Home Computer Audio Asylum

Music servers and other computer based digital audio technologies.

RE: Linear Power Supply or Battery on Mac Mini - pics

"But how do you know that these 'droops' are detrimental ?"

The circuits that the power rail is feeding will have some inherent noise rejecting character. The key to success is understanding this character, what the supply can deliver, and how the resulting performance due to interaction of power supply and the load circuit systems compare with required performance. It's a multivariable equation at least.

"And remember, those measurements were taken before the additional filtering module installed within the Mac Mini. And another thing, decoupling caps right at the Vcc source pin to a component tend to help with those fast 'droops'. There are several such caps in most digital designs."

It's true, for differential noise measurements like this you definitely have to measure right at the load to get a realistic idea of what is truly going on where it counts. Measuring upstream of the filtering will tell you very little about the power quality as seen by the load.

Though most audio gear these days, depending on application of course, is pretty awesome at rejecting differential noise but much less effective at rejecting common mode noise which is coincidentally cropping up more regularly.

Less talked about and less well spec'd on power supply equipment is the common mode noise performance on the outputs with respect to earth referencing as most common audio equipment uses. Getting common mode noise way down in earth referenced audio gear power supplies is critical. The humongous problem here is testing gear for doing proper evaluation at an audiophile level is going to cost a fortune. Your 8 bit scopes and high end fluke dmm's just wont have what it takes to see -120dB throughout the audio band and a preferably a reasonable bit beyond. A good audio adc could probably be helpful fur the lower frequencies but what about the 200kHz and up? the answer is $$$$$ gear I can't afford. Even my work won't buy that kind of stuff. It's specialty gear and gonna cost ya.



Edits: 12/23/14

This post is made possible by the generous support of people like you and our sponsors:
  Amplified Parts  


Follow Ups Full Thread
Follow Ups

FAQ

Post a Message!

Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.