SV: Re: SV: Re: SV: [sdiy] Re: (sdiy) English lessons

[harrybissell]

LOL !!!

You were correct.

You CAN base it on a stable power supply... but NOT on the "assumption
of a stable power supply".   You would be a fool to count on that !!!

This is a mistake that many people make in their designs. Just because YOUR
supply was good, does not mean the next one will be. Might add that sometimes
they don;t become BAD until you add the next module.

I had a hell of a time with an EFM VCO4d and an EFM VCF2e combo.  When I would
crank the VCF to the highest frequency, it would oscillate. That made the VCO
drop about a half step in frequency. The ultrasonics rode the power supply
rails, and got into the ramp reset comparator which was derived from the power
supply. The decoupling caps on that particular layout were not located where
they could help.

Adding more decoupling helped. Using an on-card voltage reference for those
critical
points killed the bug dead.

Another funny story was my Aries VCO and VCF... which had very bad noise
problems as delivered by the factory.   I cured them by adding decoupling to
the trim pots. These were old metal shell types. I assumed that the metal shell
was picking up noise and my
decouping the pots stopped it.  SILLY NEWBIE.  What I was really looking at was
my own sh!tty power supply.  The noise was self inflicted... and they used the
rails as reference, so the noise walked right in.

When I rebuilt these a couple of years ago, I found those added caps and had a
good
laugh... because I realized right away that I had done the right thing, for the
wrong reason.

Unless you are building a closed system from the ground up, remember to NOT use
the
power supplies for critical reference voltages.  If its a closed system, do
what works for you !!!

H^) harry

karl dalen wrote:

> > > > After words:
> > > > In any additive wave thing in wich phased saw waves actuaclly are
> > > > wave amplitude are the crucical inferno. So dont base your phase
> > > > waves on the asumption of stable power supplies! ugh!.
> > > > Its very simmliare to the basic saw to triangle converters!
>
> I just relized, what an absolute ludicrous/preposterous thing i just said!
> Shure you can base it on stable power supply, everything are based on that!
> Im sorry for that horrendous goofing! heh! :-)
>
> KD