11

Fgenerators 

Introduction

The TD features two main generators. They are Voltage controlled thus, you could call them VCO's (Voltage Controlled Oscillator's). Why they are named fGen1 and fGen2 is to distinguish these type of generators from the classical VCO's as they can be found at classical Synth's.
The fGenerators differ from the classical synthesizer VCO design in various ways.

• 1) The fGenerators have linear FM inputs instead of exponential (logarithmically) -
  Although the two added LOG units create exponential control too.
• 2) The frequency range also invokes low and very low frequency ranges.
  Thus, also functioning as a VC-LFO or VC-VLFO.
• 3) Direct Amplitude Modulation is included without additional circuits.
  Equals the inclusion of a VCA and two-quadrant multiplier.
• 4) A pure sinusoid wave form is included without additional circuits.

Thus a fGen is a basically a VCO with extra possibilities. It is called fGen which stands for "Function Generator" to make it short and easy and to relate it to the fact that the chip that is used to create it is called a "Function Generator" chip - mostly used to generated all kind of wave forms for laboratory tests of electronic equipment.
So, it is nice to know that the TD generates music and weird effects on an artist level centred around a chip that was meant to serve science.

Have a view at the simplified diagram of the two fGenerators and how they are tied to the other units and together.

At first glance it all looks quiet complicated. There is no other way to represent how all features are implemented because the fGenerators simply has many and it will take some time before you get acquainted with all of its possibilities.

List of Controls

A list of all controls, switches, inputs and outputs with a very short description.

(x) a number in brackets means which names are valid for the 2nd fGenenerator (these numbers can be printed at the front panel).

Turn Pots

• F-coarse (CRS) To set the Coarse frequency manually.
• F-fine To set the fine tuning of the frequency manually.
• FM1 (3) To set the depth of the frequency modulation (with polarity option).
• FM2 (4)) To set the depth of the frequency modulation.
• AMP To set the Amplification of the SIN / TRI output wave form (polarity option).
• AM1 (2) To set the depth of the amplitude modulation.
• Balance 1 (2) (BAL) To set the balance between the selected waves of fGen1 and 2.

Switches

• Range (frequency) To choose the operational frequency range.
• FM1 (3) input select To choose the FM1 (3) input signal.
• Delay select (FM1 (3)) To select a delay time of the FM 1 (3) input.
• FM2 (4) input select To select the FM2 (4) input.
• Am1 (2) input select To select the AM1 (2) input.
• Wave form select TRI/SIN To select between Sinusoid and Triangle wave form out.
• Wave form select TRI/SAW/SYNC To select between Triangle, SAW or RAMP wave form or to switch to the external SYNC mode.
• Sync select To select between SOFT or HARD SYNC.
• Waves select 1 (2) To select the wave form which will be connected to the BALANCE pots.

Inputs

• FM1 (3) External FM input
• FM2 (4) External FM input
• AM1 (2) External AM input
• AUX 1 (2) External wave select input
• BAL 2 L External balance pot input left - second balancer.
• BAL 2 R External balance pot input right - second balancer.

Outputs

• SIN/TRI 1 (2) Wave form output: sinusoid, triangle, saw tooth and ramp
• SQR (1) (2) Wave form output for square
• TTL1 (2) Wave form output for square at TTL level (logic control)
• Out SEL 1 (2) WAVES select output for fGen
• Out BAL 1 (2) WAVES select output for the balancers.
  - BAL1 output also has a large jack connection.
• Out FGEN1 (2) The SIN/TRI waves output with large jack connection.

Frequency

The fGenerators have 4 Frequency controls. COARSE and FINE to set the center frequency, and two Frequency Modulation (FM) controls with external inputs and source selection switches. With a Frequency Range switch you can set the generator to operate at a certain frequency range
All these features will be discussed below.

Coarse & Fine

With the Coarse control pot you can set the frequency of the fGen close to the desired center point. The control covers the whole frequency range. Since the frequency of the fGen is voltage controlled the Coarse control is nothing more than setting manually a certain preset voltage . This voltage is mixed with the other voltages (Fine and FM voltages) and the sum of this mix determines the frequency of the fGen.
With the Fine control you can vary the frequency just a little. It is meant to fine tune to the exact center frequency you want to set. The Fine control works the same as the Coarse control - summing a certain voltage to the voltage mix which determines the frequency but, the voltage range is much smaller than that of the Coarse control.

