Would shielding the input and output leads inside the case reduce the noise floor?

Gotta love my  WTPA2 but I wish it wasn't so noisy via external input.   I'm tempted to open it up and put in shielded wire from the jacks to the boards, with the shield wired to ground/  Would that help?  Has anybody done it? 

I don't want to risk screwing it up unless there's a potential pay off for the work. 

Comments

  • A couple things that helped me when I was building my unit were:

    1.)  Making sure all the signal wires were short
    2.)  Experimenting with different wall warts (some are way worse than others -- using a 9v battery will clear up most noise most of the time)
    3.)  Keeping your audio and DC input power paths separated from the jack board to the inputs.

    I'm guessing separating the DC power ground and input ground on the jack board, and running a shielded wire from the audio in on the PCB to the audio jack, and a dedicated wire pair from the DC jack to the DC input on the PCB would make a big difference.  I remember doing something like that a long time ago.


  • ok so 

    1.)  Making sure all the signal wires were short
    WELL FROM THE CASE IN TO THE BOARD, HOW DO I GET THOSE SHORTER???


    2.)  Experimenting with different wall warts (some are way worse than others -- using a 9v battery will clear up most noise most of the time)
    OK WILL TRY THAT AND REPORT BACK 


    3.)  Keeping your audio and DC input power paths separated from the jack board to the inputs
    WHAT DOES THAT MEAN IN REAL TERMS.  FOR SURE AUDIO GOES IN TO THE JACK, POWER GOES IN TO THE JACK, THE JACKS CONNECT TO THE BOARD, HOW DO I "SEPARATE" THEM. 

    I'm guessing separating the DC power ground and input ground on the jack board, 
    HOW?


    and running a shielded wire from the audio in on the PCB to the audio jack, 
    OK THAT'S EASY 

    and a dedicated wire pair from the DC jack to the DC input on the PCB would make a big difference.  
    OK WILL TRY THAT 

    I remember doing something like that a long time ago.


  • Would a couple of electrolytic caps help in the power path stabilize the DC IN?  to level out any ripple?  
    could you recommend the values?
  • Hey --
    Sorry to be slow.
    Some electrolytics would not hurt, but they may not fix the problem.  A common mode choke might help too (one of those cable clamp ferrite things).
    Two 470uF in parallel with some small ceramics might be a fun experiment.

    By "separate the grounds", I mean the wires, not the voltage nodes.
    More specifically, the connections from the jack board to the main board.  So, run a ground wire from the power jack directly to the power input (next to the power + wire).
    Run an audio ground wire from the audio jack to the audio input (next to the audio +).  This is the one to use shielded wire for, if you're going to do that (and that will help, generally).

    IIRC the grounds are connected on the jack board, which was a silly young engineer thing to do.  You can cut a trace there if you are careful and feel like you've exhausted other options.

    Try not to run the DC wires and the audio wires in parallel -- like don't ziptie them together, break up the ribbon, etc.

    By "keep the wires short" I mean don't use excessive length between the jack board and the main board.

    Hope this helps.
    Let me know how it goes!
    TB

  • What TB describes is exactly what I did for the audio lines, (running separate shielded cables direct from jacks to the board inputs, not the ribbon connector points), and
    it made a huge difference, noise floor is very low (much lower than WTPA 1) and overall sound quality is better on samples. Highly recommended!
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