There is a trick using SCR's that can be used to reduce the voltage of a transformer for a power supply (see attached).
The gate trigger voltage is obtained from a divider between the transformer peak voltage and the output voltage. When the output voltage rises there is a point where the voltage on the gates doesn't rise high enough to trigger the SCR any more, thus limiting the output voltage.
It has a few "gotchas" however;
- at higher voltages the gates may need to be protected by diodes
- the output voltage is a function of the gate trigger voltage which is itself a function of the SCR temperature, so this simple circuit may show a high temperature sensitivity
- SCR's and audio generally don't make for good partners and there may be considerable, and objectionable, high frequency buzz in the output