Bottlehead Crack W Speedball Paintball

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Bottlehead Crack W Speedball Paintball Average ratng: 3,7/5 7765 votes

The Bottlehead Crack is a superb introduction into the world of DIY audio. The parts quality is very good, the documentation is truly excellent, the Bottlehead forums provide fantastic peer-to-peer assistance, and construction is very easy. The Bottlehead Crack is an outstanding first project for the novice audio DIYer.

Bottlehead has been known to me many years before I purchased my first kit from them. Doc and Queen have been in the business of selling tube-based kits for quite some time and have earned an excellent reputation for providing easily accessible and excellent sounding kits. All of the kits follow a rather unique naming structure: S.E.X., Foreplay, Seduction, Quickie ... you get the idea ;)
The Bottlehead Crack is a very inexpensive kit, for only $219 (as of Feb 2011) you get all of this:
The Bottlehead Crack Kit


The amp runs on a single 9 pin 12AU7 and an 8 pin 6080 / 6AS7. I'd recommend a little bit of tube rolling on this little guy as it can sound very nice with the right compliment. The manual is included on the CD in PDF format with step by step instructions. The kit includes an aluminum top plate that comes pre-drilled for the stock parts. Since it's aluminum, it's a piece of cake to drill out any additional holes or enlarge existing ones if you decide you'd like some different parts in there. I used a Hammerite spraypaint to add a bit of personality to the top plate and transformer bell cover. A Northwest Alder wood base is also included, you glue it together and finish in the color of your choice. I used a combination of MinWax products to get the wood to a deep red finish and a Polyurethane finish to preserve it.
Below are a few of the initial build photos:
Bottlehead Crack W Speedball Paintball
After a number of steps into the build, with DACT mounted

Fitting the large Solen 100uF Film Caps

I decided that I wanted a little more than the standard Bottlehead square emblem adorning the wood base. I managed to find a promotional products supplier that fashioned metal badges. I designed a vintage looking logo in Adobe Illustrator and fired it off to them, the results turned out well.
Finished Wood Base with EAR Feet and Custom Emblem

Bottlehead offers an excellent upgrade to the Crack called the Speedball... again with the crazy names. This, more specifically, is the Camille Cascode Constant Current Source upgrade. Bottlehead states on their page: The most immediate thing you will notice is a better sense of clarity. Things get tighter and quicker, bass and midrange get cleaner and more dynamic sounding, and the background gets more quiet.
Speedball Upgrade Fitted
Final Build with PSU bypass cap and Pilot Light
Custom made 10 gauge power cord for the Crack
Obbligato Bypass caps peaking out from the vent holes

As always, a few tweaks here and there are always welcome. This Crack features the following upgrades:
  • Cardas Rhodium RCAs
  • DACT 100k stepped attenuator
  • Kimber TCSS wiring
  • Kiwame Resistors
  • Neutrik Locking Plug
  • Obbligato 1uF Copper coupling caps (hidden under Speedball board)
  • Solen 100uF Capacitors
  • Teflon Tube Sockets
  • Woo Audio Tube Socket PCBs
  • Auricap Bypass
  • Vintage Pilot Light
The Crack, with Speedball, is an excellent sounding headphone amp for high impedance headphones (think ~300 ohm like Sennheiser's higher end cans) and a great value for the price. It can be a little bright with certain tube compliments in my humble opinion, so be sure to get a few to roll.
UPDATE (5/1/11):It's been a little while since I worked on the Crack, so I figured I would give it a fresh upgrade :) I managed to squeeze in a Solen 220uF film cap in the final electrolytic power cap location, sitting on a pair of standoffs. I also took the time to bypass the other two power caps with a pair of low-cost Audiophiler 2.2uF film caps.
All these parts just narrowly fit in the stock case

Leads were cut and longer Kimber TCSS wire was run

2.2uF Audiophiler bypass caps on left and right
UPDATE (5/18/11): Since I can't leave well enough alone for longer than 5 minutes, I opted to add a choke to the power supply for even further refinement. I selected a Triad C7X with a rating of 270ohms to take the place of the final resistor in the power supply (also 270 ohms). Since pretty much all the real estate has been used up on the plate, I opted to add two 2' aluminum standoffs to raise the choke above the capacitor near the RCA inputs. This required adding 1' spiked feet to the bottom of the wood base for adequate clearance, just like in the Bottlehead S.E.X. build. I think this baby is finally done.
Triad C7X choke right above the power supply cap

Spiked feet for added clearance and ventilation


Please remember that building circuits and performing circuit modifications can be dangerous to you and/or your surroundings and should only be performed by a certified technician. The owner of this blog and all associated parties can not / will not be held responsible if you attempt a build or modification posted above and cause physical harm to yourself or your surroundings. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard. Please keep this in mind.


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 😉

Bottlehead Crack Amp

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.

Bottlehead Crack Kit

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.

Bottlehead Crack W Speedball Paintball Gun

Next Page: Mike’s Impressions