The Schiit Freya + will do just that, see below:
Mike
Whisper-Silent Tube Stage—With Tube Shutdown
''Now, you can enjoy a tube preamp without the hiss and hum of classic designs. Freya+ offers super-quiet tube modes with DC heaters and semi-circlotron, noise-cancelling output stages. Better yet, the tubes turn off when you’re not using them! That’s right, both the tube heater and high voltage rails go away when not in use, so you can preserve lifetime of costly tubes.''