Bottlehead Crack

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

  1. OJneg

    OJneg The Most Insufferable

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    cont from the last forum: http://www.changstar.com/index.php/topic,2799.0.html
    1. @Jeb's 6080 tube overview: http://www.superbestaudiofriends.org/index.php?threads/bottlehead-crack.120/page-3#post-13651
    2. @Jeb's 6AS7 tube overview: http://www.superbestaudiofriends.org/index.php?threads/bottlehead-crack.120/page-3#post-13711
    3. @Jeb's 12AU7s & variants overview: http://www.superbestaudiofriends.org/index.php?threads/bottlehead-crack.120/page-3#post-17100
    4. @gurubhai's 6080/6AS7 tube overview: http://www.superbestaudiofriends.org/index.php?threads/bottlehead-crack.120/page-4#post-18828
    5. @Hands' driver tube overview: http://www.superbestaudiofriends.org/index.php?threads/bottlehead-crack.120/page-5#post-21230
    6. @Jeb's Crack Modding Notes: http://www.superbestaudiofriends.org/index.php?threads/bottlehead-crack.120/page-7#post-36762
    [​IMG]

    My brief thoughts on the Crack I have. Thanks to /u/DeletetheWeak on /r/headphones for loaning it out to me :)

    -------------
    DRIVER TUBES
    -------------
    Baldwin 12AU7 = Overly smooth, not engaging enough, not enough attack.
    GE 5814 = Bit more attack up top, more alive. Has a certain etch. Not as fast and clear as HK. Somewhere in between MW and HK.
    MiniWatt ECC82 = Neutral w/ HD800. Euphonicly sweeter in mids. More dynamic. Images are most focused. Favorite of the bunch.
    Harmon Kardon ECC82 = More upward tilt. More tense than Miniwatt. Wider stage but less clear in between. Less bass punch than MW.
    ------------
    OUTPUT TUBES
    ------------
    USN Chatham 6080WA = Slightly lusher. Love guitars coming into focus. Vocal immediacy. Meetier
    TungSol 5998 = Bass is on weak side. Start to notice slight hardness (think upper mid) in this tube (not necessarily the tube's fault). Wider stage, killer stage actually. More dynamic and extended up top. More alive
    JAN Philips ECG 6080WC = Lacking clarity. Perhaps slightly less thick than WA. Bass is not very dynamic
    -------------
    CAPACITORS
    -------------
    Mundorf Mcap = Sounds great as far as I can tell. Nothing to AB to.
    ???
    ???
    -------------
    ATTENUATOR
    -------------
    Stock open frame pot 100k = lacking extension on both ends. worst part is weak bass. Awful channel imbalance
    TOCOS Cosmos 10k = Much better bass, perhaps getting slightly accentuated/warmish. Still slight channel imbalance on low levels
    Alps RK27 50k= A bit dead up top. Funny sounding.
    VALAB Stepper 100k = Solid sound. Maybe slightly smoother nature.

    ------------
    POWER SUPPLY CHOKE
    ------------
    Triad 10H 90mA = More dynamic, cleaner sound allows deeper stage to see through. Kills a wee bit of hum on the highest end of the knob. Highly recommended overall


    ------------
    CONCLUDING THOUGHTS
    ------------

    The Crack maintains its warm sound regardless of tweaks and tube rolling. In this build, I found the treble could range from more laid back to more snappy depending on tubes. I recommend the 5998 tube over all the other output tubes, and then picking the input tube based on your preferences. The Crack is mostly held back by its lack of resolution and inner detail. It's the one quality that keeps me from saying this could be an end-game amp for HD800 dorks. Other than that the Crack has a great tone that matches well with the Sennheisers (and Beyers). Staging and dynamics are excellent as well. In that past I've only heard stock Cracks which sounding like they were dragging their feet through mud. Now that I've got to spend time with a fully tricked out Crack I can say that the hype is justified.

    Eager to hear other folks thoughts on this amp. Run wild :cool:
     
    Last edited by a moderator: Feb 27, 2016
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  2. Armaegis

    Armaegis Friend

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    Do you think there are any further mods which can improve the resolution?
     
  3. OJneg

    OJneg The Most Insufferable

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    I can't think of anything else to do.
     
  4. dubiousmike

    dubiousmike Friend

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    Great post OJ and thanks for reporting back on the choke mod! Sounds like I will have to add that to my list.

    The only other potential mods I know of that may or may not improve resolution, which I agree is crack's primary weak point, are the speedball resister switch mods to facilitate running (arguably) better input tubes, at proper operating points, and adding a dc supply for the tube heaters. Otherwise, you are in the realm of wholesale psu redesings along the lines of crackatwoa.

    Crack also doesn't quite have the ultimate refinement (particularly in the trebles), transient speed or bass tightness of really high end amps - but it already punches so far above its price that these nits should go without saying. Bass can be adjusted somewhat through high transconductance output tubes (eg 7802 has even higher transconductance/lower output impedance than 5998s and 7236s), but you are trading amplitude for control. The GEC 6as7gs really are the best standard 6as7/6080 varient, but the pricing is just stupid for something that is only a subtle upgrade on a chatham 6080 - which I think you have described perfectly above. (I own one of the former and a couple of the latter.) Many will prefer 5998's anyways for their liveliness and holographic sound stage - and sexy looks.