When you like to set a desired center frequency you then first set the Fine control into its middle position. Then you tune with the Coarse control as close as possible without fumbling too much and then you use the Fine control to precisely tune your center frequency.

Frequency Range

With the Range switch you can select the frequency range that you like to have the fGen operate within. There are 3 ranges to select. They are named as LF, AU and VLF.

• LF (Low Frequency range)
  The Low Frequency range is used to generate waves for modulation purposes. The frequency range for the fGenerators is set to:
  fGen1: ...
  fGen2: ...

• AU (Audio frequency range)
  The Audio frequency range is used when you like to use the fGenerators to function as a 'normal' VCO to produces tones. The frequency range for the fGenerators is set to:
  fGen1: ...
  fGen2: ...

• VLF (Very Low Frequency range)
  The Very Low Frequency range is used to generate waves for modulation purposes. The difference with the LF range is that the frequency range is much more lower to also generate very low frequencies. The frequency range for the fGenerators is set to:
  fGen1: ...
  fGen2: ...

FM (Frequency Modulation)

Each fGen has two FM inputs - each with a Depth control and a source selection control. The FM inputs are essential to use the fGenerators as a VCO because they make it possible to control the frequency of the generators by any external voltage source. Without an FM input a VCO would not very useful as an analogue synthesizer module.
Via the FM input you can inject a voltage to the VCO voltage control node (voltage summing point) and with the Depth control you can set the amount of this injection. Thus the external applied FM voltage is summed with the Coarse and Fine manual voltage settings and their sum determines the frequency that the VCO will generate.
Setting with the Coarse and Fine controls a certain center frequency means to set a steady voltage which can be modified by using the FM input and Depth control.

When you think about this when having the fGen operating in the Audio (AU) frequency range and having the fGen output connected to an amplifier, you will hear a tone (a frequency) which is modulated in height by the FM input. This FM input maybe an analogue keyboard which delivers a voltage as a function of the key position which is played. Thus, with a keyboard you could modulate the preset voltage (Coarse & Fine) and as a result play all the notes that correspond with the keyboard scale. What you hear is a tone scale but what you actually are doing is changing the voltage in a stepping manner according the keyboard key position.

Instead, you also could FM modulate the VCO fluently by using another source that produce a control voltage. For example a triangle wave form from another fGen (VCO of LFO etc..) to produce a vibrato effect: slightly changing the frequency repetitive with a frequency between 3 to 7 Hz.

What you have to understand - to feel - is that a VCO is just a module that produces a frequency with a certain wave from (repetitive voltage curve) and that this frequency is a function of the applied voltage. Coarse, Fine, Pitch, Wheel, Modulation Wheel, Pitch Bender, Velocity, Key pressure - controlling by Envelope, guitar through a frequency to voltage module etc. It all goes about setting a certain voltage and/or modulating it by using other modules and interfaces which all produce a voltage as a function of their way to control it. On a keyboard this function is key position, for a ribbon control it is the analogue slide position and for a bend wheel the bend angle which is translated into a voltage and is used to control a VCO via its FM control(s) inputs.

FM Control & Speed

Normally you interface to a VCO with a relatively slow changing Voltage change. No matter how fast you play at a keyboard, it still is relatively slow. If you can hit 20 keys per second you play fast and the VCO will be controlled by 20 voltage changes per second. A VCO - when designed for it - can deal with a much faster response than 20 changes per second. The fGenerators of the TD can respond to more than 11.000 changes per second. This opens the way to also FM modulate it with another audio frequency and this leads to many interesting effects. Because each fGenerator has two FM inputs you can combine both 'slow' FM modulation (keyboard etc.) and fast FM (by another audio frequency).

