HammondWiki - Diff: TypesOfToneGenerators

Differences between current version and predecessor to the previous major change of TypesOfToneGenerators.

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Newer page: version 13 Last edited on May 30, 2016 8:55 pm. by 2601:1c2:900:f3be:946f:aeb7:17c5:23de
Older page: version 10 Last edited on May 25, 2016 9:39 pm. by JimCook
@@ -4,18 +4,20 @@
  
 The organ described in [Lauren Hammond's|LaurensHammond] patent application was never marketed and existed in prototype form only. The tone generator illustrated in the patent produced 89 frequencies starting at C0: 
  
 <pre> 
- 5 tonewheels of 2 teeth 
- 12 tonewheels of 4 teeth 
- 12 tonewheels of 8 teeth 
- 24 tonewheels of 16 teeth 
- 12 tonewheels of 32 teeth 
- 12 tonewheels of 64 teeth 
- 12 tonewheels of 128 teeth 
+ 7 blank tonewheels  
+ 5 tonewheels of 2 teeth C0-E0  
+ 12 tonewheels of 4 teeth F0-E1  
+ 12 tonewheels of 8 teeth F1-E2  
+ 12 tonewheels of 16 teeth F2-E3  
+ 12 tonewheels of 16 teeth F3-E4  
+ 12 tonewheels of 32 teeth F4-E5  
+ 12 tonewheels of 64 teeth F5-E6  
+ 12 tonewheels of 128 teeth F6-E7  
 </pre> 
  
-In the patent organ the number of teeth on the tonewheels change at F instead of C as in the production organs. Also note that there are twice as many 16 toothed tonewheels as the other octaves. This required two different sets of [Gear Ratios|GearRatio] that changed at F3 to make this odd arrangement of tonewheels work correctly. There are no tones above the sixth octave like there are in the production organs because the hobbing machine used to cut the sinusoidal "teeth" in the tonewheels could not cut 256 teeth. Hammond didn't solve this problem until just before the Model A was introduced (see Early Model info below). 
+In the patent organ the number of teeth on the tonewheels change at F instead of C as in the production organs. Also note that there are twice as many 16 toothed tonewheels as the other octaves. This required two different sets of [Gear Ratios|GearRatio], one set for E3 and below and a different set for F3 and above to make this odd arrangement of tonewheels work correctly. There are no tones above the sixth octave like there are in the production organs because the hobbing machine used to cut the sinusoidal "teeth" in the tonewheels could not cut 256 teeth. Hammond didn't solve this problem until just before the Model A was introduced (see Early Model info below). 
  
 !!! Early Model 91 Frequency Generator 
  
 The following organs were produced from the mid 1930's to the early 1940's and have a 91 frequency generator: 
@@ -29,20 +31,20 @@
  Player : # 9,000 - # 9,209 
  
 All 91 frequency models have: 
  
- 12 tonewheels of 2 teeth 
- 12 tonewheels of 4 teeth 
- 12 tonewheels of 8 teeth 
- 12 tonewheels of 16 teeth 
- 12 tonewheels of 32 teeth 
- 12 tonewheels of 64 teeth 
- 12 tonewheels of 128 teeth 
- 7 tonewheels of 192 teeth 
+ 12 tonewheels of 2 teeth C0-B0  
+ 12 tonewheels of 4 teeth C1-B1  
+ 12 tonewheels of 8 teeth C2-B2  
+ 12 tonewheels of 16 teeth C3-B3  
+ 12 tonewheels of 32 teeth C4-B4  
+ 12 tonewheels of 64 teeth C5-B5  
+ 12 tonewheels of 128 teeth C6-B6  
+ 7 tonewheels of 192 teeth C7-G7  
  5 blank tonewheels 
 </pre> 
  
-After the patent was issued and before production began, Hammond figured out a different combination of GearRatio''''s that would change the number of teeth at the Cs rather than at the Fs. To simplify production he kept one standard set of [Driving Gears|DrivingGear] and [Driven Gears|DrivenGear] for each octave. 
+After the patent was issued and before production began, Hammond figured out a different combination of [Gear Ratios| GearRatio] that would change the number of teeth at the Cs rather than at the Fs. To simplify production he kept one standard set of [Driving Gears|DrivingGear] and [Driven Gears|DrivenGear] for each octave. 
  
 He also figured out a way to generate a top half octave without 256 tooth tonewheels. The ratio of a perfect fourth to unison is 4:3 or 1.333 times higher. Since 256/192 is approximately equal to 1.333, Hammond cut the top tonewheels to 192 teeth and changed the gear ratio between the driving gears and the driven gears to that a perfect fourth above the desired pitch. In other words, the gear ratio for the upper C was the same as that used on the F tonewheels below it. Because 256/192 is not exactly 1.333, the upper seven pitches are slightly sharper than the other other octaves (another reason a tonewheel generator sounds different than most clones with perfectly divided digital octaves). Only seven tones could be produced using these gear ratios so most generators produce 91 tones. But, because of the way the tone generator was designed, the number of tonewheels in a generator had to be divisible by 12. So five blank tonewheels with no teeth (and no magnetic pickups) were used to keep everything running smoothly. 
  
 Because it was impossible to build a "single-toothed" tonewheel that could rotate without unbalancing the [Tone Generator|ToneGenerator] the lowest octave in the organ had no "subfundamental" tones and the key contacts were left disconnected. If only the first drawbar was pulled out, the bottom octave in both manuals were silent if played. In other words, these early organs lacked [Harmonic Foldback|HarmonicFoldback] in the lower octave. 

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