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



I really hope they drop this again…
I also really like the look of the Fireflies, but at the end of the day I love my BHC. Which makes me want to try more tube amps :grin:. I’ll probably do the speedball soon and start tube rolling soon also…so much fun to be had, so little time


If the tube says GE on it, skip it.



It’s built - I just haven’t installed it yet.

I still want to do some “before” measurements, as well as record the output for some test tracks so I have a primitive way to compare before/after. Plus … lack of time …

Though I may just skip all that and wait until my 2nd Crack 1.1. arrives, and keep one stock and one with the Speedball.


I think I’ll go after the S.E.X. as the next Bottlehead build…


Well, back home and listening on the BHC and no more whine… I think it was Gremlins, as the weird build up noise is gone also! I must say the BHC is such a joy to listen to (yes I’m biased, I have no qualm saying it…I put it together and put my own little spin on it, therefore it is special to me) I highly recommend anyone who has the chance to build one do so! Well I think it’s time to take it apart and start the process of putting the speedball on…


It could also just have been a tube taking longer than normal (I don’t know how many hours you have on your BHC now) to settle/burn in. Some never do and either are perpetually noisy or exhibit other spurious issues.

That can be an interesting situation for people that are new to tube amps and/or new to a specific tube/amp. If you get a tube with issues from the outset, troubleshooting can be a bit of a pain. You need to give them time to burn-in to see if it’s an actual issue or not. And if there is an issue, and you decide to replace a tube to fix it, you will likely have to go through the burn-in process with the new tube to see if that did fix the problem.

The problem with that comes when the replacement tube winds up being one with issues as well! Fortunately it’s a rare occurrence - but it is a frustrating one when it happens.

Which is one reason why people that focus on tube amps tend to keep known-good tubes around, even when they no longer specifically need them (e.g. they’ve sold the amp that used them). It makes for a much quicker path to validate the performance of an amp and to do troubleshooting/comparisons later on!


@Torq thank you, I need to buy more tubes for tube rolling soon lol. Update right before I unplugged everything in prep to put the Speedball on…the whine came back on both the El DAC and the RME ADI-2DAC, I can consistently get it to go away by unplugging everything and powering down then plugging it all back in, but it will apparently find its way back to the whine. Hopefully with new tubes and the upgrade to speedball will fix the issue. Otherwise I’ll be forced to pick up a S.E.X. sooner than later lol…


Did you ever reflow all the solder joints?

I know you “checked” them, but I’m not sure what that actually entailed.


I didn’t, I figured it would be the perfect time to do that when I updated to the speedball…