Re my e-mail to John R. Grant (95.12.30) and his reply.

John, I believe there IS a fundamental difference between electric
valves and electric "key-pushing" transducers: the former is a low-
power control device, while the latter is designed to produce _big_
power (force x distance).  In modern solenoid pianos the transfer
function of the playback system is monitored (or "calibrated"
periodically) to maintain consistency, therefore the inherent
stability of the solenoid system (and friction) is not critical.

The electric valve for a pneumatic piano, however, doesn't get
periodic calibration cycles like a solenoid piano, and therefore it
must have good stability.  Adding an electric valve to a reproducing
piano must not degrade the piano's performance in any way, which
means that "tightly controlled" specifications must be achieved, and
the valves must remain "in spec" with no more maintenance than the
pneumatic system gets. (And we're lucky if the owner pumps out the
pouch bleeds regularly!)

I agree that 24 volts or more is better suited to transistor control
than the 12 or 15 volt "magnets" traditionally used in organs.  (I
wonder if that's related to the standard 6-volt and 12-volt
automobile electric systems?)

I don't have any data on the Reisner valves, nor facts on their
proposed new design. Perhaps one of our subscribers can provide
information.

When I test the different electric valves I'll mount each specimen
on a wood "sounding board", the same size as Horst Mohr and Walter
Tenten used.  Then I can compare the sound produced using a
microphone and oscilloscope. Most of the impulse "thump" or "click"
will be transmitted to the "drum-head" sounding board, which is
representative of a piano installation.  Admittedly, this test is
pretty subjective!

Happy New Year!

-- Robbie Rhodes