Hello all,  I have a British Pedal Electric Duo-Art Weber grand and I
also had access till recently to an American-made Steck grand Duo-Art.

I restored and compared the two mechanisms and I found that the
American expression box is constructed in a simpler way with less
moving mass driven by the accordion pneumatics. In the British model,
the accordions are actually a distance away from the box and there are
long cumbersome mechanical metal levers that connect to the actual
regulator shafts.

Just purely looking at physics, I would state that the operation of
this box can never be as quick as the American one where the accordions
pull down on the regulator shaft directly.

I will not say which piano has the better sounding expression to my
opinion.  Silence is golden! :-)

I also have to say that I find the British way to adjust the zero level
better.  There is no lock nut and no worm drive that has play in it.  It
is simply two screws and that is really neat.  Also really nice is that
the British box can be taken apart and no cracking open is necessary.
It has screws and gaskets.

Another two cents worth on box adjustment:  Often overlooked is the
fact that there are really five basic adjustments.  The spill cut-off
at level 10, the Accompaniment zero level setting and the actual change
in the accompaniment level from 0 to 1.  The same holds true for the
theme with one degree louder.

The service manuals are not too clear here because they assumed that
the springs were already factory fitted and correct.  It is a
simplistic statement that the springs should simply be adjusted not to
rattle, but this is where the adjustments should start.

It does not matter how much the zero level is adjusted with the
adjustment screws, the piano will never work right if the correct point
of this adjustment is not set.

Mike Kitner elaborates about this in his Duo-Art rebuilding notes and
I have to fully agree with him and the method because it works for me!
This is how it is done:

  Initially Adjust the spring tension for no rattle.
  Measure the Accomp vacuum level at level 0.
  Measure the Accomp vacuum level at level 1.
  Adjust the 'zero adjustment' screw until the maximum change between
level 0 and level 1 is obtained.  This should be about 1" vacuum.
  Now adjust the spring tension until the correct 5" or whatever zero
setting is obtained to play, and not play the arpeggio on the test
roll.
  Repeat the whole procedure to check.
  Repeat for Theme with .5" to 1" louder and to pass test roll test.

It will be found that not much tension change is required on the spring
to meet the zero level.  Check that the other tests, especially the
increase in volume, pass thereafter too.

I have actually seen and duplicated that one can adjust for the correct
zero level with the adjusting screw only.  It is then found that if the
spring is not at the correct tension, there is very little difference
between level 0 and 1 and not audible at all.

Who has tried this method and can give a second opinion?

Regards,
Bernt Damm
Cape Town