Tube Synth PSU 6.3V output

[xto]

Hi everyone,
i have built a few power supplies for my tube synth modules following Eric Barbour's design at the Power Supplies for Tube Synthesizers page from Ken's site.
The voltage output from the 6.3V circuit with no load will vary between 8.8 and 9.1 depending on the voltage fluctuations on the mains. This is as expected: 6.3 / 0.707 = 8.91VDC.

However, in the article Eric states: "The +6v is suitable for tube heaters (all of our tubes use 6.3v heater supplies - it need not be exactly 6.3v.) .... (Heater power need not be extremely clean - regulation is not really required.) "

Four of my modules when used together require a total of 2.5A for the heaters. When I plug the modules to my psu, the voltage drops to 6.1 - 6.2V and gives me exactly 2.5A current. This is excellent.

My worry comes when I use my psu as a bench supply (non-regulated) and I wish to experiment with single tubes.
I was recently working with a 12AX7 miniature tube with heaters in parallel which has a current rating of 0.3A, 6.3V.
If I remember correctly, the voltage on the psu dropped to approximately 8Volts, but current measured exactly 0.3A on my meter.

Should I be using a voltage divider or a voltage regulator circuit to always get 6.3 volts when using single tubes (or combinations that use less than 2.5A of current)?
Is it acceptable to use a higher voltage than 6.3volts as long as the tube uses the current required for its operation?

Any insight would be greatly appreciated.

Chris

[PHOBoS]

[xto]

Thanks PHOBoS, your answer echoes my suspicions. I will be trying out the 7806 in the next few days.

The datasheet specifies 10% tolerance at 6.3V which swings from 5.67V to 6.93V which is a bit far from the 8V I have been getting.

Hopefully, I won't burn out any tubes before I find the correct way of balancing my voltage output.