/diy/ - Do It Yourself

your toroidal transformer is completely unsuited to the task. what you need is a transformer with an input voltage equal to your line voltage (either 120Vac or 240Vac) and two secondaries, one of around 200Vac to generate +250Vdc and either a 6.3Vac or 12Vac to power the heaters in the tubes. you can use 6.3V and wire the heaters in parallel, or put two in series and wire them to 12V.

if you like to live dangerously, you can get the 250Vdc directly from the power lines, with no transformer, and get shocked every time you plug something in.

doing the 2-transformer trick in >>1215713 is certainly doable, but it's heavy, expensive, and takes a lot of space.

also, your toroid is rated for 120W, which is better suited to a power amplifier, rather than a pre-amp. but the voltages are wrong for a power amp as well.