Crack;Bottlehead OTL

Discussion in 'Headphone Amps (full-size)' started by ironbut, Mar 9, 2010.
  1. bigfatpaulie
    So it begins.... Again.

    JamieMcC and Quadfather like this.
  2. Allanmarcus

    I've done it. Just add the RCA jacks and wire to the headphone out. One needs to have a plug in the headphone jack to keep the connection active, but other than that, nothing special.

    Here's a cable I made that works well as a pre-out:

    here's an old crack that I added RCA pre-outs. Unfortunately, I cannot find pics of the wiring, but it wasn't hard.
    Mightygrey likes this.
  3. Paladin79
    IMG_2795.JPG IMG_2796.JPG With names like the Crack, and Mainline I thought perhaps this 8-ball amp I just built might fit into the drug related theme. It is a hybrid DIY amp I built into a toy Magic 8 ball, the bottom is flat so it will sit on a desk. Remove the top and you have a headphone amplifier. I am also working toward mounting a few in tobacco tins, headphone racks, and even scotch bottles but I got an easy build out of the way first. Naturally I have built a few Crack amps but I am branching out a bit, hopefully it is not grossly off topic.
    Last edited: Jul 6, 2018
  4. kevlar51
    Just finished my Crack build yesterday—I’ll start the Speedball upgrade in another week or so after I’ve given the standard build a fair shake. Then on to tube rolling and then of course I’ll be all done:wink:

    In the meantime I’m hoping someone can advise on my setup—currently I use HD650, fed by some Schiit products: Eitr>Mimby>Jotunheim

    The Jot has the phono preamp onboard, and a modified AT LP-120 feeds into that (I’ve cut the preamp out of the turntable).

    The Jot also feeds into an old Onkyo receiver that powers some speakers for when I feel up to it.

    Currently the Jot’s controls switch nicely between all of these functions. But now I’ve added a Crack into the mix for different flavor. What are some opinions on a good setup? Am I selling myself short to use the Jot as a preamp to the Crack? I’m not sure I see a way around when I’m listening to vinyl, unless I buy a new separate phono preamp.

    Thanks for any thoughts.
  5. Allanmarcus
    Sounds like a good set up. You can always spend more money for a very incremental improvement.
  6. bigfatpaulie
    I forgot how good the Crack is. Holy smokes, talk about value!
    buke9 and JamieMcC like this.
  7. Rhamnetin
    Especially when you pay only $300 for a Crack 1.1 + Speedball.
  8. Stillhart
    So I've got an itch to build another DIY amp (I've built a Project Solstice before) and the one I want to build is rather complicated. I thought I might start with a Crack and mess around with mods and stuff to build up a little more knowledge before tackling something more complex.

    Some questions for you fine folks: I haven't actually heard one before, I only know them by reputation. The only high impedance cans I have at the moment are my trusty HD800. How do they fare with the Crack? By comparison, I'm currently driving them with a Liquid Carbon.

    How often do they go on sale? I've seen the $200 price mentioned in the last few pages, but it's nowhere near that right now. Am I going to be waiting until Black Friday or is it more of a regular thing?

    Can I use my tubes from the Solstice in the Crack?
  9. Allanmarcus
    Crack and HD800 with good tubes sound great. Good tubes are about a $100 or less a set, so not a big deal. With the stock tube the combo will sound good.
    The crack goes on sale a couple of times a year, sometimes with the speedball upgrade. Subscribe to their newsletter to get notified. Hard to know when the next sale will be. From what I can tell last sales were:

    May, 2018
    Oct 2017
    Mar 2017
    Sep 2016
    April 2019

    So you can extrapolate from this data the next sale will likely be oct. Sometimes they lower the price, sometimes they include a free speedball.
    Last edited: Jul 12, 2018
    DavidA and Stillhart like this.
  10. bigfatpaulie
    Hello all,

    I built my new Crack (this is my second one and 3rd BH amp) and it worked perfectly. Now I added in the Speedball - all the voltage checks passed, all the LED's light up but there is no sound on the right channel. I also posted on the BH form.

    I've checked continuity on all the paths. I've flowed the solder on every connection on the SB boards and on the joints that I work on tonight. I've switched L/R RCA cables, the side issue stays on the same side. I've tested the headphones on a different amp and they work.

    Added: I tested every transistor and diode.

    Added: I've checked every resistor.

    Added: I've rolled both tubes.

    I should also not that the left channel sounds great.

    Any thoughts? Could it be a DOA part? What am I missing?

    Thanks for any advice.

  11. kevlar51

    I had no sound in the right channel both after the Crack build and the Speedball build, measurements were fine on each. For the Crack, resoldering the joints between and on the headphone jack and the volume attenuator did the trick (not sure which joint was ultimately the culprit).

    For the Speedball, no resoldering was necessary, I found some bare wire touching where it shouldn't in the octal socket. I believe it was a wire soldered to A7 pushed over and touching A8. It's a cramped spot, but once I separated them, my issues were fixed. Initially after the Speedball install, I also had a hiss at the low end and the high end of the volume. Same fix took care of it.
    Rhamnetin likes this.
  12. kevlar51
    So far I'm not super thrilled with using the Jot as a preamp to the Crack. I'm getting extra hum and hiss that I don't get when I plug my mimby directly into the Crack (or mimby into the Jot when I listen through the Jot). I might just need to play around with the volume and see if there's a spot that works. It's already on low gain.
  13. bigfatpaulie
    Thanks. I just double checked both tube sockets, all clear.

    I reflowed all the joints in the right audio channel path as well.

    No dice.
  14. Allanmarcus
    Looks like you have an opportunity to buy or build an RCA switch box!

    Alternative, you can try simple RCA Y splitters and run the DAC output to both the Jot and the Crack.

    I have some info on RCA switch boxes here:
    Last edited: Jul 12, 2018
  15. Allanmarcus
    When you added the first board of the speedball, did the crack work fine? That would help for you figure out if the issue is with the first board or the second board. Also, post lots of pictures of the boards and the wiring, including under the boards.

Share This Page