Bottlehead Crack

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

  1. ohshitgorillas

    ohshitgorillas Almost "Made"

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    I used Dayton Audio film caps in mine, bypassed by 1 uF paper-in-oil and 1 nF teflon for shits and giggles (both russian military NOS). The form factor of the Daytons helps it fit in the Crack case pretty well I think and the price is reasonable compared to some alternatives. Fitting all the mods in there is challenging, my suggestion to those that want to supermod their Crack is to make use of the ample vertical space. Once you've installed film caps in the output stage, there isn't much left to work with. The Dayton caps will even fit with their long axis perpendicular to the chassis plate, if you're careful about how they're mounted. That's how I also fit a choke and a 100uF power supply cap in there as well. I think the diodes are a great upgrade, but dwarfed by the impact of the choke and some simple power supply cap bypasses. In any case, I would recommend doing the film output caps first as those are going to be hands down the biggest upgrade. Keep in mind that the film caps take a couple hundred hours to burn in and sound their best, they are a bit stiff and stale at first but the increase in detail and clarity should be immediate.
     
  2. elmoe

    elmoe Friend

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    Unfortunately I want to mount the caps on turrets which I am still waiting on so it's likely I'll do those last. The diodes helped clear up noise, it's not a huge difference but considering the price it was definitely worth it.

    Next is the choke, then the Alps pot, and the mcaps last.

    I installed the choke this morning, and am surprised at how much of a difference it made. Clarity/resolution is a notch above, with blacker background. This takes the Crack + Speedball from "decent" to "very good" to my ears. I would definitely recommend doing this. Though mounting options are scarce, if you raise it up with spacers which seems to be what others typically do, it's a fairly quick and easy add-on:

    [​IMG]

    After listening for a few and making sure everything works properly, I opened it up again and installed the Alps pot. It's a tight fit with the PCB in there but I'm able to flip it top side without having to trim the PCB. I'm not sure this made any difference sonically. Volume seems better matched at low gain, and transitions more smoothly when lowering/raising. Worth it if like me there are times you listen at low volume, or if you're the type to adjust volume a lot:

    [​IMG]

    Next will be the caps once I receive the turrets, a new volume knob that fits the 6mm Alps pot better, and I'll consider this build complete.
     
    Last edited: Jun 8, 2019
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  3. AllanMarcus

    AllanMarcus Friend

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    The pot is what I found made the most difference. Better control at lower volumes as easily discernible.

    The new volume knob is clearly your biggest upgrade :) It will take the amp to a new cosmetic level!
     
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  4. ohshitgorillas

    ohshitgorillas Almost "Made"

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    FYI mounting the choke above the transformer is not advisable. I've done it before and didn't notice any major issues, but "best practices" dictates that it should ideally be somewhere not in the path of the transformer's magnetic field.

    And yeah, the choke makes a clear difference. I was kinda floored by all the new details I was hearing once I installed mine.
     
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  5. elmoe

    elmoe Friend

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    It's really more behind than on top, though hard to see in the pictures. I didn't notice any noise in fact adding the choke helped in that department.

    @AllanMarcus for sure that volume knob will take it to another level.
     
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  6. ohshitgorillas

    ohshitgorillas Almost "Made"

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    I have rebuilt mine a few times so it's not pretty but it is DEAD quiet, beautifully detailed and dynamic, great with micro-detail and micro-dynamics, subtle, lively, intimate but well defined sense of space, clean bass extension, never fatiguing treble... I bet this thing could go toe-to-toe with some TOTL amplifiers and while it might not win, it at least wouldn't embarrass itself.

    upgrades:
    -Speedball
    -Bottlehead DIY power cable
    -Tung Sol 5998 -- Psvane CV181T mk3. my favorite input tube, Raytheon 6SN7WGT brown base, became microphonic a few days ago, RIP :(
    -CREE diodes
    -2.2uF WIMA film cap bypasses on 1st and 2nd power caps
    -choke between 2nd and 3rd power caps -- I had one of the mounting tabs removed so it could fit vertically on an L-bracket
    -3rd power cap replaced w/ Panasonic 100 uF pp film w/ 1 uF paper-in-oil bypass
    -Cardas RCA jacks (the 'cheap' ones)
    -Neotech UP-OCC copper signal wire & DIY RCA cables
    -Audio Note potentiometer
    -Dayton Audio 100 uF pp film output caps w/ 1 uF paper in oil and 1 nF teflon bypasses

    [​IMG]
    [​IMG]
     
    Last edited: Jun 8, 2019
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  7. elmoe

    elmoe Friend

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    Nice build, that's one loaded crack!
     
