Bottlehead Crack

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by OJneg, Oct 3, 2015.

  1. AllanMarcus

    AllanMarcus Friend

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    Nice mod.

    Ok, I did more reading and I think I understand.
     
    Last edited: Mar 19, 2018
  2. dasman66

    dasman66 Almost "Made"

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    I just picked up a Tung-Sol 6AS7G untested for dirt cheap (I know, you typically get what you pay for, but for $10 I figured what the heck). The tube appears brand new, came in original box has Tung-Sol logo and date code on the base, but...

    Mine doesn't have the silver fins... I have all black fins. Mine also has "shields" on the bottom fins (which I don't see in Jeb's picture). I've googled and did find a photo or two showing tubes that look like mine, but is there reason to believe this isn't as advertised?
    [​IMG]

    Another question/concern... I get an arc inside the tube (with a pop) when powering up. I can't say that any of my tubes have ever done that. Problem?

    It sounds great otherwise. Both channels are strong and clear (more volume than my NOS Winged C), but right now I'm afraid to use it.
     
  3. Jeb

    Jeb Friend

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    @dasman66 - unfortunately, I think you're right to be suspicious. That looks like a rebranded RCA 6AS7g. The metal 'shields' at the bottom you mentioned are typical of the RCAs.

    I'm not sure about the light show and the popping you're getting on start up, but I'd be cautious about that too.
     
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  4. dasman66

    dasman66 Almost "Made"

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    Oh well, only $10... roll the dice, sometimes you win and sometimes you lose. The pop on power on has already taken it out of consideration anyway.

    Thanks Jeb... greatly appreciated. Also, your contributions to this thread are outstanding :bow:
     
  5. Melvillian

    Melvillian Friend

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    @AllanMarcus
    Hope the photo below of the board, the rectifiers, and where each point on the PCB is to be soldered helps. you're replacing the stock rectifier diodes(at top of photo) with the cree schottky CSD01060A. The PCB allows for clean installation of the rectifier bridge. Below are links for the diodes and the PCB.

    https://www.mouser.com/ProductDetail/Wolfspeed-Cree/CSD01060A?qs=/ha2pyFaduha8e7L7P6H8AQPAaWzRYR18hPNYjU5%2bzc=

    http://www.partsconnexion.com/product26996.html

    [​IMG]

    Edit** Forgot to mention that I drilled tiny holes at the very edges of the PCB and used plastic screws and nuts for installation.
     
    Last edited: Mar 20, 2018
  6. AllanMarcus

    AllanMarcus Friend

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    Perfect! Many thanks.

    Turns out parts connexion has the diodes too, so probably over all a few dollars less to get them one place.
     
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  7. Mban

    Mban Almost "Made"

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    Some slight mods for my Crack ;) (P.S. It's for sale if anyone is interested, contact me for details)

    [​IMG]

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: May 9, 2018
  8. CEE TEE

    CEE TEE Massdrop's Golden Child (MOT)

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    ^Looks awesome!!
     
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  9. Elnrik

    Elnrik Super Friendly

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    Very nice.

    Last 3 pictures are broken on Chrome.

    What kind of wood is that? I'd guess a rosewood, mahogany, or walnut.
     
  10. rtaylor76

    rtaylor76 Can't wipe his tag

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    Slight he says.
     
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  11. Mban

    Mban Almost "Made"

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    Black Walnut. Coated with boiled linseed oil.
     
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  12. Elnrik

    Elnrik Super Friendly

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    That's a gorgeous piece of Walnut. Good job
     
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  13. dasman66

    dasman66 Almost "Made"

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    anyway to see the other 3 pics? It doesn't work in internet explorer either...

    And... any shots of the guts? Looks gorgeous
     
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  14. Mban

    Mban Almost "Made"

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    Will retake the pics of the guts, and re-post the pictures soon.
     
  15. Cspirou

    Cspirou They call me Sparky

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    @Mban - What are the chrome obelisks and the three knobs you got there? And why did you add an XLR output?
     
  16. AllanMarcus

    AllanMarcus Friend

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    XLR is probably for convienience. Nice upgrade.
     
  17. Mban

    Mban Almost "Made"

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    Top knob is coarse volume steps, bottom 2 knobs are fine volume steps for left and right channels. XLR is purely for convenience as I have one of my HD650 currently wired for balanced. The polished aluminium obelisks are oil/wax filled polypropylene caps. Big ones are 100uF, small ones 15uF. These caps are in the high voltage power supply for filtering (instead of using electrolytic as used in the stock crack).
     
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  18. Mban

    Mban Almost "Made"

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    Shots of the guts. Transformer is nearer to the front of the amp.

    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: May 11, 2018
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  19. Mban

    Mban Almost "Made"

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    Larger transformer has benefit of being able to run this beast:
    [​IMG]
    [​IMG]
    [​IMG]
     
  20. Cspirou

    Cspirou They call me Sparky

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    Is that an Antek transformer? Looks like you didn't really make a Crack but a Crack Clone. Nice job! I have all the parts to make a similar one.
     
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