Using Torroidal Transformer for 1/2 Secondary Voltage

[Wavewhipper]

I have a 120/240:45 0 45 volt transformer , full wave 120v in gives +/- 65 vdc.
300VA
Any problems I should know about if I use it wired for 240 volt input with 120 vac input so I can run a +/- 35 volt amp at 200 watts ?

EDIT:

I must have had to put myself on the spot to figure out the secondary windings may be too thin to handle 200 watts at +/- 35 vdc but would be rated for the 300VA at +-65 vdc, 1/2 current of 300VA at +/-35 VDC.

 

[FauxFrench]

Your intuition seems right to me.
You will have more resistance in the primary winding when you double the number of windings, so the output voltage will sag more when loaded than with the 120V winding. That comes on top of the proportional reduction in output voltage. You may get 28-30V rather than 35V. Probably you will get less than half the 300VA at the output (you use only half the voltage capability and have a further increase in current induced losses).
At least you should not harm the transformer and do you need 200W?

 

[rayma]

Any problems I should know about if I use it wired for 240 volt input with 120 vac input so I can run a +/- 35 volt amp at 200 watts ?

Using a 300VA transformer on half line voltage makes it a 150VA transformer with the same current rating as for 120V.

 

[Wavewhipper]

I would like as much power as the drivers can tolerate, I am currently experimenting with bass amps. They need lots of power, especially for a 5 string.

 

[FauxFrench]

A trivial possibility is to use your 120V winding, get the +/-65V and use linear regulators on both polarities. Then you have a "stiff" +/-35V output with generous input ripple margins.

 

[Wavewhipper]

I did think of that, plenty of margin for a zener, driver and output transistor.
I was actually thinking of making an adjustable +/- power supply with a higher voltage 300 watt toroid since I experiment with so many different voltages and wattages.

 

[googlyone]

IF you are building a bass amp, why not just make it to run off the +/-65V? Sure as eggs, you will be looking for the power the first time you crank it up.