[sdiy] Novachord resonator

ASSI Stromeko at nexgo.de
Thu Jul 23 19:01:34 CEST 2015

On Thursday 23 July 2015, 07:02:29, Lanterman, Aaron wrote:
> fig13.jpg is an overall schematic showing how the main oscillators, divide
> down units, resonator section, and keys all hook together. It’s a bit
> hard to read, but you can get the main idea from it.
> fig20.jpg shows the resonator section. I’m confused by “input from 4
> tubes” marking. That suggested to me that there might actually be six
> instances of the Figure 20 schematic, one for each octave, with maybe
> different values for the inductors for different octaves, and the rotary
> switches being giant ganged rotary switches.

Figure 16 and 17 show you that 4 adjacent control tube plates are directly 
ganged together, something alluded to in the main schematic as well.  You 
need to read the schematics a lot more losely as each not has it's own 
control tube.
> But… looking at the pictures of restorations, for instance this one from
> the CMS website, it seems like those rotary switches aren’t ganged:
> http://www.discretesynthesizers.com/nova/photos/filters.jpg
> So it looks from that like every sound from every key is going through one
> instance of fig20.jpg.

I don't think so.  There's just a lot more of these input networks than 
shown in the schematic (18 to be exact) and each of them is quite likely a 
bit different if I read the values correctly.

> Anyway, I thought it might be fun to build the resonance section on
> fig20.jpg as a stand-alone module. But some of the values are mysterious…
> the capacitance CN20, for instance, and inductances LN2, 3, 4, and 5, and
> the resistance values of switched by the rotary switches (shown on
> fig13.jpg, but that doesn’t show actual values).

I've not seen these documented anywhere, so you'll have to guess.

+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptations for KORG EX-800 and Poly-800MkII V0.9:

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