The output voltage of the generator coil is fixed by~:
* the distance between the magnet and the tone wheel
- * the number of turns in the coil
+ * 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.
-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..."
+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. 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
.
+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
.
-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.
+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.
