New anticipated Micro Champ build!

Discussion in 'Shock Brother's DIY Amps' started by dfrosto, Nov 3, 2019.

  1. dfrosto

    dfrosto TDPRI Member

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    Hi, fellow tube ampliphiles!
    I'm gearing up to make a Micro Champ, per Rob Robinette's website. I'm looking for any guidance you might be able to provide regarding ordering parts. I understand that it's widely recommended to order a kit for a first build, but I'm not aware that that's an option for the Micro Champ.
    So, I'm open to all input. What do you know now that you wished you'd known before you put your first order in, etc?
    Trying to save some heartburn by appealing to those who have already walked this path!
    Thanks- Steve
     
  2. sds1

    sds1 Tele-Afflicted

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    Parts shopping is hard, another skill that will be honed with experience. It's pretty much impossible to source all the parts from a single vendor. You will be placing multiple orders and then you should pretty much count on placing at least one more order later to account for parts you inevitably miss the first time around.

    Start with your bigger items first -- where will you get your board? Chassis? Transformers? You can try to get the smaller parts from the same places.

    Off the top of my head, for that amp you could probably get it done with Hammond trannies, Hammond chassis, and a generic turret board in two orders: Mouser and AES. A third order if you wanted a custom Hoffman turret board and a fourth if you wanted one or more non-Hammond transformers like ClassicTone, etc.
     
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  3. boredguy6060

    boredguy6060 Friend of Leo's

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    Ask Rob directly what he would recommend, you can’t go wrong getting info straight from the source.
     
  4. dfrosto

    dfrosto TDPRI Member

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    I've sent in my first orders for the Champ Micro , and as you said, I couldn't get everything from one vendor, which seems a little odd to me. No doubt there'll be an additional small order at some point. I found it a little baffling when tracking down resistors- metal foil? Carbon composite? I don't have any basis for a preference at this point, but at least they're inexpensive for the most part. Let the games begin! Meanwhile, I'm still trying to make sense of this schematic, etc.
    I couldn't locate a 39K, 2W voltage dropping resistor at either of the vendors I used. Any downside to using a 39K 3W instead? I bought a 33 K and 47 K in the 2 watt, not sure of the ramifications of going above or below the recommended values?
    Yeah... that's why you buy a kit!
     
  5. sds1

    sds1 Tele-Afflicted

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    Only the minor increase in size.

    Higher and lower supply voltages, respectively, at B+2 -- from 250VDC to 270VDC or 220VDC, more or less. Either way it's a fairly insignificant difference. If it were me I would not place a separate order just for the 39K...
     
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  6. King Fan

    King Fan Friend of Leo's

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    Good advice here. My $.02:

    Go slow. You'll have your whole life to enjoy the amp, and you want to enjoy the build process. Figure out if you want MF or CC resistors before you order 'em. Ditto every other decision. Planning is free and super-fun; fixing an amp that doesn't work can be expensive and super-frustrating.

    A micro-amp is 'simple' but not *simple.* You aren't finding a kit because these aren't common widely-built amps like the Champ. Hunt up every micro build thread and video you can. Look at every build pic -- collect 'em on your computer. And read a lot of standard Champ, 5f2a, and even 5e3 builds to learn about the dozens and dozens of choices and best practices for safety and sound.

    These little amps, not being totally standardized, actually give you a lot more choices, and choices are confusing. Every time you have a choice, ask here. If the answers aren't clear, explain what more info would help. Say we tell you it depends on what B+ you want -- ask about the effects of high or low B+.
     
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  7. dfrosto

    dfrosto TDPRI Member

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    sd1 and King Fan- Thanks for the responses! That's good info, and extremely sensible advice. I've decided to continue cipherin' on these little amps and not get ahead of myself!
     
  8. dfrosto

    dfrosto TDPRI Member

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    I've got most of the parts for the Champ Micro. Can you recommend a turret board for this model? One of the Champ Micro BOMs cites 30 turrets. The Champ style boards I'm seeing seem to have 25, any problem there? Thanks-
     
  9. dan40

    dan40 Tele-Afflicted

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    Rob's layout includes solid state diodes on the board itself whereas the original Champ uses a 5y3 rectifier tube for the rectification duties. This is the reason that his board needs more turrets than a standard Champ board. Since the amp is not available as a kit, you will need to build your own board or have someone like Hoffman make it for you. This is a very basic amplifier but it will require a bit of builder's knowledge to put it all together without a kit. You will need to drill or punch a chassis and figure out the proper placement for all of the related parts and components. Take your time and study as many build threads and pics as you can to get an idea of placement and building order for all of the parts. Hoffman also sells excellent hardware that you will need to mount the transformers and sockets. Stock up on 4-40 and 6-32 hardware because you will need quite a bit of it to mount everything properly.

    https://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Screws&ORDER_ID=!ORDERID!

    https://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&thispage=CustomBoard.htm&ORDER_ID=!ORDERID!
     
  10. Mongo Park

    Mongo Park Tele-Holic

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    I think you already orders, I use this place:
    https://www.justradios.com/

    You could go point to point, a style that is gaining popularity.
    Cheers Ron.
     
  11. Prophetsnake

    Prophetsnake Tele-Meister Silver Supporter

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    There's also a guy on eBay selling boards for Rob's amps. This is for a Deluxe micro, but maybe you could drop him a line and see if he has what you need.

    http://rover.ebay.com/rover/1/711-5...0001&campid=5338148343&icep_item=153437932473
     
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  12. dfrosto

    dfrosto TDPRI Member

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    Thanks for the suggestions! I've contacted the ebay vendor, I'll see what he says. I'm also looking at ordering a custom board from Hoffmann, or a Champ or generic turret board along with some extra turrets.
    I'm curious what other Champ Micros have used, trying not to reinvent the wheel here.
    One more question- is there any substantial advantage to using turrets over eyelets?
     
  13. Junior Little

    Junior Little Tele-Meister

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    Myself, I scratch build all of my boards and I prefer eyelets. They're just easier to deal with if any components need changing or mods need to be done. Yea, they might require using a extra board for backing, but they sure are forgiving.
    Of course, you're likely to get a range of opinions.
     
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  14. King Fan

    King Fan Friend of Leo's

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    Yep, and a small amp doesn't usually need the 2- or 3-story layering ability of a turret, and backside wires are simpler with eyelets, and best of all, eyelets/insulator boards are less likely than turrets and standoffs to get in the way of the offboard bits in a small chassis.
     
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  15. dfrosto

    dfrosto TDPRI Member

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    Thanks, @King Fan and @Junior Little, I didn't know that. I could probably use a more forgiving board. I contacted the ebay seller that @Prophetsnake mentioned, and he does have a Champ Micro board in his files. So, that's on the way.
    I'm building a large 10 x 6 x 2 chassis, to make it construction little easier on myself. Hopefully there's no downside to the roomier box?!
     
  16. King Fan

    King Fan Friend of Leo's

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    Good stuff. Smaller on the tubes, not the chassis. The standard Champ chassis is already way too "micro."
     
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  17. dan40

    dan40 Tele-Afflicted

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    No issue going with a slightly larger chassis. Many 5f1 builders will use a 5f2 chassis just for a little extra working room. Just be sure to place your transformer and sockets in roughly the same orientation of the original amps. This will ensure that you don't run into any surprises with the wiring layout that will cause issues down the road.
     
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