5687, 12B4, and even the 2A3 or the 300B, works well. Of course these tubes are all on the low mu side, but then a line stage amplifier does not need a lot of gain.
  Just as the use of a choke at the plate eliminated half of the needed B+ voltage requirement, using a choke in place of the cathode resistor could eliminate the need for a negative power supply. The schematic at the right makes the point. Here a high inductance choke supplies the only current path to ground for the common cathodes. The tubes still bias up correctly, as

the DC resistance of the choke's wire equals the same value of the resistor that the choke replaced. But in the presence of AC signal, the choke's impedance could be much greater than its DCR value.
   A further tweak is the use of an additional plate resistor. This resistor serves to establish an equal plate voltage on the first triode as on the second. Its value matches the DCR value of the choke at the second triode's plate. True, this resistor will permit some signal to develop at the plate of the first triode, but as the resistor is small in value, the gain realized will be slight. (Of course, the higher the quality of the choke is, the less the DCR of the choke will be, and consequently, the smaller the value of the balancing resistor will need to be, and thus, the lower the signal amplitude at the plate.)

Who's Afraid of Transistors
   For those who are not transistor-phobic, the stipulation of equal plate voltages can be easily realized. Since this is a tube circuit of the Month article, we will keep the explication of this circuit brief. The common cathodes are tied to a constant current source (current regulator). The second triode receives the same treatment with its plate working into a constant current source. The first tube's plate voltage is locked to the same value as the second triode's plate by the use of an emitter follower. The string of resistors and diodes that set the bias points for all the transistor based current sources and the emitter follower draws less than 2 mA.

Dissimilar Plate Voltages
  A different tack is to compensate for the unequal plate voltages by adjusting the bias voltages for each triode separately. Remember that the design goal for a Common Cathode amplifier is that the two triodes conduct an equal amount of current. By adjusting the grid-to-cathode voltages for each tube individually, we can maintain an equal current flow in spite of the differences in plate voltages.
  The simplest way to maintain the correct bias voltages for the two grids would be to introduce some additional resistance in the first triode's cathode connection to the second cathode. This would allow the first triode to see