Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 23 of 23

Thread: Teensy 3.6 + Audio Shield huge noise

  1. #1
    Junior Member
    Join Date
    Feb 2017
    Posts
    6

    [SOLVED] Teensy 3.6 + Audio Shield huge noise

    Hi guys,

    I'm having an issue with Teensy 3.6 and Audio Board. I stacked them one on top of each other and loaded one of the example projects.
    Teensy is USB powered (dedicated and powered dLink USB hub), audio from analog out.

    Here's what I get...
    https://www.dropbox.com/s/vx0ojei06q...Noise.wav?dl=0

    I'm totally new to this, so may I ask you an advice about that? I supposed this should work straight away.

    Thanks!
    Luca
    Last edited by zioaxiom; 02-23-2017 at 10:39 AM.

  2. #2
    Senior Member+ Frank B's Avatar
    Join Date
    Apr 2014
    Location
    Germany NRW
    Posts
    6,874
    Are they soldered ?

  3. #3
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Posts
    21,814
    Sounds very much like a bad ground loop problem.

  4. #4
    Junior Member
    Join Date
    Feb 2017
    Posts
    6
    Hi guys,
    yes sounds like a ground issue to me too, but that's new to me since I work with audio professionally every day and never got such issues.

    Here are a couple of pics of my boards.

    Click image for larger version. 

Name:	IMG_0457.JPG 
Views:	100 
Size:	80.5 KB 
ID:	9636Click image for larger version. 

Name:	IMG_0458.JPG 
Views:	93 
Size:	66.7 KB 
ID:	9637

    Thanks,
    Luca

  5. #5
    Senior Member+ KurtE's Avatar
    Join Date
    Jan 2014
    Posts
    6,624
    Is the audio adapter plugged in all the way? Picture 2 sure looks like either the pins are really long or it is not pressed in...

  6. #6
    Junior Member
    Join Date
    Feb 2017
    Posts
    6
    Yes, it's all the way. the pins are long

  7. #7
    Junior Member
    Join Date
    Feb 2017
    Posts
    6
    Any advice? I supposed it was easy to start working with Teensy.

  8. #8
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Posts
    21,814
    You're probably going to need a ground isolator.

    This problem comes up occasionally, so I recently bought a batch of them for PJRC to start selling. They're sitting right here in a box, waiting for me to get around to testing one and then adding them to our store.

    It's a common item. Here's one on Amazon you can buy right now.

    https://www.amazon.com/Mpow-Ground-I...dp/B019393MV2/

  9. #9
    Junior Member
    Join Date
    Feb 2017
    Posts
    6
    Thanks Paul. I'll check if I can get one and hopefully fix this issue.

  10. #10
    Junior Member
    Join Date
    Feb 2017
    Posts
    6
    Thanks Paul! The ground isolator totally fixed that. Since I'm planning to develop an external fx, it would be advisable to use those same kind of transformers on the board?

    Thanks,
    Luca

  11. #11
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    I have a similar issue with the Teensy 4 and the new audio shield. When I attach it via USB to my Mac the sound is horrible. I got myself a ground isolator like in the link. That improves the sound tremendously but it still is plain bad. Lot's of noise. Since I was planning on building a USB MIDI synthesizer around the Teensy I would be very glad to hear if there are any other proposals of what I could do. (The general audio quality and especially the horse power of the Teensy 4 is really great for such a project).

  12. #12
    Senior Member+ Frank B's Avatar
    Join Date
    Apr 2014
    Location
    Germany NRW
    Posts
    6,874
    See Post #3 / Post #8

  13. #13
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    Hi Frank, thanks for your reply. But I wrote "I got myself a ground isolator like in the link." which means I read those and bought the isolator which helps only somewhat. The result is by far not good enough for a synth.

  14. #14
    Senior Member+ Frank B's Avatar
    Join Date
    Apr 2014
    Location
    Germany NRW
    Posts
    6,874
    Ah, ok, sorry..
    Is the shield soldered to the Teensy? Any cabling?

  15. #15
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    Yes, the shield is soldered. No cables except for the USB cable and now the ground isolator.
    EDIT: When I use the USB only for power and connect to a USB wall wart then there is not noise at all.

  16. #16
    Senior Member+ Frank B's Avatar
    Join Date
    Apr 2014
    Location
    Germany NRW
    Posts
    6,874
    Ah, OK... hm.. in this case, I can't help.. (Have you tried a USB Hub?)

    @Paul?


    edit: self-powered USB Hub?

  17. #17
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    That's a good idea, I will try that. Thanks!

  18. #18
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012
    Posts
    21,814
    Quote Originally Posted by Frank B View Post
    @Paul?


    edit: self-powered USB Hub?
    If it's a ground loop problem, and you want a direct audio connection for best signal quality, then the other thing you can try is isolating the USB. Here's a product when I have personally verified works with Teensy 3.x.

    https://hifimediy.com/Accessories/usb-isolator

    They also make a 480 Mbit model that's approx $90, which does not work with any Teensy, even Teensy 4.0.

  19. #19
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    Thanks a lot, Paul. I will try that as well. It would be a shame if I could not use the Teensy 4 for that project. With the audio shield t is such a nice and powerful board for that purpose!

  20. #20
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    So finally I got the USB isolator. It improves the situation a bit more. Still when connected to the computer over USB unfortunately the sound is far from the great sound I get when just connecting to a power supply.

  21. #21
    Junior Member
    Join Date
    Dec 2017
    Location
    Skiathos, Greece
    Posts
    11
    Hello Paul . Just yesterday I realised that teensy 3.6 has no connection from shield of headphones output to any ground. That was making a lot of noise for me, when I was trying to listen from headphones while I was transferring audio using usb or line in. I tried to connect the shield from the headphones out to any ground pin to hear the result and fortunately I am so happy to tell that the ground noise disappeared when I attached the cable from headphones shield to GND pin (when I attached the cable from shield to Analoge GND creates an other kind of ground loop noise). I am so happy that I have crystal clear sound with absolutely no noise from 3.6 without buying any ground audio or usb isolator . I can not measure the SNR percentage, however I can tell that in my ears is not recognised any noise from this board . Thank you Paul ! I am in love with Teensy boards, they are so powerful .

  22. #22
    Junior Member
    Join Date
    Jul 2013
    Posts
    11
    Hi Antonis, that sounds interesting. Which pin are you talking about exactly? Are you talking about the VGND pin on the audio shield where it says "caution: do not connection VGND to GND". Or some other pin? Thanks!

  23. #23
    Junior Member
    Join Date
    Dec 2017
    Location
    Skiathos, Greece
    Posts
    11
    Quote Originally Posted by stevie View Post
    Hi Antonis, that sounds interesting. Which pin are you talking about exactly? Are you talking about the VGND pin on the audio shield where it says "caution: do not connection VGND to GND". Or some other pin? Thanks!
    Hello Stevie. Yes I took the risk to connect VGND to GND. You can see to this photo the black wire that does this connection https://imgur.com/a/jEoYzgd . This is the project that I am about to finish and I fill so proud. https://imgur.com/MSWCCxb This is the first time that I am building something so big. With Teensy boards I fill that I am living in since fiction movie.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •