Using shielded cables inside chasis

Discussion in 'Shock Brother's DIY Amps' started by radiocaster, Feb 25, 2020.

  1. radiocaster

    radiocaster Poster Extraordinaire

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    I've seen this done in some amps, generally for just running to the input jacks, and the shield is not always connected to ground (if it's not, it's simply left unconnected).

    Does this help in making the amp quieter, avoiding some hum?
     
  2. sds1

    sds1 Tele-Afflicted

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    Not just hum but any noise.

    If the shield is not connected to ground, the result is opposite of the intended effect -- the shield becomes an antenna. Hopefully you didn't see this. it should be grounded on one end only. If the shield is connected on both ends, conditions for a ground loop noise are created.

    It's never a bad idea to shield input into first stage as this is the most sensitive part of the amp -- noise induced there gets amplified downstream. In higher gain amps, add'l shielding in later stages can prevent oscillations that couldn't otherwise be avoided by optimizing the layout.
     
    Tom Kamphuys likes this.
  3. dogmeat

    dogmeat Tele-Afflicted

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    and only ground one end, not both or it can become a conductor instead of a shield
     
  4. jimgchord

    jimgchord Tele-Afflicted

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    Yup
     
  5. Bill Moore

    Bill Moore Tele-Afflicted Silver Supporter

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    I also shielded the reverb wires on my "Twin" clone, (1st build), but I didn't on my DR clone, I can't tell the difference.
     
  6. alathIN

    alathIN Tele-Holic

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    Related question - Ive heard that the shield should be connected to ground a the end of the cable where it terminates, not originates - ie, grounded at the end where the signal's "destination" is. Does this really matter?
     
  7. TobyZ28

    TobyZ28 Tele-Meister

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    The idea is to always ground "downstream" (shortest path to ground) as best practice. Doing so minimizes any chance of interference being generated on the way back. It would be worse to not ground it than ground it upstream... and worse yet to ground it at both ends.
     
  8. gusfinley

    gusfinley Tele-Holic

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    I like to cram a lot of features in my DIY amps. I use 3D modeling to make sure that things "fit." So there often isn't room for optimal layouts.

    I've grown tired of chasing weird signals leaking/crossing/coupling and now just put shielded wire in the more susceptible places.

    I recently fixed up some old builds that always had problems in order to sell them. I used a lot of shielded wire and quasi-star grounds and they never worked better! At least the were at their best when I sold them.
     
    Last edited: Feb 26, 2020
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