My friend Randolph Herr brings up a good point about sustaining pedal
compensators on Ampico "A" mechanisms.  I usually send emails out
privately to those who ask specific questions on MMD to avoid
controversy but I feel like chiming in on this.  I can't keep quiet
when it comes to Ampico "A"s.

One reason Ampico might have been slow to respond to the need for as
sustaining pedal compensator as opposed to the Duo-Art is that the
Duo-Art relies heavily on the volume of vacuum which is passing through
the expression mechanism where the Ampico relies on regulated vacuum.
This is a factor in considering a need at all for a sustaining pedal
compensator on an Ampico "A".

Up until two years ago I was under the impression that the vacuum level
in an Ampico "A" was totally regulated.  That is to say, if a certain
level was called for, all the notes controlled by this level would be
played at the same volume.  I was under this belief until I recorded
rolls on my "roll to MIDI" recorder.

If you have Cakewalk as I do, check the MMD Archives and look at the
recordings I have made with my recording unit.  You will see that there
is some variation in each level due to the fact that the vacuum level
does drop a bit lower when a large number of notes are called for in a
short period of time.  However, the Ampico does in fact have the ability
to self-regulate it's vacuum levels to a great degree and therefore
eliminate the need for a sustaining pedal compensator.

I'm known for having a very good musical ear.  I have never heard the
Ampico play any louder when the sustaining pedal is called for.  I know
that you can figure it out on paper that the piano will play louder
with the sustaining pedal on.  In practical terms, if you hear the piano
getting louder when the sustaining pedal is called for, I think it would
have to be your imagination.  I think if you were blindfolded and had
a friend randomly disconnect the compensators you could not tell by
listening to the music if the compensators were hooked up or not.
Listening is the ultimate test, not what can be figured out on paper.

Also, I do not respect the Ampico "A" sustaining compensators because
they are of a poor design.  After spending many hours insuring the
workings of the expression mechanisms I do not want anything interfering
with their efficiency.  These compensators apply pressure to the spring
pneumatics on all levels of vacuum.  They only need to operate during
soft passages.

I do not believe the factory put these units through development nor
did they figure their forces on the mechanisms mathematically.  If
the factory did put these devices through the rigors they would not
magically just happened to measure a perfect one inch square.  When
I restore a late "A" I recover these compensators but I don't connect
the linkage to the spring pneumatics.  This preserves the units for the
next generation but does not interfere with the expression.

Paul Manganaro