Module A-101-8 is a 8-stage phase shifter which uses light-sensitive resistors (LDR) and is a replica of the Compact Phasing A manufactured by the company Schulte in the seventies. The actual phasing circuit is identical to the historic model. Only the illumination control of the LDRs is different: the A-101-8 uses LEDs to illuminate the LDRs, the historic model used incandescent miniature lamps. And the A-101-8 has no built-in LFO but can be controlled by any external control voltage source (e.g. LFO, ADSR, random, Theremin, ribbon controller, sequencer, midi). The phasing offset (i.e. the base value for the phase shifting) and the modulation depth of the external control signal can be adjusted separately. The Compact Phasing A had no offset control but only a depth control for the built-in LFO. Feedback and mixing ratio of the output signal are set by two controls. The audio input is equipped with an attenuator. The module has two audio outputs available (same as the historic model) and a visual display of the phase shifting.

The module has these controls and in/outputs available:

• Control Man. : manual control of the phase shift offset (base value)
• Control CV: attenuator for the signal applied to the CV socket
• Control Feedb.: Feedback or Resonance (similar function as filter resonance/feedback/emphasis)
• Control Mix: sets the mixing ratio between original and phase shift signal appearing at output 1
  • fully CCW: only the modified input signal appears at output 1 (see note below *)
  • center: a mixture between the modified input signal and the phase shift signal appears at output 1, that's the standard position for the classical phasing effect
  • fully CW: the pure phase shifted signal appears at output 1 (e.g. for vibrato effects)
• Control Input Level: attenuator for signal applied to the In socket
• Socket In: audio input
• Socket CV: control voltage input 
• Socket Out 1: audio output 1 (mix signal)
• Socket Out 2: audio output 2 (modified input signal)
• LED: visual control of the phase shift

The module has some peculiarities (same as the historic model):

• The input signal is processed at first by a pre-stage which outputs a "modified" input signal (*). This signal is not processed by the phase shift stages but is affected by the feedback setting. Only when feedback is set to zero this signal is identical to the input signal. Otherwise it contains feedback components.
• This signal is output on socket Out 2.
• When both output sockets Out 1 and Out 2 are used as stereo channels one obtains a spatial stereo sound effect. 
• The same signals is also used for the CCW position of the mix control. With mix control fully CCW the unmodified signal appears only if the feedback control is set to zero. Otherwise it contains feedback components.
• The historic model had two audio inputs: one 5-pin DIN socket and a 1/4" jack socket. The DIN socket was intended for high-level line signals. When the 1/4" jack socket was used the amplification of the pre-stage increased by about 100. The 1/4" jack socket was intended for low level signals (e.g. electric guitars or microphones). For this feature the A-101-8 has an internal jumper that can be used to increase the amplification. As long as the module is used within the A-100 system usually the lower amplification is used to avoid distortion.
• The 8 photo resistors and LEDs are assembled within an small lighproof box. In addition the pc boards are made of lighproof black material to avoid interfering light from other modules or the bus board.

Merk:

Doepfer

Type:

Chorus, Phaser, Flanger

Nummer:

A-101-8

Diepte:

45mm

Breedte:

4HP

Power:

30mA @ +12V, 30mA @ -12V

Module A-114 contains two separate ring modulators.

A ring modulator outputs the product (Multiplication X • Y) of the signals at inputs X and Y. It's similar to a VCA, but whereas a VCA only responds to positive voltages at the inputs (2-quadrant multiplication), the ring modulator responds to both positive and negative voltages (4-quadrant multiplication). The ring modulator thus provides a refinement of amplitude modulation (AM). Ordinary amplitude modulation will output the original carrier frequency fC as well as the two side bands (fC - fM, fC + fM) for each of the spectral components of the carrier and modulation signals - but ring modulation cancels out the carrier frequencies, and just lets the side-bands pass to the output.

A ring modulator is used for the production of bell-like sounds, alien voices, or just to produce new timbres

Merk:

Doepfer

Type:

Ringmod, Frequency shifter

Nummer:

A-114

Diepte:

40mm

Breedte:

4HP

Power:

40mA @ +12V, 30mA @ -12V

Module A-115 is a four-way frequency divider.

The frequency of a signal at the input is halved (half frequency = first sub-octave), quartered (1/4 frequency = second sub-octave), and so on. In this way, the DIVIDER produces four sub-octaves (F/2 down to F/16). At the output, the A-115 produces a summed mix of the original and the four sub-octaves. There are attenuators to control the amount (ie. Amplitude) of the original signal and each of the sub-octaves. Bear in mind that the sub-octaves output by the A-115 are all true square waves. At the output there are always four square waves and the original signal available.

