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Bottlehead Crack W Speedball Game Rules

When I ordered my Bottlehead Crack kit, I also ordered the Speedball upgrade right away. Everybody that tried it, including reviews, said it was a night and day difference from the default Crack setup, and that you basically had to upgrade it. So of course I wanted to hear that for myself. Bottlehead recommends building the default Crack and make sure it works properly before moving on to the Speedball upgrade, so this is why I have done so.

Bottlehead Crack overview:

  • Part 1:Â Cabinet and chassis
  • Part 2:Â Mounting the parts
  • Part 3:Â Soldering the components
  • Part 4:Â Speedball UpgradeÂ
  • Part 5:Â Hot Rodding with film caps

The Crack has gone up in price a little bit since its introduction 3+ years ago, but it’s still quite a value. I also highly recommend the Speedball upgrade, which replaces the plate loads on the tubes with a constant current source and brings this amp into its own with added detail and transparency. My personal preference is for slightly euphonic amps (Lyr 3, Valhalla 2, Bottlehead Crack) for pure enjoyment and more neutral amps (JDS Atom, Magni 3) for music recording and gaming. Why I am interested in measurements of the Bottlehead Crack and any other tube amp is to see if it is possible to figure out what specific distortion gives them.

Well, almost a year later and over the holidays, I finally built my crack w/ speedball kit. Having built a couple of bottlehead foreplay preamps before, I knew exactly what I was in for – straight forward instructions, quality components, and something to marvel at in the completed build. True to form, the crack was much fun to put together. I have had my Crack w/speedball for awhile (+year) and have nine amps of all sorts, SS, Tube, DIY etc. The Crack has always worked well with T1 and T90's here for me. I did two things in the recent week that has me wondering how much better than this can it get with the cans I have and the way my Crack is set up. Bottlehead Crack W Speedball Pen here.If file is deleted from your desired shared host first try checking different host by clicking on another file title.

It’s quite difficult to explain in technical therms what the Speedball upgrade is all about, but it’s basically about feeding the tubes in a more linear way, resulting in a more dynamic sound, rather than one controlled by available and changing current. Bottlehead explains it this way:

“A Camille Cascode Constant Current Source is applied to each triode—both halves of the 12AU7 voltage amplifiers and both halves of the 6080 cathode followers. By loading a triode voltage amplifier with a high impedance, such as an active current source, it operates in a more linear region and produces less distortion. A second advantage, not as widely appreciated, is that the current source provides a great deal of isolation from the power supply. A good current source will provide a high impedance over a wide range of frequencies including radio frequency interference. It is otherwise extremely difficult to stop RFI that is carried on the power line, because power supply chokes have a leakage capacitance and the large capacitors used will also have some inductance at high frequencies. Isolation from the power supply also removes the power supply capacitors from the signal current loop.”

Pretty technical stuff, or at least it is to me. The good news is that you don’t have to understand this, to enjoy and appreciate the Speedball upgrade or even to make it yourself.

Bottlehead Crack Amp

The most important thing here is that the Speedball upgrade makes a huge difference. Faster, deeper bass, more detailed and wider soundstage and dead silent background. But let’s start with how these circuits is added to the Bottlehead Crack design.

Bottlehead Crack Speedball upgrade parts.

This is basically all there is to the $125 Speedball upgrade. Not much to look at, but I assure you it makes all the difference in the world. Or that’s what my ears are telling me.

Lets begin with the large Speedball PC board.


Twisted resistors

Two pairs of 22.1k ¾ watt resistors is twisted together and then soldered together.


Then they are installed along with 4 LEDs, two smaller transistors and some resistors.

Soldering Speedball PCB

The Speedball PCBs are double sided and the solder needs to run though like this.

Bottlehead Crack W Speedball Game Rules

Speedball transistors with heatsink.

The transistors is mounted directly to the heatsinks with thermal pads, fiber washers and nuts and bolts.

PC boars with transistors and heatsinks upside down.

Then they are soldered to the PC board. The lugs on each heatsink needs to be soldered too. A 40 watt soldering iron is almost too weak to do this job, because the heatsink removes the heat too fast.


Teflon wires is used to make interconnections on the PC board. Same type of wires is used to make connections to the Crack amplifier later.

Completed Speedball kit ready to install in Bottlehead Crack

Two identical smaller PC boards is finished and there you have the Speedball kit ready to be installed in the Bottlehead Crack amplifier.

Your precious Crack needs to be partly deconstructed, to make room for the Speedball upgrade.

The Speedball upgrade makes the plate 22k1 load resistors redundant and they need to go, along with the 3k cathode resistors.

Nylon standoffs are installed in front of the octal socket and and around the nine pin socket. Â The standoff between the nine pin socket and the terminal strip is VERY hard to fit, because of all the solid core wires going through this very spot. After some heavy negotiations, there is room enough for the standoff.

Black and red teflon wires basically have to go where all the resistors used to be, because the Speedball upgrade is going to do the same job they did, but hopefully a better one.

The standoffs is supporting the PCBs nicely. There isn’t much room to connect the wires to the boards.

My kit was missing two screws for the main PCB, but a couple of HDD screws did the job nicely, although a little bit of a tight fit.

This is what the finished installation of a Speedball upgrade looks like.

After doing another round of voltage checks on the Bottlehead Crack and Speedball upgrade, the new and improved Crack was fired up. It didn’t disappoint in any way. But I’ll get back to that in my review of the Bottlehead Crack.

Bottlehead Crack W Speedball Game Rules

Bottlehead Crack Kit

Go to Part V: Hot Rodding with film caps