Electric Valves
By Robbie Rhodes
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
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(Message sent Mon 1 Jan 1996, 23:56:49 GMT, from time zone GMT-0800.) |
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