Doepfer A-137 Handleiding

Doepfer Niet gecategoriseerd A-137

Lees hieronder de 📖 handleiding in het Nederlandse voor Doepfer A-137 (6 pagina's) in de categorie Niet gecategoriseerd. Deze handleiding was nuttig voor 188 personen en werd door 2 gebruikers gemiddeld met 4.5 sterren beoordeeld

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doepfer System A - 100 Waveform Multiplier A-137

1. Introduction Module A-137 is a Voltage Controlled Waveform Mul-

tiplier. The basic idea of a wave multiplier is to multiply

the waveform of an incoming signal (e.g. triangle from

a VCO) within one period. This leads to additional

harmonics. The period and consequently the pitch of

the signals remains unchanged - in contrast to fre-

quency multiplication e.g. with the PLL module A-196.

The A-137 works as a kind of "inverse low pass filter",

i.e. it adds a lot of harmonics to the incoming signal.

Consequently the best results are obtained with signals

that contain none or only a few harmonics (e.g. triangle

or sine waveforms). The A-137 can be used with signals

rich in harmonics too (e.g. saw) but the effect is not as

remarkable as for triangle or sine waves.

The A-137 is a very sophisticated wave multiplier that

offers much more features, more controls and more

waveform manipulations than other wave multipliers

available so far. In addition all four parameters are both

manually adjusted and controlled by external volta-

ges:

• Multiples: number of waveform multiplications

• Harmonics: adds more harmonics similar to the re-

sonance/emphasis control of filters

• Folding Level/Symmetry: value and symmetry of

the upper/lower folding level

A-137 Waveform Multiplier System A - 100 doepfer

2. Basic principles

The signal is processed by a standard linear VCA and 4

so-called wave folding stages. The amplification of the

VCA is identical with the Multiples parameter. This is the

working principle of the folding stages: As soon as the

signal goes beyond the upper resp. below the lower

folding level the signal is reflected resp. folded back. The

values for upper and lower folding level are derived from

the input parameters folding level and symmetry. Both

can be adjusted manually and controlled by an external

control voltage (CV). Folding Level determines the di-

stance between the upper and lower folding level, Fol-

ding Symmetry the position of both levels relating to the

zero line. The internal upper and lower folding level are

calculated by adding resp. subtracting the voltages for

Folding Level and Folding Symmetry (refer to fig. 3).

The working principle of one stage by means of a

triangle signal is shown in fig. 1. The upper picture

shows the incoming signal. The areas to be reflected are

filled black. The lower picture shows the output signal of

the stage. In this example the symmetry is slightly posi-

tive and the reflected areas are not symmetrical.

Fig. 2 shows the folding function of three stages. The

amplification (i.e. the Multiples parameter) is increased

for the succeeding pictures to see the effect of incre-

asing Multiples. Stage 4 is not shown because of clear-

ness.

Fig 1: Folding function for one stage

Fig 2: Folding function for three stages

doepfer System A - 100 Waveform Multiplier A-137

As the amplification resp. the Multiples parameter in-

creases even the peaks of the folded signal reach the

folding levels of the succeeding stage and the signal is

folded once again as shown in fig. 2. As the module

contains 4 folding stages up to 8 foldings are possible (4

at the upper and 4 at the lower clipping level). Conse-

quently the maximum multiplication factor is 9 (8+1). If a

second A-137 module is added even more multiplicati-

ons are possible.

The Harmonics parameter sharpens the waveform slo-

pes and adds some overshoot at the edges - a little bit

like the resonance resp. emphasis function of a filter.

Internally the harmonics feature is realized by an additio-

nal VCA for each folding stage.

Fig 3 shows the complete schematics of the A-137

module. For each of the four parameters Multiples,

Folding Level, Symmetry and Harmonics a manual con-

trol and an external control voltage input with attenuator

is available.

The external control of each parameter can be realized

with the usual modulation resp. CV sources: LFO,

ADSR, random voltage, MIDI-to-CV, Theremin, ribbon

controller, joy stick, foot controller and so on. Of course

simultaneous control of several parameters with diffe-

rent CV sources is possible (e.g. Multiples controlled by

and ADSR and Harmonics by a LFO).

As the signals within the A-137 are fully DC coupled the

module can be used to process control voltages too.

Fig. 3: Overall view

Product specificaties

Merk:	Doepfer
Categorie:	Niet gecategoriseerd
Model:	A-137

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