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Crack;Bottlehead OTL

Discussion in 'Headphone Amps (full-size)' started by ironbut, Mar 9, 2010.
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  1. hawkwindx
    What is that preamp called? Looks cool!
  2. i luvmusic 2
    If you are refering to my DIY Preamp, Just call it ''I Have No Clue" Preamp:L3000:.

    DavidA likes this.
  3. Paladin79
    This weekend I hope to add a speedball upgrade to my standard Crack amp and compare one Crack with and one without said upgrade. I also need to go back and try my favorite tubes in a stock Crack to be certain I am comparing apples to apples.

    I also realized that my Valhalla 2 is a great way to get the signal to my Crack but i can reverse the process and use the Crack as a source into the Valhalla and get more use from my lower impedance headphones. I will have to check this out to see if I am as pleased with the results as the other way around.

    I also need to start shopping for Dacs that will compliment the Crack amp, possibly tube type output. I have people wanting me to hand them a modified Crack and headphones but they will still need a DAC. Hopefully I can find something decent around $500 since most want to keep the three pieces around $2,000 or thereabouts. Any suggestions are certainly welcome.

  4. MattTCG
    For a complementary DAC, I'd look no farther than Modi MB. The price/performance is as good as it gets and pairs very well with the Crack.
    Paladin79 likes this.
  5. Paladin79
    That DAC is certainly worth considering and i really like the Valhalla 2 I own. Price is great but it does max out at 24/192; apparently the Bifrost Multibit is probably the next step up and costs considerably more but offers upgrade-ability. One of the gentlemen is an EE so I best give him a choice.

    Thanks for the input Matt.
  6. MattTCG
    No problem. When comparing the Modi MB against the Bifrost MB, the difference was there but somewhat subtle. Then stepping up to the Gungnir MB was quite noticeable but then there's the price and that's it's best used balanced.
  7. Paladin79
    IMG_1954.JPG Yeah it is a pretty good price jump so the Modi is still in contention. I suppose anything I found with tubes is only using them in the pre-amp out stage but I definitely want the folks to have a quality DAC section no matter what.

    Ok the big difference between my stock Crack and my modified Crack is the volume control (my modded one has dual Alps single gang pots). They sound pretty similar with the same tubes but I love the smoothness of the Alps when cranking the volume and being able to tweak each channel a bit if needed but other than that it is tough to discern much difference so far. I will see what happens with the speedball when I get back into town later today.

    I installed the speedball in my standard Crack amp and it is a little too early to tell how much difference it will make but at least it is up and running.

    There were a few things I found to be a little sloppy in the speedball kit compared to the amp but it is going so I am thankful I have some things laying around my shop I could use. If any of you do the install and have issues and need a quick response contact me and I will try to help.

    There is an obvious difference, I have only tried a half dozen songs so now I have to figure an easy way to switch back and forth between amps on the same music, at the same volume level with similar tubes on the same headphones. I am picking up a bit better separation of channels and and perhaps a more prevalent mid-range but those are just preliminary thoughts.
    Last edited: Jun 11, 2017
  8. i luvmusic 2
    This should do it a simple 3P ON-ON Switch from any OUTPUT to AMP 1 and AMP 2.Sorry! for my unconventional schematic Drawing.
    Last edited: Jun 11, 2017
  9. Paladin79
    Yeah I definitely understand the switch portion but what I will need to do is build a splitter cable going from both amps to the same headphones. Both signals will not arrive there at the same time what with the switch but I want to be able to hear one amp, then the other in the same headphones. Same music, same volume level, etc. I did not want to use my extra bulkhead mount female 1/4 trs so I will grab one that is cable mount. I also have a slight delay with letting other listeners judge the sound differences but that will take place in a week or two so I have plenty of time.

    As far as the switch I have audio/video switches set up with female rca connectors so it will save me wiring something like that.

    When done i will be able to switch between Crack amp with speedball and Crack amp without. While the tubes i will use will be as identical as possible i will swap them at some point and do the same testing all over again.

  10. Allanmarcus
    Since it can take 60-120 seconds for our brain to adjust to sound input, you are probably fine just splitting the output of your DAC into both amps, then simply listen to one amp for a couple of minutes, unplug the headphone from A and plug them into B, then listen for a couple of minutes to the same part of the song.
  11. Paladin79
    I understand about the adjustment period but I will also be looking at various signals using test equipment and prefer not to plug and unplug as I test. 15 minutes of cable building is not an issue for me and with other folks involved (giving me their opinions on which amp they prefer), a switch will make it less obvious which amp I am engaging at any given time.

    I am now set up with switch box and Y cable so testing will begin soon on Crack with and without Speed ball upgrade.

    Also early in my career I worked with a gentleman who designed speakers and we could switch from speaker to speaker to speaker as a comparison. I like the instantaneous approach personally so that is what I will use. It is also a very good way to tweak in the volume level as one goes back and forth between amps. The more things I can have equal, the better.

    Last edited: Jun 12, 2017
  12. i luvmusic 2
    Or get two identical Headphones one for each amp,There you go BOB is auntie!:L3000:
  13. Paladin79
    IMG_1968.JPG hmmm and four ears! I do have plans to build another set like the ones I modified but not quite yet. Right now I am just doing a bit of comparison and then I need to build at least two more Crack amps that I do not mind giving up. If it turns out I like the amp better without the speedball, I will have a complete kit unused and will not order it with my future Crack purchases. I seem to recall some liked the amp better without it but I try to stay open minded.

    I am going as far as building two identical sets of interconnect cables.

    I set this up quickly and it is not pretty but right now I can quickly switch back and forth between both amps, lower standard version with speedball, modified cabinet version without. After I have tried this out for a bit I will post my findings.

    There is obviously less background hum with no signal on the speedball version. Obviously this has been said before, I just read it described as a "black" background with speedball upgrade. I tend to form my own opinions before doing a lot of research so much of what I am saying is no doubt redundant.

    I used Mogami Neglex 2534 throughout the test set up with a short final stage of some Belden Brilliance series. Top of the line Neutrik 1/4 inch connectors.

    This is also a quick and easy way to compare tubes. Early on yesterday I thought the speedball made the midrange a bit cleaner, it was cleaning up the low frequency noise that caused that effect. I have no doubt I will be able to see a difference on a scope, that will have to wait till this weekend but for right now there is certainly an audible difference.
    Last edited: Jun 13, 2017
  14. Paladin79
    IMG_1975.JPG IMG_1970.JPG I am going to attempt to use all shiny copper on my next crack build. It should look good with this quartered oak and I will probably use the patinated copper in a limed quarter oak box, just to make the patina jump out a bit more.

    Another way I can achieve the height I prefer is to use two of the bottlehead crack cases one on top of the other. By using those I can build my own wooden case and use the size plates I prefer. I can achieve this with a jigsaw and dremel tool since I do not own a lot of big power tools.
    Last edited: Jun 17, 2017
    i luvmusic 2 and hawkwindx like this.
  15. Paladin79
    IMG_1981.JPG ok I know this is a bit crazy but some time back I read about some headphones that mostly made their appearance about 12 or so years ago, Darth Beyers. I did not own a pair, till now...250 ohm and match up well with the Crack. Zebra stripe meets tiger
    stripe. They look bizarre but the bass is incredible. Something I would call a ported closed design, or semi open.The cup allows the bass to reverb a bit, old school but interesting.

    Last edited: Jun 20, 2017
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