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  8. fp627

    fp627 Friend

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    Added Jantzen Cross-Caps and replaced the pot with an alps blue velvet on my BH crack earlier today - lost sound in the right channel but haven't had time to troubleshoot yet. Did hear a noticible improvement in sound on just the left channel though.

    Last few things I need to do include extending the legs of the Jantzen caps by soldering some wire on - not ideal, but the short-ish legs and 57mm diameter means I can't fit them both in properly with SB installed as the board + heatsink gets in the way, trimming pot stalk length, getting an extra 6080 or equivalent replacement, bypass cap/s on psu, and possibly adding the choke... undecided on that one though.
     
    Last edited: Jun 9, 2019
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  9. elmoe

    elmoe Friend

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    @ohshitgorillas did those PSU upgrades make a big difference? The WIMA bypasses, the Panasonic cap + paper in oil bypass specifically?

    I've been thinking about adding paper in oil bypasses on the 100uF output caps also after I've had a chance to give them a listen, was it worth it for you adding those also?
     
  10. ohshitgorillas

    ohshitgorillas Almost "Made"

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    - The bypass works best on the last power cap. Bypassing the 1st and 2nd capacitors has a fairly small return, however, the caps are about $2 apiece and you're already paying more than the price of three in shipping from whatever supplier, so why not?
    - The difference between a bypassed 3rd cap and a full 100 uF film cap was surprisingly small. I am not entirely sure this was worth the pain of finding a way to mount the damn thing, but it does lead to some improvement in clarity and background noise. On the other hand, these caps take a while to burn in so the difference grew with time but it's still not a massive improvement. I can't comment on the PIO bypass here since it was installed at the same time as the film cap.
    - The choke is by far the best upgrade to the power supply imho, followed by power cap bypasses.
    - Asking if it was "worth it" to add those PIO bypasses is asking the wrong question since they were given to me for free :p they don't make a night and day difference like Speedball or the choke but they do make a fairly small improvement the tone, treble extension, dynamics/transients. given that they are $1 apiece (iirc) shipped from Ukraine, why not? The friend that gifted them to me had his wood base modded and added 10x 20uF PIO caps in a chain in his output stage. THAT sounded absolutely fantastic and opened things up quite a bit, but I haven't had the willpower to do it myself
     
    Last edited: Jun 9, 2019
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  11. elmoe

    elmoe Friend

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    Thanks I appreciate your thoughts. Sounds like it might be worth getting a few WIMA caps and only bypassing in the PSU.
     
  12. ohshitgorillas

    ohshitgorillas Almost "Made"

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    Yeah I really think the bypasses will get you 85-90% of the way there and don't require solving a jigsaw puzzle to mount like the Panasonic film cap I used. Especially on the last power cap, bypassing yields a big improvement in detail, clarity and speed. I used 2.2 uF wima caps
     
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  13. elmoe

    elmoe Friend

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    Here's the cap upgrade mounted on turrets:

    [​IMG]

    [​IMG]
     
  14. elmoe

    elmoe Friend

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    Film output caps made a pretty large difference. I would say in terms of difference: Speedball > Output caps > Choke > Cree diodes > volume pot (debatable here as everything sounds much more balanced at low volumes).

    The output caps definitely bring some magic, better timbre, more resolution, wetter bass. I don't know if it wasn't worth buying cheaper ones, but I can recommend upgrading the output caps for sure.

    I will do WIMA caps next when I've had a chance to let the output caps settle some.
     
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  15. dsavitsk

    dsavitsk Friend

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    An oscillation in a tube, or somewhere else in the circuit can cause a tube to become microphonic, so I wouldn't bin the tube just yet. I'd ideally scope the amp to see if anything else is the culprit, or at least try the tube in a known stable circuit.
     
  16. fp627

    fp627 Friend

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    Was going to wait on providing feedback but int'l shipping on parts taking longer than expected. Soldered parts earlier this week. Had been using my BH Crack for a while before all of my posts here but I didn't really have time/desire to mod it until recently.

