Bottlehead
Bottlehead Crack 1.1 OTL Headphone Amplifier Kit
Best rewarding build for discerning headphone audio enthusiasts.
Experience pure audio with this legendary OTL headphone amplifier kit, designed for high-impedance headphones. It delivers a rich midrange and spacious soundstage, offering an engaging tube character. This kit provides a rewarding build experience for beginners and rivals higher-priced amplifiers in sonic performance. The included Speedball upgrade enhances clarity and dynamics, while the universal power transformer ensures worldwide compatibility. It's an ideal choice for audiophiles seeking exceptional sound quality and a satisfying DIY project.
$369.00
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Owner Satisfaction
4.7
/ 5
Category Rank
63
/ 1078
#63 in Headphone Amplifiers
Price vs Category Average
-74%
Below average
Amplifier Technology
Vacuum Tube
/ Vacuum Tube
Who it's for
- Audiophiles seeking a classic tube sound for their high-impedance headphones.
- Hobbyists and aspiring audio engineers who enjoy building their own gear.
- Budget-conscious audiophiles desiring premium tube sound without the premium price.
Who should skip it
- Consumers preferring ready-to-use electronics or lacking soldering experience.
- Headphone users with low-impedance or highly sensitive in-ear monitors.
- Listeners who prefer maintenance-free audio components and consistent performance.
Performance breakdown
High-Impedance Performance
The OTL design creates a perfect synergy with high-impedance dynamic headphones.
DIY Build Experience
Clear instructions make this an accessible and rewarding project for beginners.
Sonic Character
Delivers that classic, lush tube warmth with an expansive, holographic soundstage.
Clarity and Dynamics
The included Speedball upgrade significantly tightens bass and improves transient response.
Component Versatility
Limited to high-impedance loads, making it less ideal for sensitive IEMs.
Aesthetic Appeal
A raw, industrial look that celebrates the beauty of exposed vacuum tubes.
Key Specs
Amplifier Technology
Vacuum Tube
Output Type
OTL (Output Transformerless)
Tube Complement
One 6080, one 12AU7
Output Impedance
120 ohms
Gain
~15dB into a 300 ohm load
Input Impedance
100K ohms
Power Output
~10V into a 300 ohm load
Dimensions
13 in x 7 in x 6 in
Know before you buy
This amplifier is specifically designed for high-impedance headphones, such as the Sennheiser HD 600, HD 650, or HD 800 series. Because it is an OTL (Output Transformerless) design, it performs exceptionally well with these higher-resistance loads, delivering a rich, spacious sound that lower-impedance headphones may not fully realize.
Yes, the Bottlehead Crack is widely considered one of the best entry points into DIY audio. The kit includes detailed, step-by-step documentation and a supportive community, making it a manageable project for someone with basic soldering skills and patience.
The Speedball is a constant current source upgrade that replaces the stock plate resistors. It significantly improves the amplifier's clarity, tightens the bass response, and enhances overall dynamics, providing a more refined sonic performance.
No, you do not. The kit includes a universal power transformer, which allows the amplifier to be wired for various international voltages, ensuring it functions correctly regardless of your location.
The Crack 1.1 uses a standard tube complement consisting of one 6080 power tube and one 12AU7 driver tube. These are widely available, allowing you to experiment with different brands and 'tube rolling' to fine-tune the sound to your preference.
Generally, no. The OTL design is optimized for high-impedance dynamic headphones. Planar magnetic headphones typically require low-impedance, high-current amplification, which is not the intended use case for this specific circuit.
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