[sdiy] That old modular power supply question (again)

[m.bareille at free.fr]

Hello,

> Lots of people saying run all from 12v or all from 15v, but im left wondering
> why?

It is more simple to have only one +/- voltage to manage than two ;)



>
> What is the advantage of any option?

With +/-15V it  is quite easy to produce the +/-12V : add  7812/7912 regulators
on your +/-15V rail and it is done ( do not forget the small heatsinks )

It is herard to increase the 12V to get 15V ! :)

I prefear 15V rails because your headroom level is higger at east with opamps.
The opamp range under +/-15V is around +/-12.5Vmax = 25Vppmax before clipping  .
With a +/-12V psu you have a op amp range of +/-9.5V ( or +/-9.8V ) before
clipping ...

Usualy ,more headroom you have, better the sound is!  This is true with almost
all analog audio devices .

There is no real cost difference between +/-12V and +/-15V PSU. The only reason
to reduce this voltage is when you want to power your device with batteries,
imho...


>
> Again just having 2 power supplies (one for 12v, one for 15v) or just one
> large 15v psu, and regulating down to 12v on the busses
> themselves seems like so much more simple that i cant understand why there is
> need to do otherwise?

I have 4 cabinets on my modular actualy and a small PSU inside each one.
Cabinets are ground wired on the back with bananas patch cords. It work
perfectly without any noise or problems.  The tip is to correctly drain all
ground lines and to wire them like a 'star' with large gauge wires or to twice
all ground wires like on a PC psu... Another advantage of multiple small PSUs is
that you can have 100% independant cabinets .

A central big PSU can be a good solution too , but this is more expensive usualy
and the regulator section will be much more complex . You can take example of
large mixing desk PSU. You will also need to evalutate the total power and size
your big PSU accordingly.


Thanks,

Marc B.