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Pics of my newest project - KT88 SET Amp

PWRRYDPWRRYD
in DIY
I was able to finish making the hickory case before the weather turned cold here.  The top aluminum plate is 0.090" thick and is painted with Duplicolor 500F engine paint.  The color is cast iron blast.  Boy that stuff has terrible fumes but has a really nice finish!  Probably should have been wearing a respirator.  Anyway, here are some pictures of my progress so far:


MzissersonD1PP1Ngreywarden
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Comments

  • PWRRYDPWRRYD

    MzissersonD1PP1Ngreywarden
  • PWRRYDPWRRYD

    MzissersonkennykD1PP1Ngreywarden
  • PWRRYDPWRRYD

    MzissersonkennykD1PP1NR-CarpentergreywardenScottSjhollander
  • isaeagle4031isaeagle4031
    Wow! Nice work Craig!
  • PWRRYDPWRRYD
    Oh and that ugly volume knob is just temporary.  I plan to turn a custom aluminum knob as well as some nice feet.
  • MzissersonMzisserson
    Awesome! I love amps with KT88's.Just a great sounding tube. 

    I always wanted to get another pair of Quicksilver Mini-mights. 25 glorious watts of Ultralinear KT-88 operation....and a 12au driver. 

    Kit?  More details? 

    Very cool.
  • PSchumacherPSchumacher
    Gorgeous.

    Why not turn a wooden volume knob to match the case?
  • PWRRYDPWRRYD
    I have a metal lathe at work is why I was thinking aluminum.  But I bet a small wood lathe from HF would be affordable.
  • PWRRYDPWRRYD
    Hi Mike,
    This is a scratch build, point-to-point wired, and is a circuit roughly based on a design Mikael Abdellah published in 2003.  I say roughly because I have redesigned the first stage to use a 6DJ8 triode.  I've also significantly changed the power supply design as I think it is nearly as important to the sound of a SET amp as the output tube and output transformer are.  Output power will be about 12 wpc in Ultralinear mode (a toggle switch will select UL or triode mode). I prototyped the circuit and it sounded great!
    Mzisserson
  • MzissersonMzisserson
    Wow! That sounds wonderful! I agree on the power supply. 

    Now the DIY-er rares its head.....Since you have done all the hard work, you gunna share? :dizzy: 
  • ani_101ani_101
    Does the top plate has to be aluminium? Or can I use some thin 1/4 or 1/8 ply? 
    Mzisserson
  • PWRRYDPWRRYD
    IMHO it needs to be metal.  The tubes get hot, very hot.  I use aluminum because it's easy for me to drill, cut, file etc.  For a quick prototype I have used a thin piece of galvanized sheet metal (HVAC duct).  I've seen steel, stainless steel, and aluminum used.  
  • PWRRYDPWRRYD
    Right now the circuit is hand drawn and the BOM are on graph paper.  When I get it done working I'll do a final BOM in MSExcel and a nicer looking schematic in Visio or AutoCAD and share.
    kennykMzissersongreywardenS7910
  • PSchumacherPSchumacher
    PWRRYD said:
    I have a metal lathe at work is why I was thinking aluminum.  But I bet a small wood lathe from HF would be affordable.
    A few of these stacked up could work nicely . . .

    https://www.amazon.com/Wood-Round-Disc-inches-pieces/dp/B0085TFL48

  • FaceFace
    PWRRYD said:
    I have a metal lathe at work is why I was thinking aluminum.  But I bet a small wood lathe from HF would be affordable.
    A few of these stacked up could work nicely . . .

    https://www.amazon.com/Wood-Round-Disc-inches-pieces/dp/B0085TFL48

    Or even better: https://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias=aps&field-keywords=hickory+dowel&rh=i:aps,k:hickory+dowel

  • hongrnhongrn
    Man, that's my next thing or things to learn: how to build a tube amp. Nice work Craig!
  • D1PP1ND1PP1N
    Its got a nice shine on it too craig. good work.
  • PWRRYDPWRRYD
    I was able to mount the power and output transformers.  Those O/T are huge, rated for 25 watts, and weigh 9 pounds each.  Even though the power transformer looks small compared to the O/T, it is actually over sized for the application and will run cool.


  • PSchumacherPSchumacher
    OTs have to be big to run to 20Hz without saturating.

    Looking good!  Where did you acquire the iron?
  • PWRRYDPWRRYD
    The output trannies are Edcor CXSE25-8-5K.  The power tranny is an Allied unit manufactured by Hammond.
  • PWRRYDPWRRYD
    I couldn't wait to see how the whole top is going to look so I just set the front power supply cap and the octal tubes in place (no sockets installed yet):


    MzissersonkennykJasonPS7910ThumperTom
  • MzissersonMzisserson
    OHMERGERD That this is beautiful. I was happy for you at first, now I am just jealous. ;)
  • ani_101ani_101
    That is real nice. Do you have a ballpark for cost of components?
  • R-CarpenterR-Carpenter
    ani_101 said:
    That is real nice. Do you have a ballpark for cost of components?
    I have even a better idea. Make that thing as a kit and I can CNC Al board and make wooden parts.
    Anyone for group buy? I wouldn't be looking to make money on machining, Cost only.
    kennykMzissersonThumperTomjhollander
  • ani_101ani_101
    I would like to get one (but not immediately - still underwater from holiday shopping... and the bills are yet to hit!). Getting the AL machined would be great - I haven't yet tried machining AL. Though i should give it a try. 

    Roman, do you have any tips for AL CNC? (on a regular wood router CNC)?
  • FaceFace
    ani_101 said:
    Do you have any tips for AL CNC? (on a regular wood router CNC)?
    Yes, wear ear plugs!
    R-Carpenter
  • isaeagle4031isaeagle4031
    I might be up for a group buy on this!
  • kennykkennyk
    Hmmmmm, I all in for a group buy.
    ............. could you hum a few bars.
  • MzissersonMzisserson
    Take my fuckin' money!
  • MzissersonMzisserson
    R-Carpenter said:
    ani_101 said:
    That is real nice. Do you have a ballpark for cost of components?
    I have even a better idea. Make that thing as a kit and I can CNC Al board and make wooden parts.
    Anyone for group buy? I wouldn't be looking to make money on machining, Cost only.
    Even though this is a modification to a pre-existing design, I think whatever the kit cost is (if it goes that way and we have enough peeps) enough should be built into each kit to cover a "free" kit for Craig as a thank you and to cover the original he built. We have to spread some love, somehow, no?
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