[LAU] Connie, an organ template for JACK

[Martin Homuth-Rosemann]

Am Sonntag, 31. Mai 2009 schrieb Nick Copeland:
> I get the click too, and also a bit of aliasing noise on my system but that
> could just be me, did not test it widely.
>
> The original keyboard did have a bit of keyclick however it was not as
> pronounced as the Hammond and as such never got picked up as a character of
> the sound. Apart from that, the Hammond was popular also with jazz
> keyboardists, the Vox only ever really penetrated the rock market.
>
> The Vox had the same multiple contacts under each key and again, pressing a
> key slowly would sound each harmonic separately, not noticeable really when
> playing - you have to like move the key with a micrometer screwguage to be
> able to hear them. Each key also had a separate generation PCB that did the
> master oscillator division, waveform extraction from the master clock and
> this probably also had a key grooming circuit to reduce noise, especially
> shelving noise from the contacts (which was a large part of the Hammond
> sound). Most of the click I got from Connie only noticable on note_off
> rather than note_on but both of these could be improved with a grooming
> circuit.

I'm just working on this problem. It clicks because I switch the signals on/off 
without every smoothing at random moments of the sine wave. I've changed the 
timing to switch at zero crossings and the clicks go away. 

> Also, as with all frequency division circuits it was not an
> equally tempered scale - every note is an integral division of the master
> clock which I understand ran at 2MHz and some notes were up to 1.6 cents
> out. There are kind of two issues with emulating that, firstly the midi
> tables here are for ET pitch rather than integer division, and then each
> wave I think is separately generated thus has no phase relation since each
> voice here looks like a separate phase accumultor. The phase accumulation
> probably has little effect since your frequency tables are going to be very
> accurate although purists might argue that ET scaling vs. an organ divider
> circuit is audible when playing chords.
>

I've got the schematics from http://www.reinout.nl/?page_id=80 and there I 
found that the (early?) Vox had twelve individual LC oscillator boards for the 
chromatic notes - the freq can be modulated via the vibrato signal. Each board 
has six astable multivibrators to divide down six octaves. These seven octaves 
are routed to the keys. So you're able to tune the "connie" ET or even 
Werckmeister - that's cool. 

My next version will have a modified freq generation. The mixture is created 
from a buffer holding one cycle and sampled at different frequencies. So the 
harmonics are in tune with the 8' stop. This reduces the clicking and also 
reduces the CPU load quite a lot - so Connie will be more eeepc friendly.

> The vibrato is perhaps a bit slow too and although the original be modified
> by a surface mounted pot I am sure that House of the Rising Sun, another
> Vox classic, had it run faster than this? The pot wasn't very accessible
> admittedly, and it was generally glued with that red paste to stop it from
> travelling however there were a few that had this pulled out to a panel
> mounted pot to be configurable, maybe only on the later Italian models
> after Jennings had sold the rights. 

The next Connie version will have an drawbar for an adjustable vibrato. 

> Perhaps just out of interest more than
> anything, the current rights to Vox and Continental is held by Korg Inc of
> Japan, not that they have done anything with rights to the organ. If you
> ever saw one of these keyboards it was pretty spectacular: reverse
> white/black keys, bright orange panel and the still quite futuristic Z Bar
> frame. They should re-release it.
>
> I have owned a couple of these over the years, an original very rare
> Jennings handbuilt with laquered wooden key action, extremely light touch,
> and then later the Italian plastic keyed dual manual Super. The latter
> actually had the original Z Bars (the Jennings model only came as is) but
> the sound was not quite as warm as the handbuilt ones.
>
> Regards, Nick.
>
> > From: reuben.m at gmail.com
> > To: linux-audio-user at lists.linuxaudio.org
> > Date: Sun, 31 May 2009 00:15:13 -0500
> > Subject: Re: [LAU] Connie, an organ template for JACK
> >
> >
> > Really like the sound of it. Has a bit of a harsh tick sound when
> > pressing a key. Not sure if that's supposed to be a "key click" or if the
> > audio generated for a new note is just sent as-is without fading it in.
> >
> > -Reuben
> >
> > Check it, yo!: Martin Homuth-Rosemann was sayin:
> > > Hi,
> > >
> > > sorry, just realized that the hammond discussion mentioned below was
> > > here and not at LAD, so please allow this kind of "crosspost":
> > >
> > > this is my first post to LAD. The discussion about a hammond simulation
> > > "Fons could you make us...", Beatrix and some research for writing a
> > > (german) wikipedia article (stub) about the Vox Continental inspired me
> > > to hack a quick organ program that simulates the internal signal flow
> > > of the "Connie" with JACK MIDI input and JACK audio output.
> > > Have fun:
> > > http://cryptomys.de/horo/Connie/Connie-0.1.tar.gz
> > >
> > > Ciao
> > > Martin Homuth-Rosemann
> >
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