Bottlehead Crack: OTL Addiction


Writing a review after Mike’s interesting and complete 2 page impressions on Facebook isn’t easy, so don’t shoot me if this review turns out short 😉

The Bottlehead Crack amplifiers arrived a little over two months after having ordered them on Bottlehead’s website. We ordered a couple of Cracks right before the price increase was announced (more on that later) so that probably explains the long waiting period. As Mike mentioned before in his Facebook notes, it wasn’t always easy communicating with Bottlehead, with emails getting lost/unanswered but a couple of phone calls and lots of emails later we got our DIY packages in the mail. Bottlehead did forget to send us the logo badges we paid for and the wood of one of the casings was slightly damaged but we were to excited to complain about that and we decided to build them like that.

The DIY Crack is a fairly easy to build amplifier, anyone having experience with soldering and a multimeter can surely build one himself. Bottlehead also includes a very detailed step-by-step manual making it almost impossible to screw up. If you don’t feel like building the amplifier yourself, you can always order a pre-assembled Crack from Bottlehead, at an extra cost of course. Anyway since Mike did the build on both our Cracks, I will let him talk more about the building process later.

Like with every Bottlehead design all in- and outputs are located on top of the amplifier (even the power cable goes in on top). That can be unhandy when you don’t have a lot of space or when your interconnects and power cable are rather unflexible. It doesn’t really bother me but I’ve seen a lot of people using L shaped plugs with the Bottlehead designs and other DIY’ers have changed the layout and put the connectors on the back and front. It’s a DIY project so if you have the skills you can do pretty much whatever you want. Some people like the look of the Crack and others hate it. While I think its looks are basic and very cool, I have to admit that having all the cables on top will probably never make it win a beauty contest. Looks do matter when buying an amplifier but in the end the sound it produces is more important, and that’s where the Crack really shines.

I’ve only been using my beloved Sennheiser HD650 with the Bottlehead amp. I specifically bought the Crack for this headphone after seeing raving posts about this combination over and over. Most of my other headphones have low impedance or are orthodynamic headphones and the Crack wasn’t developed with those in mind. I did try it briefly with the Hifiman HE-400 and while that worked, I didn’t really experience any distortion like Mike, it doesn’t really need the Crack and it also doesn’t do anything special to it. (only normal with the HE-400 not really needing any amping).

I was very happy to notice the Crack was dead quiet with the stock tubes and with my replacement tubes (it doesn’t hum at all). The volume button, being a bit bulky, is smooth to turn and I never needed to turn it further as 10 o’ clock to get to my preferred listening level, so there is more than enough power left for you to play with. Even without any music playing, turning the volume pot was completely noiseless. I rather quickly replaced the stock Electro Harmonix input tube with one of my RCA clear top tubes. The stock configuration is good but the RCA tube just gives the amplifier a bit more body and weightier bass. Overall the Crack is a very clean sounding amplifier picking up every detail the music has. Bass is deep, well defined and punchy, the mids are very natural and smooth and the treble is nice and sparkling. It is quite a different sound signature as my other OTL amplifier, the Lafigaro 339 (review coming later). This last one is overall warmer sounding, has even smoother mids, more rumble in the bass (but looser) and has less pronounced treble as the Crack. Both sound great and if I would describe the 339 as “lush”, the Crack would be “clean”. In other words I could say the Crack is more transparent and colors the music less making it very enjoyable but also very non-fatiguing to listen to. I found myself listening for 6 straight hours to the Senn & Crack combo during work without even taking one break, that’s how hard it is to get off Crack (I just had to make one lame drug joke).

Of course it’s easy to modify the sound somehow using different tubes. I tried the very popular Tung-Sol 6AS7G and the rare GEC 6AS7G brown base in combination with the RCA 12AU7 I rolled in earlier but after several listening session I kept going back to the stock Westinghouse branded 6080 Tung-Sol. Only needing one power tube and one input tube, tube rolling is one of the most fun things to do with the Crack, and you can easily tune the sound to your liking.

This basic version of the Crack doesn’t have the speedball upgrade and was available for $219 as a DIY kit. Getting this kind of sound for such a low price is simply amazing and an absolute bargain. Nowadays the Crack is available for $279 (+27%) but it still is an extremely good deal if you can build it yourself. Bottlehead also offers a pre-built version of the Crack for a supplementary $150, making it $429 without shipping. Unfortunately for those not having the time or knowledge to build it themselves, the Crack is getting close to the prices of amps like the WooAudio WA3($495) and the LaFigaro 339($550) which have a more professional look and an equal or better sound quality. Something to think about.

In conclusion: if you are DIY’er looking for an OTL amp to power your high impedance headphones and prefer sound quality over looks (or just like the looks of the Crack like me), don’t look any further. The under $300 Crack is all you need and it will get you addicted for life.


Next Page: Mike’s Impressions

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?