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    The "Hazen mod" for EL34 tubes



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    Join date : 2014-04-01

    The "Hazen mod" for EL34 tubes

    Post by colin86325 on Fri Apr 18, 2014 11:57 pm

    I was wondering whether this was applicable to the our Dynaco amps as well, and if anybody had tried it? It involves placing a "non-polarized film capacitor between the suppressor grid to the cathode"

    I'm still struggling to become literate enough to understand these things, but here's the link.  It might not even be applicable to the topology our EL34s live in.

    OK, just read this. Not sure it applies:

    Bob Latino

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    Re: The "Hazen mod" for EL34 tubes

    Post by Bob Latino on Sat Apr 19, 2014 8:29 am


     The Hazen "mod" will not work with any of the VTA amps or any original Dynaco amps. These all have fixed (adjustable) bias. The Hazen mod is only for amps that have cathode bias.



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    Re: The "Hazen mod" for EL34 tubes

    Post by peterh on Sat Apr 19, 2014 11:19 am

    I do not understand why/if this mod works, and certainly whatever it may do in a cathode-bias amp it should do the same in any fixed bias amp. All it does is isolate the suppressor grid and have it float on whatever level it will get.
    What level is expected : there is 2 mechanisms involved :
    - surrounded by screen and plate one might think the suppressor will exchange electrons with it's surroundigs.
    A/ It may emit an electron, by this it get more positive.
    B/ it may be hit by an electron, capturing it, this will make the suppressor less positive

    A and B will tend to balance , if the suppressor is very positive it will attract more electrons thus reducing it's positive charge. If the suppressor is negatively charged it might emit electrons thus increasing it's positive charge.

    Still i cannot figure out if and how it actually does capture bounced electrones to prevent them from reaching the screen( the very reason the suppressor is added to a tetrode). Let's listen to what more experienced people has to say.


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    Join date : 2014-04-01

    Re: The "Hazen mod" for EL34 tubes

    Post by colin86325 on Sun Apr 20, 2014 4:08 pm

    Thanks Bob, I read about that after I posted the question. Although I did come across a post on another forum where a guy with a Dynaco ST70 claims it had a quite positive effect on his amp. Go figure...

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