Merk:

Doepfer

Type:

Frequency-divide-multi.-follow.

Nummer:

A-115

Diepte:

40mm

Breedte:

8HP

Power:

20mA @ +12V, 10mA @ -12V

Module A-116 provides voltage-controlled dynamic waveform modification of audio signals. It can produce new waveforms from the standard VCO shapes, and modulate these changes in real time. The signal first of all goes through an input amplifier, which can attenuate the signal as well as amplify it by up to a factor of 2. After the input amplifier, the signal goes through two parallel processors: a clipping circuit, and an asymmetrical amplifier. The processed signals are added together and sent to the output. Clipping-Level and Symmetry amounts are not just manually controllable, but can also be modulated by control voltages, to produce complex, constantly changing waveforms.

Merk:

Doepfer

Type:

Distortion, Waveshaper

Nummer:

A-116

Diepte:

40mm

Breedte:

8HP

Power:

20mA @ +12V, 20mA @ -12V

A-137 is a voltage controlled Wave Multiplier. The basic idea of a wave multiplier is to multiply the waveform of an incoming signal (e.g. triangle/saw/sine from a VCO) within one period of the waveform. This leads to additional harmonics of the incoming signal. The period and consequently the pitch of the signals remains unchanged (in contrast to frequency 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 a signal that contains none or only a few harmonics (e.g. sine or triangle waveform). In contrast to that a low pass filter removes harmonics from a signal that contains a lot of harmonics (e.g. saw or rectangle waveform). Consequently the best results are obtained in combination with input signals poor in harmonics (e.g. sine or triangle). 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. For rectangle signals none or only little effects are obtained. 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 parameters are both manually adjusted and controlled by external voltages. The Multiples parameter (manual and ext. CV) defines the number of basic wave multiplications within one period. With the Folding Level and Symmetry parameter (both manual and ext. CV) the upper and lower clipping levels of the wave folder units are controlled. The Harmonics parameter (manual and ext. CV) adds some harmonic content by sharpening the waveform edges and adding overshoot peaks. It works a little bit like the resonance control of a VCF. The module is fully DC coupled, i.e. even control signal can be processed with the modules.

Merk:

Doepfer

Type:

Distortion, Waveshaper

Nummer:

A-137-1

Diepte:

65mm

Breedte:

14HP

Power:

40mA @ +12V, 20mA @ -12V

Module A-137-2 is another version of a wave multiplier. In contrast to the A-137-1 Wavemultiplier I the A-137-2 generates four phase-shifted copies of a VCO signal applied to the audio input. The four shifted signals are added to the original signal to obtain a fat sound similar to five independent VCOs. The phase shifting is made by a simple circuit that works only for sloped signals like sawtooth, triangle or sine, but not for rectangles or pulses.

Merk:

Doepfer

Type:

Distortion, Waveshaper

Nummer:

A-137-2

Diepte:

50mm

Breedte:

14HP

Power:

30mA @ +12V, 20mA @ -12V

Module A-160 is a frequency divider for clock/trigger/gate signals, designed to be a source of lower frequencies, particularly for rhythm uses.

The Trigger input will take clock signals from, eg., an LFO, MIDI sync, or the gate from a MIDI-CV interface. At the outputs, you have access to the sub-divided clock signals, from half the clock frequency down to 1/64. The low/high levels of the output signals are 0V and about +10V.

The A-160 also has a reset input. Whenever a reset signal is sensed, all outputs are set to zero, until the reset voltage disappears.

The Clock Divider can be used in combination with the A-161 Clock Sequencer to produce stepped sequences with a length from one to eight events.

Merk:

Doepfer

Type:

Clock Divider, Frequency Divider, Clock & Trigger

Nummer:

A-160-1

Diepte:

40mm

Breedte:

4HP

Power:

40mA @ +12V, 0mA @ -12V

Module A-160-2 is an enhanced version of the standard clock divider A-160. The module is a frequency divider for clock/trigger/gate signals, designed to be a source of lower frequencies, particularly for rhythm uses.

The Clock input will take any digital signal from, eg., an LFO, MIDI sync, or the gate from a MIDI-CV interface. At the outputs, you have access to three sets of seven different sub-divided clock signals, from half the clock frequency down to 1/128. The low/high levels of the output signals are 0V and about +10V.

