Recently I designed a Hi-Fi Preamp, but it needs a tightly regulated DC to work well. The preamp is almost entirely comprised of constant current sources, so it will present itself as a perfect load to the regulator. This means you can skip on the negative feedback and go straight for a simple zener design. The bootstrap here seems to greatly improve the stability of the CCS and thus the ripple rejection, to above -120dB. This means that the preamp will work without any supply noise whatsoever. Adding an input filtering capacitor of 470uF will increase the ripple rejection to above -150dB. The series diode is a temperature compensation for the zener.
