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5E3 Micro pre-build prep

Discussion in 'Shock Brother's DIY Amps' started by pmacaula, Nov 4, 2020.

  1. pmacaula

    pmacaula Tele-Meister

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    Am getting ready to do this build & have a few questions about some of the components. Below is my shot at the Bill of Materials (taken from RobRob's site and augmented with some items not explicitly listed by him). The list does not have a few things loke wire and standoffs.

    Questions are:
    1. Resistors & Capacitors- is it very important to use a specific type of resistor or capacitor (beyond the basic specs) for specific roles ? If yes which ones are critical in that regard ?
    2. Chassis - What is a reasonable size assuming I am going to use a tube rectifier and a turret board ? Would 10"x6"x2" (Hammond has this chassis size) be big enough w/o making it really awkward to position the pots and switches reasonably ?

    Any other observations on the list below greatly appreciated.

    Thanks. Patrick. upload_2020-11-4_19-2-6.png
     

    Attached Files:

    Last edited: Nov 4, 2020
  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The voltage dropping and bias resistors should be fire proof type. Usually metal oxide but it is more important to be fire proof of any type. The other resistors can be metal film. Don't bother with carbon comp resistors.

    I use name brand caps. For this type amp polyester works well. You don't need anything fancy.

    The pF caps can be silver mica, or anything really but I would shy away from ceramic discs.

    The electrolytic can be axial or radial. The radial may not mount as easily, depending on your design.

    You may want to try a 2.2uF or 4.7uF on the V1 cathode, so you may want to order some to have on hand. Those values will help to get rid of some un-necessary low frequencies.

    If you think you may want to have a switch for a mod, the Bournes 1M push-pull potentiometer can be convenient. No extra holes in the chassis.;)
     
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  3. pmacaula

    pmacaula Tele-Meister

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    LLC - Thanks !

    Am I correct to assume for the V1 Cathode cap, you mean the Tone Cap (4.7nF in the plans) ?
    The extra switching capability in the pot is a great idea. I think I would like the option of turning off the bright cap.

    Any thoughts on the appropriate chassis size ? Is 10"x6"x2" big enough if I am using in a tube rectifier & want both a headphone and speaker out jack ?

    Cheers. Patrick.
     
    Last edited: Nov 5, 2020
  4. Paul-T

    Paul-T Tele-Holic

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    I think that would be the Cathode Bypass cap which will be 25uF. There's a good explanation of how this functions on Rob's How the Deluxe Works page:

    "Another way to trim the 5E3's low end 'fat' and tighten up the amp is to reduce tube V1's or V2A's cathode bypass capacitor. Both have a 25uF 25v cap that is large enough to boost all guitar frequencies but many modern amps use a bypass cap as low as .68uF (680 nano Farads) to boost only mid and high freqs. If you wanted to alter just one of the 5E3's channels you'd have to separate the V1A and V1B cathodes by adding another cathode resistor and bypass cap (see the Voice a Lead Channel mod)."
     
  5. Javier668

    Javier668 Tele-Meister

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    I used the champ chassis.
     
  6. Tom Kamphuys

    Tom Kamphuys Tele-Holic

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  7. panacea

    panacea TDPRI Member

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    I used a chassis from Mouser for my 6L6SE Harmonica Amp project, it was about 13 bucks. 13.5" x 5" x2" #546-1444-18. I would have rather had a slightly deeper box so I would provide more space for the faceplate in IMG_1266.JPG IMG_1267.JPG completeM.jpg the 5e3 style cab I built. This last pic is from the site where I found the plans, Lonewolf. IMG_1220.JPG
     
  8. pmacaula

    pmacaula Tele-Meister

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    PT - thanks on the Bypass Caps. I must have been getting dopey last night.

    Javier - thanks. I see the Champ chassis is 2 ⅝“ (H) x 8 ¾“ (W) x 4 ⅛“ (D), so quite a bit smaller than what I was thinking.

    Panacea - thanks. Nice job on the amps.

    TomK - thanks for the link. The info on component composition (metal film, etc) is great. I am less sure on Mr Aiken's advice on component Wattage ratings.

    For a 5E3M, isn't 5W/750V/1% for Voltage Dropping resistors pretty huge overkill ?
     
    Last edited: Nov 5, 2020
  9. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    This build is a *Micro*. I have not heard the micro in person but the youtube videos do not seem to promote the lows like a full size 5E3. I would still suggest a lower cathode capacitor but I am not sure I would change the coupling caps. The micro is a single channel amp so voicing the other channel is not an option.
    As Paul-T said the caps I suggested would replace the V1 25uF cap.
    A 10x6x2 chassis is big enough, IMO. Planning the location of the parts would be the only concern.
    The 2W and other values suggested by Rob are quite adequate. (Actually the dropping resistors could be 1W and the preamp resistors could be 1/4W. Smaller resistors are noisier though so I would stick with Rob's suggestions but the circuit will not burn up the resistors.)
    I would choose a 5W for the 10 ohm resistor for the headphone jack. The 3W may be fine by the numbers but I'd like a little more assurance in that area. OMMV.
     
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  10. screefer

    screefer Tele-Holic Silver Supporter

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  11. pmacaula

    pmacaula Tele-Meister

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    LLC - Thanks again.
    Screefer - thanks! I missed that. As 10x6x2 is the size I had in mind, that is good :) You also confirmed that aluminum is ok.
     
  12. MatchlessMan

    MatchlessMan Tele-Holic

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    Here's the 5E3 Micro I re-built recently (the original build had oscillation problems). I recycled the cab from an Epi VJ clone, and used a Hammond aluminum Chassis about 12in x 7in x 3in as this was the closest size to the original steel chassis (but I had to adapt it to fit the cage nuts). PT is from an old radio and the rectifier is solid state. There is loads of bottom end, even through an 8in Jensen. I expect I could mod some of that away with smaller caps as has ben suggested, but I actually like the fact that it is sounds like a grown-up amp.

    [​IMG] [​IMG] [​IMG] [​IMG]
     
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  13. pmacaula

    pmacaula Tele-Meister

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    MM - very nice job !
    I finally ordered all the parts this evening. Ended up having to buy from three different vendors (Hoffman, Mouser & TubeStore) to get all of the parts. Some parts were only available at one of the three, so I had to do some balancing to minimize shipping/customs/duty costs.
    Will start a build thread once everything arrives. Looking forward to it !

    The current plan is to build just the amp/chassis and to either plug into a speaker cabinet we already have or headphones. Once it is working, may make a cabinet to put it in (along with a suitable speaker).
     
  14. drneilmb

    drneilmb Tele-Meister

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    My 5E3 Micro is built as a head and I am a big fan of the variety that I get by plugging it into an open-back 1x12 or a closed-back 2x10. For a small, raucous tweedy amp, it's nice to have a couple of speaker voicings easily at hand.

    Can't help on the chassis. I'm such an ugly guy that I don't even try to make my gear look good!

    0104201921.jpg
     
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