THE SYNTHESISER AS AN OVERALL

Now, explaining a bit in more detail, but at the same time general topics, we would discus about the components that modify the sound of our synth. For example, the two envelopes placed on the right hand side and the middle of the synthesiser. The kinds of envelopes we used here are ADSR envelope, as for our final sound purpose; it would give us the options we need to modify the basic parameters. Now, the main role of the envelope placed in the middle of the synthesiser is to modify the signal coming out from the gate and then sent to the components; concerning VCO, VCR, the 2 LFOs and the simple scope.

The other envelope is mainly the filter envelope; in this case, it would modify the signal of the VCF and produce a wha wha effect.

 

ADSR ENVELOPES

This synthesiser is designed with two LFOs, and the main reason why we chose two is mainly because of the modulation it gives to the sound; so by turning some knobs on the LFO 1 would give us certain modulated sounds; then by adding to that an LFO 2, would make the sound much more interesting with facing changes and something more than just a simple vibrato. The one in charged of combining the two LFOs is the LFO selector knob placed on the left hand side of our synthesiser.

LFOs

knob selector between the LFOs

Although, some of the effects and modulations we want to achieve with the two LFOs are not noticeable enough, we will do some more research in order to make it sound properly; just as we want it to do.

So far, and generally, these are the main components that we have managed to build up on our synthesiser in order to create as much modulation as possible for the signal and the sound.

Summing up we could say that we have a Tremolo and a pair of LFOs that modulate the sound in terms of a fluctuated gain. Apart from that, an envelope that modifies the signal that comes out from the gate and which is split to the rest of the components. Also a second envelope that affects the frequency of the VCF having as a result a wha wha effect.

Some of the options and features we would like to add to our synthesiser and of course after going deeper into more information about synthesiser effects and components would be a 4 band EQ that can be easily seen, understood, and easy to use.

It would also be very useful to have some dynamic effects such as compression, some others like reverberation, delay, doublers and so on, which are features that would also make a synthesiser much more interesting.

By adding graphics for each of the effects and components that are added to the synth will make it more easily to be understood, and also would give it a nice looking.

Synthesizer Explain

And now we should get in more depth with our subtractive synthesizer. I will try to explain what my colleague Than stated about the main parts of a subtractive synthesizer and how we did them.

Sound is created by applying a voltage that continually repeats a specific pattern at a really fast rate this repeated pattern is called an oscillator.

Oscillators form the basics to create instruments, in order to achieve rich tones and sounds we have to combine the patterns of those called oscillators by using more than one oscillator. This is the fundamental process of a subtractive synthesizer. A great deal of sounds can be created only by combining the 4 fundamental tones known as: Sine, Saw tooth, Triangle and Pulse

(Simple Synthesizer with the main Oscillator Patterns)

This is how a simple synthesizer look in Reaktor: Where the NotePitch gives a number between 0 and 127 depending on the key you pressed on your keyboard, the gate dictates for how long it keeps the signal going towards the oscillator, the 4 main patterns stated above and a switch that helps us to choose between the waveforms.

In order to achieve a different behaviour of the oscillators we have to use an envelope. There are many kinds of enveloped but the most common and widely used one is the ADSR (Attack, Decay, Sustain, Release), despite the fact that the ADSR envelope is not capable of shaping all range of sounds like for example a Spit Brass that goes like a spike at the beginning falling down and then raising to its full amplitude, the ADSR is the best envelope for our purpose.

(Envelope Added to the Synthesizer)

To change the sound even more we had to embed different types of filters in our synthesizer like a Low Pass filter 2-pole and 4-Pole and a High Pass filter also 2 and 4-pole, the reason the filters are called 2-pole and 4-pole is that for each pole we get 6dB decrease per octave so 2-pole means -12dB and 4-pole means -24dB. By adding those filters we allow the synthesizer to get rid of some harmonics that builds the actual sound for example a sine wave is an exception and doesn't have any harmonics but the triangle wave contains only odd harmonics (1, 3, 5 and so on) like the square wave but at higher frequency the triangle wave harmonics roll of much faster and last but not least the Saw tooth wave that contains all the harmonics odd and even.

(LP and HP filters)

This was all I knew till that moment so I started reading some more regarding Synthesizer and especially subtractive synthesizers, by reading their history I learned what to do next, at least theoretically, so I started looking at today synthesizers and by analysing them I made up a scheme with what our synthesizer should contain. Finding out from Sound on Sound and Sound Synthesis and Sampling that many synthesizers have an actual envelope in the filter section I started doing some research and implement the ideas gathered in our synthesizer.

   (Filter Macro)

The Gate enters once again in the envelope shaping area but this time with a difference.

(Filter Envelope)

Because the output of the envelope varies between 0 and 1 and is an audio output, the first problem encountered was to transform the audio signal into an event signal so I went to the Reaktor 5 help guide and I found out that I can actually change the type of the signal. Because the cut-off frequency of the filter has values between 20 and 120 and the envelope varies from 0 to 1, I needed a way to increase the signal to 100 (by adding a multiplier with a control knob between -100 to +100 we also added the possibility to invert the envelope) the on and off switch enables the user to activate or deactivate the filter envelope. A problem we had was when we tried to make the filters follow the note, because the notepitch has values from 0 to 127 I was thinking to add them together and lower the value of the cut-off frequency (between 0 and 80)then I will get the filters to follow the notepitch but it worked only for low pass filter, for the high pass I had to built and addition module with a constant of +40.

