MS-404 MIDI Analog Synthesizer
User's Guide
Even the MS-404 Service-Manual
(only in German language) is available.
Fig. 1: MS-404 Front Panel Controls
01 - Learn Push Button
02 - Learn/Gate LED
03 - Glide LED
04 - VCO Glide Time
05 - VCO Frequency
06 - Pulse Width
07 - Wave Form
08 - VCO/Noise
09 - LFO Effect FM/PWM
10 - LFO 1 Amplitude
11 - LFO 1 LED
12 - LFO 1 Frequency
13 - LFO 1 Frequency Range
14 - VCF Frequency
15 - VCF Tracking
16 - VCF Envelope Amplitude
17 - LFO 2 Amplitude
18 - LFO 2 LED
19 - LFO 2 Frequency
20 - LFO 2 Frequency Range
21 - VCF Resonance
22 - VCA Accent
23 - Envelope Attack Time
24 - Envelope Decay Time
25 - Envelope Sustain Level
26 - Envelope Release Time
Fig. 2: MS-404 Rear Panel
27 - AC Power / Fuse / Power Switch
28 - External Audio Input
29 - Audio Output
30 - Gate Output/Input
31 - CV Output/Input
32 - External Audio Input Level
33 - MIDI Input
34 - MIDI Output (Thru)
35 - (For Service only!)
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MS-404 Controls
No. Label Function
Front Panel
MIDI
1 LEARN (push button) push button for activating the learning mode in which the MS-404 MIDI functions (MIDI channel, reference tone, control functions for VCF and VCA, Re-Trigger on/off) can be set
2 LEARN (LED) Learn / Gate LED displays the receiving of a MIDI note command (gate function) or the learning mode (flashing)
3 GLIDE (LED) Glide LED displays whether the glide function, controlled via MIDI, is activated or de-activated
VCO
4 GLIDE (rotary control) VCO glide time (portamento)
5 TUNE VCO pitch
6 PULSE WIDTH pulse width
7 switch for selection of wave form:
high: pulse
middle: VCO off
low: saw tooth
8 VCO / NOISE switch for selection of sound source:
high: VCO
middle: VCO and noise off (for use with external audio input or with VCF self-oscillating)
low: noise
9 LFO 1 / FM / PWM switch for selection of LFO function; determines whether LFO 1 affects VCO pitch (FM) or pulse width (PWM):
high: frequency modulation (FM)
middle: no modulation
low: pulse width modulation (PWM)
10 LFO 1 / LEVEL LFO 1 amplitude
11 LFO 1 / (LED) LFO 1 LED
12 LFO 1 / FREQU. LFO 1 frequency
13 LFO 1 / RANGE switch for selection of LFO 1 fequency:
high: slow (up to minutes)
middle: fast (up to the audio range, approx. 5 kHz)
low: standard LFO range (several Hz)
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VCF
14 FREQU. filter cut-off frequency
15 TRACKING switch for selection of filter frequency tracking:
high: full tracking (VCF follows VCO)
middle: off
low: half tracking
16 ENVELOPE influence of envelope (ADSR) on the filter cut-off frequency
17 LFO 2 / LEVEL LFO 2 amplitude
18 LFO 2 / (LED) LFO 2 LED
19 LFO 2 / FREQU. LFO 2 frequency
20 LFO 2 / RANGE switch for selection of LFO 2 frequency range:
high: slow (up to minutes)
middle: fast (up to the audio range, approx. 5 kHz)
low: standard LFO range (several Hz)
21 EMPHASIS filter resonance
VCA
22 ACCENT influence of the envelope (ADSR) on the VCA (accent)
ENVELOPE
23 ATTACK envelope attack time
24 DECAY envelope decay time
25 SUSTAIN envelope sustain level
26 RELEASE envelope release level
Rear Panel
27 w/o label AC power input / power switch / fuse
28 AUDIO IN external audio input
29 AUDIO OUT audio output
30 GATE gate input / output (depending on jumper position)
31 CV CV input / output (depending on jumper position)
32 INPUT LEVEL level control for external audio input (28)
33 MIDI IN MIDI input
34 MIDI THRU MIDI output (Thru function)
35 CV ADJUST calibration of CV spreading (for service only)
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Introduction
The MS-404 is a MIDI-Controllable Monophone Analog Synthesizer which combines the tonal advantages of pure analog sound synthesis with the control benefits of MIDI technology. Today you will find synthesizers with pure analog sound synthesis only on the second-hand market - partially for excessive prices. Additionally you have to pay for a MIDI-CV-Interface for controlling the instruments via MIDI. This is where the MS-404 is the solution, since it replaces a correspondingly equipped analog synthesizer and the required MIDI-CV-Interface. In addition to this, the MS-404 provides CV and Gate signals. Therefore, it can also be used as a MIDI-CV-Interface for an additional analog synthesizer having no such interface. Alternatively, the MS-404 can also be controlled by the CV and the gate instead of via the MIDI.
