* the distance between the magnet and the tone wheel
* the number of turns in the coil
* the fixed speed at which the magnetic flux changes by the rotating tone wheel.
-Since
the output voltage is constant, the output current is inversely proportional to the total resistance of the parallel keying circuits. So when the contact 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..."
+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 contact 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..."
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. To correct this, Hammond began adjusting the output voltage of the generator coils so that higher frequencies produce lower voltages. The early Model B organs have a very pronounced bass. The later organs, including the B3, have a noticably lower bass output.
In later organs, Hammond also added different values of resistance wire between the generators and the key contacts to ''taper'' or ''voice'' the organ so that as additional key contacts are closed, the increase in output current is non-linear. Resistance wire values ranged from 10 to 100 ohms and depended 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.
But 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.
