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A very strange effect....

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Drewan77 View Drop Down
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    Posted: 27 Nov 2015 at 2:06pm
I am now home for the weekend from several weeks overseas with work, where I use a Bitzie + Shure SE535s on long-haul flights and several other pairs of in-ear phones for airport lounges, short-haul etc.

For the past week I took an old pair of Sennheiser CX-300s to Scandinavia & I had trimmed the plastic area around the jack plug a couple of weeks ago to make it fit the hole in my phones' cover. 

For some reason, my cack-handed trick has managed to eradicate the vocals on the majority of albums on the phone (in the case of 'Nathaniel Rateliff and The Night Sweats', vocals totally disappeared except very faintly on one track) but at the same time the rest plays just like a backing instrumental version of the same album, clear, full stereo, full frequency and in phase! I have no idea how I have achieved this. 

Whatever I have done must be summing L-R somehow to remove anything that appears at equal strength on each channel. Very weird Confused




Edited by Drewan77 - 27 Nov 2015 at 2:08pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 8:45am
In shaving the plug you have cut the ground connection so the L- and R- are connected together but not to the 'sleeve' of your 3.5mm stereo jack plug which is how they are normally connected to the ground or - on the headphone output socket. This means the left and right earphone are wired in series between the left and right output like this:

Plug tip:      Bitzie Lout: CX300 L+
Plug sleeve:   *              CX300 L-connected to CX300 R-
Plug ring:    Bitzie Rout: CX300 R+

* this is where the Bitzie ground was/should be

It is giving you the difference between the Left and Right channels. That eliminates signals that were equal in both channels, i.e. central in the stereo mix like vocals and bass, kick drums etc. Some karaoke style equipment uses the same L-R mix (usually with a high pass filter to retain some of the central bass and kick signals) to eliminate the original vocal. That is what you have inadvertently recreated.

This difference signal is how Hafler surround was derived and how Dolby Surround derives its 'rear' signal from encoded 4:2:4 signals (with L+R for the 'centre' channel) before applying some clever gain control to steer sounds between the channels.

It may be possible to fix this fault if you have the tools but any bridging wire you add may come off as you squeeze the modified plug into your adaptor. Even if successfully repaired the ground connection may break again whilst you are away so I suggest the obvious solution is to take the Shures on your trips.



Edited by Fatmangolf - 28 Nov 2015 at 8:57am
Jon

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Drewan77 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Drewan77 Quote  Post ReplyReply Direct Link To This Post Posted: 28 Nov 2015 at 1:50pm
Thanks for the explanation Jon, I guessed it must be something like this.

As I mentioned, these are 'old' headphones so I won't be using them again until I cut the cabling and solder on a new jack plug rather than attempt to patch this one up. I have quite a selection of other IE types but the Shures have a REALLY large moulding around the jack plug so only get used with the Bitze.
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