    In any event, thanks for inspiring me to get on with implementing the choke and speedball resister switch mods. Think I'm going to pick up an amperex e80cc PQ to go with the latter and see how it compares to my excellent tung sol 12bh7.
     
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  5. gurubhai

    gurubhai Friend

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    Upgrade the rectifier diodes - I used MUR460 in my amp to great effect(had few of them lying around), though MUR160 should suffice.
    You might also want to try upgrading the wire-wound power resistors, iirc the stock amp uses those white brick types which aren't all that great.

    P.S. I am a bit surprised that the choke makes that much of a difference in a speedballed amplifier, would have expected the CCS to shield from the effect of power supply.
    Good to know!
     
  6. OJneg

    OJneg The Most Insufferable

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    Speedball gets rid of those

    Choke definitely killed some hum. Also found it to improve sonics FWIW. Not too surprising given I know the choke in the Torpedo improves things.
     
  7. Cspirou

    Cspirou They call me Sparky

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    Bottlehead actually offers a premium version of the Crack called the Crack-a-two. The basic circuit is the same but also includes CCS loads and high voltage shunt regulation of the power supply. The input is is upgraded as well with 3 inputs and an added balance control, something needed with potentiometers because of channel imbalance. This can be upgraded to a stepped attenuator.

    Price is around $600.
     
  8. fishski13

    fishski13 Friend

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    OJ, the paint scheme on the TX suggests like you have a secret flux capacitor mod that could do some serious Jiggawatts. does it glow in the dark? that poor lonely RK27.

    [​IMG]
     
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  9. dubiousmike

    dubiousmike Friend

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  10. gurubhai

    gurubhai Friend

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    I am all for chokes and also think that they improve sonics and impart a more blacker background. They are quite bulky though so I was wondering if a CCS could allow us to get away without using a choke. Your experiment confirms that it doesn't which is, like I said earlier, good to know!
     
  11. Freddy1201

    Freddy1201 Rando

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    Hello,

    my system is : yggy-->lyr 1 with 6n1p-->modded hd800

    I cannot afford a end game amp for the moment, so do you think the bottle head crack will make a significant upgrade or a sidegrade?
     
  12. Bill-P

    Bill-P Level 42 Mad Wizard

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    Crack will be an upgrade in terms of tonality, I think, while it'll also simultaneously be a slight downgrade in resolution/detail retrieval. In your case, I'd highly recommend the Speedball upgrade.
     
  13. OJneg

    OJneg The Most Insufferable

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    if you do stock Crack yes. Fully-pimped Crack is a different beast
     
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  14. audiofrk

    audiofrk Guest

    Oj

    Crack vs torpedoe
     
  15. Bill-P

    Bill-P Level 42 Mad Wizard

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    I did get to hear a fully pimped Crack, and yeah, I agree. Though the problem is keeping the stock tonality the same. I've heard a fully-decked out Crack that basically has... new everything, including solder type (really?), and it just sounded so very different from stock Crack. Not in a good way either. Stock HD600/650 were the only headphones that would play nice with it. Everything else would be kinda thin/lean/bright sounding, even a modded HD600. So it would kinda defeat the purpose of the Crack IMO.

    On the other hand, maybe it'd be worthwhile if you could somehow maintain the stock tonality while improving on other things. I'd seriously LOVE a Crack that has higher resolution. That would seriously kick ass!
     
  16. kapanak

    kapanak Canucklehead - Friend

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    What you seek does exist ... Apex Teton. 10x the cost though.
     
  17. Bill-P

    Bill-P Level 42 Mad Wizard

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    Need to hear it first to confirm. But I've had my suspicions since Pete Millet tuned that amp, and I kinda know from the TTVJ Portable Tube Hybrid amp that his tuning does have a flavor very close to Crack (but not quite like a "portable Crack").
     
  18. Jeb

    Jeb Friend

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    I just finished watching Tyll's latest video on the Big Sound experience. It was fun to see he briefly gave the Bottlehead Crack/HD-600 system an honourable mention - putting it into context with all the expensive equipment.

    I've been running the stock-crack with HD-650s for the last few months & thoroughly enjoying it, experimenting with many different tubes. I'm just at the point where I'm ready to add the speedball, a new volume pot and then some different capacitors & a choke. I'm looking forward to seeing what happens - I would certainly enjoy a bump in resolution and tightening of the low-end but I guess I do wonder a little about losing the tone I have enjoyed so much.

    Still, only one way to find out... and if I don't like it I can always remove it.... or build another! Prior to building the Crack I had zero experience with electronics - It's been a really great, confidence building experience. I don't think I'm going to become a serial DIY'er but it has certainly helped me re-evaluate some of my other gear as well as being a small step in de-mystifying what goes on inside all these little boxes.
     
    Last edited: Oct 15, 2015
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  19. Freddy1201

    Freddy1201 Rando

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    Is the resolution/detail similar with the speedball upgrade??

    Meaning speedball or with other mods??;)
     
  20. OJneg

    OJneg The Most Insufferable

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    My Torpedo is on tour and currently waiting for Ni-core Cinemag transformers to replace the Edcors. Once it comes back around to me I'll do a comparison

    Resolution and detail get picked a notch up with Speedball. I don't recommend Crack w/o Speedball FWIW
     
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