5E3 1/4 power switch?

Discussion in 'Shock Brother's DIY Amps' started by Uncle Daddy, Jun 13, 2018.

  1. Uncle Daddy

    Uncle Daddy Tele-Holic

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    Has anyone tried Robrob's 1/4 power switch on a 5e3?

    https://robrobinette.com/5e3_Modifications.htm#Quarter_Power_Switch

    I've found the resistors to be a bit large to comfortably fit inside the bottom of the chassis, so was thinking about mounting them on the back wall, next to the P/T, and using the redundant ground switch hole for the selector. That'd mean 5 wires running up to the switch. To simplify that, I've moved a couple of connections, and was just looking for confirmation that this would be ok, being a bit of a newbie.

    Thoughts, please?

    P1120449.JPG P1120450.JPG
     
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  2. Gunny

    Gunny Tele-Holic

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    Works for me.
     
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  3. Tapatio

    Tapatio Tele-Meister

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    This is mine. This was my first build which is why it's kinda sloppy. I have added a few mods and have had no issues. It was really hard to find the space, but I got the resistors in somehow. The signal in your layout will be routed close to the power supply side of things, but since everything has already gone through the amplification stages, I don't think you will have any hum or noise issues. Please post results!
    The 1/4 power mod works well, but don't expect it to deliver bedroom levels at above 3 or 4. It's still loud! I feel the difference much more in a larger space.


    5e3_Qtr.jpg
     
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  4. Uncle Daddy

    Uncle Daddy Tele-Holic

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    My tiny brain is struggling to understand how this works. According to Robrob, the 8ohm resistor is in series with the speaker. Won't that affect the signal to the speaker, as there's no bypass for it? With the switch in the position shown in the diagram, does the current take the path of least resistance, and thus bypass the 8ohm resistor?

    Quarter_Power_Switch_Schematic.png
     
    Last edited: Jun 22, 2018
  5. symbiotic

    symbiotic TDPRI Member

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    Current then passes through the closed switch, which is in parallel with the 8-ohm resistor.
     
  6. Wyatt

    Wyatt Tele-Afflicted

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    Simple answer? Yes.
     
  7. timewaster1700

    timewaster1700 Tele-Meister

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    How does it sound with the 1/4 power switch? I’m very interested in this
     
  8. RustySterling

    RustySterling Tele-Meister

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    Hum! I wonder, would this mod work on a 5F2A or a 5F1? Imagine a Tweed Princeton or Champ at just over 1 watt. I think that would likely be bedroom volume.
     
  9. jhundt

    jhundt Doctor of Teleocity

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    I made a thing like that in a box; copied it from a Fender design, on an Eric Clapton amp I think. I did not find it particularly useful, and after trying it out I put it in my box of things I don't use. The difference in volume wasn't enough to make the amp any more useful at home levels.

    I would suggest mocking it up in an external enclosure and trying it out, before going to all the trouble to incorporate it inside an amp build.
     
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  10. jimgchord

    jimgchord Tele-Holic

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    1 watt is very loud. Hardly bedroom volume
     
  11. timewaster1700

    timewaster1700 Tele-Meister

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    Interesting I would have thought cutting the power to 25% would be a dramatic change.
     
  12. Uncle Daddy

    Uncle Daddy Tele-Holic

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    I tried an L-pad attenuator in a Champ I built. That worked well enough, albeit with a little treble loss at low speed.
     
  13. jhundt

    jhundt Doctor of Teleocity

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    no, power in an amplifier is deceptive. It has to do with how we perceive sound and volume. The classic example is the difference between a Deluxe Reverb and a Twin Reverb. If you put the 20-watt Deluxe through the Twin's speakers, it will be ear-shatteringly loud - almost as loud as the 100-watt Twin.
     
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  14. FenderLover

    FenderLover Friend of Leo's

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    Change the 8 ohm to 16 ohm, and the 16 ohm to 12 ohm for 1/9th power (11%) and 8 ohms total load.
     
  15. timewaster1700

    timewaster1700 Tele-Meister

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    That's an excellent idea!
     
  16. Prophetsnake

    Prophetsnake Tele-Meister Silver Supporter

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    I have a Vox AC4 with a an attenuator onboard. You can select 4W, 1w, or 1/4W. 1/4 watt is still pretty loud.
     
  17. timewaster1700

    timewaster1700 Tele-Meister

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    Is the attenuation done just with resistance like the above mod? My Weber Mini mass has a voice coil assembly I think or something along those lines that's supposedly supposed to make it mimic more of the loading of a speaker rather than just straight resistance. Sounds great whatever they did.
     
  18. claes

    claes Tele-Holic

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    Intresting. Have a 5f1 and a 5f2A and going to try it (ec has it in the vibrochamp to).
    Wondering if you could have lower values in a 5watt (20 or 15) and preserv more tone?
     
  19. Prophetsnake

    Prophetsnake Tele-Meister Silver Supporter

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    I think it's just resistors, though it's been a few years since I had it open. It works very well, I have to say.
    I also have an attenuator I use for my other amps. A Carl's amp Super Soak. It was cheaper than buying the componenets and building one myself and it works well enough.
     
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  20. timewaster1700

    timewaster1700 Tele-Meister

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    Thanks for posting. I want to build a 5E3 stock but I'm awefully tempted to put this switchable 1/4 power mod (but probably higher values for lower than 1/4)
     
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