Looking for advice on power distribution

[Bob Zimmer]

Thanks to all that have responded to this question!

Seems that everyone is recommending onboard regulation.  Think that I'll
definitely go this way!

>... Or use pre-regulators (+/-18V) for the whole system and a +/-15V regulator
>on each PCB. ...

>... So I would do both, using the big central regulator as a
>pre-regulator. ...

This never even occurred to me.  This is stimulating some new thoughts that
I'll have to look into!  See comment below about card edge connectors!

>Don't use 7815/7915 regulators - I only had problems with these in my
>pre-regulated system.  ...

I'm going to assume that this also applies to the L versions (100ma) as
well.  I had thought that these regulators (7815/7915) were pretty much a
staple!

>.. Since I use these tiny +/-15V tracking regulators (4195), everything is
>just fine. ...

I was interested in the LM125 (+/- 15V 100ma) from National Semiconductor,
but can't find a distributor that has it in their catalog (looked in Allied,
Digi-Key and Mouser).  Didn't know about the 4195, I'll have to look it up!

>... A word of caution about this, however. Since the modules will probably 
>have some kind of connector for power, that means that there will 
>probably be lots of connectors, and therefore lots of opportunity for 
>connector failure, loose contacts, pluggin/unplugging with power on 
>(whether intentionally or by mistake), etc.

Part of my goal is to be cost conscious and use top quality surplus when
possible.  I was intending to use 44 pin card edge connectors (gold plated
if I can get them!) since they offer a lot of connections for a low price
(less than $1 each). I've seen that if you use .062" boards, they fit snug
and generally don't (in my limited experience) work loose (my modular will
be only used in a studio, not on the road).  I was thinking of wiring them
together with #18 stranded, where a ground would be run as every other line,
allowing for separate digital and analog grounds. This should also allow
keyboard CV, gate and trigger to be distributed as well.

I was concerned about interference from unregulated DC interfering with
these, but a pre-regulator should help to eliminate that concern!  In my
inexperience, ripple can mean hum?

>... The most important and overlooked aspect I've found when building large
>modulars is a very good ground between all the cabinets and modules. These
>ARE voltage controlled synths remember. ...

I am thinking about using PAIA's FracRak which includes 1/8" aluminum
panels, connected to metal cross members.  Structurally this looks sound,
and hopefully with the ground lines mentioned earlier, it would be
sufficient.  I am wondering about ground loops though!


  >=== Bob Zimmer -- Philadelphia PA ===<
  >=== bzimmer at voicenet.com          ===<