Crack;Bottlehead OTL

Discussion in 'Headphone Amps (full-size)' started by ironbut, Mar 9, 2010.

  1. DavidA
    One vote for option C, its a nice contrast
     
  2. Paladin79
    Thanks David, I am leaning toward that direction. I can now get the proper level of patinization in about five hours and it is so much easier to not have to try for a high gloss copper finish. I will clear coat the top to maintain the shine and then start on the electronics. I have so many inputs and outputs on the back I will have a third side plate for AC input and power switch. The blade switch on the top will be functional but I will probably just use it to control the magic eye tubes in the front row.
     
  3. DavidA
    Do you have access to a photo studio or some where with a seamless background and controlled lighting? I'd love to see your creations in a nice product shoot since they are quite beautiful/imaginative in design.
     
  4. Paladin79
    IMG_2239.JPG IMG_2244.JPG I can probably get some better quality photos later on. I already shipped one amp to my son and my current build will be shipped out once completed as well but it is going to take some time. I have not thought through all of the electronics yet but at least all the tubes, jacks, and pots are in place. Right now it is mostly on my workbench cause it is a work in progress.

    My amps look a lot better if you stand back a ways and squint your eyes but I will see what I can do. Oh yeah if I get all the features going on this particular amp it will most likely be one of a kind unless the recipient wants to go into production on them, this is a bit of a beast to build quickly.

    Here is an example of patina that I achieve in about 5-6 hours. I need to brush off the excess and clear coat it but the process produces some wondrous colors.

    Here is also a top view with tube and transformer layout. The transformer covers have vents and I am using toroidal transformers. I still have to figure out some top vents for the top copper plate, mount and wire the blade switch, make a circuit board and then wire everything. Cabinet is twelve inches square and about six inches tall so I have plenty of room inside.



    Tom
     
    Last edited: Oct 24, 2017
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  5. FunyunBreath
    Finally finished the exterior of my build after a long time of kicking around different ideas, figured I'd post in here for inspiration :)

    IMG_0149.jpg
     
  6. Paladin79
    Nice job on the build. I particularly like the feet, I ordered a similar set in silver for a Crack I gave away.
     
  7. FunyunBreath
    Thanks! The cool thing is they looks awesome and they're actually pretty practical. I have a few power tubes that can be pretty microphonic and the feet isolate them really well from vibrations on my desk.
     
  8. Paladin79
    Do you mind saying where you got the feet? If not that is perfectly fine. Most of my builds are with copper or brass but I happened to do one in silver and black carbon fiber for my son and I have the feet coming out of China.
     
  9. FunyunBreath
  10. Paladin79
    Ahhhh I had seen some there and had not noticed the gold ones. I may grab a set for this amp, I just have sliders on it for the time being so I can easily turn it as I work on the build. IMG_2281 (1).JPG I rarely have trouble with the electronics but it takes me a while to decide appearance. This is not a basic crack build of course but it contains many of those parts and there are circuit similarities.
     
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  11. DavidA
    @FunyunBreath very nice build, also a great choice in the headphone :beerchug:
     
  12. wolfmath
    I'm having a little difficulty with my Crack. I've built it just fine, and it sounds awesome with my HD 650's. I am however having issues with the volume, and channel imbalance. Not a big problem, it's addressed in the Crack FAQ (I love the rhyme btw); it's numbers 3 and 4. I just don't understand the phrase, "Attach and solder one 33K resistor between each outer pair of lugs on each level of the volume pot and the ground lugs on the pot."

    Where are each pair of lugs on each level of the volume pot and the ground lugs on the pot? I've been staring at the underside of my Crack for a long time now (LOL), and I can't figure out where those resistors are supposed to go! Any ideas?
     
  13. Paladin79
    I do not have photos or drawings in front of me but as I recall, the two lugs on the right with the black wire going through them are the ground for that control pot. Notice they are on top of one another so to speak? A dual ganged pot is nothing more than two pots of the same type sharing a common control shaft. The grounds are joined together but the red and white wires going to the pots are the right and left channels respectively so you can consider them sharing the same control shaft just like the ground lugs. If you go from the red wire or the white wire to the ground lugs with a resistor, you are affecting each channel equally. This is not balanced audio so there is a common ground just like when you wire a 3.5 mm or 6.5 mm TRS connector and there are three connections. I have not used the stock pots permanently in any of my builds and you could also just eliminate that pot and go with a dual gang Alps 100k audio taper pot, or do what I did and use two single gang pots then you can control each channel independently. Just remember on the pot you are using, left and right lugs are lining up the same way the ground lugs are and you should be fine.
     
  14. gwompki
    That looks fantastic! Very similar to what I have envisioned for my own kit that is incoming. Do you mind sharing how you finished the case and the chassis? The finishing aspect is probably the part I dread most since I have so little experience with it :)

    Also out of curiosity, will I receive a tracking number once the kit ships? I ordered during the last sale so I know they got crushed with orders. I think mine should ship sometime in the next 2 weeks since it has been around 4 weeks since I placed the order. I'm very excited to put it mildly lol.
     
  15. FunyunBreath
    Man that looks sweet! What's under the hood on that?

    :) Thank you! Really liking the hd800s as well.

    Yup! I used Krylon black hammered spray paint on the top chassis, transformer bell, and volume knob (about 4 coats or so). The wood base was actually incredibly easy, it's not stained or anything. All I did was sand to 220 grit and then I finished it with Briwax creamed beeswax applied with 0000 steel wool (about 3-4 coats)
     

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