Crackatwoa Headphone Amplifier

Crackatwoa is a premium version of the direct coupled Crack circuit with the C4S active loads of the Speedball incorporated, and also shunt voltage regulation in the form of two 6AQ5 tubes along with a bigger power transformer. There are three pairs of RCA input jacks and a volume and balance control. The standard potentiometer controlled volume/balance setup will be upgrade-able to a coarse and fine stepped attenuator very similar to the BeeQuiet attenuator used in the BeePre preamp and a similar style used in our most premium Mainline headphone amp. Like Crack this amp is intended to be used with high impedance headphones (200 ohms or higher) like Sennheiser HD600/650/800, Beyerdynamic 250 and 600 ohms headphones, etc.

The chassis is twice as big as the Crack chassis and along with fitting in the extra inputs, shunt regs and attenuator components there is plenty of space for those humongous output coupling caps everyone wants to add to their build.

Crackatwoa sonics? Compared to the Crack the shunt regulation gives a slightly more quiet background and a sense of better bandwidth and bass control. The balance control allows one to compensate for the tolerance variations in the volume pot that create imbalance at low volume settings in some Crack builds. Upgrading to the stepped attenuator is as big an improvement in the OTL circuit as we have found it to be in all of our other circuits that incorporate it – the presentation is more resolved and more natural, particularly vocals.

CRACK OR CRACKATWOA, WHICH SHOULD I BUY?

If you have never built a kit, buy the Crack kit. It is intended for first time builders and the more simple layout makes it much easier to digest as a first build.
If you have building experience and like to upgrade stuff, buy the Crackatwoa. It includes upgrades that, while making the build a bit more involved, you would want to incorporate. It also offers more space to add further upgrades like insanely large capacitors.
If you want the end-all be-all go to the Mainline page.

All of these amps will work great with high impedance headphones (and Mainline will work with low impedance cans too). The more premium the amp, the more resolution and control you will get. This will be audible on any good cans like Sennheiser and Beyerdynamic.

“I completed building the stock Crackatwoa last evening and have been enjoying listening to it. It’s character with both the ZMF Auteur and HD800S ideally matches my preference. It’s transparent in the presence region, noticeably tighter in the bottom end than my Crack/Speedball and delivers explosive dynamics. Truly a keeper! Over the next couple of days, I’ll do some tube rolling. A few weeks from now (or when the spirit moves me), I’ll build and install the Two Quiet upgrade. And, some time after that, I will probably install a pair of 100 uF Clarity CSAs I’ve got set aside. I’d be remiss if I didn’t, once more, thank the Bottlehead crew — Doc, Paul and Eileen — for your comprehensive and methodical build instructions and support. As with my two previous builds, I find the process immersive and therapeutic. Can’t wait to build my next kit(s)! Be well, Joe”

“I’m totally intoxicated by the sound of my recently completed Crack-a-two-a. There’s an immediacy to the sound, which fosters a real emotional connection for me. I’ve rolled a couple tubes and settled — for now — on a mil-spec Sylvania JHS 6189-12AU7WA in the input-tube position, NOS Chatham Electronics 6080WB with slotted graphite columns in the output position and a pair of NOS GE 5-star 6005s in the shunt-regulator spots. The overall character is one of crystalline clarity, airiness and silky smoothness in the mids and highs with well-rounded, incisive, punchy and robust low end when called for. So glad I made the decision to purchase this fine amp! And on top of that, there was the bonus of being able to immerse in the build process.” Joe

“My first full weekend off since July, and the Crack-A-Two-A just happened to show up on Friday. What better way to spend my time off than building a new kit. The build went pretty smooth, and I had no issues during the resistance and voltage checks. It powered up perfectly first time, and sounds great. Like the Crack but much more resolving and refined. It’s the perfect pairing for my HD-800s.” -Rocketman248

Crackatwoa vs. Crack

“…the difference is in your face, its really obvious. The bottom octave is unmistakably extended down, the lower notes that were crushed together and now added freq spectrum with all the different tones and their own dynamism that comes with the extra range. The noise floor is lower, their is noticeable silence between notes that with the crack just wasn’t as black, and with that the low level information can be heard so clearly, its just wow, its good. The other thing that is really noticeable is the tightness around notes, there is no flabby reverb or sliding into sharp notes, its just neat and tight. The mid range and vocals. I am listening to The Tennessee Waltz (allan Taylor & Chris Jones, TAS 2008 ex Stockfish) and its like your ear is hard up to the end of the mics, its uncanny. The little intonations in the voice, the playing around and tapping on the strings between and after notes, you hear it. Its smooth and tight and feels accurate. The tones and intonations in the tones and voices are fully heard. Its not quite front row feels 5th row, just back at row 5. The other uncanny thing is it just seems at ease and a clear step more relaxed than the crack, the crack always feels its struggling to keep up the 2 is a body builder lifting a ten pound weight.” -netosullivc