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LED link to headphones

Discussion in 'd.i.y.' started by Jim Audiomisc, May 14, 2022.

  1. Jim Audiomisc

    Jim Audiomisc pfm Member

    Raising this as a result of an earlier posting on the general 'audio' part of PFM getting no response.

    Anyone know of a DIY system to use something like mark-space modulated LEDs to send 'wirelessly' stereo audio from an existing stereo system to a pair of existing headphones?

    i.e. *not* a digital link, nor one tied to a specific pair of headphones. But something that could take an analogue input from a stereo system and send it to a portable box the user can wear and plays the audio into their chosen pair of headpnones.
     
  2. cctaylor

    cctaylor pfm Member

    My friend is hard of hearing and gets a device when he visits the local theatre. I understand it picks up audio over an infrared link and feeds it into a stethoscope type headset.
     
  3. bravem01

    bravem01 Active Member

    Quite common in theatres is a sennheiser ir system, don't know if its hifi though
     
  4. davidsrsb

    davidsrsb pfm Member

    An FM system is more likely, I used to have a pair like this.
    VCO in the sender
    PLL receiver
    A 1994 patent https://patents.google.com/patent/US5548654
    I was doing the same in 1983 for sending audio in my GEC McMichael days
     
  5. Ian G

    Ian G pfm Member

    I'm sure my father in law had such a system for watching television, I had a listen and it wasn't hifi but fine for TV especially if you were as deaf as a post.
     
  6. Jim Audiomisc

    Jim Audiomisc pfm Member

    My first DIY thought was a system that used LEDs to carry a stereo MPX and decoder based on that of FM radio.
     
  7. Jim Audiomisc

    Jim Audiomisc pfm Member

    Good thought! I'd forgotten about those systems as I've not been to a theatre in years because of covid, etc. I'll see if I can find something that make that can be used, or bodged.
     
  8. davidsrsb

    davidsrsb pfm Member

    If you want good quality, a S/PDIF interface driving a proper infra red LED and PIN diode receiver with a limiting amplifier would give you 44.1 ksps stereo over a few metres
     
  9. Jim Audiomisc

    Jim Audiomisc pfm Member

    I had wondered about the spdif route. But FM via LEDs -> detector diode is tempting.

    I just had a look to see if sennheiser sold anything like this, but all I could find was headphones/buds with it inbuilt

    Canford sell links, but with mains powered TX and RX which would clearly be a problem for the RX being carried about in the kitchen! Nomimally 3A which would be a bit much for a battery pack if real. 8-] ...and their systems may be lossy. Coulding find a spec on that.
     
  10. jpk

    jpk pfm Member

    How about this...?
     
  11. Nara

    Nara Well-Known Member

    What about adding a bluetooth transmitter to your Hifi and then pairing to a bluetooth headphone? The main problem would be limited range.

    A transmitter like this: https://www.amazon.co.uk/dp/B08FT7HJW7/?tag=pinkfishmedia-21 (I've not used this, just the first Amazon results. I'm sure you can get them with different inputs/ranges etc.)

    And you could use something like the Fiio BTR5 to make your existing headphones bluetooth: https://www.amazon.co.uk/dp/B09G9TNB2R/?tag=pinkfishmedia-21 (I'm sure cheaper options exist)
     
  12. Jim Audiomisc

    Jim Audiomisc pfm Member


    That's quite interesting! Thanks. :) Snag is that my hands/eyes aren't what they were so I doubt I could build it these days as shown. :-/

    Sending as LPCM is good and and spdif in is OK as I can use an ADC in front of the TX.
     
  13. Jim Audiomisc

    Jim Audiomisc pfm Member

    Thanks. I'll have a look in detail. Need to see how well the link actually preserves the info, etc. Also, I don't have a phone/tablet/etc so any system I use needs to work without needing such things to control it.
     

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