The A-160-2 also has a reset input. Whenever a reset signal is sensed, all outputs are set to certain levels which depend upon the selected mode.

Merk:

Doepfer

Type:

Clock Divider, Clock Multiplier, Clock & Trigger

Nummer:

A-160-2

Diepte:

35mm

Breedte:

4HP

Power:

50mA @ +12V, 0mA @ -12V

Module A-170 contains two separate slew limiters, also known as portamento controllers or integrators.

The first SL has just one joint control, which sets both rise and fall times (c. 0 ...10 sec). The second SL has separate controls for rise and fall times, and can therefore be used as a simple AR envelope generator. Over and above this, you can set the overall range for these parameters, with a three-position switch, as on the full ADSRs.

Both slew limiters have two LEDs each, to show the state of the rising and falling voltages.

Merk:

Doepfer

Type:

Slew Limiter, Quantizer

Nummer:

A-170

Diepte:

40mm

Breedte:

8HP

Power:

20mA @ +12V, 20mA @ -12V

Much more than just a plain slew limiter, the A-171-2 is a multi-functional module for generating and processing control voltages and audio signals in the manner of a function generator. LFO, envelope generator, slew limiter... plenty functions are possible! You can even use the module as a simple waveshaper or a filter. The A-171-2 has been created in licence from Ken Stone.

These are the most important features:

• Manual control of the Slew-Up time
• CV control of the Slew-Up time with polarizer
• Switch for linear/exponential shape of the rising section of the response curve 
• Manual control of the Slew-Down time
• CV control of the Slew-Down time with polarizer
• Switch for linear/exponential shape of the falling section of the response curve
• Signal input: the "to-be-slewed" signal
• CV Up Input, affected by the CV Up Control and the corresponding exp./lin. switch
• CV Down Input, affected by the CV Down Control and the corresponding exp./lin. switch 
• CV Up and CV Down sockets are normalled
• exponential CV input: named "V/Oct" in the original design but as it's not really exactly 1V/Oct we will name this input probably "exp.CV", mainly used for VCLFO/VCO applications in cycle mode or as common exponential control for both up and down times in slew mode 
• Trigger input: used for envelope generation or retrigger in VCLFO/VCO mode, a pulse at the trigger input will start the envelope or retrigger the VCLFO/VCO
• End output: turns high as the output falls below about 20mV, turns low as the outputs goes beyond about 3.5V, in cycle mode a rectangle signal is generated
• Cycle on/off switch: when "on" the End output is internally connected to the Trigger Input to generate cyclic signals like an VCLFO/VCO
• Output: the signal output of the module
• LED display: displays the slew limiter output signal

Merk:

Doepfer

Type:

Slew Limiter, Quantizer

Nummer:

A-171-2

Diepte:

60mm

Breedte:

8HP

Power:

30mA @ +12V, 30mA @ -12V

The small module combines three functions already available in Doepfer's dual modules: ring modulation, sample & hold and slew limiting.

It is recommended for compact systems where space is an issue or for users who don't need two ring modulators or two slew limiter for instance but a small and multi-functional utility instead.

The upper section consists of a half of a A-114 ring modulator and has inputs for the signals X and Y. The X*Y output emits the multiplied / ring modulated signal. The bottom section is a sample & hold followed by a slew limiter. It has an input for the sample signal and a trigger input. A switch select mode of operation as the module can work as a sample & hold or as a track & hold. When in T&H mode no trigger is applied this section can be used as an individual slew limiter.

Merk:

Doepfer

Type:

Slew Limiter, Sample and Hold, Random, Ringmod, Frequency Shifter

Nummer:

A-184-1

Diepte:

40mm

Breedte:

4HP

Power:

40mA @ +12V, 30mA @ -12V

Module A-196 contains a so-called phase locked loop (PLL).

A PLL consists of three parts: voltage-controlled oscillator (VCO), phase comparator (PC), and low-pass filter (LPF). All parts are normally connected to form a closed-loop frequency-feedback system.

This is how a PLL works: The output of the internal VCO (linear CV control, rectangle output) is compared with an external signal (e.g. the rectangle output of a A-110 VCO) in the so-called phase comparator (PC). The output of the phase comparator is a digital signal (low/high/tristate) that indicates if the frequency resp. phase difference of the two input signals is negative, zero or positive. The output of the phase comparator is processed by a low pass filter (LPF) to generate a smooth voltage that is used to control the frequency of the internal VCO. The 3 units VCO, PC and LPF form a feedback loop that works like this: The control voltage (output of the LPF) increases as long as the external frequency is higher than the frequency of the internal VCO and stops increasing when both frequencies become identical.The control voltage decreases as long as the external frequency is lower than the frequency of the internal VCO and stops decreasing when both frequencies become identical.

