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5E3 Variable Boost Mod

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  • 5E3 Variable Boost Mod

    Hi,
    I want to mod my 5E3 based build to have a boost, though a pot rather than a switch.
    This is what I am thinking of implementing. Does anyone have a better suggestion or can see an issue with my plan?
    Thanks in advance.
    Click image for larger version

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  • #2
    The main issue I see is you already have a 25uf cap bypassing that cathode. Adding another 0.68uf in parallel will do nothing. I don't have my calculator, maybe 3% tops? The difference between 25uf and 25.68uf.

    A real 5E3 has a 12AY7 input tube, a 12AX7 would have higher gain. Then you could add a pot, but dial it down to the original level as "normal", then turn it up for some boost. Just a thought.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Originally posted by Enzo View Post
      The main issue I see is you already have a 25uf cap bypassing that cathode. Adding another 0.68uf in parallel will do nothing. I don't have my calculator, maybe 3% tops? The difference between 25uf and 25.68uf.

      A real 5E3 has a 12AY7 input tube, a 12AX7 would have higher gain. Then you could add a pot, but dial it down to the original level as "normal", then turn it up for some boost. Just a thought.
      Hi Enzo,
      I already use a 12AX7 in that position. What I want to be able to do is dial in some pre-amp distortion for lower volume playing.
      Are you suggestion use a pot instead of the 820R cathode resistor to drop the value?

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      • #4
        Actually, reading around it seems a master volume mod will do a better job of it. Only involves swapping the 1M resistor with a 1M pot Pre PI.

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        • #5
          A master volume mod won't include any of the good power tube clipping at lower volumes. In fact, you won't get much distortion without power tube clipping with that amp. Which means that distortion = loud WRT that model. I think your best option would be an attenuator.
          "Take two placebos, works twice as well." Enzo

          "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

          "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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          • #6
            Originally posted by Chuck H View Post
            A master volume mod won't include any of the good power tube clipping at lower volumes. In fact, you won't get much distortion without power tube clipping with that amp. Which means that distortion = loud WRT that model. I think your best option would be an attenuator.
            Wanted to avoid that really. Same way I want to avoid have a pedal sat in front of the amp on the floor as the amp mostly lives at home. Thanks for the suggestion though.

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            • #7
              I just added this master volume mod to my newly built 5e3
              https://robrobinette.com/5e3_Modific..._Master_Volume
              using a 1 meg audio pot I've installed it on the back where the ext speaker jack use to be ,I'm not really impressed ,it goes from hardly any sound to about 1/2 volume right away turning the rest of the way increases slightly .also it sounds kind of anemic untill it gets up to almost full volume .
              I think i will reverse this mod . I really like this amp cranked with a Boss SD 1 boosting it .
              "UP here in the Canada we shoot things we don't understand"

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              • #8
                That's not a surprising outcome. I tried to warn against it in post #5. This is why I suggested an attenuator. That the amp doesn't start sounding good until the master is almost maxed is a clue. I understand that you want to avoid an attenuator... If what you want is master volume type amp then a 5e3 was a bad choice. If what you want is a 5e3 sound at lower volume then an attenuator isn't a bad choice. Sometimes we need to make concessions. It's an "if... then..." scenario.
                "Take two placebos, works twice as well." Enzo

                "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                • #9
                  The easy fix for your problem is to simply get the right pedal or a smaller amp. I constantly see people trying to mod a great amp for an application for which they are simply not suited. Get a $100 five watt head, set it on top or behind it, and plug in the speaker. Use a 50 watt Weber Mini Mass attenuator if needed. Case and point. I was playing some small venues a while back. I got lots of compliments on the sound of my ratty old 1960 Ampeg Rocket amp. It wasn't even switched on. I had an Epiphone VJ head behind it plugged into the speaker. AND the speaker was an Eminence ceramic magnet replacement, lol. But it sure looked like I was getting the vintage mojo from a ratty old vintage amp!

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