External Stereo Mic Adapter for SJ8

Discussion in 'SJ8 Series' started by nianeko2, Jul 10, 2018.

  1. Sulev Svilponis

    Sulev Svilponis Elite

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    Let's be honest, SJCAM does not advertice or recommend (nor even list as an option) using external mic together with external power supply.
     
  2. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Correct, they don't, and that in itself is a product development failure. I realize SJ8 is an "action" camera, so the main intention is for it to be used on battery, but still, the external mic + power requirement is such a common need that it is hard to justify not having implemented it in a good way. There is a very large market of educators and lecturers who are pining for a compact, capable, go-anywhere camcorder that will allow them to record their presentations, and of course they care about good sound. What was SJCAM thinking to have botched such an important feature? GoPro at least tried to take care of this, albeit in their characteristically expensive and complicated way, by having a brick of a dongle about half the size of the camera itself that does the analog-to-digital conversion off-camera and costs $50. When all is said and done, GoPro's solution is more than twice the price of SJCAM, but at least it works. SJCAM was so close to beating the competition decisively, but instead, ends up driving away aspiring and admiring users like me.

    As for honesty, how about SJCAM's reply to my support ticket, where they tell me that this function is not supported by their SOFTWARE? That was dishonest, indeed. And when I asked a follow-up question, pointing out that this issue has nothing to do with firmware, they simply ignored it.

    I do very much appreciate YOUR interest and help in getting to the bottom of this problem. I wish SJCAM staff had the same attitude...

    I will certainly try to record using a power bank, as you have suggested, and report back when I have the answer.

    Thank you!
     
  3. Sulev Svilponis

    Sulev Svilponis Elite

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    Did you try to record at PAL framerates? Was there any changes?
     
  4. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Well, guess what... When recording at 50 fps, the noise frequency becomes 50 Hz (see attached screenshot). So, now we know the real origin of the noise, and it's coming from the video circuit inside the camera, after all. The question for SJCAM engineers, if they ever get around to looking at this issue, is why the noise is being picked up by the external mic circuit, but not by the internal mic.

    By the way, I wanted to ask you, what program did you use to display the waveform in the screenshot you posted earlier?
     

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    Last edited: Apr 15, 2019
  5. Sulev Svilponis

    Sulev Svilponis Elite

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    Ok, now it's clear, that the noise is not coming form the power grid and improving the power source wont help.
    The software is WaveLab (by Steinberg). Yours is from Audacity, I see.
     
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  6. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Yes, Audacity all the way. :)

    Thanks for all your help!
     
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  7. Troy

    Troy Administrator Staff Member

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    That's weird (Though I must admit I haven't read through everyone's comments). t
    In my experience, and from what I understand with concert and studio audio devices, you can tell if a noise is coming from a power source that a system is picking up, either through cables or through unshielded boxes. It's usually a hum.
    Most "chargers" (wall chargers) are not meant to power devices, but are designed only to charge batteries.
    A powerbank however, can power devices without causing AC (alternating current) noise to near or adjacent devices.
     
  8. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Dear Troy,

    I hope you DO read through at least the last five messages in this thread, because there you will find a precise response to what you said in your message. We were able to establish CONCLUSIVELY that the noise is NOT coming from the charging circuit at all, but rather, from the video circuit. This is purely an engineering issue that I hope SJCAM takes notice of and fixes, as otherwise, it'll lose more clients. As sad as I was to have to sell my SJ8, I ended up doing it, because it was useless to me with this problem...

    Regards,
    Oleg.
     
    Last edited: Jul 25, 2019
  9. Troy

    Troy Administrator Staff Member

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    Thanks for pointing out where to look in the thread Oleg.
    I'll have this reported to the tech team, and hopefully they can reproduce the issue to address it.

    Best Regards,
    Troy
     
  10. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Hope SJCAM can fix this. By the way, a part of the problem here was that your tech support completely ignored the issue when I brought it to their attention via a support ticket. I explained what was happening in minute detail, providing the same audio samples as I have on this thread. They only replied that the functionality of recording with an external mic and charging as the same time was "not supported," which, of course, is complete nonsense, given that this feature DOES, in fact, work, but unfortunately suffers from a serious issue. When I challenged that reply, my message wasn't answered. All this happened weeks before I started this thread. If I were SJCAM's management, I'd be interested in talking to the support people involved, because that's no way to treat a serious bug report from a conscientious customer.

    Regards,
    Oleg.
     
  11. Multisoft

    Multisoft New Member

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    SJCAM saves on filters, capacitors, that's the whole reason ... =)
    It is necessary to install ceramic capacitors on + and - to powerbank, but first you need to measure the signal on an oscilloscope in order to calculate which values you need.
    To get rid of noise in an external microphone, you must ground it with a resistor.
    Take a 10-15kOm variable resistor and connect to the + external microphone and GND camera. You can also use a ceramic capacitor and a resistor in series to get rid of interference alternating current.
     
  12. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Have you read the previous postings in the thread, where I demonstrated conclusively that the noise is coming from the video circuit, not the power circuit? Would your suggestions still apply in view of that information?
     
  13. Multisoft

    Multisoft New Member

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    This is a problem with many cameras.

    If you don’t try - you don’t know!
    I don’t have a Type C connector to check.
    Measure the resistance of Video OUT and GND, they should be 75Ohms, is that so?
     
  14. Oleg Gorfinkel

    Oleg Gorfinkel New Member

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    Unfortunately, I no longer have the camera. I sold it a few months ago after realizing it was useless to me with this problem. Perhaps someone else can make this test. In reality, though, this is an issue for SJCAM engineers to solve. When I first reported it to SJCAM support, they ignored it. In the end, though, someone from the SJCAM team found this thread and did react. Perhaps they'll fix the problem in the next camera version.
     

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