FM Delay

The TD Cross Generator thanks its name to the way that the FM inputs of the 2 fGenerators are linked to each other. This Cross linking from one generator to the other and vice versa through their FM inputs can generate specific sounds but also may lock both generators to each other because they stabilize each other.
The Delay switch is meant to delay this locking effect and so have both fGenerators respond to each other change in a delayed way. The result of this delay is that more interesting sound patterns can be achieved when you play with the manual Coarse and Fine controls and/or use external FM control.

Phase Control

Each fGen has one FM input (FM1, FM3) which has the possibility to reverse the effect of the applied FM voltage. In the middle position of the depth control there is no modulation. Turning the control to the right means that you give more depth to the FM in normal phase (a positive voltage = positive and negative voltage = negative) but when you turn it from the center to the left, then the polarity change (Pos=Neg and Neg=Pos).

To give a concrete example: When you connect the V/OCT output of a keyboard to the FM1 input and turn the FM1 depth control to the right, then the tone will go up when you play the keyboard accordingly but when you turn the control to the left the keyboard will operate in reverse order (reversed keyboard).

The Phase control is realized with using a voltage inverter between the FM source (what you get when turning to the right) and the left junction of the control (which thus stands for the inversion of the applied FM voltage.

Wave Forms

Each fGenerator can generate the most common wave forms. These are Triangle, Sinusoid, Saw Tooth, Ramp, Square and Pulse.
When these wave forms are seen from an audio perspective the differences between them lays in their way their harmonic content is build up. A sinusoidal wave has no harmonics. Only the pure ground tone is produced and therefore a sinusoid sounds very round. A triangle has some harmonics, a Square has many harmonics but only the even ones. Very useful to imitate a classical organ sound. A Saw Tooth and Ramp have many harmonics too and they content both odd and even ones. This give you the most rich timbre and allows you very well to use a tracking filter (VCF) to control the amount of harmonics (subtractive method - removing harmonics based on the VCF settings and track this control with the keyboard position).
The Sinusoid, Triangle, Saw Tooth and Ramp waves are all available at one output. Which wave from will be available depend on the settings of two wave from switches.

When using the fGen as a modulation generator, then the wave form selection does not concern the harmonics anymore. Instead, the modulation effect of the selected wave form is essential (the modulation curve). For example: a sinusoid used to create vibrato sounds more natural than a triangle curve. A Saw Tooth may let the tone rise and then fall back abruptly while a Ramp does the opposite (rise abruptly and then goes down slowly).

WF Switches

With the wave form switches SIN/TRI and 3 way switch SAW/SYNC you can set the wave form.
When the 3 way switch is in upper position toy either create a sinusoid or triangle wave form - depending on the TRI/SIN switch position.
When the 3 way switch is in SAW position you create a Saw Tooth wave and the TRI/SIN switch determines how the top and bottom of the Saw Tooth are sharp or round (SIN=round TRI=sharp) and this also as effect on the amount of harmonics.

Amplitude

Each fGenerator has a two-quadrant multiplier build in. This multiplier is actually a VCA which respond both to a positive and negative control voltage. Thus increasing the control voltage negatively has the same amplitude increasing effect as when increasing the control voltage positively, but the phase of the output will be reversed. For an output within the audio range this only will be noticed only in some rare occasions but, when the fGen functions as a low frequency generator for modulation purposes the phase of the signal becomes rigorous when using a Saw Tooth wave form because reversing it will turn it into a Ramp wave form.

AMP Control

With the AMP control you can set the amplitude level of the SIN/TRI wave form output (The SQR output is not affected). When the AMP control is set in its middle position, the output amplitude is zero. Turning the AMP control to the left or right will increase the output amplitude.
Turning to the right will increase the output amplitude of the wave with keeping it in its positive phase. Turning it t the left will increase the output amplitude of the wave with in a reversed phase of the wave.

Practically

Reversing the phase manually by using the AMP control goes smooth. Rather than a reversing switch which would abruptly switch a Saw Tooth to a Ramp you can turn the AMP control from one side to the other to reverse and your speed of turning determines a certain flow of this reversing. This becomes valuable when the fGen is used to generate low frequencies to modulate other units.

AM (Amplitude Modulation)

Of course you also can externally modulate the multiplier by using the AM input and Depth control.
By applying an external control voltage to the AM input in combination with its Depth control and the manual AMP control setting, you can create a variety of effects.

