Electronic – Another question about Lighting up Vacuum Tubes

Three comments:

1) You'll want to regulate the voltage down to a stable voltage, say 5V, using a high-line-rejection regulator. A simple linear regulator with a couple of capacitors can provide > 80 dB rejection here.

2) You're presumably using a tube pre-amp to get a sound that has significant tube (saturation?) distortion instead of possible transistor (zero-crossing?) distortion. Why would you then introduce transistor distortion from an opamp on the output signal? Isn't that kind of counter-productive?

3) All tube characteristics (linear and non-linear) can be modeled efficiently in a low-cost DSP, to within limits of measurability (which are more sensitive than human ears.) So there's probably a much cheaper and easier way to get the sound you want, with less energy waste and smaller space.

As Dave said, you don't have to actually run the tube in a real circuit to get the visual effect. All you have to do is power up the heaters.

Your particular tube actually is two tubes in one package and has two heaters. Each heater is 6.3 V. You can put 12.6 V accross pins 4 and 5, or 6.3 V accross both pins 9-4 and 9-5. In the latter case, you connect one side of the 6.3 V supply to pin 9, and both pins 4 and 5 to the other side.

Don't worry about the exact voltage that much. These things were intended to be run directly from a 6.3 V output winding of a power transformer. It will be OK with variations of this 6.3 V due to input line voltage variations. Get a "6.3 V" transformer intended to run from whatever power you have in your location and the tube will be fine.

You do have to make sure the transformer is rated for the total current of all the heaters together. For example, if you are powering 5 heaters that all take 6.3 V at 300 mA, then the tranformer output must be rated for at least 1.5 A.