Power LDO PSU with TL431

Thank you so much for your help.

Is the 560 ohms due to the 0.6 V needed or the Hfqe of the Darlington . If I use a tip 142 instead the BD244 (because have it already), I stay with the 560 ohms also ?



For the symetrical shematice for negative voltage, the sense of the TL 431 is reversed I will use a tip147, but should I stay with the BC337 as well ?
 
Hello Everyone
I'm building a power supply where I plan to use this circuit, but I also need negative rail, so I make the circuit in MC12 , it works but I didn't have enough experience with MC12, and I can't verify it's stability,
My requirements from this power supply is 500mA ,+-15Vdc or 18V will work too
here is the MC12 file

please check it if anything is wrong let me know I'll do practical test on weekends
Screenshot (212).png
 

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