AM Depth Control

As already explained, a positive versus negative control voltage influences the phase of the output wave form of the fGen. Therefore the AM control has the ability to reverse the input signal applied to the AM input. Setting the AM depth control in its middle position is equal to set a zero AM modulation depth. Turning it to the right causes the effect of the AM input to increase in phase with the AM input signal. Thus a positive AM voltage will control the multiplier also as such and a negative voltage will also remain as such. But, when turning the AM depth control to the left, the AM input signal will be a reversed control signal (pos=neg / neg=pos).

AM Practically

To illustrate the possibilities of combing the setting of the AMP control and the AM control possibility to reverse its control voltage some examples:

1) As a normal VCA

Setting the AMP control in its middle position will set the output amplitude to zero. An applied envelope signal to the AM input and the AM depth control turned to the right will cause the output of the fGen wave form to follow the envelope by turning the envelope voltage curve into an amplitude curve (volume curve if the wave form is connected to an amplifier). The "volume" becomes a function of the applied AM voltage curve.  

2) Wave form inverting VCA

When you have set the AMP control at its middle (neutral) position, then the fGen output will be zero. When an Envelope curve comes in through the AM input and the AMP control is turned fully to the left then the positive AM signal will be inverted and becomes negative. Due to the two quadrant function of the multiplier the output signal of the fGen will now follow the AM applied voltage curve as in example 1) but now there is an important difference in the phase of the fGen output signal: the wave form now is reversed (inverted). For symmetrical wave forms such as a triangle this has no effect (normally) but a Saw Tooth now has turned into a Ramp wave form!  

3) As a mirror (anti) VCA

When you turn the AM control fully to the right the output amplitude of the fGen is at maximum when the AM signal is at zero Volts. When the AM control is fully turned to the left (inverting position) and a positive AM signal comes in (envelope curve for example) then, the result is that the VCA follows this curve reversed and thus the output amplitude of the fGen becomes less when the AM applied input signal becomes higher and vice versa.

Practical use:
Imaging that fGenerator1 is functioning normally (for its VCA as in example 1)) and the second fGen has a VCA function in mirror mode (as in example 2) and Balance pot 1 is through the Wave form selectors connected to a sinusoid for fGen1 and a Saw Tooth for fGen2. Then the same AM signal is both applied to fGen1 and fGen2 - for example an envelope signal. What will happen? To go short: The Balanced output will a dynamic mix between the two wave forms (a round sounding one and a sharp sounding one). The mixture of these wave forms will fully depend on the AM control voltage. When both generators are tuned and FM controlled equally, the frequency will stay the same for both fGenerators but the Timbre will change under influence of the applied AM control signal. This also can be called a Voltage Controlled Wave form shaping because the mixed wave form at the output of the Balancer is varying as a function of a control voltage.

Another use is to have the output amplitude of the fGen depend on a keyboard voltage: The higher the keyboard voltage (key more to the right) the less the amplitude of the fGen output. With this one could control (compensate) the amount of upper tones relative to the keyboard position. Either creating more upper tone when higher notes are played or vice versa. Or, when routed to an effect device add more or less the effected fGen to the total sound depending on the keyboard position.

Another use is to use the mVCO modulation signal to modulate both fGenerators in a opposite VCA function and created a special timbre tremolo or modulation.

4) Rare phase shifting VCA

When you do not turn the AMP control fully to the left but only a part, then the zero point of the Envelope curve is actually shifted to another point in the curve. The effect is that from a preset fGen output amplitude, the amplitude goes down for the first part of the Envelope curve, then goes up and down according the following part of the curve and then goes back to the preset amplitude again - following the last part of the curve. Thus there are two moments that the fGen output amplitude crosses zero level. Also, two times the fGen output signal reverses its phase which becomes very effect full when using low frequency signals for modulation purposes (a Saw Tooth turns into a Ramp and back again. This is really something you have to experiment with.
When you turn the AMP control to the right, you also set the fGen to a certain output amplitude. When you do not set it fully to the right and add an envelope curve, then from a preset amplitude, it will increase and decrease again following the Envelope signal.

