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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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RF
Joined: Mar 23, 2007 Posts: 1502 Location: Northern Minnesota, USA
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Posted: Tue Apr 29, 2008 4:44 am Post subject:
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Hi loss -
I don't know what the 'scanner' you mention is - but for the Hammond organ "leslie" type of sound, MFOS has a module that will simulate that.
For simple vibrato, you can run your lfo thru an attenuator then into the CV input of your VCO...at least that's how I do it. |
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Wout Blommers
Joined: Sep 07, 2003 Posts: 4529 Location: The Hague - The Netherlands
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Posted: Tue Apr 29, 2008 4:53 am Post subject:
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http://theatreorgans.com/hammond/faq/hammond-faq.html wrote: | 1.3 Hammond Vibrato
Provided on the organs so equipped are vibrato and chorus settings V1,V2,V3 and C1,C2,C3.
Vibrato is the periodic raising and lowering of the pitch, and is thus fundamentally different from tremolo which is a variation in only the loudness of the pitch. The Hammond vibrato is implemented using a tapped delay line, really a low-pass filter. The signal is applied to the delay line and a rotating scanner, attached to one end of the tone generator assembly, picks the signal off of the delay line at the tap points. The scanner, a single-pole 16-throw air-dielectric capacitor switch, is wired so that the tap point will traverse the entire delay line twice, once up the delay line and once back down, for each scanner rotation. As the delay line is traversed phase is added-to and then subtracted-from the signal.
The chorus signal is produced by adding non-pitch-shifted signal to the pitch-shifted signal.
The three settings each of vibrato and chorus correspond to different amounts of total delay thus different amounts of total pitch shift.
In addition to the pitch shifting function, the vibrato, as implemented in the Hammond organ, also acts as a sweeping low-pass filter. There is some frequency response and amplitude variation as the tap point of the filter is swept.
1.4 The Scanner
The scanner is used in the organ as a single-pole 16-throw rotary switch. It is constructed as a multi-plate air-dielectric capacitor with 16 stator poles and one rotor. It is used, in conjunction with the vibrato delay line, to create the chorus/vibrato. |
Wout |
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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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Chet
Joined: Nov 19, 2004 Posts: 231 Location: Lititz,PA,USA
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Posted: Tue Apr 29, 2008 5:01 am Post subject:
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You can simulate a Hammond chorus/vibrato circuit with an eight-stage delay line, an eight-input crossfader, and a triangle LFO.
The delay line lengths are fixed. The eight outputs are fed into the crossfader, and the crossfader is swept by the LFO. The crossfader alone produces the vibrato effect; mixing it with the original signal produces the chorus.
The lengths of the delay line are pretty critical. The sweet spot isn't very wide. |
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Wout Blommers
Joined: Sep 07, 2003 Posts: 4529 Location: The Hague - The Netherlands
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RF
Joined: Mar 23, 2007 Posts: 1502 Location: Northern Minnesota, USA
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Posted: Tue Apr 29, 2008 5:31 am Post subject:
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That's very cool. Thanks for posting that drawing. There is no chance I will ever try to DIY something that mechanical. It would make me insane.
bruce |
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bearblock
Joined: Sep 27, 2006 Posts: 90 Location: uk
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frijitz
Joined: May 04, 2007 Posts: 1734 Location: NM USA
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Posted: Tue Apr 29, 2008 7:21 am Post subject:
Re: hammond scanner vibrato? what is it? |
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loss1234 wrote: | can anyone here shed some light on this? what is a scanner?
i have been trying to find a way to incorporate vibrato into my synth for organ type sounds but it seems to be more rare than i had thought.
thanks |
Here's the page on the JH emulator.
http://jhaible.heim.at/scanner_vibrato/jh_scanner_vibrato.html
I have to say that when I visited his studio, this unit was something that really jumped out as special.
Ian |
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loss1234
Joined: Jul 24, 2007 Posts: 1536 Location: nyc
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blue hell
Site Admin
Joined: Apr 03, 2004 Posts: 24230 Location: The Netherlands, Enschede
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