GGG Ultra Clean PSU High voltage drop

[Cliff Schecht]

Why does the GGG Ultra Clean power supply reccomend a 24v transformer going into the circuit? That's a really high voltage drop down to nine volts and it seems a bit excessive, especially when one considers the amount of heat the 317 has to dissipate. I'm using a 13v 4A Altec Lansing psu and I have a trimpot installed in the circuit so I can tweak the voltage, but even that causes a decent amount of heat to come off the 317, although the 317 stays just barely hot to the touch. I also just mounted the 317 to the 1590B chassis with  a Mica shield with thermal compund on either side. 24v just seems a bit excessive and a lot more current is lost this way.