Since the MS-404 has a 19" rackmount case with 1 height level, it can be integrated into a 19" rackmount system without mechanical problems.
If you are familiar with analog synthesizers, you will be able to work with the MS-404 ery quickly. The controls on the front panel should be well-known to you from other analog synthesizers - with the exception of the MIDI Learn Push Button. However, for getting significant results, you should definetly read the chapters "Advices for Use", "MS-404 Connections" and "MS-404 MIDI Functions" before using your MS-404.
The sound synthesis of the MS-404 is orientated on the classical paragons for voltage-controlled modular systems. The MS-404 has the following modules:
1 VCO (voltage-controlled oscillator)
1 NOISE (noise generator)
1 VCF (voltage-controlled resonant filter)
1 VCA (voltage-controlled amplifier)
1 ADSR (envelope generator)
2 LFOs (low frequency oscillator)
and
1 MIDI-CV-Interface with 3 control voltages and Gate.
The block diagram (Fig. 3) on the next page shows how these modules are inter-connected. Each parameter has its own rotary control or switch; it is immediately accessible and can be changed in real-time. Front panel controls are clearly arranged in groups.
The tonal "raw material" either serves the VCO, the noise generator or the external audio input. The selected signal is fed through the VCF, then through the VCA before it reaches the audio output. An envelope generator of the ADSR type is available for both, VCF and VCA .
You can select between the wave forms saw and pulse with the VCO. The pulse wave can be adjusted in width. LFO 1 which is provided for the VCO can either modulate the frequency of the VCO (frequency modulation FM) or the pulse width (pulse width modulation PWM). The LFO provides 3 frequency ranges; frequency is adjusted from a multi-minute duration upt to the audio range. The VCO has a glide function (portamento) which can be turned on/off via MIDI.
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The cut-off frequency of the VCF can be influenced by several factors: manual rotary control, VCO tracking (switchable, off/half/full), envelope generator and LFO 2. Resonance can be adjusted until self-oscillation occurs.
The VCA has an adjustable ACCENT parameter. The position of the ACCENT rotary control determines how much the MIDI velocity affects the amplitude of the envelope controlling the VCA.
The ADSR envelope generator provides the 4 parameters Attack, Decay, Sustain, Release.
The analog sound modules are controlled by the MIDI-CV-Interface. A note command at the MIDI input determines the pitch of the VCO and starts ("triggers") the envelope generator (ADSR). The velocity value of the note command can be used for controlling the VCF frequency and the VCA accent (envelope amplitude for VCA); this function can be turned off. The following functions can also be controlled via MIDI controller commands: VCF frequency, volume (envelope amplitude for VCA), glide on/off, sustain on/off and legato on/off.
Fig. 3: MS-404 Block Diagram
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Safety Instructions
Please follow the given instructions for use of the instrument because this will guarantee correct instrument operation. Due to the fact that these instructions touch on Product Liability, it is absolutely imperative that they be read carefully. Any claim for defect will be rejected if one or more of the items was observed. Disregard of the instructions can endanger the 6 month warranty.
The instrument may only be operated with the voltage written on the power input on the rear panel. Before opening the case disconnect the power plug.
All eventual modifications must only be carried out by a qualified person who will follow the valid safety instructions. With the introduction of a third person the warranty will be lost. In case of a destroyed warranty seal, any warranty claim will be rejected.
If the fuse has to be replaced, you must use a fuse with a rating of 1 A max. fast. The fuse holder is located directly beside the power switch on the rear panel. Inside the case there are highly dangerous voltages. Never try to get into the case through opening, using a conducting object.
The instrument must never be operated outdoors but in dry, closed rooms. Never use the instrument in a humid or wet environment nor near inflammables.
No liquids or conducting materials must get into the instrument. If this should happen the instrument must be disconnected from power immediately and be examined, cleaned and eventually be repaired by a qualified person.
Never subject the instrument to temperatures above +50 øC or below -10 øC. Before operation the instrument should have a temperature of at least 10 øC. Do not place the instrument into direct sun light. Do not install the instrument near heat sources.
Keep the top side of the instrument free in order to guarantee proper ventilation, otherwise the instrument could be overheated.
Never place heavy objects on the instrument.
Transport the instrument carefully, never let it fall or overturn. Make sure that during transport and in use the instrument has a proper stand and does not fall, slip or turn over because persons could be injured.
Never use the instrument in the immediate proximity of interfering electronic devices (e.g. monitors, power supplies, computers) since this could create disturbances within the MS-404 and corrupt memory data.
The instrument should only be shipped in the original packaging. Any instruments shipped to us for return, exchange, warranty repair, update or examination must be in their original packaging! Any other deliveries will be rejected. Therefore, you should keep the original packaging and the technical documentation.
The instrument may only be used for the purpose described in this operating manual. Due to safety reasons, the instrument must never be used for other purposes.
