(14 votes, average: 4.07 out of 5)

Loading...

I had my eyes on Crack for quite some time. I’m going though phases of getting different After exploring various amplification designs—from Push-Pull and SET to Hybrids—I finally turned my attention to the world of OTL (Output Transformer Less) amplifiers. Based on my research, the Bottlehead Crack is widely considered one of the premier representatives of this category, especially at its $279 price point.

The Crack is available as a kit or pre-assembled, but I opted for the DIY route. Not only is it more enjoyable, but it also provides a deeper understanding of the amp’s internal architecture. The shipping was prompt, arriving in just two weeks, and the customer service from the team at Bottlehead was exceptional—responsive, helpful, and clearly passionate about their products.

The Build and Initial Impressions

The construction is refreshingly simple. Even for someone who couldn’t wait to get it running before heading to bed, the build only took about four hours from start to finish. I initially tested it with my Sennheiser HD650s using the stock tubes. While many kits include generic current-production tubes, Bottlehead provides a very solid vintage Raytheon 6080 and an Electro-Harmonix 12au7. Right out of the box, the sound was impressive, though the Electro-Harmonix tube did show some slight sharpness in the high frequencies.

Sound Quality and Tube Rolling

The real magic happened when I began tube rolling. Replacing the stock set with a Sylvania JHS 5814 significantly expanded the depth and richness of the audio, effectively doubling the soundstage. On Diana Krall’s “You Are My Thrill,” the level of detail was superb; I could hear every breath and the nuanced loneliness in her delivery—details that seemed lost on other amplifiers.

When testing the low end with Michel Jonasz’s “Le lac gele,” the amp provided a very adequate response. While it doesn’t produce the earth-shattering tightness of a solid-state setup, it handles deep frequencies with grace. On warm vocal tracks like Lisa Wahlandt’s “Here, There And Everywhere,” the Bottlehead Crack truly shined. The voice felt personal and embracing, while instruments like the piano and double bass remained clear and well-positioned without being overpowered.

A Brief History of Bottlehead

Founded by Dan Schmalle (known to the community as “Doctor Bottlehead”) in the early 1990s, Bottlehead began as a Northwest-based enthusiast newsletter called Valve. The company eventually transitioned into producing high-quality vacuum tube kits, becoming a cornerstone of the modern DIY audio movement. They are famous for their minimalist “bang-for-the-buck” circuit designs and for fostering a massive, supportive community of “Bottleheads” who modify and upgrade their gear. The Crack, in particular, has become a legendary pairing for high-impedance headphones since its release.

Final Verdict

The Bottlehead Crack is a tremendous piece of equipment regardless of the price. It is an absolute must for owners of high-impedance headphones, offering a level of intimacy and detail that transforms the listening experience. If you enjoy the process of building and tweaking your gear, this is one of the most rewarding projects in the hobby.

Enjoy the music, join the growing community of Crack addicts :), support the awesome company!!!

Bottlehead’s Website