Notice that you can play with both the polarity of the AMP and the AM signals by turning their position to the left or the to the right to change this polarity (thus inverting the signal) and create all kind of AM control effects.

Practical use:
Phase shifting is a tricky thing in how it will end up in a resulting sound.

When it comes to Audio signals a phase shift of 180 degrees is only effect full in relation to a signal that can be seen as a counterpart of that signal and being in a certain state of phase differently. "TWINS out of phase" would be a good abstract description of possible imaginations of the effect. Two persons - looking from the outside the same but due to their differences in character interact 'unexpected'. From a technical point of view it can all to be predicted but the musical working out has may surprises in stock.

In the audio range the Phase difference becomes interesting at the point of change (the point of phase change relative to the counterpart). In the Low and Very Low frequency range the phase change is very much noticeable. Either because the wave form is not symmetrical or the timeline experience in relation to the timeline of the phase-change is slow.

Balance

Each fGenerator is equipped with an output balance control which can balance the output signal between a selected wave form from one fGen and a selected wave from form the other fGen.

Wave form select

With the wave form select switch, you can select from 6 positions - each representing a wave form variation.

• +SIN Sinusoid/Triangle/Saw Tooth (in Phase)
• -SIN Sinusoid/Triangle/Ramp (inverted phase)
• +SQR Square (in phase)
• -SQR Square (inverted phase)
• +TTL Positive Square only (for logic control)
• N Negative Square only

Each of these wave forms has is own possibilities.

+SIN / - SIN

An inverted Sinusoid looks the same as a non inverted one since a sinusoid is a symmetrical wave form. This also is true for a Triangle wave form but, when you set a fGen to a Saw Tooth function, then inverting this wave form becomes effect full - it turns into a Ramp wave form.
For audio signals this means that the harmonic content changes (timbre) and when using low frequencies form modulation purposes, the effect becomes dramatic.
As you may notice, the +SIN and -SIN positions in context to the Saw Tooth and Ramp wave forms are arbitrary because with the AMP control turned to the left the +SIN position turns into a Ramp instead of a Saw Tooth wave form and thus the -SIN position into the opposite too.

Practically

Whatever patch you made, it is always useful to simply play with the wave form selectors to see what effect is has on the sound/control. Sometimes you will not notice any difference between changing from +SIN to -SIN but for other occasions it might be useful.
Of course, change form SIN to SQR always has an effect because for the audio range the harmonic content changes dramatically and when using the wave form as modulation voltages, the curve change dramatically.

Using the SIN/TRI output of the fGen (in Phase) in combination with the wave form selected balanced output set at -SIN, gives you two outputs with the same wave form and frequency but in inverted ration. This can be useful to control two functions (parameters) in opposite directions.

For example, using the SIN/TRI output, at low frequency, to modulate the frequency (FM) of the other fGen and using the selected -SIN balanced output to control the AM input of that other fGen. What will happen: as the frequency increases, the amplitude goes down and vice versa.
First routing one of the sinusoids to the LP unit and turn open the SLOPE control will delay this sinusoid and thus not fully invert the signal (inverting means 180 degrees shifting) but instead create a phase shift others than 180 degrees. Combing both normal and inverted & delayed wave form to control various parameters is interesting and worth playing with.

Realize that the +SIN and -SIN positions not only means selecting a Sinusoid wave form but, also the Triangle and Saw Tooth and Ramp wave forms - depending on the SIN/TRI 2-pos and SAW/SYNC 3-pos switches.

+SQR / -SQR

The difference between these two position is, from a phase point of view, the same as with the +SIN and -SIN positions. Everything that was said about the +SIN and -SIN positions are more or less valid for the +SQR and -SQR positions.
A extra possibility to mention is that when you are using the SQR wave form to control logic input controls is that combining both normal phase and reversed phase for two different parameters is equal to shift the moment of certain events to occur.

