Bottlehead Crack

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

  1. m17xr2b

    m17xr2b Friend

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    It's not about big caps per say, trying out the different types as I'm not about to roll the same build of capacitor from all companies, that madness is solely for the tube rolling maniac.
    I'm trying to get a good grip of how each sound in different positions besides the it's better aspect: basic electrolitic, audio electrolytic such as jensen, unicon etc, above mid level film with the clarity TC and the oils with the jensens 50uF and mundorf aluminium.
    I do like the go big part, it's cheaper to buy good from the start than to upgrade and be left with unwanted parts.

    As I mentioned in the DNA thread yes, that's why I have the big caps, the gyrator and SiC boards but now I'll surely build another set for the crack.
     
  2. Azimuth

    Azimuth FKA rtaylor76, Friend

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    Those caps actually have a bigger impact because they are not power supply cap upgrades, they are IN the audio path.They are the last thing before getting to your headphones as such with AC coupling.
     
  3. penguins

    penguins Friend, formerly known as fp627

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    Can anyone recommend a DIY amp similar to the Crack sound-wise with the following:

    - OTL - specifically want an OTL sound signature for use with 300ohm HD6xx and ZMF Auteur drivers
    - Similar relax-fi, easy listening / non-fatiguing sound without dissolving into warmpoo, punchy-poo, etc.
    - Compatible with same tube families (12au7 and 6080) if possible - I want to use existing tube inventory
    - Total expenditure under ~$500 - rough cost of previous modded crack build
    - Similar footprint and heat signature - I don't want a space heater

    - Readily available components - I don't want to hunt for holy grail tubes, transistors, test batches of 100+ to find a good unit, etc.
    - OK with a slightly more complex or technically complicated build, possible troubleshooting required, etc.
    - OK with metal or plastic housing instead of wood, but I don't have easy access to machine shop equipment if I need to machine a custom case or even just drill holes, etc.

    I may move this post to the DIY sub-forum but figure this would be a good place to start.
     
  4. m17xr2b

    m17xr2b Friend

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    You've basicly described the Crackatwoa. Other than that you'll have to be creative and draw your own schematic to build. Bottlehead is unique in what it offers, it's an itch only a bottlehead kit can scratch.

    Myself, I'll go solo to satisfy the need, the schematic research has been so much fun over the past months. Now unexpected chassis complication as in, I didn't expect to have to think about it, layout where and how. Overcoming the challenge is part of the fun.

    Keep in mind, the Teton a super amplifier isn't that different than the crack, overbuilt psu and posh components but the signal basics are about the same.
     
  5. penguins

    penguins Friend, formerly known as fp627

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    Sounds like I'll have to do research on it later then.

    Didn't get the crackatwoa as it needed more tubes, was a bit bigger, and didn't want to spend $950 for the kit with stepped attenuator. I have 2 primary amps already and am more than happy with them, another crack or crack-like build was more for long term experimentation or possible future office use.

    Never looked into the Teton much but I'll have to look a bit more now.
     
  6. Alchemy

    Alchemy New

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    The Crack and Teton run in the Van Waarde family if you want to do some looking around, I've actually looked into this myself and have found a number of schematics that use the same topology.

    A Crackatwoa is actually pretty simple step up from the crack imo, and 6aq5's are very cheap indeed. If you went off script and built it from schematic it is also much, much cheaper than the kit.

    Other than that I recommend you look into the Wheatfield HA-2 which is the predecessor to the Teton. Pete Millet publicized the user manual a while ago which includes the schematic. http://www.pmillett.com/Wheatfield/manual.pdf

    I have never understood why the Teton is 5 grand, if you look inside it is still very much an HA-2 with what looks like a CCS and a few other bells and whistles. (I am basing this opinion off of what I heard about the HA-2 retailing for 1 grand).
    [​IMG]
     
  7. Curado

    Curado New

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    Great info!

    I know little about transformers, but I'm interested in replacing the stock transformer if I were to build my second Crack. The 3.5A current in total from the stock transformer narrows the selection of tubes (e.g. I can't use 6336 tubes, or other tubes require higher heater current), So I'd like to use a larger transformer.

    So can you elaborate some more specs on the custom Sowter transformer (say, if I were to buy one, what parameters I should tell the transformer builder)?

    Do you mean the Sowter transformer takes in 230V AC on its primary winding, then outputs 150V 150mA AC to the diode bridge rectifier from its 1st secondary wiring and outputs 6.3V 4.5A AC to tube heaters from its 2nd secondary wiring?

    Thanks a lot.
     
  8. m17xr2b

    m17xr2b Friend

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    I'm a learning noob myself when it comes to circuits yet I find the following statement holds up: if you have to ask you shouldn't do it when it comes to electronics.

    Let me tell you why you probably shouldn't replace the stock transformer:
    - different winding resistance, different secondary voltage which may push B+ too much in either direction. Dropping resistors for heaters may be needed.
    - different mounting hole spacing, have the tools to mod the top plate? If not be confident it fits.
    - bigger rating -> larger size -> won't fit. I designed a new top plate for it, no chance to fit on stock
    - IMO replacing the transformer without tweaking the PSU isn't worth it and PSU upgrades > new trafo
    - cost, my Sowter was 250£ and two months wait, that's another crack.
    - 6336s are super cool but I wouldn't dream or running it in the Crack. You'll have massive heat to deal with an already warm chassis and I'd run that tube at higher bias to get the best out of it.
     
