My first amp build (Deluxe Reverb) questions

Discussion in 'Shock Brother's DIY Amps' started by Greg M, Apr 13, 2019.

  1. Greg M

    Greg M Tele-Holic

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    I'm planning and sourcing my first amp build and have a few questions for you seasoned pros. I'm sure this won't be the last time I pick your brains/ask for advice either.

    If the amp plan calls for 16uF 500V electrolytic caps, I'll assume 475V won't do?

    Are these carbon comp resistors suitable for an amp build? https://www.mouser.com/ProductDetai...aPJPXcftGCnd9KA/IzCLRYLUIDeMg/Sy6qO1d4fJMV2nK

    Those are 27 cents each and the ones at Mojotone are like $3.50
     
  2. boredguy6060

    boredguy6060 Friend of Leo's

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    The ones from Mouser are rated at 350v, you should have higher rated resistors imho.
    Mojo tone is not the place to get components Mouser is very good and they have a vast catalogue, but there are many others too. I think it best to deal with sellers who only sell components.
    Good luck.
     
  3. Greg M

    Greg M Tele-Holic

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    Any advice on other sellers I should look into, specifically?
     
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  4. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Regarding the cap rating, it will depend on the power transformer you're using. 475 VDC / sqrt(2) = ~336 VRMS. So if the PT is something like the ClassicTone 40-18016 with 330-0-330 secondary, this is probably cutting it a bit close. 330 VRMS will produce a nominal rectified DC bus of 467 VDC (at first filter cap).

    But I'll defer to the seasoned pros, because as you can see, I'm new to the forum and this amp building business. Accumulating parts for my own first build - 5E3. I'll be joining you on this great forum with questions!

    Best...
     
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  5. boredguy6060

    boredguy6060 Friend of Leo's

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    Oh, on the E/caps, if they call for 500v, get at least that much if not more, like 600v.
    Always over build when the option is available, but never under build, you’re just asking for trouble.
    Good luck,
     
  6. boredguy6060

    boredguy6060 Friend of Leo's

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    Welcome,
    All knowledge is good, nobody cares how many posts you have. If you have something to say or contribute, don’t let your seniority hold you back.
    You sound like you know more than most, glad to have you.
     
  7. King Fan

    King Fan Friend of Leo's

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    Are you looking at F&T caps? I've only used their 475V-rated caps in smaller amps, where they're very highly regarded. I'll be curious to see if anyone would use them in a DR -- I kInd of assumed the rating was just super-conservative, but I claim no insight.

    I imagine most carbon comp resistors are much the same; FWIW I can find CC resistors at Mojo for 41 cents.

    The huge parts places like Mouser may save you a few dollars, but the search/filter steps can kill you on a big project like a DR, and I've sometimes ended up ordering what turned out to be a weird specialty item when I wanted 'the usual.' I like smaller amp-specific sites like Hoffman, AES, or TubeDepot to easily find typical guitar-amp parts. Hoffman in particular carries much of what you need and ships super-fast and very inexpensively.
     
  8. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    Thanks for the encouragement, boredguy! I'm blown away by the amount of knowledge available and shared on this forum...
     
  9. schmee

    schmee Poster Extraordinaire

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    -Yes get the higher voltage on the E caps. 20uf are fine in a DR. Atom caps are nice but too expensive and they are much smaller inside the blue can than the can anyway.
    -CC resistors are fine, personally I prefer metal oxide as they often rate closer to spec and dont get noisy over time. But traditionalists like the CC. I dont order less than 1 watt, although Fender specified 1/2 watt for many. Metal oxide are expecially good under the doghouse or etc.
    -I would buy a chassis and faceplates from a supplier and spec my own other parts.
    -Dont scrimp on Jacks, ONLY Switchraft.
    -Mojo's chassis are nice and sturdy, their faceplates are heavy thick steel though. Standard length Jacks and pots are barely are long enough to get a nut on with their faceplates, but usually work.... unless your star washers are too thick.
    -Remember to get plenty of star washers for post and jacks.
    -CE Distributing (AES) is a good source and much easier to use web site than Mouser.

    -There's a lot of BAD push back wire out there, it frays if you look at it wrong. You are trying to build a nice neat unit and by the time you're done the wire ends are terrible. I like waxed cloth wire from Marsh amplification: http://store.marshamps.com/index.php?cPath=69
    -BTW, 22 gage wire (like all the rest wire in the amp) is fine for the green heater wire and the 18 gage is hard to deal with and puts stress on today's cheap tube socket solder tabs.
     
    Last edited: Apr 13, 2019
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  10. King Fan

    King Fan Friend of Leo's

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    Good one. I like green for heaters but as you say the 18ga is just too hard to wrap into socket lugs.
     
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  11. muswell_hillbilly

    muswell_hillbilly Tele-Meister

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    I overlooked the voltage drop across whatever rectifier you're using :(

    This is also important to know when considering component rating. A solid state full wave bridge rectifier (which I'm fairly certain you're not using) will drop as little as 1.5 V, while tube rectifiers will drop anywhere from 10 V (GZ34) to 60 V (5Y3). So a 330-0-330 PT output through a 5Y3 rectifier diode will present something closer to 400 V (nominally) to the first filter cap - unloaded (330*1.414 - 60 = 407).

    As boredguy correctly stated, it's better to go for over-rated than under. But for me, it's also helpful to understand what the rating is based on, which puts me in a better position to make a judgement call like you originally posted.
     
  12. David Barnett

    David Barnett Doctor of Teleocity

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    Mouser is an excellent vendor, the problem is that there's a vast selection and no guidance, so you have to know what you're looking for.

    The smaller specialist DIY audio vendors with easy-to-navigate web shopping probably get most of their components from Mouser. :)
     
  13. Teleguy61

    Teleguy61 Friend of Leo's

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    At 47 ohms, is it in the power supply rail?
    1/2 watt is not large enough.
    With Mouser, it is very important to check the in-stock status of each item before ordering. This particular item is back-ordered, to the tune of 24,000 units.

    I suggest
    https://hoffmanamps.com/.
    Doug has many tried and true parts for tube amp building, and his service is top shelf.
     
    Last edited: Apr 14, 2019
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