[Lingwendil]

I'm working on a tube preamp for a power amp, and was wondering what the best way to make a separate subwoofer output with level control, and possibly tone control. If I can do it with all tube, even better, I've got 12au7, 12at7, 12ay7, 12ax7, and 6111's all on hand, if any combination of those will work. B+ will be about 30v. It basically needs to have the option of turning the sub up louder than the L and R channels, due to efficiency variations in drivers, amps and such. A tone control for giving just low tones to the sub is also desired. Any ideas or links?