Would it be possible to sub 6n6p tubes for 12bh7 in the vta st70? 
2 posters
vta st70 driver board tube option
detoxer- Posts : 10
Join date : 2011-08-17
Roy Mottram- Admin
- Posts : 1839
Join date : 2008-11-30
try it, and let us know . . .
it does require more filament current 750ma VS the usual 300ma of a 12AU7 or 600ma of a 12BH7
it does require more filament current 750ma VS the usual 300ma of a 12AU7 or 600ma of a 12BH7
detoxer- Posts : 10
Join date : 2011-08-17
will I have to rewire the filament pin out?
Roy Mottram- Admin
- Posts : 1839
Join date : 2008-11-30
yes, definitely, the connecting trace between pins 4 & 5 on each tube of the VTA70 driver would have to be cut,
and these tubes would use a total of 2.25 amps of filament current compared to the 0.90 amps of current for 12AU7s,
which is also the same 0.90 amps used by the two original Dyna 7199 tubes. Hope you like hot power transformers!
If you really decide to go for it, I'd recommend adding an extra 6v filament transformer rated at 3 amps,
or maybe just a 1a one to run the center tube
and these tubes would use a total of 2.25 amps of filament current compared to the 0.90 amps of current for 12AU7s,
which is also the same 0.90 amps used by the two original Dyna 7199 tubes. Hope you like hot power transformers!
If you really decide to go for it, I'd recommend adding an extra 6v filament transformer rated at 3 amps,
or maybe just a 1a one to run the center tube