@@ -9,11 +9,11 @@ * the distance between the magnet and the tone wheel
* the fixed number of turns in the coil
* the fixed speed at which the magnetic flux changes by the rotating tone wheel.
-The number of turns of wire is set at the factory and the speed of the tonewheel is set by the SynchronousMotor. Only the distance between the magnet and the tonewheel can be adjusted by a technician, ToneWheelGeneratorOutputLevels. The closer the magnet is moved towards the tonewheel, the greater the output voltage (although this does affect the tone quality as well). While the organ is being played, these things never change so the output voltage from each coil is constant.
+The number of turns of wire is set at the factory and the speed of the tonewheel is set by the SynchronousMotor. Only the distance between the magnet and the tonewheel can be adjusted by a technician, ToneWheelGeneratorOutputLevels. The closer the magnet is moved towards the tonewheel, the greater the output voltage (although this does affect the tone quality as well). While the organ is being played, these things never change so the output voltage from each coil is constant. While the voltage is fixed, the output current is inversely proportional to the total resistance of the parallel keying circuits. So when the resistance drops by half when two key contacts are closed, the output current doubles. This doubling of current is evenly split between the two key contacts so, as Hammond noted, "...the current flow through each of the different circuits will be substantially the same..." Note that this relationship is linear
.
-While
the voltage
is fixed,
the output current is inversely proportional
to the total resistance of the parallel keying circuits. So when the resistance drops by half when two key contacts are closed
, the output current doubles
. This doubling of current
is evenly split
between the two key contacts
so, as Hammond noted, ".
..the current flow through each
of the different circuits wil be substantially
the same
..."
Note that this relationship
is linear.
+But
the ear
is not a linear device! When
the Model A
output coils were adjusted
to provide
the same output voltage at each coil
, the organ was considered too ''bright''
. This is because the ear responds better to higher frequencies than to lower frequencies. Hammond began correcting this problem by adjusting the distance
between each magnet and
the tonewheel
so that lower frequencies have a higher output voltage than higher frequency generators
. As a result, early Model B organs have a very pronounced bass
. In later console organs, Hammond replace
the fixed 15 ohm wires with different values
of resistance wire between
the tone generators and
the key contacts to ''taper'' or ''voice'' the organ
. As additional key contacts are closed, the resulting increase in output current
is non-
linear.
-But the ear is not a linear device! When the Model A output coils were adjusted to provide the same output voltage at each coil, the organ was considered too ''bright''. This is because the ear responds better to higher frequencies than to lower frequencies.
Hammond began correcting this problem by adjusting the distance between each magnet and the tonewheel so that lower frequencies have a higher output voltage than higher frequency generators. As a result, early Model B organs have a very pronounced bass. In later organs, Hammond added different values of
resistance wire between the tone generators and the key contacts to ''taper'' or ''voice'' the organ. As additional key contacts are closed, the resulting increase in output current is non-linear. Resistance wire
values range
from 10 to 100 ohms and depend
on the frequency of the generator and the harmonic to be used. In effect, Loudness Robbing was intentionally created to ''compress'' the range of loudness between settings with few and lots of harmonics. This allowed the organ to have a consistent volume as more harmonics are added.
+Hammond used
resistance wires with
values ranging
from 10 to 100 ohms and connected these wires based
on the frequency of the generator and the harmonic to be used. The resistor ''wire-harness'' is a carefully constructed bundle of pre-cut wires tied together in a specific order and arranged to connect from the generators to each key contact.
In effect, Loudness Robbing was intentionally created to ''compress'' the range of loudness between settings with few and lots of harmonics. This allowed the organ to have a consistent volume as more harmonics are added.
-Resistance tapering is not provided in the Model M and other spinet organs since the extra effort to taper the manuals added to the production cost. In the spinet organs, the resistance is fixed at 16 ohms. As upper harmonics are added by the drawbars, the player must adjust the volume pedal to keep the preceived loudness the same. This is one reason why ''classic'' B3 drawbar settings sound different on the spinet organs.
+Resistance tapering is not provided in the Model M and other spinet organs since the extra effort to taper the manuals added to the production cost. In the spinet organs, the resistance is fixed at 16 ohms. As upper harmonics are added by the drawbars, the player must adjust the volume pedal to keep the preceived loudness the same. This is one reason why ''classic'' B3 drawbar settings sound different on the spinet organs. For those thinking of tapering their M3, beware! It would be a huge undertaking to add a console organ-like wire harness. It ''may'' be possible to insert individual resistors or trim pots between the wires and the key contacts but even this would be a lot of work
.
