It was uneventful, as Bottlehead includes excellent documentation and instructions, including extensive safety precautions. Here is the amplifier with the hardware applied prior to circuit assembly.Īssembly of the stock circuit was done over one week, using my Weller soldering station and Cardas quad eutectic silver solder. I individually polished each screw with a Dremel tool to match the mirror finish of the top plate. I am a masochist, so I also chose to replace the included Philips-head hardware with button cap nickel-plated hardware. It was accomplished by sanding the plate to 800 grit via detail sander, doing a hard cut via buffing wheel and White Diamond buffing compound, and finishing it off with Blue Magic metal polish and an orbital buffing tool. The aesthetics of the amplifier were built around my plan to polish the aluminum top plate to a mirror finish, which predictably was no easy task. I finished the gel topcoat at a later date after the circuit was completed and used a buffing wheel to bring the finish to a gloss (not pictured until final build). The base was assembled and sanded, the hardware for the spiked feet was applied to the Cardas blocks, which were subsequently glued to the interior of the base, and they were stained together. For the sake of convenience, I picked up these myrtle wood cubes from Cardas to add my spiked feet for that premium audio component "look".Īfter playing around with some test-staining, I decided on a General Finishes Walnut Gel stain and gel topcoat. The plan was for the top plate of the amp to be sanded and polished to a mirror finish, so I thought having matching chrome knobs would give the amp a real premium lookĬardas Golden Cuboids with Dayton Audio spiked feet. Mundorf SUPREME EVO Silver and Gold RC filter capacitor on driver C4S board.Īudio Note 25mm Polished Chrome volume knobs. Mundorf MCap EVO Aluminum Foil and Oil output capacitors. Japanese Azuma gold-plated ceramic socketsĪudio Note silver-plated RCA jacks, for aesthetics. Here is a list of components I planned to add after completing the stock circuit. I decided I wanted a Crack on.crack, so to speak, and planned a "statement" amplifier build around the Crackatwoa, featuring a few choice component upgrades, a stepped attenuator, and hopefully, excellent aesthetics. I was the owner of the original Crack + Speedball and a sizable tube collection to match. It takes a 12AU7 input tube, 6080/6AS7 output tube, and 6AQ5 tubes in the shunt regulator. at Bottlehead, after watching this community for some time, thought customers' money would be better spent on an improved overall circuit rather than boutique components or small circuit modifications, and thus the Crackatwoa with its upgraded power supply was born. The amp has a 120 Ohm output impedance, so is only recommended with high Z dynamic headphones (Sennheiser, Beyerdynamic, ZMF).Ī large modding community developed around the original Crack, with builders adding upgraded volume pots, stepped attenuators, film output capacitors, bypass capacitors, filter chokes, cree rectifier diodes, among many others. The original comes in a base form, or for an additional cost, can be upgraded with a Camille Cascode Constant Current Source (C4S) known as the "Speedball" the Crackatwoa comes with the Speedball C4S board included at stock. The original Crack headphone amp is a high output Z, cathode follower, OTL topology that has garnered much praise in the headphone community for its sound quality and reasonable price, particularly when paired with Sennheiser's 300 Ohm HD6XX headphone lineup. The Crackatwoa is an upgraded model of Bottlehead's popular DIY Crack OTL headphone amplifier with a larger power transformer, shunt-regulated power supply, multiple inputs, and optional addition of a Bottlehead's TwoQuiet stepped attenuator. This amp was built last year, so this is more of a retrospective, but I'm very proud of it and thought you might be interested Wanted to share my build of my Bottlehead Crackatwoa headphone amplifier.
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