"Hum pot" in J5Mk1

  • I want to use a "hum pot" (a circuitry with one variable resistor between 6.3V heater wires) in order to reduce hum of this amp. Will it work? Perhaps someone has experience with this kind of modifications for J5 or other amp.


    Best regards
    Alvaro

  • Re: "Hum pot" in J5Mk1


    Quote from eBernd


    Hi,


    I did it and it has a strong hum reduction effect.
    The trimming resistor has a value of 220 ohms.


    Bernd


    Thank you Bernd! But for any reason I am unable to download your schematic. Is there any other way I can see it?


    Best regards
    Alvaro

  • Re: "Hum pot" in J5Mk1


    Quote from eBernd


    maybe you have to clear the cache of your computer...


    Bernd


    It is strange, because I am already logged-in but when I click on the link, a new screen appears asking for my login and password, and when I write them and click ok, I am directed to the forum home, logged-in, but no image appears. Repeating again this yields the same result.


    So, Bernd, can you describe the resistors an connections used in your hum pot? If you obtained good results I would like to play safe and use the same configuration as you :D. Or perhaps you can send that image to my email (drfigueiras@vodafone.es) .


    Best Regards
    Alvaro

  • Re: "Hum pot" in J5Mk1


    In words:
    Connect each end of the pot to one end of the heaterwinding, connect the wiper to ground, fire up your amp and adjust pot for minimal hum. Really simple.


    Cheers, Thomas

    "It's such a fine line between clever and...and..."
    "...stupid?"
    "Yeah, stupid, right."

  • Re: "Hum pot" in J5Mk1


    Quote from eBernd


    Hi,


    I did it and it has a strong hum reduction effect.
    The trimming resistor has a value of 220 ohms.


    Bernd


    Thank you for your image. I used a trimming resistor connected that way and adjusted until humming reached its minimum. Very effective noise reduction! :D

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