When using the instrument in Germany, the appropriate VDE standards must be followed. The following standards are of special importance: DIN VDE 0100 (Teil 300/11.85, Teil 410/11.83, Teil 481/10.87), DIN VDE 0532 (Teil 1/03.82), DIN VDE 0550 (Teil 1/12.69), DIN VDE 0551 (05.72), DIN VDE 0551e (06.75), DIN VDE 0700 (Teil 1/02.81, Teil 207/10.82), DIN VDE 0711 (Teil 500/10.89), DIN VDE 0860 (05.89), DIN VDE 0869 (01.85). VDE papers can be obtained from the VDE-Verlag GmbH, Berlin.
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MS-404 Connections
The connections of the MS-404 are located on the rear panel of the instrument (see illustration 2).
Connect the MIDI-IN jack (33) with the MIDI-Out jack of your MIDI transmitter (e.g. MIDI master keyboard, synthesizer, sequencer). If the incoming MIDI data at the MS-404 should fed to another instrument without being modified, connect the MIDI-THRU jack (34) of the MS-404 with the MIDI-In jack of the subsequent instrument. Otherwise leave the MIDI-THRU jack open. The MIDI-THRU jack should not be used for bigger quantities of data (e.g. dumps) because delays in time or loss of data could occur, due to the fact that the Thru function is carried out by software.
Connect the audio output (29) with the audio input of your mixer, amplifier or similar.
Connect the power input (27) on the rear panel of the MS-404 with mains power (220 ... 240 VAC / 50 ... 60 Hz) by using the delivered power cord. Turn on the MS-404 with the power switch (27) on the rear panel. The Gate LED must light for a short moment, then it goes out whilst the Glide LED (3) lights permanently. Both of the LFO LEDs (11, 18) must change their intensity in rhythm to the LFO frequency. If this is not the case, please refer to chapter "Analog Sound Synthesis with the MS-404 / Trouble Shooting"). The power fuse of the MS-404 is also located at the power switch. If the fuse has to be replaced, make sure that you use a fuse of the same type (1 A max., fast).
If you are not familiar with analog synthesizers and are using the MS-404 for the first time, you should set all controls to their default position which is described in chapter "Analog Sound Synthesis with the MS-404". Please read this chapter carefully.
If an audio signal is to be used for the MS-404 instead of a VCO or noise generator, the external audio input (29) has to be used. The level of the external audio signal must be adjusted with the level control (32) in such a way that the subjective volume is equal to that of the VCO. In case of saturation the level must be reduced slightly. The VCO / NOISE switch (8) must be put into middle position (VCO and noise off) when using the external audio input.
Both of the connections GATE (30) and CV (31) are preset as outputs at the factory. Another synthesizer with the appropriate CV and gate inputs can be connected to them. The characteristic of the control voltage is 1 V/Octave, the Gate output provides a voltage of +5 V when activated and 0 V when de-activated. If the synthesizer which you want to control has another voltage characteristic, you cannot use the CV and GATE outputs of the MS-404. In this case we recommend one of our MIDI-CV-Interfaces MCV 1 or MCV 8.
The GATE (30) and CV (31) connections on the rear panel of the instrument can also be modified into outputs. This modification must only be made by authorized service because the warranty seal will be destroyed when the case is opened, and warranty will become invalid. After this modification, the control of VCO and ADSR via MIDI is disabled. The modification is described in the service documentation, which will be supplied free of charge on request, indicating the serial number of your instrument.
Behind the opening CV ADJUST (35) there is a potentiometer for calibrating the CV voltage spread. This calibration is provided for service only and may only be carried out by an authorized service center. The calibration screw is sealed and must not be turned. Otherwise warranty will become invalid.
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MS-404 MIDI Functions
At the left part of the front panel there is a framed field named "MIDI", having a push button and two LEDs inside. The MIDI parameters are set and displayed with these controls.
In the normal operating mode, the following MIDI commands will be recognized and processed:
Note on/off on the selected MIDI channel of the MS-404, ranges from the selected reference note up to a maximum of 5 octaves (refer to 'learning mode', see below). The velocity values of the note commands can be used for controlling accent and VCF cut-off frequency (see below).
