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What would adding a choke to the 5e3 be like?

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  • What would adding a choke to the 5e3 be like?

    reading through the thread pages looking for choke experience..I didn't see much about the use of choke in 5e3.
    How much trouble is it to do?
    Is it worth the trouble?...what can I expect in terms of power/tonal differences?
    Any methodology you're willing to share is very thanked and welcomed.
    So far I've been advised to simply place the choke between the rectifier and 5k1 resistor
    and
    Placing the choke this way defeats the tonal influence the choke would have to a great extent.
    Should I:
    1 put the choke betwen the recto and 5k1 resistor?
    2 replace the 5k1 with the choke?
    3 reduce the 5k1 by the DCR of the choke...
    I obviously am sketchy on understanding the choke, it's DCR Vs. Inductance Vs. AC resistance [excuse any misnomers here...].

  • #2
    You replace the 4k7 to 5k1 screen node, voltage dropping resistor.
    The result is better screen and preamp filtering... not really needed...and much higher screen and preamp voltages... not really desired most of the time.
    Also with higher screen voltages comes higher power tube idle current... the tubes are already idling in very high current, near the tube's max limit.
    Now if you are trying to get a different sound out of the amp that is a different matter.
    The choke mod will net you a little more output power and the amp can sound
    slightly brighter with a little more preamp gain.
    You will need to change the cathode biasing resistor of the power tubes to a larger value, like 330 to 360 ohms (or maybe more depending on the power transformer used), in order to keep the power tubes from running too hot.
    You should rewire the power tube sockets with one to two watt, 470 ohm to 1000 ohm screen resistors too.
    The amp will also sound a very tiny bit stiffer as the B+ rail will be higher and the screen voltage will be a little more stable.
    Bruce

    Mission Amps
    Denver, CO. 80022
    www.missionamps.com
    303-955-2412

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    • #3
      Excellent information Bruce thank you again !!

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