  9. Curado

    Curado New

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    You are right that replacing the transformer can be much more challenging than a simple swap of capacitors.

    But the only part I really dislike in Crack is the power transformer. Its limited capacity makes it impossible to roll tubes. Amps like Elise or Euforia have much more robust transformers where you can throw in all kinds of different tube combinations to try.

    Is it possible to get a custom transformer that outputs the SAME voltages (but with much larger capacity) so that we don't need to change the circuit after replacing the transformer? Say, the new transformer outputs same 6.3V AC to tube heaters (but with a larger capacity of 6A current) and same voltage (not sure how much it is?) to the amplification circuit.
     
  10. m17xr2b

    m17xr2b Friend

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    Think add instead of replace. Keep the existing transformer for the output tube heater(s) and add a small 6.3V or whatever you want for the input. Play around with the config you like and see if it's worth it to do the full replacement. I'd even add it outside at the back somewhere in a crude enclosure for ease.
     
  11. Alchemy

    Alchemy New

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    Antek AS-1t150 worked great for me and Mban. Super cheap too. I was actually able to run 2x 6aq5, 6336, and DC rectified 6SN7 without issues (they claim +20% power on 60hz so 7.1A 6.3v). Another bonus is the oodles of HV current which I'm putting towards my rebuild right now. Furthermore it comes with dual windings which I have put to use in a dual mono power supply.
     
  12. barbz

    barbz New

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    I've read through this thread a couple of times now and I'm till torn as to whether I should install the speedball or carry on with my other mods.

    From what I have read the speedball makes this crack less lush, tightens bass, improves resolution and makes the sound leaner across the board.

    I'm keen on the improves bass and resolution but enjoy he warmth of the amp.

    Current tubes in use is a tung sol 6080 metal base and brimar cv4003.

    Planned mods (of which I have all the parts) include alps pot, cx7 choke, panasonic square capacitors (ease of mounting).

    I have crackatwoa on route as I enjoyed the project side of he build so the crack will eventually go up for sale.

    Should I speedball?
     
  13. JeffYoung

    JeffYoung Friend

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    For sale probably so.

    But I never installed my CCCS on my Bottlehead SEX. I have other amps that have better resolution (Torpedo III clone and PASS HPA-1 clone), so it seemed better to keep my SEX what it is.
     
  14. CEE TEE

    CEE TEE MOT: NITSCH

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    Yes- clearer, cleaner but still fun/enjoyable. Then tubes take it even farther.
    Crack+SB, ZDT Jr./NBM, & SW-51 are the value/enjoyment champs.
     
  15. zfeldma

    zfeldma New

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    I hadn't had a true tube headphone amp in 15+ years (Mapletree Audio before), so reading through here and elsewhere I couldn't tell what the jump from low end hybrid was going to be like. I found conflicting opinions about if it would be an upgrade or sidegrade from a Vali 2.

    After a few months with the Crack...for me it was a HUGE jump.
    [Vali 2 with several tubes...Siemens is my favorite.][Crack with Speedball/Goldpoint Stepped Attenuator/Various tubes][Qobuz>>CCA and PC>>Modi Multibit>>SYS>>][HD6XX]

    Vali 2 was missing all texture. Not sure if it would be considered plankton? But the edges on violin and trumpet were missing. The Crack really brought the urgency and attack to these instruments.

    YMMV...but when comparing Vali 2, Massdrop CTH, Crack...gap between Vali 2 and CTH was bigger than the gap between CTH and Crack. After listening to the Crack I could still listen to the CTH...not so with the Vali 2, promptly sold it.
     
  16. Lycos

    Lycos Acquaintance

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    BH Crack is my 2nd OTL amp.
    I already had Darkvoice 336SE and was happy with it - but I read too many good things about Crack that I decided to try it.

    To do comparison, I used the same power tube (TS 5998) and preamp tube (Sylvania 6SN7WGTA - with 6SN7 to 12AU7 adapter on Crack).

    Stock Crack has different sound characteristic than DV .
    Both are warm but DV sounds airier and more hollow. BH is smoother and has more body.
    Clarity-wise, i think they're on par.

    With speedball upgrade however, Crack really shines.
    Clarity is improved. Sound is even warmer and thicker.

    I think Crack is a clear upgrade from DV only when speedball is added.

    [​IMG]

    [​IMG]
     
    Last edited: Dec 19, 2020
  17. Walderstorn

    Walderstorn Friend

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    I am confused.
     
  18. Lycos

    Lycos Acquaintance

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    Sorry typo. Fixed.
    Was meant to say Stock Crack is almost on par with DV.
    Speedball upgrade imo is what gives Crack a clear advantage over DV.
     
  19. Baten

    Baten Friend

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    How about noise, have you tried more sensitive phones? Which has more hum between the two.
     
  20. Lycos

    Lycos Acquaintance

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    I tested them only with HD6xx and HD800s. No noticeable hum
     

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