    Roughly agree with elmoe in terms of upgrades:
    Different Tubes (depending on tubes) anywhere from >> to >= SB > output caps > choke > new pot (in terms of difference in sound, not practical functionality). Waiting for various Russian PIO and Paper and Aluminum Foil capacitors of different values to arrive for use as bypass cap on last cap in power supply. Will post pics and comments once bypass caps show up and I decide on which ones to use.

    If I could only pick one though due to budget I'd actually pick new pot even over the SB - if 6/6:30 was min and 4:30/5 was max, I had total channel imbalance where I was completely missing the right channel up to 8, severely imbalance between 8 and 9, and above 9, it's probably 80-90% balanced but already a bit too loud for my listening preference. Finally balanced at 10 and I wouldn't be able to listen at this level comfortably for more than 1 min.

    Still testing between tubes, not all have arrived yet. May post more later after listening through all the tube combos.
    6080/equivalent: Sylvania 6AS7G black plate, Sylvania 6N13S, Tungsol 6080, 6080WA Thomson, stock RCA 6080 (don't like this one much)
    12AU7 and equivalent: Brimar, Tungsol (modern production) 12AU7W, Tungsram (Hungary), RFT (German)

    Subjective audiophoolery generic descriptions of components here (/s). Won't say much as there seems to be so much online about this already.
    - SB - overall better, less warm, and took from about a 4/10 to 2.5/10 muddy. (may not be worth it for those who just want a warm relaxing signature.) This may have also been my wiring, soldering, etc. but after adding the SB I had more noise in the background. Went from about a 2 or 3 depending on the day to a 5/10 in noise with pot under 9/930. Will have to see how bypass caps do - looking online, it seems like many other have bad noise past 12 on pot w/o bypass cap on power.
    - Output caps - overall better in most aspects, most noticibly it seems to "open" everything up/give separation. Using Jantzen Audio Bypass Caps (could have used better ones etc., but I wanted to keep the caps under ~$65)
    - Choke - seemed to bring a little more blackness to background and took resolution from about 3.5/4 to 5/5.5 out of 10. (used same old/already burned in tubes before/after) but did NOT resolve noise that occurs as volume increases.
    - Alps Blue Velvet 100k pot - fixed channel imbalance except at extremely low levels, minimal to no change in sound. If there was any change, this pot made the amp sound slightly more "solid state" or more "D/S glare". Again, minimal enough that it may even be placebo, parts burning in, having the wrong lunch and dinner, or any other nervousa here.

    Lastly, I thought of the Solaris DAC after all of these mods as the 2 biggest strengths on the Solaris are the 2 biggest weaknesses here: resolution and soundstage. But I really enjoy this amp despite it's faults. I didn't enjoy the Solaris as much as this amp even though on paper it checks a lot of boxes for things I like/want.
     
    Last edited: Jun 14, 2019
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  17. elmoe

    elmoe Friend

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    I agree with the above about the output caps, it definitely opened things up a good deal and separation is better, more distinct. I put in the 3 WIMA caps a couple of days ago, as mentioned replacing the last cap helped with detail/clarity and especially speed, that was worthwhile in my opinion, the other 2 I'm not sure help with anything but they were cheap so why not:

    [​IMG]

    This morning I added a couple of mundorf Supremes as bypasses to the mcaps. Again not convinced that helped a ton, a little extra sparkle on the top end, will need to let it all burn in some:

    [​IMG]

    I'm gonna call this build complete at least for now, let the new caps burn in some, and will do some tube comparisons:

    [​IMG]

    Here's the finished product:

    [​IMG]
    [​IMG]
     
  18. Cspirou

    Cspirou They call me Sparky

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    Did you modify the stock plate or make one from scratch? Where did you get this done?
     
  19. m17xr2b

    m17xr2b Friend

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    From scratch. Spent a couple of days drawing the project in CAD and sent it to a laser cutting company in the UK.

    Got my replacement plate with both holes cut. Doing two cracks now since I can, my original maxed out idea and a stock non speedball one.

    Thinking of doing nickel plating on the dark case and black paint on the other both with black bells.

    Both are a tad wider and longer than the original to fit the large caps I plan and I shaved off some length and width from the wood itself.

    [​IMG]
     
    Last edited: Jun 16, 2019
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  20. JeffYoung

    JeffYoung Friend

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    I think nickel plating would look really nice.

    I used a black wrinkle-finish paint on the bells on my S.E.X. (Just don't cure them in the oven, or the oven rack will leave lines on them. Sigh.)

    SEX front.jpg
     

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