I think Spencer Chase covered about all of the things in his list that
can cause a Duo-Art to play too loudly.  It never is quite possible to
explain everything fully in a letter when talking generally about a
problem of this nature.

I will say, however, that cross valves will cause this same problem,
although round valves will not.  Here is how it works: All Duo-Arts rely
on a little bit of leakage in the stack valves to prevent building up
pressure when no notes are being played.  (That is when they leak just a
little-- at the low intensity.)  This could not happen with a self-
compensating mechanism like the Ampico, but in the Duo-Art, the stack
pressure is created through a knife valve.

Consider for a minute how this looks to the pump.  Visualize an in-line
valve that cannot get perfectly airtight, in series with another valve
that can get just as tight as it can.  Close them both off.  Place a gauge
between the two in-line valves and what do you read?  Zero?  Nope.  You
read exactly 1/2 the pressure at the pump! Now suppose your first in-
line valve (the knife valve) was just a little warped, curved away from
its slide.  After all, it's maple, and maple can do that.  Now you read,
say, 15" when both are closed, with very, very little extra leakage from
the knife valve (that is, when the pump is at 20").

With cross valves, you will have a number of valves which have taken a
"set", shaped like the cross valve itself.  When new leather is used, it
will take a number of years, but will do the same thing even worse,
because it is GARMENT LEATHER, tanned to be soft.  Original Duo-Art valve
leather was pre-stretched, industrially staked leather designed for the
trade! That is a tremendous compromise, and very few people realize it.

Only with a round valve are you going to permanently prevent this
problem.  Later Duo-Arts ALL used round valves, with the same expression
system and worked just fine, but the cross valve was retained in the
larger players whose stacks had been built earlier and were still
waiting for a piano order to place it into.

Just as a pouch would hold a few of the valves up just high enough to
leak, so also will a few valve leathers which have taken an impression
of the cross seat and have gotten rotated, sitting cross-wise so that it
can leak when the vacuum level called for is low.  Now when the vacuum
called for is high, those valves get "sucked" down tight and don't leak
at all.  But the only adjustment is to the zero intensity, so you have to
set the lowest intensity higher just to get the notes to play.  That
raises everything, and really blasts you out of the room once the
intensities get over #10.

The normal valve leakage in a Duo-Art is required, as I said, but if
only one valve is being suspended even 1/64-inch on one corner, either
by a pouch or an embossed valve leather sitting crooked, this is what
you will have.  Sometimes you can fix this cross valve problem
temporarily by replacing the expression box with a suction box of vacuum
cleaner on each side, separately.   Keep the piano hammers from playing
or dampen the strings with towels and run your fingers back and forth
over the tracker bar.  Do this enough times and sometimes cantankerous
valves will re-seat.  It takes about 60 inches of vacuum and usually
about 5 minutes of back and forth on each side to do it well.  If the
problem is a pouch though, you won't be able to fix it that way.

To find a tight pouch, put a gauge on that half of the stack and suck on
each pouch nipple momentarily when you have the zero intensity set to a
normal 5" or so -- the pressure it should be working at but doesn't.
Each time you find a tight one, you'll see the gauge move up.  If it is
the only valve on that side leaking, the gauge will stay up.  If you have
more of them, the gauge will drop back down.  Granted, your own vacuum
adds a little, so just factor that out.  You'll see the difference after
a few valves.

I assume here that everything else has been tested and is okay, because
this is the only symptom given.  An overly large motor pulley was
actually used on concert grands, by the way.  It doubled the power.

The linkage referred to by Robbie is a regulation problem, but also a
real trapeze act that would be difficult to explain in a letter, and
would most probably be misunderstood if I were to get into it.  Let me
make it more simple: Given that everything else is right about the box,
look at the photograph of the Duo-Art Expression box in the reprint sold
by Player Piano Co.  You will see the normal position of the lever which
is operated by the accordions.  It sits at about a 10-15 degree back
angle.  Start with that.  From there, if you still have the problem, you
are close enough to conclude that that isn't the problem.  Doesn't mean
it's perfect, but as close as Aeolian ever got one.

Spencer also mentioned the Theme valves leaking.  When the theme valve(s)
leak, the accompaniment zero intensity will not go low enough to really
set the instrument softly enough.  To make sure this is not the case, set
the solo side of the box to about as low as you can get it.  That takes
it out of the circuit.  Then set the accompaniment side to whatever
produces a soft but even response.  Now raise the solo side to, say 7-8
inches of water on the gauge when the theme valve is opened.  Now return
again to the accompaniment side and see if your setting has raised.  If
it raises over about 1/8" your one-way theme isolator valves may need
some attention.  By the way, do not use suede both sides to replace
these, because suede leaks unless it has a sealing side.

Craig B.