> > A) "standard" 2.5mm headset (mic+phones) connector, where you have to buy a
> > cheap adapter if you want to use your "old" headphones, (the way like it's
> > for GTA01/02)
> A!!! And please also provide the adapter:)

I agree that this would be suitable, but I don't really like the idea of
yet another small piece of plastic to lose or forget.

I think 3.5mm with 4 connectors and intelligence such as this built in:


Regards, Msquared...

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