Bottlehead Crack: OTL Addiction


I think I’m far more excited about the Crack than Lieven is. While the initial frustration regarding the ordering almost made us gave up, by the moment I received the package I really couldn’t wait to start the build and to finally hear what the Crack is all about.

A little DIY Story

If you’ve done DIY before, then you know that doing a clean case work is always more time consuming than doing the electronics part itself. If you’re lucky, the amp that you want to build can be ordered as a package, meaning all the correct parts needed are sold as a package, and you don’t need to order them one-by-one, sometimes from two or three different vendors. So, if I can break down the DIY amp building process, it’s probably something like:

  • 20% getting all the right parts ordered and shipped to your door.
  • 30% installation and soldering.
  • 50% case work: measuring, designing the case for best layout, cutting boards, measuring, drilling, sanding, tapping, all the way to the smallest finishing details.

The last amp I build was a moderately complex electrostatic amp, but I was lucky to have my friend calico agreeing to do the casework for it. So the moment I finished the amp and got it running, I sent the boards assembled and mounted on a plain aluminum plate, so he could start on the casework. I think it took him roughly 6 months to finish the casework, even with his advanced CNC know how. In comparison, it took me 1 month to finish the assembly from the time I got all the parts together.

I still had other DIY projects that I had prepared to build, but I decided to postpone doing any DIY work for an indefinite amount of time, simply because I don’t feel like having to deal with the messy case work.

Building the Crack

In the case of the Crack, I agreed to build the two amps (one for me and one for Lieven) because I knew that the assembly should not be that complicated, and that since we’re buying the package complete with the case and everything being pre-drilled, all I have to do is solder everything together and make sure not to flip the polarity of the diodes and the capacitors.

The Crack arrived, and to my surprise they had included a user building guide that includes step-by-step with pictures! Awesome! I don’t think any other DIY project comes with step-by-step pictures, and it makes such a big difference especially for less experienced DIYer.

The way Bottlehead designed the layout of the amp and the use of mounting posts (for soldering your components into) makes the build easier than a typical point-to-point build. The last point-to-point amp I built was Pete Millet’s SSMH, and though it’s simpler by parts count, the build process was harder than the Crack as it was pure floating point-to-point wiring. Anyway with the Crack, I think they went the extra length to design a layout that’s easy to build. There are some spots that are quite tight for the soldering iron, so it helps to look several pages ahead to see what other components will need to be soldered into that area, and if it would be easier to do the other component first.

On the soldering junction that involves several different components together, the manual clearly state when to solder everything together, again making for a very smooth building process. I also appreciate the fact that Bottlehead included a solid-core hookup wire that makes the wiring work so much easier (solid core wires tend to hold their shape very well, so they don’t move around when you try to solder them). The hookup wire also comes with a heat resistant insulation sleeve, so they don’t melt easily when you’re doing the soldering part.

It’s always wise to take the build slowly, double checking the parts orientation, checking for shorts and ensuring every solder joint is strong and solid. Rushing through the build may lead to mistakes that would take much longer to pinpoint and troubleshoot. Not to mention if you blow a capacitor and need to order a new one to replace it.

I didn’t have any problem with both builds, other than the fact that on my first build, the power switch I received was faulty so the amp is always on (I have to unplug the power cables to turn it off). Out of the three kits we ordered, two amps had the same faulty power switch, so it’ll be good to double check with Bottlehead on this one. On the second amp, I took my time to make for a very clean wiring path, so I can have a nice looking amp for the photos for this article. 😉

I think it took me roughly 6 hours for the first build with the simplistic wiring, and 8-9 hours for the second build with the clean wiring. It took me longer on the second build as I was not in a rush to listen to the amp anymore, and because I needed to measure the length of the hookup wires and to bend them at precise lengths to create a clean look.

If you feel like trying to do a build, I think the Crack is a good project to take on. Not only because the amp sounds very good, but also because it’s relatively simple and it comes with a kickass building manual. All of the parts used are relatively big in size (except for some diodes and LEDs), so it’s not like you have to mess with a lot of tiny transistors, SMD parts, or tiny little op-amps.

I’m so enthusiastic about the Crack mainly because of the sound. Of course the fact that I didn’t run into any problems during the process does make the overall experience easier to enjoy, but ultimately it’s the sound that excites me.


Continue to the next page…

Bottlehead Crack: OTL Addiction
3.86 (77.14%) 7 votes


Lieven is living in Europe and he's the leader of the gang. Coming from a musical family he's always been interested in good sound. Unlike his family members the only musical instruments he plays are amps and DACs. He loves playing with old tubes and discovering new products while staying faithful to the good old Sennheiser HD650.

  • where i can get this if i’m from indonesia?

    • L.

      You could ask Analog Head in Jakarta, I think they were planning on selling it. If not it will have to be directly from Bottlehead in the USA

      • thanx L..i will wait till analog have it to sell it

  • where i can get this amp at indonesia?

    • ryan

      Probably you could ask mike to build one for you 🙂

      • @ryan79:disqus no no no…

        • ryan

          What if the money is good? 🙂

          • L.

            I doubt Mike can be persuaded 🙂

            • ryan

              Bottlehead charges $150 if I remember correctly. Mike should charge $300

              • L.

                Bottlehead stopped doing it

                • ryan

                  Another reason why Mike should build it for $300

                • Trent_D

                  Actually, I think they will still do it, but I believe that they would be charging an hourly shop rate of around $65. So, even if they build it in an extremely swift four hours, that would still be $260.

                  • L.

                    I’m sure there are some DIY’ers in Jakarta that want to build one 😉

                    • I really enjoy the building process actually… it’s just that I’m not sure I can commit to a reasonable time frame, unless he would be content with a 12 months timeframe. 😉

  • Steve

    Can anyone recommend me a DAC for the Bottlehead Crack with speedball and HD650’s?

