5F6a Frondelli MV

Discussion in 'Amp Tech Center' started by capohk, Sep 3, 2020.

  1. capohk

    capohk TDPRI Member

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    Hi All

    I'm implementing this from Rob Robinette's instructions here https://robrobinette.com/5F6A_Modifications.htm#Frondelli_Master_Volume

    I'm using some shielded 4+1 cable labelled 'MIZU' 4 CORD COMPUTER DATA CABLE 26AWG FOIL SHIELDED.

    I'm just checking that this is beefy enough for the purpose, and whether it is advisable to ground the shield at one end of the cable. It would be easy enough at either end, either to the back of the pot, or to the board ground bus.

    For the two leads going to the power tubes, is it better to use shielded again, or a twisted pair?


    Thanks all as usual

    Matt IMG_1155.JPG
     
    Last edited: Sep 3, 2020
  2. capohk

    capohk TDPRI Member

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    IMG_1153.JPG IMG_1154.JPG
     
  3. David C

    David C TDPRI Member

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    Shields are always grounded at one end or the other, never ground both ends. Both ends grounded defeats the purpose of the shield. I would recommend grounding at the opposite end from your potentiometer or where the power comes from, which isn't the pot. You have a ground bus somewhere near there anyway.

    Rob's drawings suggest using shielded wire to your tubes, as I read his recommendations.
     
  4. capohk

    capohk TDPRI Member

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    Thanks David

    Just checking that 26AWG is up to the job? American wire gauge 26 supposedly rated for 2.2A maximum in chassis wiring.
     
  5. King Fan

    King Fan Poster Extraordinaire

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    I don't know the shielding/sonic qualities of computer cable, but at least your cable and its conductors *look* kinda like the nice Canare *mic* cable Rob uses. Mic signals (which can get as low as 1 microvolt!) are super-sensitive to RFI, EMI, and other noise, so I'm sure they have good shielding. Computers may also, dunno.

    upload_2020-9-5_11-10-5.jpeg
     
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  6. robrob

    robrob Poster Extraordinaire Ad Free Member

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    That cable should work fine. Ground whichever end is easiest.
     
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