sorry, you are right - I was careless in what I posted. I was thinking at
the time I wrote this of a proportioning valve used in aircraft servos (I
can't remember the name, the valve drove a "modulating piston" with an LVDT
for rate feedback, and the mod piston drove the actuator) - you are right
that this valve is pneumatic - did you notice the 80 Hz frequency response?
that's enough to use it to drive one heck of a subwoofer (or a super stiff
servo)

"Don Foreman" wrote in message
...
On Sat, 27 Aug 2005 19:05:12 -0700, "william_b_noble"
wrote:

There was some discussion a little while back about some precision control
of air or hydraulic pistons - I don't remember which - anyway, this valve
that I ran across is directly applicable - very cool valve (detailed
description in the listing, I won't take up space here)

here's the link
http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7542065234

In that listing you describe a hydraulic valve (5000 PSI, 1 GPM) but
the mfrs lit describes a pneumatic device.