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PC World has an article on why USB-C has not been a viable alternative for the 3.5mm audio jack. Problems with USB-C include variable handling of digital to audio conversion, incompatible SOCs inside the cable, and non-standard analog-passthrough. In short, the cables which contain computers themselves are not standardized in behavior and the author's conclusion is that mobile devices must have 3.5mm jacks until the USB-C cable technology gets sorted out enough that they become usable.
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Bring Back the Headphone Jack: Why USB-C Audio Still Doesn't Work
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Nadia Comaneci, simple perfection.
-- '76 Olympics
(Score: 2) by Immerman on Wednesday September 12 2018, @02:11PM (6 children)
The problem I see with magnetic induction is cross-talk - how do you prevent the stereo-left transmitted signal from bleeding in to the stereo-right received signal, when both transceiver pairs are operating in extreme close proximity? Maybe you could pull it off with an inch or two of separation - but then you're talking about a credit-card sized "plug" on your headphones, which I doubt would go over well.
(Score: 2) by Aiwendil on Wednesday September 12 2018, @05:48PM (5 children)
I'm basically picturing that the sender-blocks being half the size of receiver-blocks as well (hence 12:6), as long as the receiver block is larger than the distance sender-receiver it should also be reduced somewhat by only sending from whatever sender-block covers dead center of receiver blocks. Also a bit of shielding between the blocks (ie, between sender-blocks, as well as between receiver blocks) could probably reduce it a bit. To reduce even further add more sender blocks and try to cause more directionality. The goal being to aim for as short range as possbile (basically putting enough current through 3-4mm at most)
This is really not my field (as stated - I'm having a cold and shooting from the hip), and have no idea how to do the math for range (it is about 1v@20mA per channel iirc for normal earbuds. So let's say about 2v@40mA as a design target).
Pointing out crosstalk made me realise my order was weird, a better order would be magnet, left, reserved, mic, control, right. (to alternate the paths with more expected signal).
(Score: 2) by Immerman on Wednesday September 12 2018, @07:35PM (4 children)
Certainly you can do various things to reduce cross-talk, but if you're delivering enough power to drive a headphone speaker, you're going to be delivering a notable amount of power to any other receiver in close proximity as well, including the other channels.
A much easier (and cheaper) route would be to just use a magnetic connector to deliver direct physical contact, and make sure your contact pads are well bonded to the insulating substrate so that water can't get in. After all, you don't really care if the contacts get wet, you just need to make sure the water doesn't penetrate your device.
Or, if you *really* want to go contactless, use a single induction pad to deliver power, modulated to deliver a digital signal as well, and then decode the signal into multi-channel audio fed through a DAC to get your analog speaker-driving signal.
Basically, once you go analog crosstalk becomes an issue - and it's made far worse through wireless broadcasting. You can still achieve any desired level of isolation, but the cost of doing so increases rapidly.
(Score: 0) by Anonymous Coward on Thursday September 13 2018, @02:19AM (3 children)
I got a degree in electrical engineering.
You don't know what you are talking about.
(Score: 3, Touché) by Immerman on Thursday September 13 2018, @02:57AM (2 children)
So do I. Care to elaborate?
(Score: 0) by Anonymous Coward on Thursday September 13 2018, @05:46PM (1 child)
This forum is not the place for a very technical back and forth.
I will just say that I suspect you do not work in the audio industry as a design engineer.
(Score: 0) by Anonymous Coward on Thursday September 13 2018, @05:52PM
Hey Immerman,
I got your response mixed up with the guy you were responding to because your posts were long and you paraphrased the guy you were responding to a lot in your reply.
I apologize.