Bottlehead Crack

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

  1. elmoe

    elmoe Friend

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    Interesting, I rolled all my old 6sn7s (Sylvania vt231 bad boys, Ken rads vt 231s, NOS Tung sols, NOS RCAs and a bunch of others) but still stuck with the Siemens 12au7 in mine. It always sounds better than the 6sn7s I tried to my ears.

    Really like the rail idea. What's the third RCA for in your build? And what did you add next to the power cable connector there, I can't tell, looks like a 12V input maybe?
     
  2. m17xr2b

    m17xr2b Friend

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    The third RCA input is for the remote volume control, but that will be used on the other speedball crack build and couldn't leave an empty socket in this case.

    Next to the power connector is a vintage style fuse holder.
     
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  3. elmoe

    elmoe Friend

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    Aha, gotcha!! What kind of remote volume control are you implementing? I've been looking to add one to my MPX3 but I haven't settled on anything yet. I've been looking at possibly going with a Goldpoint stepped attenuator and a remote kit from bent Audio http://www.bentaudio.com/parts/step.html but the prices are steep...
     
  4. m17xr2b

    m17xr2b Friend

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  5. m17xr2b

    m17xr2b Friend

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    I'm really surprised by this Crack. Even if it's non speedball it sounds better than the speedball version ever did.
    The Mundorf evo oil caps I disliked before have none of the darkness I heard before. I've also put a 100uf Mundorf Mcap bypassed with a 1.2uF clarity cap as the last one in the psu.

    The amount of detail this thing can extract is ridiculous. I've always thought of the crack as a slow warm amp.
    Separation is up there with the best, extension especially at the top with a Bendix and Sylvania 6F8G is kind of hard to believe. Neutral in the mids, tons and tons of detail with very little sign of grain. Love how cymbals shimmer. Soundstage isn't the largest but still feels spacious with every instrument in its distinct place. Even with fast paced music it keeps up easily.

    I wonder why(better components)?

    [​IMG]
     
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  6. elmoe

    elmoe Friend

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    First off, that amp is gorgeous. I really like how you got the wood to look.

    Components made a big difference in my build. Switching out output caps in particular really took the amp to another level. That being said, I also use a Bendix tube and to me ears that made the biggest difference, even more so than the 12AU7s I rolled, comparing it to the stock 6080. That tube in that amp is a very very good match.
     
  7. m17xr2b

    m17xr2b Friend

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    I've used the same tubes and caps before but it didn't sound as good. The OG crack wasn't built by me. I suspect the upgraded wiring and resistors might have something to do with it.

    Bendix 6080 slotted is my nr.2 tube, only surpassed by the GEC 6AS7G. It has slightly more detail than the bendix but rounder edges in a good way so it sounds more musical.
    Poping in the GEC is dangerous especially at night, it's hard to stop listening and turn it off.
     
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  8. elmoe

    elmoe Friend

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    You're killing me, now I'm gonna have to hunt one down... ;)
     
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  9. m17xr2b

    m17xr2b Friend

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    The crack is finished. I'm still shocked at how good it sounds without speedball. The Apex Teton has the same topology as the stock crack only with a much better power supply and running the tubes at higher bias I'm sure.

    The huge output caps are russian 100uf KZK white line. Performance wise they sit in between the Mundorf MCap and Evo Oil. They don't have the richness of the oils but at less than half the price it's hard to complain and are miles better than the electrolitics.
    I love the fact it's dead silent, with the headphones plugged in, switching it on I can't hear any difference in background.
    This little piggy will soon go to the market.

    [​IMG]

    [​IMG]
     
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  10. m17xr2b

    m17xr2b Friend

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    Fresh from vacation I started the second crack. Diverging from the standard build takes exponentially more time for the small bits.

    Took 12 hours to reach this point:
    [​IMG]

    Custom support for the PSU
    [​IMG]

    20 hours later I was ready for the first switch on.
    [​IMG]

    Worked from the first go. 5 hours later the PSU was ready:
    Jensen 2x220uF screw terminal electrolitics, 3x50uF Jensen oil, two UK made chokes and cree diodes.
    [​IMG]

    The SQ jump from the standard electrolitic to the oils was significant. Next up speedball:
    [​IMG]
    [​IMG]

    Increased depth and size of soundstage, more dynamics but overall the jump wasn't as significant as the psu upgrades.

    Output cap upgrade with more oil.
    [​IMG]

    The biggest sonic benefit and completes the amp. Makes sense as the output caps were an obvious bottleneck and this lets all the components shine.

    I have four other mods in mind but I'll want to enjoy and familiarise myself with the sound.
    I used star grounding instead of daisy-chaining because I didn't want to use the top plate as signal ground.
    The build was carefully planed over the past months to make sure I use as much of the space as possible.

    The power transformer is a custom ordered Sowter 50VA and I want to let it and the other new components burn in for a while.
     
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  11. JeffYoung

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    Yeah, that's my one beef with the Bottlehead designs. But at least it's easily corrected.
     

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