Pitch Bend on the selected MIDI channel for additional control of VCO pitch
Controller #7 on the selected MIDI channel determines volume
Controller #XX on the selected MIDI channel controls VCF cut-off frequency
Controller #64 on the selected MIDI channel controls the sustain hold function
Controller #65 on the selected MIDI channel controls the glide function
In the normal operating mode the lower LED displays Gate function while the upper LED displays the Glide function. The Gate LED is lit when the MS-404 receives a valid note-on command and goes out as soon as the note-off command is received. The gate signal itself controls the envelope generator (ADSR). The Glide LED is lit when then glide mode is activated, i.e. the glide rotary control determines the gliding time between to subsequent tones with different pitch. If the LED is not lit, the glide function is de-activated and the tone jumps - independantly of the position of the glide rotary control - immediately to the next pitch. When the MS-404 is turned on, the glide function is always activated. It can be turned off/on by receiving a portamento off/on command (MIDI controller #65 with data 0 / 127) on the valid MIDI channel. E.g. if you work with a sequencer you can use controller #65 in order to determine whether it should glide or jump for each tone of a sequence . Within a sequence, controller #65 must be sent directly before the note command (data = 0 : glide off, data = 127 : glide on). If you have a keyboard allowing connection of a foot switch which is programmable for MIDI controller #65 (e.g. Doepfer LMK 3 or LMK 4), you may control the glide function during a live performance by using the foot switch.
By pressing the LEARN push button you enter the learning mode, indicated by the flashing Gate LED. In this mode the MIDI parameters of the MS-404 are determined by incoming MIDI commands. During the learning mode (flashing Gate LED) the MIDI commands listed below have a meaning. After receiving one of these MIDI commands, the Gate LED goes out and the MS-404 returns to the normal operating mode. If more than one parameter has to be changed, for each parameter the learning mode must be activated and the corresponding MIDI command must be sent to the MS-404.
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Note-On
The MS-404 will take over the MIDI channel of an incoming note command as the new MIDI receive channel (MIDI channel set-up). The tone pitch (MIDI note number) will be interpreted as the lowest tone pitch of the MS-404 (transpose function). In practice you enter the learning mode by pressing the LEARN push button and press the key on your MIDI keyboard which should be the lowest tone of the MS-404. The true (absolute) pitch of the lowest tone depends on the position of the TUNE rotary control.
Controller #XX
The controller number of an incoming controller command will be taken as the controller number for MIDI control of the VCF cut-off frequency (controller XX). You should choose a variable controller (controller #0 ... 63) but no switch controller like e.g. the sustain controller (controller #64).
Program Change #1
This function only works, if the ACCENT rotary control is not in ccw position. The command establishes MIDI controller #7 (volume) as controller for volume of the MS-404 with velocity having no influence on the accent function (non-dynamic operation). The MS-404 volume is solely controlled by controller #7. When the instrument is turned on, controller #7 will automatically be set to 127 (maximum volume).
There is always a small amount of the envelope being sent to the VCA independantly on this function. In the instrument this offset is fed over a jumper; it can be turned off by removing this jumper. This modification must only be made by authorized service because the case must be opened and the warranty seal will be destroyed, and the warranty will become invalid. If the jumper will be removed, the MS-404 will be mute when receiving a controller #7 command with data = 0 (volume = 0). You will find more details in the service documentation which will be supplied free of charge on request, indicating the serial number of your instrument.
Program Change #2
This function only works, if the ACCENT rotary control is not in ccw position. The command establishes MIDI controller #7 (volume) as controller for MS-404 volume with velocity influencing the accent function (dynamic operation, volume = controller #7 data multiplied by velocity of the note command). Controller #7 controls volume while the velocity data of the note commands control the accent.
Program Change #3
This command establishes MIDI controller #XX (see above) as controller for filter cut-off frequency with velocity having no influence on the filter. The VCF cut-off frequency is solely controlled by controller #XX . When the instrument is turned on, controller #XX will automatically be set to 0 (filter totally closed).
Program Change #4
This command establishes MIDI controller #XX (see above) as controller for the filter cut-off frequency with velocity influencing the filter (cut-off frequency = controller #XX data multiplied by velocity of the note command).
Program Change #5 / #6
These Program Change commands turn the re-trigger function on (#5) or off (#6). When re-trigger is turned on, the envelope is triggered whenever a key is pressed no matter if the previous key was released or is still being pressed (legato). The MS-404 works with high-note-priority, i.e. if multiple keys are pressed simultaneously, the highest note will be chosen. This principle applies to most of the analog synthesizers (e.g. Mini-Moog).
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Analog Sound Synthesis with the MS-404
If you are not familiar with analog synthesizers, you should read this chapter carefully because the theoretical foundations of analog sound synthesis (subtractive synthesis) are dealt with here. The settings of MS-404 sound parameters are explained using a concrete example. Furthermore, this chapter will help you to find errors if your MS-404 does not perform in the desired way.
Before turning the MS-404 on, connect MIDI input, audio output and power as described above. Now put all controls to their default position (0 = ccw position, 6 = middle position, 12 = cw position):
No. Function Default Position
4 VCO GLIDE 0
5 VCO TUNE 6
6 VCO PULSE WIDTH 6
7 PULSE / SAWTOOTH PULSE
8 VCO / NOISE VCO
9 LFO 1 FM / PWM PWM
10 LFO 1 LEVEL 0
12 LFO 1 FREQU. 6
13 LFO 1 RANGE low
14 VCF FREQU. 0
15 VCF TRACKING middle
16 VCF ENVELOPE 12
17 LFO 2 LEVEL 0
19 LFO 2 FREQU. 6
20 LFO 2 RANGE low
21 VCF EMPHASIS 0
22 VCA ACCENT 12
23 ENVELOPE ATTACK 0
24 ENVELOPE DECAY 6
25 ENVELOPE SUSTAIN 6
26 ENVELOPE RELEASE 6
Set the MS-404 to this default position when you have adjusted the controls so that no tone appears at the output and you are not certain of the cause.
