Daburu Output Transformers The only way to get identical idle current

Hints And Tips

A few words about driver stage: There is one little hint.
With this operating design that uses 2K2 resistors for top and bottom triodes, signal currents cannot be equal in each triode: the bottom 6SL7 always gets a higher load value than the top tube.

The Tube Cad journal suggests the solution to find the optimal value for Rak. Calculating of this value is the only way to get identical current (AC) in both tubes. Simplest formula promises to give us the value of Rak (R6 14K4) that yields the biggest, cleanest voltage swing into the load resistance.

Magnetic Fields:

  • Try orienting the choke's laminations 90° to the power transformer and see if you get lower noise/hum that way
  • Always twists any AC wires
  • Always solder a wire from the grounded pot connections back to the ground point of the stage, where pot is used
  • Always use insulated from chassis phono RCA sockets


Level Five 2A3 Schematic