Cgs synth

A number of my designs use a pot wired as a voltage divider to control speed
etc. In most of these cases, the pot is connected to an input socket that is
normalized to +15 volts so that without an input, the pot acts as a DC
control pot.

This may cause problems with any module that is plugged into one of these
sockets because for a brief moment, +15 will be backfed into the output of
that module. If the module has a resistor in line with its output as per
good practice, or an opamp that can handle such shorts, there will be no issue.

Perhaps though, there are some less well designed modules that could be
damaged by this. No one has had a failure directly attributed to by this
that I know of. Nonetheless a wiring error on a friends system caused a
similar situation that did do damage to a module.

My recommendation is that the +15 is fed to the normalized connection on the
socket through an additional 1k resistor, therby limiting the current. Some
of my later designs already have this in place.

Ken
_______________________________________________________________________
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Hi Ken,

> My recommendation is that the +15 is fed to the normalized connection on the
> socket through an additional 1k resistor, therby limiting the current. Some
> of my later designs already have this in place.
>

Would you provide examples of cgs modules with and without this
'correction', just so that some of us (well, maybe just me) have concrete
examples to refer to.
Thanks, Jeff

Lacking the resistor are the V8 sim, Voltage controlled divider (division
input), Digital noise "Speed CV",

The Wave folder has them - the R+ pads, though they are not shown on the
circuit diagram, because I have not drawn any pots in with that arrangement.
I must update that article.

Ken