When starting to play on your keyboard after proper setting of MIDI channel and reference tone (see chapter "MS-404 MIDI Functions"), you should hear something at the audio output of your MS-404. If this is not the case, you should check the following:
1. Are both of the LFO LEDs (11 and 18) lit and do they change their intensity corresponding to the LFO frequencies which can be changed with the LFO frequency controls (12 and 19)?
no instrument is not turned on
connection to power not o.k.
fuse defect
yes continue with 2.
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2. Is the Gate LED lit when playing on your MIDI keyboard?
no MIDI channel and /or reference tone do not correspond with your MIDI keyboard; set the proper MIDI channel and reference tone as described in chapter "MS-404 MIDI Functions"
yes continue with 3.
3. Is there any audio signal at your MS-404 when playing your MIDI keyboard?
no Your MS-404 is not properly connected with your mixer, amplifier, etc.
default settings not correct; check all settings
Your MS-404 is now ready to play and you can start now with the Introduction to Analog Sound Synthesis. We will try to stick to the structure of the front panel sytematically as much as possible, going from left to right. The MIDI functions which can be set with the push button (1) and are dislayed with the LEDs (2) and (3), are described in chapter "MS-404 MIDI Functions". The numbers in brackets correspond to illustration 1 ("MS-404 Controls at the Front Panel").
This introduction is structured in such way that the theoretical fundamentals are treated first (marked with a gray background) before the corresponding setting examples for the MS-404 are described. If you are not interested in the theory, you may skip the chapters marked with a gray background.
VCO, LFO, NOISE
With analog synthesizers the tonal "raw material" is produced either by voltage-controlled oscillators (VCO) or by noise generators. Normally, a VCO provides several wave forms. Standard wave forms are pulse, saw-tooth, triangle and sine. Less used wave forms (spaced saw-tooth, graphically editable wave forms) are not dealt with here. The wave forms differ in their overtone spectrum, i.e. they contain different harmonics. An overtone is called harmonic if its frequency is an integer multiple (2, 3, 4, ...) of the base tone frequency. A saw-tooth contains all harmonics with descending amplitudes. The symmetrical pulse wave ("square wave", pulse width = 50 %) contains odd harmonics only (see Fig. 4). An unsymmetrical pulse wave (often called "pulse wave") contains all harmonics with their amplitudes being dependant on the pulse width. The more the pulse width differs from the symmetrical 50 %, the stronger the higher harmonics emboss the sound, i.e. its timbre becomes "nasal". If the width of a pulse wave is modulated by a low frequency oscillator (LFO), the overtone spectrum of the pulse wave continuously changes. The resulting sound is similar to a beat wave which is the result of two, nearly equally tuned oscillators. The modulation frequency must be very low (approx. 1 Hz or lower) since the oscillator seems detuned otherwise. The triangle and sine wave forms have only a weakly pronounced harmonic structure resp. no harmonics at all (sine). The triangle wave form contains only the odd harmonics like the saw-tooth but their amplitudes decreases by the power of two while with the saw-tooth they are decreasing linearely in their numerical order and therefore much slower.
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Fig. 4: Different wave forms and their harmonics spectrum
wave form harmonic spectrum
square
saw-tooth
triangle
sine
The amount of overtones of the base material is decisive for the possibilities in sound shaping with the subsequent voltage-controlled filter (VCF) since subtractive sound synthesis with a VCF (see below) only allows to cut-out or amplify overtones that exist. Therefore, the sine and triangle wave only play a minor part here. Under the condition that a VCF works as sine wave oscillator when resonance is set to maximum, it can be used in this way if a sine wave oscillator is required for a special sound.