For example: controlling the Sequencer clock to have the Sequencer step forward and the S&H clock to set control the moment of choosing a sample point can be set differently by using a single SQR control signal but inverted to each other. When you control the Sequencer clock by the 'normal phase' SQR signal and the S&H unit by its inversion, then the S&H will refresh half way the time period of each Sequencer change. This is because both Sequencer CK input and S&H CK input respond to the positive up going edge of a Square wave and the -SQR is relatively to the +SQR / +TTL shifted by 180 degrees (based on a 50/50 duty cycle).

+TTL / N

The +TTL position is from a functional point of view the same as the +SQR position but electrically they differ. The +SQR and -SQR positions deliver a voltage between minus 5 and plus 5 Volts. The +TTL deliver a zero to plus 5 Volts signal. This has to do with the fact that usually logic controls not operate with negative voltages. All the TD inputs are protected for out ranging voltages but are other external devices too? You never can be sure, thus when you like to control external logic inputs by the fGenerators and thus you will use a SQR signal, please use the TTL output and/or wave from select unless you know for sure that you are allowed to apply negative voltages to the inputs of the external devices.
Another difference in practically using a +TTL signal versus a +SQR or -SQR signal is that the voltage jump of the +TTL wave form is from zero to +. This means, for example, that when you create a 2 step note sequence by using the +TTL output (FM use), you will jump from your preset frequency (Coarse and Fine) to a note which is determined by the depth of the FM control. This in contrast to using the +SQR or -SQR signal because this will let you jump down to the center frequency and up with the same distance from the center frequency.

The "N" position is an inverted +TTL signal. Thus instead of jumping between zero and +5 Volts its jumps from zero to -5 Volts. You cannot use this signal for logic control but you can use it for analogue control. The effect is the opposite of the +TTL signal. In context to the above described FM control, a 2 step sequence will go down from its center position instead of going up.

Balance Control

The Balance control is an important control in combination with the Wave Form select for using both fGenerators in Cross Generate mode. This is because the internal connections between the two fGenerators. Both balance outputs are in Cross Connection to both FM controls (AM can be patched). This means that the input selection of the FM input can be routed to the balancer of the other fGen by using the input select switches.

This internal wiring (which can be selected/broken as wished for) is an important playful matter. It is the essence why the device is called "Cross Generator". Controlling one generator with the other is nothing special but feed backing the controlled generator back to the one that controls makes the conceptual difference.

Putting both the FM input selection switches into their "E-BAL" position let both fGenerators control each other by FM trough both balance controls and their selected wave forms.

Cross Feedback

You may notice that each balance control is balancing between its own selected wave from and one selected from the other. This in context to having the fGenerators into Cross Feedback control creates a complex controlling each other function. Here the motto is definitely: experiment with the wave form select, the balance control position and the way that one or both fGenerators are simultaneous controlled (FM and/or AM) by external sources too. Also, by using patch cables to inter link the balance controls to the AM inputs. Use a 'FM cross' and a single AM path from one to another fGen and route the other AM and another FM path through the Sequencer and S&H units will lead to very unexpected sounds which are hard to predict other than mentioning the idea of it in abstraction.

Explore!

Let there be something to explore without the designer already at forehand knows what is possible or not. When the "FF Cross Generator" was designed in 1984, it was the idea to design a potential of letting the user to become an explorer whom could find its very own originality. Now, with the "TD Cross Generator" this concept is copied with many extra features to challenge the user to go even deeper.
I can tell you that, besides all the 'standard' patches, there lays a Hugh potential in the way that the TD is realized for you to explore. At the moment of writing this manual I even did not produce any sound with the TD. I checked all the specifications as designed in abstraction - watching certain signals on an oscilloscope and making calculation to verify my theories. These theories, of course, are based on a very long term interaction between my ideas and the realization of them in concrete - exploring the designed abstractions as a real device with knobs, switches and in/outputs to interconnect all the sections.

Although, the balance stages in Cross Generating patch seem to be a quiet simple idea, the conceptual ground and the way it is realized go beyond existing manufactured designs. The reason that manufactures did not implement this Cross Generator idea lays probably in the fact that aiming at the creativity of the user from a commercial point of view is at least problematic.

To go short: here lays an opportunity to explore possibilities for creating your very own sound by taking the energy to research my suggestions and realize that they are nothing more than suggestions in abstraction - on purpose not worked out to give space to the individual approach.