    • Steve,
      The HRT MS2+ or the DAcport LX works very well for $300 level DACs.

    • L.

      I usually use the Fiio E10 when I use the Crack + HD650

      • Bradford

        Is this still your goto? The Crack + HD650’s are a lot of $$ together. Can I get by with the E10? Or must I splurge on the MS2+? I see the Modi has good reviews for around $100. The Audioengine D1 Premium is also under $200.

        • I don’t know about the Modi but the Fiio E10 or E7K works pretty good for the HD650. The Crack however is on a totally different level.

  • Best review I read on the cracks..Thank you

    • You’re welcome!

      Sent from my mobile device. Sorry for any mistype.

      • I couldn’t just decide whether I could build it or if the stock crack would have been “good enough”. Well, speaking of the Stock version it is very enjoyable and I bought one after reading this and Tyll’s review. Are you planning to do a review of the Crack with the Speedball upgrade soon?

        • L.

          We do have a guest review coming up that will cover the crack with and without the speedball (in combination with the HD650) But I can’t tell you how soon we will get this

          • Trent_D

            As long as the voltage checks go fine, I suck with a multimeter, the speedball will be added this weekend, so I would like to say two weeks on the review. Detailed DIY work doesn’t become me with my big sloppy butcher’s hands.

    • L.


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  • Hariadi Mastoyo

    I like the sound of my PS1000 just the way they are but I don’t mind adding a bit of a warm tone to them. I am tempted to build this amp myself but I wonder the quite low impedance (32ohm) of my Grado might not suitable with Crack. I also considering ALO PAN am. Which one is better match? I really appreciate some suggestion here. Thanks a lot guys!

    • It’ll be good if you can come and test things out really. The PS1000 is not a very common headphone and so I have very little experience pairing amplifiers with it.

  • netmask254

    Can some crack owner help telling the 3-dimension of the finished box? Posted on Bottlehead forum but no response. Thanks a lot!

  • Arya

    Mike, I like to build crack, but I’am green with any electonical and soldering. Is it really easy to do it? Oh, what kind of lead that you used for soldering your Crack? Is it the same as lead for ordinary electrical PCB?

    • Dave Ulrich

      If you go slow and follow directions, it isn’t that hard. If I can do it, most people should be able to manage.

      • Arya

        Okay. Thank you Dave.

      • True.

    • Soldering skills is a must have for building the crack.

      What lead? You mean the internal wire? They supplied their own solid core wire which is very good and easy to solder.

      • Arya

        Oh, I mean the copper you used to solder, Mike. I’m sorry for my previous word, my friend said “lead” instead of copper. Hahahaha

        • You mean the tin?

          I use whatever I have. We just finished a new built using Oyaide tin and it does sound better than my first build.

  • Andy Kurniawan

    Hi Mike and L,
    A bottlehead fan here, can u tell me what tube you prefer with the crack?
    I use speedball plus tungsram e80cc or valvo e80cc with tung sol 5998, iknow that doc prefers the mullards but i have no experience with it.

    • L.

      Wasn’t that mentioned. Stock power and 12AU7 RCA clear top for me 😉

      • Dave Ulrich

        I like the RCA 6AS7G for the power tube and the current production tung sol 12au7.

        • Andy Kurniawan

          I read about the new tung sol production in Russia. Basically they bought the brand name and stick the label on their own tubes. Are they any good?

          • L.

            I wouldn’t say they’re terrible but they’re not close to the NOS tubes

          • Dave Ulrich

            I have found this tube in particular to be excellent. It was recommended over on the bottlehead forums awhile back. With the RCA 6AS7G, I would take it over the Clear Top for sure (I have a clear top, as well).

    • I prefer STOCK tubes by far.

      So much I like the Stock tubes that when the stock tube broke I tried really hard to pry it from another Crack owner’s hands but they won’t sell me. Eventually I got another stock tube from Bottlehead.
      And I’ve tried LOTS of different tubes with the crack. None of them has the bass and the soundstage depth the stock tube has.

      • Andy Kurniawan

        Is it just me, because I noticed noise even when there’s no music playing with the stock driver. It’s gone when I switched to e80cc.
        I don’t even know what my stock tubes are, all the markings gone on my stock tubes.

        • L.

          Well that’s what tubes can do unfortunately

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  • Linuels

    Mike and L,

    I’m planning to purchase this or the S.E.X. 2.1 for my HD 650. However, I don’t have any soldering experience. Can you provide me other pre-built desktop amp that has the same performance/sound signature of the OTL crack even if it is more expensive?

    • L.

      Lafigaro 339 or 336, Woo Audio WA3, Woo Audio WA2

      • Linuels

        Thanks mate. I will look these amps.

  • Igor Sheykin

    Hello! Can you give short summary for the devices and source used to build Crack? Used sort of tin, length of wires, …
    I mean if you tried different variants, and one is definitely better than others.

    • L.

      Just use what you can get and follow the instructions. Should be good 🙂

      • Igor Sheykin

        Thanks. Just have to wait till it arrives to Germany.
        Here I have one more small question: if compare T90 and HD700 with Bottlehead Crack as amp, who would win? Who pairs better?

        • L.

          I dont think there is a better. They both perform exceptionally good with the Crack. Just choose the headphone which sound suits you most

      • Igor Sheykin

        Important question: what do I need to make it?
        soldering-iron, tin, pliers, wire cutters, ???

        • L.

          yes, all of that

  • Sergio Mejia

    Hi, I have two questions, could help me please

    What Fiio device would result is the best combo for HD700 + CRACK Bottlehead, basically fulfilling the function of a DAC?

    You better just be a DAC or ideally buy a Amp / DAC to also fulfill the function of portable amp?