* 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
.
-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.
+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. There are two ways to
correct this, either adjust the output voltage of the tone generator by shifting the magnet or adjust the resistance between each tone generator and the keying circuits. Hammond used a combination of these two techniques.
Hammond first
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.
