Pete Knowbloch asks about measuring the leakage of a stack:

> The only place that I can find in The ORCHESTRATION BUILDER'S MANUAL
> that references stack leakage is on page 201 (Appendix G).  Using
> the Bubble Jar to read differences across a player stack (2nd Way).

   If you will check on page 198 of Appendix G, you will find a device
called a supply throttle. Build one of those and test it for tightness
first, then go ahead and use it to measure everything you want to find
a relative amount of leakage for.

   By the way, I misstated myself in the last letter. I said  I try for
1-1/2 3/32" dia. hole equivalent leakage for a stack, and meant for
each half of the stack, instead.

   As far as the thickness of a bleed is concerned, the ones I
reference to are 1/8" thick. These holes would bleed ever so little
more accurately if I had countersunk the hole on the back side so that
it was a sharp edge, but you would not be able to read the difference
by any gauge you own. Of course, the smaller the hole, the more
difference that 1/8" thickness will make. Figure a noticeable change
when the ratio is about 3 to 1. My suggestion is to build this thing to
suit yourself, once you see the principle involved. (You can also build
it with a rolling curtain instead of a slider.)

   But first, you need to provide the appropriate fixed bleeds for your
expression box and then measure your new pressures when we can see the
difference. Just disconnect it from the stack and test it, first. After
that, check on the stack. Your numbers didn't make much sense, probably
going into a closed stack.

Craig B.