Inputs

Which signal is selected for the left side of each balance is determined by the wave form selector. Through these selectors also two external inputs can be selected. These are called AUX1 and AUX2. AUX1 connects to wave form selector 1 and AUX two to the wave form selector 2.
Internally these input are interconnected with the SQR TTL outputs of the fGenerators but, this connection may be 'broke' by applying an external signal and thus then functions as an external input for the Balancers. Hence that the wave form selector provides you also with the inverted signal of the AUX inputs (position 'N').

The second Balancer has also two inputs that connected directly to the balancer itself and thus can be used completely independently (to function as a balance unit which provides a balances signal for other purposes than balancing the fGenerator outputs and FM/AM feedback.
The inputs are called IN BAL 2 (L and R). They internally connect to the two wave form selector outputs.

You for example could patch the CN (coloured noise) output to IN BAL 2 L and the mVCO SIN/TRI output to the IN BAL 2 R input and use the balanced output signal as a source for the S&H unit. With the balancer you then can set the S&H output pattern from fully random (turned to CN) to Pseudo random (turned to mVCO). At the same time this balanced signal still is internally connected to the FM1 input of fGenerator 1 and as such can be used. The S&H result is connected to the FM2 input. This might give interesting combination of simultaneous change the S&H character of the pattern and from the same source that is causing this change also control the Frequency of the fGenerator parallel with this source signal.
Of course, when you FAN OUT the balance signal, you also can patch it to other inputs simultaneous.

Outputs

Both the wave form selectors and the balancers have outputs:

• For the wave form selectors these are called OUT SEL 1 and.
• For the Balancers they are called OUT BAL 1 and 2.
• Balancers 1 also has a 6.3 mmm output jack.

Sync

Each fGenerator can be synchronized with an external sync signal. Internally the sync inputs are interconnected to the SQR outputs of the other fGenerator. Thus the sync input of fGenerator 1 is interconnected with the SQR output of fGenerator 2 and vice versa.

Sync Select

To have the Sync feature to become active you have to set the wave form switch into its SYNC position. Whether you set the TRI or SIN position does not matter (only some change in the amount of harmonics).
It should be clear that using the SYNC feature let the fGenerator generate a SAW TOOTH or RAMP wave form.

Switch Sync: Hard-off-soft

With the SYNC switch you can select between HARD SYNC or SOFT SYNC or OFF (no sync).

Hard Sync

If the input sync signal is above 70 mV it pulls down the fGenerators output wave form down to its minimum voltage and keeps it that way until the sync input signal drops below 44 mV again. This can be also seen as a gate feature. When the sync signal also is an audio frequency the effect may be quit similar to a SOFT SYNC but not necessarily. This depends on the frequency difference of fGenerator settings and the sync frequency. The sync input frequency can be heard as dominant in the output wave form of the fGenerator.
When you use a gated signal or a low frequency you can create frequency Bursts. A frequency Burst is a stream of waves with a certain frequency that is frequently cut off.
You may use any signal to control the Hard sync.

Soft Sync

In contrast to the Hard sync, a Soft sync mode lets the frequency of the fGenerator to be dominant over that one of the sync input frequency. Only at an up-going edge of the sync input it will cut the wave of the fGenerator output shortly to its minimum. It actually will reset the wave form for a moment and then immediately let the fGenerator to continue with generating the wave.

Practically

The result of a Soft Sync is that the originally set frequency or pattern that is currently running remains intact but the timbre colouring of the frequency is determined by the frequency of the sync signal. The effect can be somewhat similar to a filter. Playing with the sync frequency will let you hear remarkable timbre changes of the frequency of the fGenerator.

If you sync fGenerator 2 for example by a static frequency (mVCO) then when playing a tune the result will a ring modulator like effect but if you sync fGenerator 2 by fGenerator 1 and have both fGenerators FM controlled by the same source (S&H, SEQ, KEYBOARD), then the by scaling them differently you will hear a melody with a constant timbre over the whole frequency range. Changing the scale (tuning) of fGenerator 1 will then change the timbre of the frequency of fGenerator 2 over the whole range. Thus the COURSE and FINE controls of fGenerator 1 will functions as the TIMBRE control for fGenerator 2.
This soft sync effect can be found in the better analogue synthesizers (Sequential Prophet T8 for example). With only two generators you can generate a timbre that somewhat sounds similar as the FM synthesis principle but it is more natural and more rich.

