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.Â 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
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 triodeâ€”both halves of the 12AU7Â voltage amplifiers and both halves of the 6080 cathode followers.Â By loading a triode voltage amplifier with a high impedance, such as an active current source, it operatesÂ in a more linear region and produces less distortion. A second advantage, not as widely appreciated,Â is that the current source provides a great deal of isolation from the power supply. A goodÂ current source will provide a high impedance over a wide range of frequencies including radio frequencyÂ interference. It is otherwise extremely difficult to stop RFI that is carried on the power line,Â because power supply chokes have a leakage capacitance and the large capacitors used will alsoÂ have some inductance at high frequencies. Isolation from the power supply also removes the powerÂ 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.
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.
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.
Two pairs of 22.1k Â¾ watt resistors is twisted together and then soldered together.
Then they are installed along with 4 LEDs, two smaller transistors and some resistors.
The Speedball PCBs are double sided and the solder needs to run though like this.
The transistors is mounted directly to the heatsinks with thermal pads, fiber washers and nuts and bolts.
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.
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.
Go to Part V: Hot Rodding with film caps