Captain ?degard
Member of the Trade
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- Feb 11, 2007
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Seeing a lot of speculation and misinformation here, so here's some info on the QC25 plug:
Bose uses a 4 pin 2.5mm plug for the headphone side of things, and a 4 pin 3.5mm headphone plug for the device side of things.
The 3.5mm plug has four pins because of mic/remote functionality.
The 2.5mm plug has 4 pins where one is not used.
Neither plug is longer than a 3 pin version, nor is a mono plug shorter. Different pin count plugs simply divide the plug differently. A 4 pin plug splits the ground from a 3 pin plug in two.
Back on the QC3, Bose used the same 2.5mm four pin plug, but used a non-standard pinout that did not use the tip (normally left channel) and instead used the other 3 in a non-standard configuration.
On the new QC25, the 4 pin 2.5mm plug uses a standard pinout, left/right/gound going from tip to root of the plug, with one of the two ground pins not being used.
Any 3 pin 2.5mm plug can be used on the QC25, as the ground area will simply cover both the actual ground pin and the unused pin of the 4 pin plug.
The same is NOT true for the QC3, where you need a 4 pin plug since the pinout is non-standard and the pin not being used is the tip.
A 2.5mm plug to 3.5mm jack adapter will work out of the box on the QC25 assuming you can physically fit it in the narrow hole.
All of the above is based on me having made custom cables for both the QC25 and the QC3. I've manually found the pinout on both, and made working cables with the correct channel layout. In the case of the QC25 I've made cables both from 4 pin plugs and from 3 pin plugs, and I've used off the shelf adapters (a local store sells adapters that only need a bit of rubber casing shaved off to work).
I use my QC25s mostly for audio books, sometimes for video, so the sub-par sound quality doesn't really matter when the comfort and noise cancellation is good. I use a custom cable with a modified, permanently attached Bluetooth receiver to get a wireless QC25

Bose uses a 4 pin 2.5mm plug for the headphone side of things, and a 4 pin 3.5mm headphone plug for the device side of things.
The 3.5mm plug has four pins because of mic/remote functionality.
The 2.5mm plug has 4 pins where one is not used.
Neither plug is longer than a 3 pin version, nor is a mono plug shorter. Different pin count plugs simply divide the plug differently. A 4 pin plug splits the ground from a 3 pin plug in two.
Back on the QC3, Bose used the same 2.5mm four pin plug, but used a non-standard pinout that did not use the tip (normally left channel) and instead used the other 3 in a non-standard configuration.
On the new QC25, the 4 pin 2.5mm plug uses a standard pinout, left/right/gound going from tip to root of the plug, with one of the two ground pins not being used.
Any 3 pin 2.5mm plug can be used on the QC25, as the ground area will simply cover both the actual ground pin and the unused pin of the 4 pin plug.
The same is NOT true for the QC3, where you need a 4 pin plug since the pinout is non-standard and the pin not being used is the tip.
A 2.5mm plug to 3.5mm jack adapter will work out of the box on the QC25 assuming you can physically fit it in the narrow hole.
All of the above is based on me having made custom cables for both the QC25 and the QC3. I've manually found the pinout on both, and made working cables with the correct channel layout. In the case of the QC25 I've made cables both from 4 pin plugs and from 3 pin plugs, and I've used off the shelf adapters (a local store sells adapters that only need a bit of rubber casing shaved off to work).
I use my QC25s mostly for audio books, sometimes for video, so the sub-par sound quality doesn't really matter when the comfort and noise cancellation is good. I use a custom cable with a modified, permanently attached Bluetooth receiver to get a wireless QC25