triode heater ground question

[gary h]

Hi all,

in the schematic below, I assume I can leave the 12au7 heater ground pin (9) unattached.

Am I wrong? Is there a better way?

thanks,

gary

[Hearinspace]

Pin 9 is the heater centre tap . If pin 9 is unused the power supply has to heat the entire series length of the heater which properly takes 12.6 volts. By (electrically) folding the heater filament "in two" or back on itself you heat the two halves in parallel requiring half the voltage (6.3) but twice the current.

So connect one end of the the 6.3 Volt secondary to both pins 4&5 together, and the other end to pin 9.

[gary h]

thanks,

of course, and it gives the series/parallel voltages right on the spec sheet.

g