J5Mk1 16 Ohm: R19&R20 recommended values?

  • I want to make J5MK1 for a 16 Ohm speaker directly (I do not have 8 Ohm speaker, but 16 Ohm).
    From FAQ I know I have to change the values of R19/R20 in order to obtain a cathode current for < 45mA for V3.
    My Hammond 125E OT has a primary impedance of 5600 with the secondary at 15 Ohm. While standard configuration for 8 Ohm is Pri. 4200 / sec. 8 Ohm. My problem is that I lack the knowledge required to calculate the values of R19/20 for 16 Ohm configuration.

    So anyone can help me?

  • Re: J5Mk1 16 Ohm: R19&amp;R20 recommended values?

    Hi Martin. Thanks for your reply.

    I did not completed the J5Mk1 yet, but I am close to finish it. I go slowly in order to check twice and to avoid problems later. My purpose was to solder the right resistor values from the first time.
    But if those resistors might be right even with OT output for 16 Ohm, perhaps I will not need to change them. All right. I will measure current at that point with a multimeter. If it is > 45mA I will have to increase these resistor values, right?

    Best regards
    Alvaro

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