digital/pga power supply... separate or same as lm3886?

[geekysuavo]

right now, i'm trying to realize a completely digitally-controlled gainclone amplifier (a related post can be found here), which raises the question: how to supply the +5Vdc for the micro and relays and the +/-15Vdc for the PGA2310/OPA2134?

my first thought was to simply attach a LM7815/LM7915 pair to the output of my current design for a +/-35Vdc unregulated, snubberized, high-capacitance supply. since a |Vi-Vo| of 35V for these linear regulators is pushing the boundary of my comfort, my idea for a solution was to first reduce the voltage of each rail using series zener regulators. almost as an afterthought, an LM7805 could be attached to the +15Vdc rail for micro/relay supply voltage. (the circuit is attached...)

but after some thinking, the most pressing question in my mind has been: will this introduce distortion into the audio circuit due to uneven loading of the power supply? a second toroid (15+15) and separate supply would be the solution in such a case...

so, what do you think? is a separate supply for 5V and +/-15V necessary to ensure the best quality audio? anyone with past experiences on this here?

thanks a million!
~ brad.

[geekysuavo]

sorry to have made the first post seemingly without using common sense, but i do that from time to time.

after thinking about the operational requirements (microcontroller basically managing all aspects from startup to attenuation and source selection to shutdown) of the project, i've realized a separate supply for the non-lm3886 voltages is required.

lolz, thanks,
~ brad.