Fender 6G2 Re-Build As Pre-Amp

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by PLX, Feb 28, 2019.

  1. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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  2. HotBluePlates

    HotBluePlates Member

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    Nice!! Sounds very convincing!!
     
    Last edited: Apr 14, 2019 at 3:53 PM
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  3. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    It's amazing the difference it makes in the tone saturation to raise or lower the line out volume from the 6G2.
     
  4. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    Getting a ground loop hum when I connect the pre-amp directly into my audio interface (Scarlett 2i2) which is a USB device that connects directly to the PC running my DAW.

    It's weird because this PC is powered from an isolated ground outlet in my home studio.. when I plug the pre-amp into the same grounded outlet, there is no hum until I turn on the pre-amp..

    However, if I plug the pre-amp into another outlet that is not an isolated ground, I get the hum as soon as I plug it in - without ever switching it on.

    Wondering about installing an audio transformer in the line out of the pre-amp to isolate it and break this loop ?

    I have a Jensen JT-6110K-B audio transformer that I used previously in load boxes. :dunno
     
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  5. Bluesful

    Bluesful Supporting Member

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    Into the front end or a loop return?
     
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  6. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    Front end.

    There is no loop on my 2203.
     
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  7. Bluesful

    Bluesful Supporting Member

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    As the lords of Rock intended.
     
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  8. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    No room inside the chassis for this transformer. Not sure I want it inside anyway.

    [​IMG]

    Appears to be very well shielded against EMI.

    The only good spot for it appears to be centered between the pre-amp tubes, which sounds like a horrible idea. :facepalm

    Unfortunately, that's exactly where the line-out jack and line-out volume pot are located.
     
    Last edited: Apr 15, 2019 at 9:21 PM
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  9. HotBluePlates

    HotBluePlates Member

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    Sounds like a plan. You pretty much have to assume ground loop hum will happen when any devices have audio connected but are powered separately. That you sometimes don't have problems, or experience the problem differently is interesting but probably not a good argument against transformer isolation.

    Your line out is presumably low-impedance (8-1kΩ, right?). The low-impedance line isn't vulnerable to picking up junk from nearby circuitry. And if your line out is also low-current (because you're knocking power/current down in the dummy load), then it probably won't radiate much into the surrounding circuitry.
     
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  10. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    Yes, as I understand it I'm just tapping a signal off the power resistors.

    They are absorbing all the energy that would normally be going to a speaker.

    The amp already has a hum loop elimination circuit, but it's not doing the job of keeping that noise off the audio signal. That's why I pulled this little audio transformer out of a box and looking to isolate the line-out signal with it.

    Agreed about the very low power going on in the line-out.. and in this transformer as well.
     
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  11. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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  12. ShredSquatch

    ShredSquatch Conspiracy Experience Director & Stunt Guitarist Silver Supporting Member

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    Sounds killer man! I wish I had the space to do that!:oops:

    ~ss
     
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  13. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    Mark Cameron told me the more holes you have in your amp chassis, the better it sounds.

    That's how the tone gets in.
     
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  14. ShredSquatch

    ShredSquatch Conspiracy Experience Director & Stunt Guitarist Silver Supporting Member

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    Well that's true but I would wait to hear from Kirk Cameron before I drilled anymore holes in the chassis! Wind and holes are what makes the brown sound come to life!

    ~ss
     
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  15. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    Drilled two more holes just to be safe.

    [​IMG]
     
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  16. PLX

    PLX MENSA member, Astronaut, Dated Your Mom Once Gold Supporting Member

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    audio transformer wiring

    [​IMG]
     
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