But there are some stumbling blocks: Different types of phase comparators with advantages and disadvantages can be made. Some phase comparators e.g. even lock at harmonics, i.e. if the two frequencies to be compared are integer multiples. But for some applications this can be used to create interesting effects. The A-196 contains 3 different types of phase comparators: PC1 is a simple exclusive OR, that even locks at harmonics. PC2 is a so-called RS flipflop and PC3 a more complex digital memory network. The user can select one of the three phase comparators with a 3-position switch. When PC2 is used a LED displays the "locked" state, i.e. when the frequency of the internal VCO is identical to the external frequency.

Special attention has to be directed to the frequency of the LPF. To obtain a smooth control voltage for the VCO the frequency of the LPF has to be much smaller than the lowest frequency of the internal or external audio signal. Otherwise the frequency of the internal VCO will jitter or wobble around the correct frequency. But for special effects this frequency jitter can be used intentionally. Example: frequencies in the range 50Hz...1kHz have to be processed with the PLL. Therefore the frequency of the LPF has to be about 10Hz or even less. Such a low frequency of the LPF causes a noticeable slew of the internal VCO. When the frequency of the external signal jumps e.g. between 500Hz and 1kHz it takes about 0.1 second until the internal VCO reaches the new frequency (like portamento). So one has to find a compromise between frequency jitter and portamento. But these remarks are valid only for the "ideal" working PLL. As the A-196 is used in a musical enviroment the "problems" and disadvantages with jitter and slew time lead to additional musical applications like portamento effects, wobbling frequencies or harmonic locking according to the type of frequency comparator and time constant of the PLL low pass filter. Instead of the internal manually controlled low pass filter the voltage controlled slew limiter A-171 can be used to obtain voltage control of this parameter. Normal audio filters (e.g. A-120, A-121) cannot be used for this job as the minimum frequency is to high (down to a few Hz or even less necessary) and the signal has to be DC coupled due to the low frequencies. Audio filters are normally AC coupled.

Another very important application of a PLL is frequency multiplication in combination with an external frequency divider. For this the output of the PLL-VCO is processed through an external frequency divider (e.g. A-163, A-160, A-161, A-115) before it is fed to In1 of the phase comparator. In this case the frequency of the PLL-VCO will be a multiple of the master frequency. E.g if the the A-163 is used and adjusted to dividing factor 5 the frequency of the PLL-VCO will be 5 times the frequency of the master VCO. Consequently frequency division (A-163) leads to frequency multiplication with the PLL circuit. In combination with the PLL low pass frequency several effects can be realized (frequency multiplication with portamento or wobbling). The frequency multiplication can even be used to drive a graphic VCO. If your graphic VCO e.g. has 8 steps (e.g. A-155) and you use a frequency divider with factor 8 in the PLL feedback the output of the graphic VCO has the same frequency as the master VCO. Another application is the generation of pseudo-harmonics (not real harmonics as only rectangle waves are available) or clock generation for switched-capacitor filters.

The PLL components are available as separate building blocks in the A-196 module. The standard PLL patch is realized by means of normalized sockets. But it is also possible to use each component separately. E.g. the VCO can be used as a simple VCO with linear control input and rectangle output. For this an external voltage has to be fed into the CV input socket. The VCO has two controls: Offset and range (switch). As the VCO has a linear control input the frequency will go down to zero (i.e. the VCO stops) if the input CV is 0V. The offset control is used to adjust the lowest frequency (i.e. the frequency for CV = 0V). The range switch is used to switch between 3 frequency ranges. The position of the switch defines the max. available frequency. For other treatments of the phase comparator output (e.g. with an external voltage controlled filter or any other processing module) the output of the phase comparator is available. Same applies to the LPF output and input 1 of the phase comparator.

It has to be pointed out that the A-196 is a very experimental module and its functions cannot be described straight forward as for other modules. Rather the user should try out the possibilities by trial and error.

Applications: frequency multiplication, special sound effects, generation of clock signals for graphic VCO (high speed VCO, e.g. for A-155 as graphic VCO), clocked audio delays or switched-capacitor filter.

Merk:

Doepfer

Type:

VCO, Phase Comparator, LPF

Nummer:

A-196

Diepte:

40mm

Breedte:

8HP

Power:

40mA @ +12V, 0mA @ -12V