[ClintonL]

Hey guys, got a bottlehead crack and playing around with the input tubes. Using a bottlehead crack and so far i have it modded to run 12bh7's. Looking to get something new not sure which is a good tube which i can find on ebay which won't cost an arm and a leg.
 
Cheers

 

[Sodacose]

There are a lot of variants of 12AU7 that should work in a Crack without bias/pinout changes:
 
5814
5963
6067
6189
6680
6CC40
7489
7730
E82CC
ECC802
ECC82
 
I don't think 12BH7 has quite so many dopplegangers, but it's a great tube.  If you're using an adjustable CCS, you should be able to play with the whole 12XX7 extended family.  It would require a little bit of loadline calculations to determine the proper mA, but no rewiring.  Not sure any of the high gain tubes would sound great, but something like a 5965 or 12AV7 might be suitable.