1. Creating a new part schematic Start by creating a new part in your project. The 6L6 pentode vacuum tube normally has 7 terminals (Anode, Grid 1, Grid 2, Grid 3, Cathode, and two for the heater). So, you would need to add seven terminals from the library
2. Setting part properties Name this new part '6L6'. You may also want to add relevant properties such as Manufacturer, Manufacturer Part Number (MPN), etc.
3. Creating a Symbol Now, the key part is to create a custom symbol for your vacuum tube. This can be done by creating an SVG representation of your part.
   • Create a symbol with SVG file In a suitable SVG editor, like Inkscape, you can draw a symbol for your vacuum tube. It would look something like a circle (for the glass envelope) with lines or rectangles (for the terminals). Remember to save this file in SVG format.
   • Add the SVG as an asset Back in Flux, you can add the SVG file you just created as an asset in your project. Click on the empty canvas in your project, scroll to the assets panel on the right, and add the SVG file.
   • Match the pin position with the custom symbol Finally, you would need to set the terminal location for each of your terminals in the part. This is done by setting the 'Symbol Pin Position' property for each terminal. This would be x and y coordinates within your symbol where you want your terminal to be.
4. Publishing Once your part is created and saved, you should publish it to your library so it can be easily used in your schematic.

1. Resistor Thermal Noise: This method utilizes the thermal noise or Johnson-Nyquist noise generated by a resistor. The voltage, V across the resistor can be calculated using the formula:

where:
- $ V $ is the RMS noise voltage
- $ k $ is Boltzmann's constant
- $ T $ is the temperature in Kelvin
- $ R $ is the resistance in Ohms
- $ B $ is the bandwidth in Hz

3. Noise Generator ICs: There are ICs available in the market (like NE602) which generate noise that is suitable for use in your circuits.

1. Create a new blank project.
2. Look up the parts (like a resistor, operational amplifier, capacitors for filtering, or a Zener diode, depending on what kind of noise source you want) you want from the library, and drag them into your project.
3. Connect the components as per your desired noise source design (For example, to create a thermal noise source, create a voltage follower circuit with an operational amplifier and connect the resistor at the input).
4. Once you have your circuit, you can add properties to your design to describe your work, and use the simulator to observe its behavior.