From a LM317/337 balanced psu giving +/- 15V i want to take + 5V using an LM7805 or another LM317. Is is worth the hazzle (not much, I know ...) to use LM317 or just pop in a LM7805? Is there a difference noisewise?
just use a 7805 for your +5V supply.
But, it adds load to your 15V supply and will increase the dissipation of the 317.
Alternatively, run the 7805 off the unregulated supply, if the 7805 can take the dissipation.
Try checking the manufacturers' datasheet, there should be information on the noise issues. I remember having read some day that the adjustable LM317 would generate less noise under certain circumstances, but I'm not sure.
