Hi! I need 15V regulated dual supply, and I've decided to go with Zeners instead of IC regulators. So I have two questions:

- what would be the value for the resistors in series with the Zener diodes?
- I'd also like to have switchable 7.5V dual supply; can I use some DPST switch which would switch on and off the 7.5 Zener diodes in parallel with the 15V ones, and also, what would be the resistor value for the 7.5 diodes?

The transformer would be +-22V or +-18V.

Thanks in advance!

 

Use IC regulators.

 

You can use LM317 & LM337. Use a resistor in each that gives you the +/- 15, and a DPDT switch to add parallel resistors for the +/- 7.5. You may need trimmers to get accurate results.

Use the 18 volt transformer. With filtering, that's still going to be over 24 volts on the capacitors. You will have to heat sink the regulators.

 

Thanks for the replies guys. However, I'm leaning towards using zener diodes because that will be regulated supply for a guitar amp project, or more precisely, a supply for the preamp, so that precise regulating isn't what I'm going for. I already built the amp, but with TDA2030 chip, and I like how it turned out, but I'd like to use different power amp to make it more loud. So that's why I'd like to know the resistor value, cause naturally, a different transformer comes into play, instead of that one that is already in the amp.