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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

    656
    Sep 26, 2015
    Maldon, England

    So I got around to wiring it up today. It seems to work best at higher volumes. It feels like about a 40% drop in volume, which guess is to do with the way power and volume interact. 75% less power doesn't equate to 75% less volume. For some reason, this build breaks up late, and at the moment I'm running a 12AY7 in V1 and a 5751 in V2, so cutting the power still doesn't get into bedroom filth. I'll report back with a tube swap later.

    It it worth it? Maybe. Time will tell.
     
  2. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Thanks for reporting back. I’m curious to here what the tube swap will do. Maybe a couple 12AX7’s will get it where it needs to be. What are your Power transformer voltages? Maybe lowering those would help too
     
  3. Outlaws

    Outlaws Tele-Meister

    344
    Jan 16, 2007
    None
    I run my THD hot plate at the -12dB setting with my 5e3 build and it’s perfect level for living rooms with a 93/94dB Custom 20oz ceramic speaker, or with a Weber 12A125A Alnico.
    It’s not apartment quiet, but nothing is shaking and the amp doesn’t feel like it’s suffocating.
    Any quieter and I’d just get a modeler so I don’t waste my vintage tubes life. I find the sound is destroyed beyond -12dB on it. Same with a JTM45 and Boogie Mark V.
    I tried opening the Hotplate up to measure what gets to their “-12” but I cannot open it. Something will break if I follow the internet instructions.
     
    Last edited: Aug 19, 2018
    robrob likes this.
  4. Uncle Daddy

    Uncle Daddy Tele-Holic

    656
    Sep 26, 2015
    Maldon, England
    I'm going to build this in a pedal box. Should prove interesting.
     
    timewaster1700 likes this.
  5. timewaster1700

    timewaster1700 Tele-Meister

    260
    Feb 17, 2016
    Utah
    Oh good idea. Please report back when you finish it. Only concern I could see is it having enough heat dissipation.
     
  6. Uncle Daddy

    Uncle Daddy Tele-Holic

    656
    Sep 26, 2015
    Maldon, England
    I've noticed that the positioning of the resistors between the board and the transformer seems to add a bit of background hum, probably coming from unshielded wiring running up to what was the standby switch. The good news is the 1/4 power position filters out most of it, making the amp quiet again. I recon it might be better as an external unit.
     
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  7. Uncle Daddy

    Uncle Daddy Tele-Holic

    656
    Sep 26, 2015
    Maldon, England
    Turns out the extra hum was partially caused by a rough V1 load resistor. I swapped them both for a 1w metal film and much of the hum is gone. There's still a bit, probably from the extra wring in the noisy end of the amp, but the 1/4 power switch totally kills it now. Putting the resistors and wire in the bottom of the chassis may well be a better alternative, that or shielded wire to the switch. It's nothing like a Deluxe Reverb on tickover though!
     
  8. Musekatcher

    Musekatcher Tele-Afflicted

    Absolutely. Trying to tame a 5e3 right now, that's giving my Twin a run for the money. I like the idea of a 1/4 power switch. Or maybe a less efficient speaker.
     
  9. Ricky D.

    Ricky D. Poster Extraordinaire

    Age:
    68
    Oct 22, 2006
    Raleigh, North Carolina
    I once had a stereo rig at home that had a power meter on the amp. I was amazed at how loud it was even at 1/2 watt, much to loud for "bedroom volume". Loud enough to interfere with normal activities in the rest of the house.
     
    robrob likes this.
  10. jhundt

    jhundt Doctor of Teleocity

    Age:
    64
    Mar 23, 2003
    Netherlands
    a friend of mine bought a massively inefficient 6" car stereo speaker which he uses when he's testing amps in his home workshop. It's small and easy to move around. He can put it in a cardboard box for less volume, or throw a pillow over it for even quieter sounds.
     
