I posted this on the Bottlehead forum, but there seems to be more activity here so I thought I'd repeat it.
This thread (http://bottlehead.com/smf/index.php?topic=5989.131) on the Bottlehead forum describes methods to mod the Crack to optimize bias for various tube types. I had added a switch and resistors to allow use of the 12BH7 as well as E80CC/5687 but wanted something neater and consequently more reliable long-term. Here's the before shot:
I decided to make my own PCB, integrating a DPDT switch and resistors, and condensing the dual boards into a single PCB.
Here's the bare PCB:
And stuffed with parts:
Installed in place of the 2 separate boards:
The first try wasn't perfect, as the mounting holes needed some dremeling to allow the PCB to clear the standoff from the other PCB. Also some of the pads are on the small side and the holes for the LEDs are too large, but it did work first time.
After spending more time switching between the 12BH7, and 5687, I find that the 5687 excels in imaging and placement, but is down on bass compared to the 12BH7.
I had to buy 10 pcs minimum and I've only got one Crack, so I've got extras if anyone is interested.
May I be the first to extend a very warm welcome to Head-fi
I very much look forward to your future contributions.