Korg PS Polyphonic Synthesizer PS-3100
Owners Manual

2. THE SYNTHESIS OF SOUNDS ^

2 - 4 Understanding The Patch And Its Use

bullet Why is it necessary to set up a patch?

Since the PS-3100 has a built-in patch many sounds can be created without ever touching a patch cord. However, there are terminals on the panel for the CONTROL WHEEL and MOMENTARY SWITCH but these are not connected to anything. Therefore it is necessary, to think about the best way to connect these terminals and use them in such a way as to improve on the effects already available to you with the built-in patch. If connections are made unthinkingly there is always the danger that the result wlll be considerably less useful than what was already there. The first and most important thing to do is clearly understand the control voltage chart (-5-+5, 0-+5, 5Vp-p etc.) and its relationship to every block diagram.

For example, once you have decided what you are going to control with the control wheel and how (In other words, if you use -5V-+5V controlled by the control wheel, what are you actually going to control with this setup?), careful attention must be paid to the rated voltage range of that which is to be controlled.

Even if -5V-+5V is applied to something that has a voltage range of 0-+5V the control voltage from -5V-+OV will have no effect. Furthermore you should understand that if you use an analog voltage of -5V-+5V for the purpose of switching a digital input marked , anything above +3V will be OFF while voltage below OV will be ON. Compared to other outputs, that of the control wheel has a relatively high output impedance. Since this may cause malfunctioning if directly connected to a digital input, as a rule it is best to connect the control wheel output to a VP input and then connect the VP output to the digital input.

The procedure to follow when thinking about setting up a patch:

(1) What kind of effect do you want and where do you want it?
(2) What type of control signal is needed for that purpose?
(3) What section of the synthesizer can you use to produce that type of control signal?

You will find that you will rarely achieve the effect you want unless you go through these steps in your thinking process. (This type of thinking is also important when using the built-in patch.)


Creating a delayed vibrato effect

Figure 45 - Creating a delayed vibrato effect

[EXAMPLE] CREATING A DELAYED VIBRATO EFFECT:

(1) What kind of effect and where? You want to apply, FM modulation with MG 1 to the SG (VCO) after a time delay.

(2) What kind of control signal is needed? A control signal is needed which will amplify the amplitude of MG1 after a delay once a key has been played.

(3) What will produce that type of signal? For the time delay: Use the GEG. To amplify the amplitude of MG1: Use the MVCA.

Therefore, set the time delay and its contour (delay time, attack time) and send this control signal to the MVCA by connecting a patch cord from the GEG output to the MVCA input. This will result in the GEG adjusting the amount of modulation produced by the MVCA.


Using the control  wheel alone to vary the depth of vibrato and the fc

Figure 46 - Using the control wheel alone to vary the depth of vibrato and the fc

[EXAMPLE] USING THE CONTROL WHEEL ALONE TO VARY THE DEPTH OF VIBRATO AND THE fc

(1) You want to use the control wheel to vary the fc and depth of FM modulation of the SG (VCO) via the MG1.
(2) Make use of the control voltage of the control wheel.
(3) Control the depth of FM modulation by means of the MVCA. Then apply the control voltage to the external fc input terminal.

Therefore connect the output control voltage from the control wheel to both the MVCA and the fc input terminals. However, since the control wheel has only one output use the JUNCTION section to distribute the signal to the MVCA and fc terminals.


Using the control wheel to completely change the contour of the envelope

Figure 47 - Using the control wheel to completely change the contour of the envelope

[EXAMPLE] USING THE CONTROL WHEEL TO COMPLETELY CHANGE THE CONTOUR OF THE ENVELOPE (from slow attack and release to a percussive sound).

(1) You want to apply an external control voltage to the envelope modifiers.
(2) Make use of the control voltage of the control wheel.
(3) Set up a patch that will control the ATTACK TIME and switch the RELEASE function ON and OFF.

Therefore all you have to do is use the output voltage of the control wheel to control the attack time and the activation of the release function as follows:

CONTROL WHEEL > VP > JUNCTION
JUNCTION > ATTACK
JUNCTION > RELEASE


Figure 48 - Using the momentary switch to alter the pitch of a sound by some amount

Example of the envelope   produced

Figure 49- Example of the envelope produced

[EXAMPLE] USING THE MOMENTARY SWITCH TO ALTER THE PITCH OF THE SOUND BY SOME AMOUNT (BY SOME NUMBER OF OCTAVES):
(This is the same whether the change is gradual or abrupt.)

(1) You want to change the oscillator frequency of the, SG (VCO) by means of a trigger signal produced by the momentary switch.
(2) Apply the trigger signal to the GEG and obtain the desired envelope.
(3) Set attacked release times with the GEG.

Therefore, set up the patch as follows:

MOMENTARY SWITCH OUT > GEG TRIG IN
GEG OUT( +5V, 0V) > SG (VCO) FREQ IN

The pitch may then be controlled by the EXT INT knob of the SG.
In this case operation is easiest if the DELAY, ATTACK, and RELEASE functions of the GEG are set at "0". (Switching the momentary switch on and off will determine the pitch difference.)

If you wish to give some time variations to the effect obtained whet the momentary switch is ON, just change the settings of the DELAY, ATTACK, and RELEASE functions of the GEG.

NOTE: By switching the position Of the SG NORMAL <> REVERSE switch you can change the pitch upward or downward at will.


Obtaining a polyphonic glissando effect

Figure 50 - Obtaining a polyphonic glissando effect

[EXAMPLE] OBTAINING A POLYPHONIC GLISSANDO EFFECT BY MOVING THE CONTROL WHEEL.

(1) You want to change the oscillator frequency of the SG (VCO) in a series of steps.
(2) You need a continuously changing voltage signal controlled by the control wheel.
(3) Connect the control wheel output voltage to the SAMPLE & HOLD input in order to change it into a signal that varies in steps.

Normally (with the built-in patch) MG1 is connected to the sampling signal input of the S/H circuit. But if you connect the control wheel control voltage to the S/H, the pitch will only change (in accordance with changes in the -5V -+5V range of the control wheel's output voltage) when the control wheel is moved. The speed of the glissando effect may be varied by changing the CLOCK FREQUENCY of the S/H.

Therefore:
CONTROL WHEEL OUT > S/H IN (by means of a patch cord.) Glissando range is adjusted with the MG1 INT of the SG section. Glissando speed is adjusted with the S/H CLOCK FREQUENCY.



2-1 Thinking About Sound Synthesis
2 - 2 Creating Sounds Using The Built-In Patch
2 - 3 The Basic Process Of Sound Synthesis
2 - 4 Understanding The Patch And Its Use



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