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

[David G. Dixon]

Whatever flips your switch... literally!

Personally, I wouldn't want to have two different rail levels in my modular,
particularly if I wanted to move modules around later, but if this doesn't
fill you with similar angst, then by all means...

However, bear in mind that the number of places in any given circuit where
the difference between 12V and 15V supplies would be important is miniscule.
Certainly, in oscillators (including LFOs) there will be places where
resistors should probably be changed, but most other modules should be
interchangeable.  There is very little chance that you will actually hurt
anything by plugging a 12V module into a 15V supply, and absolutely no
chance vice versa that I can envisage.  As we say in the scientific world,
"Suck it and see!"  You may find that you only have one or two modules where
any changes are desirable, and then only because switching supplies puts
some signal levels slightly out of whack (e.g., a signal goes from +/-5V at
12V to +/-6.25V at 15V), causes a signal to distort at a lower gain setting
(again, because the signal amplitude is bigger), or changes the sensitivity
of a module to some knob or other which is hooked directly to the rails
(e.g., frequency or pulse width on a VCO, or CV bias on a VCA).  All of this
is pretty easy to live with if you don't feel comfortable sucking parts off
your commercial boards.


> > I would suggest either option 3 or 4....
> 
> 
> Lots of people saying run all from 12v or all from 15v, but im left
> wondering why?
> 
> Effectivly what im saying is that i can run the 15v from one psu and the
> 12v from another if need be.
> 
> This would be akin to using two modulars and patching between them.
> 
> Why should i bother going to all the potential stress and trouble of
> running modules out of spec?  Again, a lot of this system is
> made from commercial modules, for which i dont have the schematics.
> 
> What is the advantage of any option?
> 
> 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?