Robbie asked in 021118 MMDigest:

>[ Can the Overture solenoid player system accommodate friction changes
>[ in the piano action, Don?  The Ampico B player had an adjustment for
>[ this purpose that was pretty effective.

Stoddard's work on this problem was effective.  In answer to your
question, yes, this is why we developed the system we call "Adaptive
Pulse Control".

With all solenoid systems now sold they are calibrated manually and
this table is used until it is recalibrated.  We found the piano action
frictions changed as it played, as well as the humidity levels of the
room.  Up-weight and down-weight changes had great effect on the power
curves of the solenoid.

The solenoid we developed has a liner power range.  On soft notes the
solenoid has to lift the key weight the full 10 mm stroke.  On a loud
note full power for 3 mm was all that is needed, then the piano action
inertia came into play.

To understand the control of these events one has to think in terms
of time.  The DSP is computing information at 32 mips, or 32 million
instructions per second.  The Overture system will calibrate as it is
playing the note.  The sensors indicate the key engaging the
underlever felt, the jack release and key motion.  On loud play back
a player will compress the dip felt and change the key travel.  The
Overture system will compensate for this also.

The early restoration work I did on reproducing pianos has helped in
the development of this system.  The engineer responsible for the
circuit design was Charles Lee.  Charlie's talent is also responsible
for other solenoid systems now being sold.

Don Dusenbury