Bottlehead Crack OTL AMP (Kit/DIY) - Official Thread



I finally got a chance to start building my Crack 1.1 OTL this weekend.

Right now I am literally waiting for paint to dry … as I’m doing a hammered bronze finish on the top plate and a metallic flake candy-apple red on the case … neither of which are the fastest drying choices I could have made!

Now it comes down to a question of whether I will have the patience to document that as I go. Or just build this one, make notes on what I want to show in a build-log/walkthrough article, and then build another one and document that … and then put that amplifier into the Preview Program or as part of a competition of some kind.


Been waiting about a month now. They must be very backed up. I can hardly wait. Still need to get solder gun.


4-6 weeks is pretty typical.

According to their site Cracks and Speedballs ordered up to 9/13 have been shipped.

I would recommend downloading the build-manual if you haven’t already, to make sure you have the other things you’ll need on hand (tape, wood-glue, and whatever you’re going to use to finish the case). And, if you decide to finish the top-plate, make sure you only do the top side! This is clearly called out in the manual, but I know a couple of people that painted it both sides before they bothered to start reading!


This is the finished top plate (which is finally dry). Well, I say “finished”. It’s painted. Still have some clean up to do in the cut-outs … which I’ll do before I mount the hardware.

Ironic that the paint/finish is likely to take 10x as long as the actually electronic assembly!


Ian A true labor of love. It’s a beaut.
Thanks for the tips on supplies.


So … it is built …

Pictures will have to wait until I finish the base; freshly-sanded primer-white is not the look I want to show off …

Now I’ve been through it once … and found a couple of things I might do in a different order, I will order up another one and do a proper build-log for it. Not that is very involved. I’ve spent more time buggering about with the finish than I did on the assembly and electronics build.

May just keep the metal stock, and stain the base on the next build.

If you’re at all thinking about building one of these - just do it. It’s very straightforward, requires a minimum of tools/skills. And the end result sounds lovely. Especially when feeding something like the HD650 (as nature intended).


Ian, Can’t wait to see the pictures. As I recall I thought you might have said you spent about 10 hrs on the finish before what you’re going to do now. I still have not gotten mine yet. Probably a back log due to the special they had recently.
Also will love to see your step by step work.


Doing the hammered-finish on the transformer bell and chassis-plate was more about getting the right paint density and drying time than anything. Hammered-finish paints need to be applied more heavily on each pass than most spray-paints (where more/multiple thin/light coats is the norm) - due to the way the various additives work to yield the hammered finish.

It was a full day before those had dried, and I gave it an extra one just to be sure.

Then I had to clean up the bottom of the chassis, where some paint had gotten underneath it, since it is used as part of the ground. Next time I would just tape off the underside, as the two minutes it would take to do that is a far cry from what it takes to get fully-cured hammer-finish paint off the metal!

Oh, and I cleaned out all of the holes in the chassis plates as well - down to the metal, since things are a tight fit (especially the fibre washers/spacers for the transformer mounting).

I let the Titebond III wood glue cure for 24 hours on the case assembly as well. Though actually assembling that only took about 5 minutes (align, tape, check alignment, final tape).

Priming was quick … but again I gave that some time to bond properly. Sanding that down afterwards wasn’t too time consuming. Maybe 20 minutes total (gently, and progressively, by hand … me, woodwork and power tools do not mix).

Now it’s just a case of waiting for a suitably dry day to do the metal-flex candy-apple red paint on the case. Which looks like mid-week - but if today gives me a weather-break I’ll certainly take advantage of it.

The actual assembly of the rest of the thing involves much less waiting as there are no glues or paints involved.

Installing the jacks, sockets, switches, pot, tube sockets and transformer didn’t take long - half an hour maybe.

And the electronic assembly/wiring and various tests you perform along the way were maybe a couple of hours (I’m not new at this, though - just hadn’t specifically built a Crack before). Though personally I would advise printing the build instructions, double-verifying everything you do, and checking off each item as you complete it.

Some things that’ll definitely make it even easier to put together (that haven’t been mentioned above) …

  • Mini-hook or alligator-clip test leads for your multimeter.
  • True needle-nose pliers (not just “long nose”).
  • A fine-point Sharpie pen, or high-graphite content pencil, for writing terminal numbers on the back of the chassis plate.

Also, the Hakko FX-8801 hand-piece/iron running a T18-D16 tip (1.6mm, chisel), was just about ideal for this build. Most of my electronics work, and 99% of my cable builds, are done using a much smaller micro-pencil (Hakko FM-2032 fed off their FM-206 multi-station), but the extra thermal mass of the FX-8801 was really beneficial due to the much larger typical connections on the Crack.

The FX-8801 is the hand-piece included with the Hakko FX-888D, which is what I generally recommend as a solid soldering station - that also happens to be available via Amazon for under $100.

I will likely assemble the Speedball boards today. I won’t be installing them until the amp and tube have a couple of hundred hours on them however, so I can do a comparison after things have properly settled in.

I may do a high-resolution recording of the output before/after the Speedball installation for comparisons, also.


I was going to do the same thing. Put a couple hundred hours on a stock Crack before putting the speedball in. I never made it to putting the speedball in. It just sounded too good the way it was. I didn’t want to kill the smooth tubey sound I had.

So let me know if the speedball is worth it! It’s just sitting here on my work bench, staring at me, making me feel guilty for ignoring it.


I have this same problem with my speedball…
It’s so judgemental…the Lil Richard…


The weather turned unexpectedly calm, bright - even sunny … so I took advantage of it to paint the base:

The very smooth looking area at the bottom of the case is just down to the reflection off the non-stick foil I have the thing sitting on. The actual finish is fairly smooth and consistent … though I may wind up giving this a going-over with 400 grit sandpaper, and giving it another round of coats - we’ll see how it looks when fully dry.

And the interior is all taped-over, so that’ll all be natural wood when I pull the taping out - again once it is finally dry.

Now I’m all anxious to put the chassis in the case and see if the overall look it what I was going for or not!


Bravo . headphones%20(1)%20(1)


@DarthPool I forgot to ask you. How was that soldering iron you used for your bottlehead? I forgot the name.


I had zero problems with it…but I am an inexperienced user.


I love your emojis. Where do you get them.


Quick and dirty-shot of the finished unit … color shifts are due to lighting.

Better shots if the light gets better (this is a quick snap in artificial light).


Now you just need some straight pipes out the back spewing flames…maybe put bigger pedestal feet in the back to really give it that Hot Rod look :wink:

Jokes aside that is a classy piece of kit!



The next one will be a much less “bright” affair - likely with a simple wood stain.

And if I was doing it again I might reverse the color scheme, and just have the top-plate be red, and the rest of the unit in the darker finish. We’ll see. I have extra bases ordered along side my next Bottlehead kit-amp purchases.


I find them here and there, put on desktop, then drag to posts


This is a nice bold look.

If the wood has good grain and color I can never bring myself to hide it. Just a nice satin/oil finish will do, or stain plus oil it’ll bring out the grain. If the wood is flawed or has no grain I happily paint it.