late one : To earth, or not to earth...

Martin Czech martin.czech at intermetall.de
Fri Jan 9 13:37:12 CET 1998


Another idea:

The best solution would be going balanced. But that's quite expensive,
using spedcial ics for balancing, unbalancing, introducing offset
etc. Is there any other possibility?

I never had problems with consumer hifi stuff, because there are no
ground loops, all chassis are separated from earth, the internal trafos
are insulating types, safe. All devices have their own power supply...

That's it!

Now, would it be a stupid idea to do this in a modular synth:  Every
module gets not only it's own regulator and overvoltage protection
(this is good practice) but also it's own trafo , rectifier etc., i.e.
now the modules have no ground connection to each other. Little PCB
mounted, safely isolated trafos are cheap, much cheaper than balancing
trafos for audio. (I would keep the trafo away from the module). If the
module case is made out of metal, this could (should) be properly
grounded, isolated jacks keep earth chassis ground appart from signal
ground. Some caps could provide a hf grounding way to earth. In this
case normal unbalanced patchcords etc. can be used, the shielding can
(has to) be connected to both sides, no extra module circuitry, an
unbalanced system could be easily upgraded und the power supply can
grow with the system.

Ok, this is a bit exaggerated, but it shows the idea. 

One could save cost with the following reduction: A two module system
won't have ground problems, and a 3,4,5,... up to n modules. This
depends on the physical size of the system, and on the wiring etc. One
could find out e.g. that a 5 module subsystem works good enough with a
single power supply. So it would be an idea to divide the whole system
into 5 module subsytems, which have their own supply.  As long as no
large currents flow through the patchcords, and the patch ground
connection has low resistance this should work.

Is there any mistake in this proposal ?

By the way: how is the Roland 100M made?
I mean, doesn't it have 5 modules with power supply per cabinet.

m.c.

------------------------------------------------------------------------
m.c. has made it finally:  3 CDs out now; 72 min. minimum; "1"
(1994-1995),"2" (95-96),"three" (96-97); experimental stuff; mostly
Eimert/Stockhausen style; but also modern popular style





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