If a low frequenvy oscillator is available, it can be used for modulating either the VCO pitch (frequency modulation = FM, also called "vibrato") or the pulse width (pulse width modulation = PWM). Simple LFOs provide frequencies in the range of 0.1 Hz to 10 Hz while better ones have a significantly wider range (0.01 Hz to 5 kHz) with switchable frequency bands for better adjustment. Modulation frequencies within the audio range should be dealt with in more detail since their result are very special sounds. If a VCO is modulated with a frequency close to its own, a completely new sound characteristic is established. In this case the VCO also produces non-harmonics, i.e. tones whose frequencies are non-integer multiples of the VCO frequency. This acoustical characteristic is the basis for the so-called FM Synthesis which is used with several digital synthesizers. If e.g. a VCO, oscillating at 1 kHz (1000 Hz), is modulated with a frequency of 400 Hz, so-called "side bands" around the the VCO frequency are created which are grouped symmetrically around the VCO frequency as integer multiples of the modulation frequency. For the given example this would result in: 1000 Hz, 1400 Hz, 11800 Hz, 200 Hz, etc.. Strictly speaking this only applies to pure sine wave frequeny modulation, i.e. if both, VCO and LFO, are sine wave oscillators. With other wave forms additional (non-)harmonics will be added. Unharmonic sounds, similar to frequency modulation, are also produced by pulse width modulation with high frequencies. In practice this priciple is used for
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creating extreme, unharmonic sounds. The degree of being unharmonic depends on the strength (amplitude) of LFO modulation as well as on the frequency ratio of VCO and LFO. "Practice is better than theory" applies here. You should try various settings for LFO frequency and LFO amplitude. Most probably the resulting wave forms are not suited for sweet, "beautiful" sounds but can be used for extreme, "vigorous" sounds instead.
Part of the VCO is the glide function ("portamento") which allows continuous gliding from one tone to the next. Normally the glide time can be adjusted with a rotary control from zero (tones will jump) up to several seconds.
Besides the VCO the MS-404 also has a noise generator. Alternatively, an external audio signal (e.g. coming from a sampler or digital synthesizer) can serve as sound source for the MS-404. The VCO of the MS-404 provides the wave forms saw-tooth and pulse alternatively. The wave forms sine and triangle are not realized in the MS-404 due to the reasons described above. The VCF of the MS-404 can be used as sine wave oscillator. The VCO glide time is adjustable within a wide range from zero to several seconds. Furthermore this function can be turned on / off with MIDI controller # 65 in real-time. When turning the instrument on, glide is active. If e.g. you are working with a sequencer, it can be determined for each tone of the sequence whether it jumps or glides from the previous tone by defining the controller from tone to tone. The low frequency oscillator LFO 1 provides 3 frequency ranges with the middle range corresponding to the standard LFO frequency range (0.1 Hz to 10 Hz). The remaining frequency ranges reach up to the audio range (approx. 5 kHz) and down to the LFO sub-range with a period of several minutes. LFO 1 of the MS-404 can be used either for frequency or for pulse width modulation. In this way the sound of two VCOs is simulated although there is only one VCO available.
But enough of gray theory. Let us now transfer the theoretical considerations into practice. Start by playing a connected MIDI keyboard or by playing a sequence (e.g. with Doepfer Analog Sequencer MAQ 16/3). Now turn the GLIDE control (4) slowly to the right. You will recognize that subsequent tones glide into each other. The more you turn the control to the right, the longer the glide time will be. The glide function can be turned on / off via MIDI controller #65 (see chapter "MS-404 MIDI Functions").
When turning the TUNE rotary control (5) you will see that the pitch of the MS-404 changes. With this control you can tune your MS-404 so that it is consistent with the tuning of your other instruments.
You can switch between the wave forms saw-tooth and pulse by using the WAVE FORM switch (7). When the switch is put to its middle position the VCO is turned off. Observe the different timbre (amount of harmonics) of the two wave forms.
With the VCO / NOISE switch (8) you can select the sound source, either the VCO or the noise generator. In the Noise position, instead of a normal tone, you will hear noise modified by the VCF and VCA (however, you can create a "playable" noise signal by setting the VCF to a higher resonance, VCF Envelope to zero and the VCF Tracking switch to the upper position. Out of this noise the VCF will cut-out a frequency band which will be shifted when playing on your MIDI keyboard; see section VCF for more details). Put switch (8) back into the VCO position.
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With the LFO function switch (9) you can select whether the LFO should affect frequency or pulse width modulation of the VCO. Please put this switch to the FM position (frequency modulation) first. If you now turn the LEVEL rotary control (10) of LFO 1, you will modulate the VCO pitch (vibrato). You should also change the LFO 1 frequency, using control (12) and the range switch (13), and recognize the acoustical effects. The LFO frequency is displayed by a LED (11). Due to the inertia of the eye, frequencies above 20 Hz cannot be realized anymore. When setting switch (13) to the middle position, you will create non-harmonics as described above. In the low position of switch (13) the LFO works in the standard frequency range while it produces extremely long periods up to minutes in the low position.
Now put switch (13) to the low position (standard LFO range) and switch (9) to Position PWM. Make sure that the pulse wave form is selected with switch (7). Adjust the LFO frequency to approximately 1 Hz or less (1 period per second or less) with the frequency control (12). Turn the pulse width control (6) to its middle position. If you now increase the LFO LEVEL (10) gradually up to maximum, you will hear a sound similar to a beat wave (chorus effect) created by slow pulse width modulation. Change the intensity (10) and the frequency (12) of this modulation and listen to the acoustical effects. If the pulse width control (6) is not exactly set to its middle position, it may happen that the sound "tears off" in rhythm to the modulation. The reason for this is that the pulse width modulation is so big that the width of the pulse goes to zero. If you do not want this effect you must set either the pulse width control (6) to its middle positon or reduce LFO amplitude (10). You should also try out PWM effects within the audio range by setting the LFO range switch to its middle position and choosing a high LFO frequency. After this turn back LFO LEVEL control (19) to zero and set the LFO frequency to approx. 1 Hz for the following experiments.