 (NotePitch following filter)

LFO stands for Low Frequency Oscillator, is named Low because the frequency area that uses is out of our audible range and by reading the sound on sound article I found out that we can use LFO in many ways. LFOs usually have the following controls: Shape which allows you to choose between different wave shapes, rate that is usually between 0.1 and 20Hz which is the modulation rate, LFOs have also a sync which basically is a gate input that resets the modulation wave to zero whenever a note is played and depth which is the amount of modulation present in the modulated sound.

LFO is usually known as modulation which creates the vibrato effect for oscillators, where vibrato is a slight variation in pitch of a sound.

           (LFO macro)

We added the modulation effect to the oscillator and filter, by modulating the filter and adjusting filter envelope we can make the sound of a violin but by adding the LFO we had a problem with the note following option on the filter so we got rid of it until we do some more research and think of an way of doing it without affecting the note follow option or the LFO. We used a send and receive module for the oscillator modulation by adding the notepitch and the LFO receiver, then we made a switch for the octave shift along with tune and fine tune. The tune knob simply shifts semitone by semitone for an entire octave and the fine tune knob shifts only half a semitone.

(Oscillator Macro)

Something we haven’t discussed about is the selector added after the oscillator which is a smooth way of changing between waveforms, this allows us to create combinations between sine and triangle, triangle and sawtooth, sawtooth and pulse enabling us to create new hybrid sounds (this method was used mainly in older subtractive synthesizers).

The mixer at the end is simply a gain, we added a gain control to our oscillator macro to adjust the amplitude (for example a sine wave has lower amplitude that a sawtooth or a triangle wave this is due to the fact that the sawtooth and triangle wave have harmonics)

LFOs are used for Tremolo and PWM as well. Tremolo is a variation in amplitude of a sound.

(Tremolo Macro)

 For tremolo we had to modulate amplitude (in our case is the gate) we know that the gate has values between 0 and 1, because our LFO is a Bi-Polar part like the oscillators ( goes from negative to positive in our case from -1 to 1) we had to make it go only positive. To make the LFO run only one way we simply multiply by 0.5 to make it go from -0.5 to 0.5 then add 0.5 we can do this in two ways one by using the x*y+z module which is a bit confusing or by using a multiplying module and then an addition module so this is what we have done in the picture above we multiplied the gate by FLO and send the signal to the oscillators of course with an On/Off switch.

PWM stands for Pulse Width Modulation which is a fancy way of saying that we used another LFO to modulate the Pulse Width (I should have said earlier that Pulse and Square wave are the same thing).

(Pulse Width Modulation Macro)

 A smart thing we did was to send the value of the knob to the PWM macro this allowed us to have an On/Off button in the PWM control panel, we did that by using another send and receive module.

We also tried to use an LFO to modulate the Hybrid control of the oscillator but we didn’t like the sound of it.

(Oscillator Macro with the PWM and Tremolo)

In the top left we can see that we added a selector before the On/Off switch for the LFO with two LFO inputs, what we had done is coping the LFO macro once again and we added a selector to combine the two LFOs together, we did the same thing for the filter.

We really made use of the macros otherwise we couldn’t explain the process because the screen would have been messy and tangled, what we had done was tiding our work out in order to make use of the space and be organized.

(Inside the Synthesizer)

Something we didn’t talk about is the Simple Scope macro that we used during the building of the synthesizer to check how the components we have built change the waveforms and affect the sound.

 (The Synthesizer Interface)

Those are the Synthesizers we analyzed till know (I mean analyzing by looking at their interfaces and try figuring out how they are build)

(Pulverisateur Synthesizer)

(ES 1 from Logic)

(Minimosta)

Introduction

                                Our objective here is to build a synthesiser with vast sound design potential and importantly need to be simple and user friendly so this it our main principal objective. Therefore, we will build the instrument without a complex envelope, LFO or filter and so on but will functioning just like any other synthesiser. Base on our research, there are numbers of synthesis techniques developed that are often different from each other such as Wavetable, Additive and subtractive synthesis etc. In our case, we have decided to build a subtractive synthesis. Because it is commonly viewed as the classic synthesis technique also has the longest history.

In order to achieve our objective, we are aware that we need to plan well and also undertaking lots of research on Oscillator, Filter, Envelope, LFO all the components that we need to understand. Understanding how they modulate and shape the sound is very important for building the synthesiser and also the type of synthesiser features we are going to use. Most subtractive synthesiser will consist of many more options and variation but in our case we have decided to start with the standard theme and then gradually build upon on that and at the end of this project we will achieve a simple subtractive synthesiser with vast sound design potential also with some effects and step sequencer on it. At the moment, we have just started with our prototype with the standard features things like VCO, VCO and Pitch control, VCA – Amplitude control, VCF – Filter and Filter control, LFO and Envelope etc.