Biasing 6G2 Princeton

Discussion in 'Amp Tech Center' started by AlbertaGriff, Apr 8, 2021.

  1. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Or this 2019 thread where I (blush here) point out the idea comes from maestro Steve Luckey in this thread....
     
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  2. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Saw that fix and I may give it a try. It's inexpensive anyway. I did swap the power tubes and it improved it a fair bit but the thump is still audible.
     
  3. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Yep thanks, I saw that later last night after posting here. Worked for you, eh? Any other tonal repercussions from putting the diode on?
     
  4. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Worked well, no downsides I can hear. And really really simple to do or undo. Still, there are many flavors of trem tick and thump, so try it and see.
     
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  5. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    I'll give it a shot - just picked up the diode at my local shop.
     
  6. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Well the diode did not solve my thump. No big deal, I doubt I'll often be at volume and intensity full on.
     
  7. radiocaster

    radiocaster Poster Extraordinaire

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    You won't get much accuracy, perhaps not even with a $500 multimeter, if you use the chassis as ground reference to calculate the voltage drop.

    Yes, you will need the plate voltage with chassis as ground reference to calculate the plate dissipation after you have already figured out the current.

    To measure the voltage drop, you need to put the minus lead on the plate and the plus on the center tap. You should get a fairly accurate reading.

    Don't think you're alone, I did it the wrong way before too.
     
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  8. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Yeah, the effect wasn’t 100% on mine, and as I say, there are different kinds of thump. Have you also done the snubber caps? Lessee, where's that recipe I got from @theprofessor ?
     
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  9. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    PRINCETON_6G2_trem_thumb_caps.png
     
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  10. theprofessor

    theprofessor Poster Extraordinaire

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    Glad I could help! But to give credit where credit is ultimately due, I got it from Jim Nickelson of Lil Dawg Amps. Those snubbers work like a charm. But don't try both the diode on the pot _and_ the silver mica snubbers. I tried the diode, too, after installing the snubbers, and it just made it way worse.
     
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  11. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    That's weird. The caps helped mine but not that much; the diode helped more. So maybe every trem thump is like Tolstoy's unhappy families -- each unhappy in its own way. :D
     
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  12. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    Yeah maybe I will try the snubber caps next. I removed the diode immediately since it seemed to have no perceptible effect for me.
     
  13. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    You know whats interesting about the trem thump is that there doesn't seem to be any consensus for why it happens? And I guess there are various reasons that could contribute, but even then there are only various suggestions for fixes.

    I have a 5F11 I built from a Mojotone kit laat year with the same trem and it is ultra quiet. It's stock except for a couple of swapped caps to slow the trem speed.
     
  14. AlbertaGriff

    AlbertaGriff Tele-Afflicted

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    On 2nd attempt, the diode did actually lessen the thump a fair bit. With intensity on 10, the thumping only appears after I increase volume past 5, and increases strength as volume is maxed. Might be an adequate solution for the time being.
     
  15. Bob Arbogast

    Bob Arbogast Tele-Afflicted Silver Supporter

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    Another potential fix is to add an e-cap (~50uF/50V) from the bias pot wiper to ground.
     
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