Alternatively to VCO and internal noise generator, an external audio signal (e.g. from a sampler or digital synthesizer) may serve as sound source with the MS-404. With switch (8) you can choose between VCO, noise generator or external signal (middle position). The external signal will be fed to the AUDIO IN jack on the rear panel. If the external audio input is used, the VCO / NOISE switch must be in its middle position so that both, VCO and noise are turned off. The level of the external signal must be adjusted with the level control (32) on the rear panel in such way that the subjective volume is approximately the same when switching between external audio input and VCO. If the signal sound distortes, the level must be reduced a little. The use of the external audio input is of advantage if e.g. a sterile sounding signal from a sampler should be revalued with the analog filter of the MS-404 or if an additional filter and / or VCA envelope should be added.
VCF
With subtractive sound synthesis the further processing of the tonal "raw material" (VCO / noise / external input) will be carried out by a voltage-controlled filter (VCF) first which is usually followed by a voltage-controlled amplifier.There are different types of filters. The basic types are low pass, band pass and high pass while the types notch and all pass are less common. The filter types differ in how they fed the frequency through. A low pass passes all frequencies
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that are below the cut-off frequency and cuts off all frequencies above. The high pass works just the opposite way since it passes all frequencies that are above the cut-off frequency and cuts off all frequencies below. A band pass passes all frequencies within a certain range (band) and cuts off all frequencies outside of this range. A notch cuts out a certain frequency range (inverse function of the band pass). An all pass passes all frequencies but it performs a phase shift dependant on the frequency. For musical purposes the low pass is the most productive filter.
Another important characteristic of a filter is slope which is measured in dB/Octave. It describes how fast the transition from passing to supressing occurs. The "ideal" filter would have an infinite slope, i.e. the transition occurs immediately (e.g. 999 Hz would pass totally while 1000 Hz would be supressed totally). In reality this transition is not a jump but a gliding, depending on the filter's slope. For musical purposes, a filter with high a value would have a slope of 24 dB/Octave but 12 dB/Octave are also useful for special applications (usually for high pass, band pass and notch).
A further filter parameter is resonance (emphasis). If the filter provides an adjustable resonance, frequencies close to the cut-off point can be emphasized. The filter becomes more of a band pass with an underlaid low pass. For musical applications it is very important that the filter resonance is able to be adjusted. VCFs without adjustable resonance are seldomly used. Overtones close to the cut-off point are emphasized the bigger the resonance is set (see illustration 5). This results in the typical resonance and tweet sounds of an analog filter. With many filters the resonance can be set to such a high degree that self-oscillation of the filter occurs (even without any input). This allows you to use the filter as a sine wave oscillator instead of the VCO for special purposes.
Fig. 5: Frequency behaviour of a low pass filter with different resonance
amplitude cut-off frequency frequency
low resonance
medium resonance
high resonance
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With the MS-404 the VCO / noise signal is input to a voltage-controlled low pass filter with adjustable resonance. There are several ways to control the filter's cut-off frequency. First, it can be adjusted manually. Furthermore the ADSR as well as LFO 2 can influence the cut-off frequency with any intensity. Additionally, the filter is controllable via MIDI (see "MS-404 MIDI Functions" for more details), i.e. its cut-off frequency can be controlled by any MIDI controller and / or by the velocity of the incoming MIDI notes. Finally, using a switch, you can determine whether the VCF cut-off frequency tracks the VCO frequency fully, half or not at all (keyboard tracking, keyboard follow). Filter resonance can be adjusted until self-oscillation of the filter occurs. Similar applies to the VCO-LFO (LFO 1) with regard to the LFO for the filter (LFO 2). LFO 2 can also produce frequencies up to the audio range. The tonal results of VCF frequency modulation with audio frequencies are similar to those of the VCO. You can create typical FM metallic sounds especially with high frequencies whether you use tonal base material (VCO / noise / external audio signal) or not. You can even create voice-similar sounds when setting the VCF to the appropriate setting and using slowly progressing ADSR envelopes. The sound will become realy extreme, if you use frequency modulation with audio frequencies for both VCF and VCO. The tonal results are nearly unpredictable. There is only one way: try it out; very often the results are totally surprising.
