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blue hell
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 Posted: Fri Aug 27, 2004 11:54 am Post subject:
NM Classic gray signals |
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In http://electro-music.com/forum/post-19063.html&highlight=#19063 modular raised the following question :
| modular wrote: | | .. what is the function of Master and Slave wich often are chained Oscillators in NM1 who is missed in G2 Editor? |
After which :
| g2ian wrote: | From what I understand, the master slave on the classic was mainly a dsp saving thing. The G2's auto optimisation now takes care of that and the G2 master oscillator now only makes controlling groups of oscillators easier*.
There were some 'undocumented' tricks that could be done with Gray cables however see ...
http://electro-music.com/forum/topic-1970.html
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The gray signals were intended to couple master oscillators to slave oscillators so that the slaves would track the master's frequency.
However, it was discovered that tricks are possible using these gray signals.
Maybe have a look at Rob Hordijks tutorial about FM synthesis at http://www.clavia.se/nordmodular/Modularzone/FMsynthesis.html
This might clarify things a bit maybe.
Patches using tricks with gray signals will be hard to convert to the G2. The tutorial mentioned will give some insight in the possible tricks.
When however they are just used to track slave oscillators with master oscillators (as they are used mostly) the same effect can on the G2 be obtained by using blue signals only.
Jan. |
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Rob
Joined: Mar 29, 2004
Posts: 580
Location: The Hague/Netherlands/EC
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| Posted: Sat Aug 28, 2004 1:06 pm Post subject:
Re: NM Classic gray signals |
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| Blue Hell wrote: |
<snip>
Patches using tricks with gray signals will be hard to convert to the G2. The tutorial mentioned will give some insight in the possible tricks.
<snip>
Jan. |
To add to this:
The interesting trick with the grey inputs is that they have a 'linear' frequency curve, as opposed to the 'exponential' curve used for the octave scale.
The thing with a digital oscillator is that, by using a linear frequency control input, the oscillator can be set to 0 Hz. Or in other words be stopped. When stopped the output signal is a fixed level at the value the output had when it was stopped. This works as sort of a sample and hold, it can create a signal that starts moving and stop moving, but will not jump in level when started or stopped, but 'go on from where it left off'. This can actually be of great musical use.
Another option with the grey input is that it can be fed with a negative value. Which in effect means that the waveform is produced in 'reversed' order, e.g. a raising slope sawtooth is changed into a falling slope sawtooth. This can be done at LFO rate, but also at audio rate, which sounds like the techniques named 'softsync'. There are several techniques named softsync, (sometimes also named 'window sync'), but they all share roughly the same particular type of sonic character.
On the G2 the Osc3 has a FM input that is actually a linear frequency control input, quite similar to the grey input from wayback.
There are two options, the input sensitivity can be stricktly linear (LinFM) or it can be set to scale the input sensitivity to the keyboard pitch, the TrkFM option (which is great for this 'softsync' sound when fed with a square or pulse wave).
When the Oscillator is set to 0 Hz (by turning the Coarse knob fully left when in Partial tuning mode) the FM input can do all the tricks that could be done with the grey input. The grey output signal is unavailable, but this output signal could only be used to scale down signals to the note played on the keyboard, and that can actually be done with the LevScaler module from the Note module group.
So, in essence it is not at all about the grey signal itself, it is instead about the tricks that can be pulled when working on linear frequency scales, instead of the usual exponential scales. 'Linear scales' is a vast subject, it can have effects while generating the audio signal, or to manipulate control signals. But it also offers the opportunity to work in harmonic scales, as those are easiest set out on a linear frequency scale.
/Rob |
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mosc
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| Posted: Sat Aug 28, 2004 1:44 pm Post subject:
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Thanks for that great explaination, Rob.
Is this linear FM the same as used in the DX7 synths? This gives a modulation products than the exponential FM traditionally used on analog synths, right? |
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Rob
Joined: Mar 29, 2004
Posts: 580
Location: The Hague/Netherlands/EC
G2 patch files: 109
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| Posted: Sun Aug 29, 2004 3:06 pm Post subject:
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| mosc wrote: |
Is this linear FM the same as used in the DX7 synths? This gives a modulation products than the exponential FM traditionally used on analog synths, right?
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No, in fact they are quite different.
The DX7 modulates the phase position of the waveform, e.g. it is like the waveform is shifted forwards and backwards by a modulation signal. The G2 OscPM does exactly this as well, as do the DX modules. Modulation takes place on the point where the waveform is actually generated.
But on the standard oscillators it is the actual frequency parameter that feeds an oscillator which gets modulated.
The difference is that PM does not detune when selfmodulation is applied.
There is also a difference in the produced waveforms. This can best be seen on an oscilloscope. The idea is to modulate a triangle wave by a triangle wave on both the Osc3 and the OscPM. Then compare the resulting waveforms.
Also a OscPM does not let itself be modulated well with a pulse wave, In fact it sounds aweful, as the waveform continuously jumps all over the place. While in contrast the Osc3 produces very useful 'softsync' results when modulated with a pulsewave.
But the OscPM can be used as a sine function, the Osc3 not.
And perhaps some more little details. Anyway, when using only sinewaves all oscs sound typical 'FM'.  |
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