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 Forum index » Clavia Nord Modular » Nord Modular G2 Discussion
zero herz mode in oscillators..what is it good for?
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3phase



Joined: Jul 27, 2004
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PostPosted: Sun Dec 31, 2006 5:04 am    Post subject: zero herz mode in oscillators..what is it good for? Reply with quote  Mark this post and the followings unread

I remember that there was some talking about the zero hz mode of the oscillators in the past but i ve forgoten what it was about..

anybody can give the info again? or point to the thread..the search here dont find a matcvhing topic..maybe it never was one sofar?

regards
Sven
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Blue Hell
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Joined: Apr 03, 2004
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PostPosted: Sun Dec 31, 2006 6:11 am    Post subject: Reply with quote  Mark this post and the followings unread

For wave shaping. When the oscillator stands still it can be seen as a lookup table that can be indexed by a phase input.

See Rob's FM workshop for more on it. Maybe there is a litle n the sync workshop as well.

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Jan
also .. could someone please turn down the thermostat a bit.
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3phase



Joined: Jul 27, 2004
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PostPosted: Sun Dec 31, 2006 6:35 am    Post subject: Reply with quote  Mark this post and the followings unread

does that say that you can drive thru the "table" with a standart uni or bipolar control signal? i tried with the pitch input but nothing happened.. so this only is usefull on the phase osc?
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Fozzie



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PostPosted: Sun Dec 31, 2006 7:04 am    Post subject: Reply with quote  Mark this post and the followings unread

You need to use the FM input (set to 'trk'). Just tried some stuff again with a guitar as input; bipolar seems to work best that way. In combination with sync you can use both (of course).

It's in the help file, probably also in the manual.

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Blue Hell
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PostPosted: Sun Dec 31, 2006 7:23 am    Post subject: Reply with quote  Mark this post and the followings unread

I used to know this pretty well, but it faded a bit .. let me try though Very Happy

First not only PM but also FM changes the phase, or actually a positive FM amount adds an offset to the frequency. The pitch control input however multiples the frequency with something, and 0 times something still is zero. The pitch input does still work though but only in the FM tracking mode.

The idea is that an oscillator has a phase accumulator, the current value of that accumulator is used as an index in a lookuptable and the looked up value goes to the output. At every clock tick a certain value is added to the phase accumulator until it overflows and is reset to it's starting value again. This makes the oscillator run.

The various PM, FM and pitch modulations all differ in the way they alter the phase accumulation process. PM is an ofset that is added after accumulation, FM is an offset that is added before accumulation, but I lost the exact details of the difference between the two FM methods as implemented by Clavia. Finally pitch modulation multiplies the added offset by something.

After all of this is done the output of the phase accumulator is then used to look up (or calculate) the output value (depending on the wave shape selected).

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Jan
also .. could someone please turn down the thermostat a bit.
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Blue Hell
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PostPosted: Sun Dec 31, 2006 7:33 am    Post subject: Reply with quote  Mark this post and the followings unread

On the G2 all of this is pretty well worked out, but on the NM Classic tricks with the grey signals had to be used to accomplish the different kinds of frequency modulation.

This has some implications for the translation process of NM 1 to G2 patches, but I'm a bit scared of burning my fingers here. A key element though is that the grey inputs are linear FM inputs (with a sensitivity that differs from the normal FM input by a factor of two, but I forgot in what direction). To make translations work OK the details of how the phase accumulation is handled should be recovered.

Unfortunately I have no working MIDI interface at the moment so I can't check things by patching it out on my NM Classic.

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also .. could someone please turn down the thermostat a bit.
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Blue Hell
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PostPosted: Sun Dec 31, 2006 8:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Here is a G2 patch tat maybe illustrates it a bit. The tellow stuff is the phase accumulator with the various pitch, FM and PM inputs modelled (hopefully a bit realistic). The blue oscillator is just used as the lookup table, it does make the wave but it does not oscillate.


diy osc.pch2
 Description:
demoing a phase accumulator thingy

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 Filename:  diy osc.pch2
 Filesize:  1.51 KB
 Downloaded:  1952 Time(s)


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Jan
also .. could someone please turn down the thermostat a bit.
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