Tube Heater Supplies

Got a 115+115 : 6.3vAC transformer ( 240v mains Australia) - using unregulated heater supply straight off the windings but getting about 6.85volts - how much will this effect the life of tubes + what is acceptible with unregulated AC heater voltages???

with or without tubes installed?

if htr voltage is 10 percent high or low dont worry about it

Trimmed easlily with a resistor, but you need to be comfortable with ohms law and I^@*R, something I am still trying to teach our engineering staff. :razz:

"If you do not have a heater center tap on your power transformer, you must run two 100 ohm 1/2 watt resistors to ground to create an artificial center tap. If you do not have a center tap, you will get 120 cycle hum. Each 100 ohm resistor is soldered to one of the heater wires. The other ends of the 100 ohm resistors are twisted together and then soldered to ground. "

I found this info on the web. How essential is this. I have noticed a few really notable pro audio circuits where there is no heater centre tap on the transformer and also one of the sides of the 6.3v secondary is connected to ground.