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    Resistor in lieu of choke in ST120


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    Resistor in lieu of choke in ST120

    Post by corndog71 on Tue Aug 04, 2015 4:53 pm

    I've asked this before but never got a straight answer.

    Has anyone swapped the choke(s) with a resistor? I know the ST35 and MkII amps used a 50 Ohm resistor (5W/10W respectively). Would 50 Ohm 10W suffice for the ST120?

    I'm really just curious to try something different. It still sounds good with the chokes but have read others prefer resistors.

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    Re: Resistor in lieu of choke in ST120

    Post by sKiZo on Tue Aug 04, 2015 5:07 pm

    If you're really serious, install a DPST switch and try both. Whichever one sounds better to you, go with that.

    You may find it's a similar situation to the PT switches. Depending on genre, either pentode or triode has it's advantages.

    Worth remembering ... a choke's primary purpose is to smooth current ripple. Not sure as a resistor would be quite as flexible in that regard.


    Re: Resistor in lieu of choke in ST120

    Post by Guest on Tue Aug 04, 2015 5:31 pm

    one of the possible drawbacks for using a resistor instead of a choke is residual AC ripple on your rectified DC line. Using a choke tends to block AC ripple better.
    However, I build amps using both, either choke or resistor, and so far have not been able to hear any audible differences.
    I think that as long as good quality electro caps are used at the correct value/s for a given amp, a resistor instead of a choke should be just fine.
    It is said, but I have not experienced it, that a power supply using a choke has less hum and somewhat cleaner and better bass response.


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    Re: Resistor in lieu of choke in ST120

    Post by GP49 on Wed Aug 05, 2015 1:16 am

    The advantage to the choke is lower DC resistance for a similar amount of hum reduction, hence a higher B+ voltage for a given power transformer and rectifier.


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    Re: Resistor in lieu of choke in ST120

    Post by zx on Thu Aug 06, 2015 2:19 pm

    I pulled the chokes out of one pr of my Mk3s.....put a new stock type chokes in a other pr of Mk3s.....I well never go back to a choke on my B+ in my tube amps. less it a 10h or it more noise....what if I were driving klipsch ..have to get a small watt SE amp.....
    the tone is so much better.....with out these  small chokes....the tube sound so diff....the new tube sound almost as I was a kt 88-100 guy....after pulling the chokes the 6550 is the best sounding tube I have ever heard.....the other kt type sound dark....less sweetnes......look it tock 40years for me to pull thses chokes....go fig...
    lot of great sounding Eico tube amps out there with out chokes..............
    all just one mans finding

    thanks for the site Bob...................................

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    Re: Resistor in lieu of choke in ST120

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