5f1 build: dummy load ?

Discussion in 'Shock Brother's DIY Amps' started by Mfa88, Feb 21, 2020.

  1. Mfa88

    Mfa88 TDPRI Member

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    Hi everyone

    I'm close to being done with my 5f1, so I wanna prepare the first start up. I have read that some uses a dummy load for this. Do you know how that is made ? Is this simply a resistor on a jack plug ?

    Also, do you think I can use my vox ac30 cabinet as speaker for this amp? It has Celestion G12M Greenback 12" (8Ω) x 2

    Thanks.
     
  2. tizianod

    tizianod Tele-Meister

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    In essence... yes, it's a power resistor or a set of power resistors. The values are chosen so it matches a specific load and power rating based on the amp its values. There are also a couple of youtube videos online, which explain in detail how to build them.

    Aiken has some handy schematics for building dummy loads. Here is the link: https://www.aikenamps.com/images/Documents/DummyLoad.pdf
     
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  3. Nickfl

    Nickfl Tele-Afflicted

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    You don't need a dummy load for startup you just need a speaker. The only time you really need a dummy load is if you're using an oscilloscope and a signal generator and you don't want to have to listen to the test signal.

    Here is a practical startup guide for your first build: https://robrobinette.com/Tube_Amp_Startup.htm
     
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  4. Mfa88

    Mfa88 TDPRI Member

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    Thanks. Do you think my Vox cabinet would work or do I risk damaging it?
     
  5. Nickfl

    Nickfl Tele-Afflicted

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    It depends,You want your speaker or speakers to provide the impedance your amp was designed to work with. What impedance was your 5f1 built for? Usually combos are 8ohm, sometimes 4, rarely 16. If your Vox cab has two 8ohm speakers, then it is either 4ohm (if they are in parallel) or 16ohm (if they are wired in series).
     
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  6. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    If it's a standard 5F1 build, I believe you'll need a 4 Ohm speaker. I liked the 8" ceramic WGS; you can pick one up directly from WGS or go through StewMac to save yourself a little on shipping, maybe.

    Actually, I just replaced that speaker with the AlNiCo version...awesome speaker. Both are nice but the AlNiCo is a little pricey!
     
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  7. Mfa88

    Mfa88 TDPRI Member

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    I believe the 5f1 is 4 ohm, 5 watts. I see on the back of my vox too that I can choose between a 16 and an 8 ohm output.

    So I guess that mix is not the best....
     
  8. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    Have you decided on a cabinet yet? Might as well start thinking about it and purchasing a speaker too. ;)

    You'll want to have that thing up and running so you can start to play through it!
     
  9. Mfa88

    Mfa88 TDPRI Member

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    Hi,

    No not really actually. I have read a few places about Jensen and Weber speakers...
    Would like to build my own very nice looking cabinet :)
     
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  10. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    Good luck to you on your build! You'll have as much fun making the cabinet as you did putting the chassis together, I'm sure.
     
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  11. Paul G.

    Paul G. Friend of Leo's

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    WGS has an 8" ceramic that you might consider. I have never heard a WGS model that wasn't really well-made and good sounding.
     
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  12. dunehunter

    dunehunter Tele-Holic Double Platinum Supporter

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    So far, I've used an Oxford (the original speaker in my SFDR), Weber (the foursome in my 5F6A Bassman clone), and a variety of WGS speakers. I've got an old Jensen 12" AlNiCo that I'm going to have reconed soon, but have not yet heard it. I've heard the modern Jensens and I'm a little cold on them (personal taste).

    In the end, I'm a big fan of the wide variety of WGS speakers I've bought and used including both the 8" ceramic and the AlNiCo version of that same speaker. The latter is clearly more articulate in my 5F1 Clone.

    But in the end, speaker choice is highly personal--just like the choice of amp driving them and the guitar in front of the amp:)
     
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