The effects of a hard sync was not often implemented in synthesizers but is worth experimenting with for rare effects.

Basic Use

The basic use of the TD fGenerators is to generate audio frequencies to be heard as tones. Either varying fluently by manual control or jumping in pattern - played by keyboard or steered from the Sequencer and/or S&H module.
Each fGenerator has all the possibilities to generate a tone in various wave forms and with FM and AM control to create many basic effects known in the analogue synthesizer range.

I have manage to create an internal patch (by interconnection signals to the switching contact of the external inputs) that suits very well to the basic needs of many 'sounds' and even beyond.
Of course, going further provides the need of the lust to experiment with using the Patch cables in combination of being open for the many suggestions that I made in this manual.
I have to mention the fact that I do not know everything that is possible with such an application as the TD. Partly the design and interconnections are chosen by intuition in combination with 25 years playful experience and of course a lot of verification on the specs of the TD and its proven formula of basic possibilities. This should be seen as an advantage because lets each user being its own genius.

Extended Use

I see it as a gift to my client to provide an application that does not limit to my own experiences and dreams. Instead, I provide a tool that go beyond my own range of experiences. This does not mean that I simply mess around with the electronic design within its 'normal' purpose. Not at all! What I do is trying to have all modules that I design respond to any idea one might come up with. This only can be achieved by breaking ones head over certain prosaic problems of electronic limitations which need to be solved in both a technical an conceptual manner.

The fGenerators not only can generate audio frequencies but also Low, Very Low and high frequencies. The Low spectrum suits very well for modulation purposes. Actually you might give the TD as a whole the function of generating a variety of complex modulation signals that interact with a synthesizer setup build from other analogue synthesizer or digital/MIDI ones with Voltage to MIDI interface. You then will find out that setting up a complex modulation setup with the TD is much more interesting than by digital/computer synthesizers. Although the TD is built as a stable piece of electronics, still the fact that it mostly contains analogue electronics will lead to just that little bit of natural existence which makes the difference towards its magic. Also, when designing the TD setup it was taken in account that the disadvantages of analogue technology can be turned into a great feature which is lacked by digital technology.

The fGenerators deliver a very stable amplitude and very low distorted output of the generated frequency. It therefor also might be used for measurement and medical purposes (hearing test).

Caution

Realize that when you generate frequencies above 8 kHz, you might not hear them so loud when attached to an amplifier headphone set but, they are very strong present. You easily can damage your loudspeakers with high frequencies attached to your amplifier since the TD give a straight forward and stable amplitude rather than a weighted frequency curve as most musical sources do (Tape, Records, CD, Radio etc.)

Remarks

If you can see all the modules that the TD features in their abstraction of simply generating signals or treating signal and pulse and Voltage levels, then you patch up many applications with it.

If you believe that plants and trees can talk --> simply add a sensitive sensor to your object of research - let it transfer the picked-up signal into a voltage and patch this to the TD. Your output will be scientifically correct translated into a tone, a sequence of pulses or -if you would like - a more creative piece of sound.

An E.E.G. Pickup set also can deliver voltages that in combination with the TD can give a remarkable output.

The reason that any other analogue synthesizer as being compiled from several base units is not so suitable for this, lays in the fact that all those mass manufactured analogue synthesizer either lack a stable technology or are designed for a musical purpose in a traditional meaning and thus focus on 'a sound'. The TD does not focus on any sound in particular when it comes to the electronics. Of course, by combining certain modules, researching and finally also adding certain options, the TD has a musical direction within its own appearance. Nevertheless all the modules on itself are highly designed for straight forward and neutral specifications and therefore can be practically seen as laboratory technology (despite the fact that the TD is not according the rules - specified in medical and/or military rules --> but this is only a choice for the sake of the delivery price and a not fundamental difference).

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