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MMD > Archives > November 1999 > 1999.11.02 > 18Prev  Next


Double Valve Player Systems
By Andrew Barrett

I was just reading the past two Digests which had articles about
restorers who disconnected or removed the primary valves in Standard
players, because they thought it would make it easier to restore and
they're "not needed."  I hate to agree with the first reason, but it's
true: it will make the players easier to restore.  But, it will also
(1) ruin the player, (2) decrease its value, and (3) give it poor
repetition.

I used to think that the more valves an instrument had, the more time
it took to sound a note because of waiting for the signal to pass from
one valve to the other, and for all the valves to seat before the note
can be sounded again.  Not so.

A couple months ago I was rolling the principle of operation for valves
around in my head, and it came to me.  The double-valve system has such
good repetition because, with two valves, you don't have to wait for
the second valve to seat before the note is sounded again.  The second
valve is only halfway down while the first valve has already been down
and up and is signaling it again.  Please tell me this is the right
theory.

Andrew Barrett

 [ Editor's note:
 [
 [ It's true, the time delay until the note sounds is not terribly
 [ important, Andrew.  What matters in a control system is that (1)
 [ the turn-on delay should ideally be the same as the turn-off
 [ delay, so that (2) the fastest repetition is obtained at all
 [ suction levels.
 [
 [ The primary valves in a player piano both amplify the weak signal
 [ from the tracker bar and also help to reduce the delay asymmetry.
 [ The double-valve system is a very fast and sensitive player
 [ action, which has nice fast repetition even at low suction.
 [ The drawback is the complexity and added production expense.
 [
 [ Dr. Hickman's task at Ampico was to reduce the production cost
 [ of the Ampico player, so he designed the ingenious valve with
 [ a tiny ball-check valve, which greatly improved the performance
 [ over an ordinary single-valve system.  That's how Ampico eliminated
 [ the primary valves of the Ampico A.
 [
 [ -- Robbie


(Message sent Wed 3 Nov 1999, 00:36:42 GMT, from time zone GMT-0800.)

Key Words in Subject:  Double, Player, Systems, Valve

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