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Mojotone Studio One inspired build

Discussion in 'Shock Brother's DIY Amps' started by reggiepe, Oct 2, 2020.

  1. reggiepe

    reggiepe TDPRI Member

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    @andrewRneumann

    As long as nothing catastrophic happens...I can give it a whirl and report back later.
    I know you mentioned it before and I pushed it back as I was trying to resolve the hum issue.
     
  2. andrewRneumann

    andrewRneumann Tele-Holic

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    By all means get a second opinion. I’m just some dude on a forum and it’s YOUR amp. Be skeptical. I know I am. :) :)
     
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  3. reggiepe

    reggiepe TDPRI Member

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    Alrighty...I will wait for someone to second your vote.
    I definitely would feel more comfortable if I could see that it has been done before....meaning the dual self split. I have scoured the forums for an example and can't find one. There are some that have them in a true push-pull arrangement with a phase inverter. But I believe that theory behind that method has been proven out with the way a pentode would work in that scenario with fixed bias. I have attached a pic of the power section from a low powered plexi that has all the cathodes tied to ground....makes sense to me for that method of biasing.

    But as I type this, maybe I should be looking at cathode biased parallel SE schematics since this has similar behaviors with the way the filaments are wired.
     

    Attached Files:

  4. D'tar

    D'tar Friend of Leo's

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    X2
     
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  5. D'tar

    D'tar Friend of Leo's

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    That attached file does not appear to be self splitting inverter nor is it cathode bias output?

    [​IMG]
     
  6. D'tar

    D'tar Friend of Leo's

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    So looking back to the studio one... Ok self split cathode bias... How are your tubes wired? On the studio 1 v4a is out of phase to v4b likewise with v5a,v5b. are your triodes of v4/v5 out of phase or parallel?
     
  7. reggiepe

    reggiepe TDPRI Member

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    ....and there it is!

    Right! That image just shows the cathodes all connected for fixed bias.

    The triodes of V4A and V4B are out of phase with each other and the same for V5A and V5B. It is working fine as is, but @andrewRneumann had mentioned that he is seeing that it may work be a bit better if V4 and V5 cathodes were connected to each other.
     
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  8. reggiepe

    reggiepe TDPRI Member

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    Just reread that...I didn't answer your question. V4 and V5 are parallel.
     
  9. D'tar

    D'tar Friend of Leo's

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    I don't think I asked clearly enough but this answers sufficiently.

    Thanks
     
  10. reggiepe

    reggiepe TDPRI Member

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    Connected the cathodes...no boom.....no smoke.......no fire. But also no discernable difference. I drove the amp at 100% and connected with a jumper. Nothing changed with gain, or tonality. Not so much as a pop or a click. I am guessing this is because both have a path to ground already.

    Now, I am going to see if I can get this to run a pair of ECC99's. Since I got to this point in the experiment, I may as well try a tube that has a little more wattage. Thinking it through....I should be able to get a pair of 12AU7's to run in there as well with a decrease in wattage. Reflected impedances adjusted for tube type of course. Thinking a little bit further...I should be able to run 2 different tubes....a 12BH7 and an ECC99. The imbalance may make for something very nice or very scary.
     
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  11. andrewRneumann

    andrewRneumann Tele-Holic

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    Sounds like a fun experiment! Good luck!
     
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