  11. Uncle Daddy

    Uncle Daddy Tele-Holic

    656
    Sep 26, 2015
    Maldon, England
    Ah, the old pillow over the amp trick. I'd be starting to sound like Wes.
     
    jhundt likes this.
  12. dannieh42

    dannieh42 TDPRI Member

    Age:
    48
    6
    May 10, 2018
    Spanish Fort, AL
    I tried the 1/4 power mid and did not like it because of the loss of some of the treble. So, I installed a pre-PI master volume. It was an easy mod and gets you to bedroom levels of you want. My circuit is a little different because my my 5E3 has the Tweedle-Dee mod, but here is a link to when I was doing it.
    https://ampgarage.com/forum/viewtopic.php?t=31140
     
  13. Uncle Daddy

    Uncle Daddy Tele-Holic

    656
    Sep 26, 2015
    Maldon, England

    It's been a while, but I eventually built this configuration into the amp, using 25w resistors with the 12 and 16ohm values. I used the standby switch hole, and mounted the resistors to the back wall of the chassis. It works really really well. For indoor use it really tames the 5e3. 1 or 2 watts is still loud in a small room, but I can take it up to the edge of breakup and still keep the neighbours mostly happy. At the moment I'm using a 12ay7 in V1, but I plan to experiment with an ax7 to see if it give up the juice even earlier.

    All in all, a happy bunny for the price of two resistors and a switch.
     
    robrob, jsnwhite619 and FenderLover like this.
  14. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    It takes a reduction in power by a factor of 10 to cut the volume by 50% through the same speaker/s.
    A reduction of 25% in power output is maybe perceptible but not anything close to significant.
     
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  15. Uncle Daddy

    Uncle Daddy Tele-Holic

    656
    Sep 26, 2015
    Maldon, England
    I gather that the 2 resistors do just that, dropping around 90% of the current to the speaker. At a guess, I'd say the effect on the volume is about 50%.
     
    robrob likes this.
  16. jtcnj

    jtcnj Tele-Meister

    Age:
    54
    488
    Feb 2, 2015
    Brick, N.J. USA
    just ordered the 8Ω and 16Ω 25w pair.
    will probably build as a hardwired cable (no switch) in a pedal box with a length of speaker cable and plug in and out and use on my 5e3 and 18w TMB builds.
    Can always drill ventilation as needed.
     
    Last edited: Nov 29, 2018
    robrob likes this.
  17. mcentee2

    mcentee2 Tele-Meister

    257
    Feb 18, 2011
    York
    Hi, did you get around to building this? How did it go?

    This sounds great flexible way of doing it!!


    Does anyone know the maths for this so I can work out all the possible combinations downwards in power?

    I get the calculation for total ohms kept at 8r, but I can't see the method to get the resulting power left ?
     
    Last edited: Feb 9, 2019
  18. jtcnj

    jtcnj Tele-Meister

    Age:
    54
    488
    Feb 2, 2015
    Brick, N.J. USA

    I did; in hindsight I would have preferred to use jacks, not use the plywood and caulk to mount the components, and used the values for 10%.
    the cable is a little short
    It gets warm but not hot
    It cuts some volume but not enough.
     
  19. mcentee2

    mcentee2 Tele-Meister

    257
    Feb 18, 2011
    York
    Does anyone know where the 8 series/ 16 parallel, and 16 series /12 parallel come from?

    Just used the Weber lpad design tool and it shows:

    6dB loss ( 1/4 power)
    4 ohm series
    8 ohm parallel

    10dB loss (1/10 power)
    5.47 ohm series
    3.7 ohm parallel


    Why should I choose these instead of the ones in this thread?


    Thanks
     
  20. harleytech

    harleytech TDPRI Member

    Age:
    56
    32
    Jun 5, 2017
    Wisconsin
    I put Rob's pre-PI master volume in... I love it.. works great !
    I can dial in what I need or go full volume.. Used the Ground/standby hole
    1M audio pot,a couple of wires and no big resistors...
     
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