The theory of filters should now be translated into practice with the MS-404. Turn the VCF ENVELOPE control (16) to zero. If you now play on your MIDI keyboard, nothing will be heard since the filter is closed. Turn the VCF FEQUENCY control (14) slowly to its maximum position and listen how the sound is hollow at first and then gets more and more bright, due to the fact that more and more high overtones will pass the filter when increasing the cut-off frequency. You should also try the same with different settings for EMPHASIS (21). The more you increase resonance, the more the overtones close to the cut-off frequency are emphasized. In the upper part of the resonance, the filter will sound more and more cutting ("tweety") until it self-oscillates and works as a sine wave oscillator at full resonance. Now turn RESONANCE control (21) to a position where the sound is convenient for you and turn FREQUENCY control (14) back until the sound becomes dull. Now gradually increase the influence of the ADSR envelope on the VCF by turning the ENVELOPE control (16). Playing on your keyboard you will recognize that the VCF frequency range generated by the ADSR envelope becomes larger the more you turn the control to the right. After this you should turn the ENVELOPE control (16) to a middle position. Depending on the TRACKING switch (15), the VCF follows the VCO fully (high position), half (low position) or not at all (middle position). Try out all 3 positions. You will observe that higher notes will sound brighter if you select full or half since the VCF cut-off frequency follows the VCO frequency. In the middle position notes will become more dull the higher they are since the cut-off frequency remains unchanged. The proper setting of the TRACKING switch is very important when using the VCF as a sine wave oscillator. For this purpose, RESONANCE (21) must be turned to the maximum, ENVELOPE (16) must be set to zero and the TRACKING switch (15) must be in the high position (full tracking). With these settings the FREQUENCY control (14) works as "tuning" control for the pitch of the sine wave oscillator. The VCO / NOISE switch (8) should be set to its middle position so that no signal is present at the filter input. This setting can be used for e.g. flute-similar sounds. After this turn the RESONANCE (12) to a middle position, select VCO as sound source with switch (8) and turn control (16) to a low position so that the ADSR affects the VCF slightly. Set LFO 2 frequency to a few Hz by turning LFO 2 FREQUENCY control (19). The frequency is displayed by LED (18).
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As with LFO 1, the frequency of LFO 2 can be adjusted in 3 ranges using the RANGE switch (20). The same remarks as for LFO 1 apply to LFO 2 but LFO 2 solely affects the cut-off frequency of the VCF. You will hear how the VCF cut-off frequency is modulated by LFO 2 if you turn the LEVEL control (17). Vary the modulation intensity with control (17) as well as the modulation frequency with the FREQUENCY control (19) and listen to the acoustical effects. You should also try out both of the extreme cases of filter modulation: LFO frequencies in the audio range with switch (20) in its middle position and very slow filter modulation with switch (20) in its high position. With filter modulations in the audio range and high resonance you can create voice-similar sounds. For slow LFO modulations, with periods ranging from seconds to minutes, you will usually use higher settings for resonance since the change of filtered frequencies will be heard better. After this turn the modulation intensity to zero with control (17) and put the resonance control (21) to a middle position.
ADSR
Envelope generators, typically of the ADSR type (attack - decay - sustain - release), produce a signal flow which is used for controlling the VCF cut-off frequency and the VCA passage. The envelope consists of 4 parameters: attack time, decay time, sustain level and release time. When pressing a key on a keyboard (note-on command / gate = on), the envelope rises within a period of time which can be set by the attack control. After reaching its maximum the envelope decays down to the sustain level within a period of time adjustable by the decay control. The envelope stays on this level until the key is released (note-off command / gate = off). Then it decreases to zero within a period of time adjustable with the release control (see Fig. 6).
Fig. 6: ADSR Envelope
attack decay release sustain
envelope
gate key pressed key released
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The MS-404 provides an envelope generator of the ADSR type. Up to now the envelope parameters have not been changed. You can adjust a required envelope with the controls ATTACK (23), DECAY (24), SUSTAIN (25) and RELEASE (26). Try out different settings for the four controls and observe the acoustical effects, also combined with different settings for VCF envelope (16) and VCF cut-off frequency (14). For percussive sounds you should choose short attack and decay times with the sustain level set to zero. For smooth, standing sounds you should choose longer attack and decay times with a higher sustain level.
VCA
A voltage-controlled amplifier (VCA) is a module whose feed (volume) is controlled by a voltage. The VCF output signal is fed through the VCA whose output is the audio output of the MS-404. The VCA control voltage is provided by the envelope generator. With the ACCENT control (22) you can determine the amount of envelope control for the VCA, dependant on the velocity of the incoming MIDI note and on MIDI volume (controller #7). You can disable the velocity in order to play non-dynamically and for controlling accent by MIDI volume only (see "MS-404 MIDI Functions" for more details).
After you have become familiar with the meaning of all MS-404 controls, nothing should stand in your way for bringing your instrument into musical use. We wish you fun and success with your MS-404.
Due to its analog design the VCO of the MS-404 will need a warm up period of approx. 15 - 20 minutes until its tuning is constant. Therefore, you should turn on the instrument approx. half an hour prior to using it.