-----Original Message-----
From: G Ramasubramani [mailto:grama@...]
Sent: Tuesday, October 30, 2001 1:34 PM
To: Electronics_101@...
Subject: Re: [Electronics_101] The need to know!

Jim,

?

?? It is tough responding to this mail since you seem to have misunderstood nearly everything I wrote.

?

Rama

----- Original Message -----

From: Jim Purcell

To: Electronics_101@...

Sent: Tuesday, October 30, 2001 9:09 AM

Subject: Re: [Electronics_101] The need to know!

Rama,

Call me Rama.

Call me anything but late for dinner.
?
?As you mention, yes - I am referring to space between the plates and dielectric. I thought that was pretty obvious.

YOu seemed to be making a distinction between plate distance and dielectric thickness when you
said they cold differ. If they differ then you must have air as an additional dielectric.
?

Are you talking leakage due to exceeding dielecric strength?

Yeah. Maybe discharge is not the correct term, but what the heck - I am not writing a book :-)

??????????????????? I'm sure that the cap will discharge but worse, it might be
??????????????????? Permanently damaged in any but air capacitors. Air is generally
??????????????????? a self healing dielectric.

If the plates were farther apart than the dielectric thickness you'd have a mixture of dielectrics, the normal dielectric plus some air (or vacuum.) I am not sure of more important or less important - both play a role.

????????????????? Easy to get that from the formula for capacitance as a function of
????????????????? physical design parameters.? In this formula the plate distance is the
????????????????? only term on the bottom and dielectric constant is on top with
????????????????? a constant and plate area. So distance has greater effect on
????????????????? capacitance. And dielectric thickness is generally assumed to be
????????????????? the same as plate distance.
?

Jim
?
?

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My church wants to run a line level, balanced output from the back of the church to the front of the church (65')? Then, after running through a wall-mounted pot, on to an amp and then to monitor speakers.? The pot is so that the choir director will have volume control over the signal.
?How do I spec the voltage/amperage on the pot?

A gain control at speaker level would be better. I haven't done PA work in a very long time but I can't recall seeing line impedance gain controls as commonly available. You might check with a local sound company to see if they are available.

Jim