---
+ Post New Thread
Results 1 to 13 of 13
  1. #1
    Member level 1
    Points: 1,622, Level: 9

    Join Date
    Mar 2005
    Posts
    34
    Helped
    8 / 8
    Points
    1,622
    Level
    9

    audio opto isolator

    Hi,

    We have two channel audio to be seperated from the final stage audio amplifier.
    Now becase of different products the final power ampifier keeps on changing and we come across gounding loop/ humming noise.
    I know that optocoupler could be used to eliminate this.
    Does any one knows any good one for audio (analog).

    I am looking for.
    1. Analog Optocoupler
    2. Least THD
    3. no ageing effects or possibly eliminated.

    thanks

  2. #2
    Advanced Member level 2
    Points: 9,335, Level: 23
    Davood Amerion's Avatar
    Join Date
    Mar 2005
    Location
    Persia
    Posts
    585
    Helped
    115 / 115
    Points
    9,335
    Level
    23



    •   Alt9th March 2006, 18:13

      advertising

        
       

  3. #3
    Member level 1
    Points: 1,622, Level: 9

    Join Date
    Mar 2005
    Posts
    34
    Helped
    8 / 8
    Points
    1,622
    Level
    9

    audio opto-isolator

    Thanks I actually read that. But didnt find a good one yet with a good linearity.
    Ageing still seems to be an issue.I was wondering if there is any other techniue to acheive audio isolation. Transformer isolation doesnt seem attractive because it takes too much space and may be cost. Is there anything like Analog's Isocoupler which does onchip transformer. The problem with Analog's one is that it is for digital seperation and cannot be applied for analog signals.



  4. #4
    Advanced Member level 2
    Points: 9,335, Level: 23
    Davood Amerion's Avatar
    Join Date
    Mar 2005
    Location
    Persia
    Posts
    585
    Helped
    115 / 115
    Points
    9,335
    Level
    23

    optoisolator audio




  5. #5
    Advanced Member level 4
    Points: 14,471, Level: 29

    Join Date
    Jun 2005
    Location
    Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
    Posts
    1,409
    Helped
    136 / 136
    Points
    14,471
    Level
    29

    opto isolator audio

    This app note shows the analog optocouples for current sensing, which should work for audio too.
    http://www.maxim-ic.com/appnotes.cfm...te_number/1867



  6. #6
    Member level 1
    Points: 1,622, Level: 9

    Join Date
    Mar 2005
    Posts
    34
    Helped
    8 / 8
    Points
    1,622
    Level
    9

    analog opto isolator

    Well Kender. It is for high voltage application. In audio what we most care about is linearity, SNR figure of the Optocoupler, THD and how to eliminate ageing.



    •   Alt10th March 2006, 20:07

      advertising

        
       

  7. #7
    Advanced Member level 4
    Points: 14,471, Level: 29

    Join Date
    Jun 2005
    Location
    Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
    Posts
    1,409
    Helped
    136 / 136
    Points
    14,471
    Level
    29

    optocopler audio

    kgeorge123, why do you need an optocoupler in your particular case? What are you going to isolate (or what from)?



  8. #8
    Advanced Member level 4
    Points: 21,510, Level: 35
    E-design's Avatar
    Join Date
    Jun 2002
    Posts
    1,293
    Helped
    245 / 245
    Points
    21,510
    Level
    35

    analogue opto isolator

    Here is something from Agilent



  9. #9
    Advanced Member level 4
    Points: 14,471, Level: 29

    Join Date
    Jun 2005
    Location
    Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
    Posts
    1,409
    Helped
    136 / 136
    Points
    14,471
    Level
    29

    audio opto insolator

    Quote Originally Posted by E-design
    Here is something from @gilent
    That's probably a very neat device. However, one thing throws me off a little bit - it has a very short datasheet, and I couldn't find a block diagram for the chip...



  10. #10
    Advanced Member level 4
    Points: 21,510, Level: 35
    E-design's Avatar
    Join Date
    Jun 2002
    Posts
    1,293
    Helped
    245 / 245
    Points
    21,510
    Level
    35

    audio optoisolator

    Are you looking at this http://cp.literature.agilent.com/lit...988-9694EN.pdf
    It is 15 pages



  11. #11
    Advanced Member level 4
    Points: 14,471, Level: 29

    Join Date
    Jun 2005
    Location
    Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
    Posts
    1,409
    Helped
    136 / 136
    Points
    14,471
    Level
    29

    opto isolator schematic

    Quote Originally Posted by E-design
    Are you looking at this h**p://cp.literature.@gilent.com/litweb/pdf/5988-9694EN.pdf
    It is 15 pages
    Yes, that's what I was looking at. The datasheet doesn't have neither "Principles of operation" section nor (as I have mentioned before) a block diagram. Internally the chip seems quite sophisticated. One can guess that it has an A/D on the right side, a D/A on the left side and the digital signal crosses the boundary. It's a very clever scheme. But in the datasheet I couldn't find such "minor details" as sample rates and number of bits on the A/D and D/A.



  12. #12
    Member level 1
    Points: 1,622, Level: 9

    Join Date
    Mar 2005
    Posts
    34
    Helped
    8 / 8
    Points
    1,622
    Level
    9

    optocoupler audio

    Thanks E-design. I have already looked into that(Optoisolator made up of ADC and DAC). The problem with using such a device is that there are THD and noise introduced by the DAC and ADC and this will adversly affect your audio(especially when they havent mentioned the resolution and sampling rate). Apart from this this part is very very costly which makes it completely out of question. We already have a system in which the data passes through an ADC and DAC and this will again introduce error.

    Kender, the purpose was to eliminate the ground loop issue. But finally I concluded that none of the current analog optocoupler are good for this application( audio groud loop isolation) because of their lower SNR of -80dB and ageing effect in the optoisolator. Typically isolation transformers are used. But that seem to be too big and out of our budget. We do not want to go for any part higher than 1- dollar.

    Thanks



  13. #13
    Advanced Member level 4
    Points: 14,471, Level: 29

    Join Date
    Jun 2005
    Location
    Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
    Posts
    1,409
    Helped
    136 / 136
    Points
    14,471
    Level
    29

    optocoupler aging

    Quote Originally Posted by kgeorge123
    Kender, the purpose was to eliminate the ground loop issue.
    If you are playing the digital sound, you can put your audio DAC on the isolated side and run the digital signals through the optocouplers. That's the cleanest solution.



+ Post New Thread
Please login