element (terminal) of electronic devices be left open (flowting)?

Pleiades lab experience has shown so far that it sounds better (more depth for example)and with low noise figure. On electron tubes, transistors (germanium so far), JFETs. Devices are left free to assume their bias, but we can steer the value by appropriate choise of Vb, load resistor etc. It reminds what can be read on the Wright Tube Preamp Cookbook that what moves must be free to move.