Bottlehead Crack OTL

General Information

An OTL headphone amplifier kit from Bottlehead (can also be ordered pre-built). Works best with high-impedence (300-600Ohm) headphones.

Latest reviews

Pros: Sounds gorgeous
Cons: Volume control not flexible in stock form but that's easily rectified
Fantastic amp. Easy and fun to build. Many opportunities to modify the amp. Vibrant on line community dedicated to the amp.

Due to it being an otl amp, it's optimized for high impedance headphones. Don't bother with Grados, for instance. I don't view this as a con, but merely as a design characteristic. Truly synergistic with my HD600's.

I've used film and teflon bypass caps to bypass all critical caps, and padded down the volume control as in stock form, it's way too loud by the 10 o'clock setting, also using beautiful NOS tubes. So no,,this isn't a stock Crack, but if you've got the DIY leaning, this is a great project.
  • Like
Reactions: BobG55
Pros: Perfect for my HD600, boosts volume/bass/soundstage, very quiet background and no distortion at high volumes, fun to build as DIY
Cons: Not many features, only for high impedance cans, aesthetics could be better
This was an amazing and fun purchase for me. It was fun to build and it makes my HD600s sound great. Very simple design that does everything I need it to for my headphones. I don't believe I'll ever purchase another amplifier unless I fall in love with a low impedance headphone that needs amplification.
Hi Mike,
Did you add the Speedball?
I have the Crack as well and love it with my HD650s. Will add Speedball in the future I think.
Pros: Incredible value, great soundstage presentation, ability to adjust sound via tube rolling, get to build it and customise it for yourself
Cons: Can't use it straight from the box :-), may take some tinkering to get the sound free from induced noise, performs best with high impedance cans
The Crack kit is easy to build and sounds incredible. Don't be scared of the DIY approach even if you're a beginner - it's fun and SO worth it!
Mine had some induced noise at first so I replaced the braided input cable with some shielded coaxial cable and it fixed it perfectly. I see that and potentially damaged/faulty tubes as being about the only real possible issue with this amp.
Once built (takes a day or 2 depending on how long you spend in one sitting) the final result is an amp with incredible staging and layering for the price combined with beautifully smooth and cohesive sound presentation. There's plenty of detail, but it's all cohesive and realistic - it doesn't pull apart your music into individual pieces.
This amp easily outperforms significantly more expensive units and is hard to beat with >250 ohm cans like the top end Beyers and Sennheisers. It sounds so sweet with my HD650s.
If you want to know more, I have two full reviews on: 1. The Build and 2. The Sound
how much is the builded version?
I'm not sure. Maybe check on Also,don't know if they ship pre-built units internationally so check that too if you're outside the USA.
If you're in Australia and need one built, drop me a PM


There are no comments to display.