DOEPFER A1013 VACTROL PHASER
DOEPFER A1013 VACTROL PHASER
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Module A1013 is a 12 stage phase shifter with vactrols as phase shifting elements. Vactrols are known for their smooth sound behaviour. For more general details about vactrols please look at the Vactrol Basics page. For a better understanding of the outstanding features a table with frequency response graphs is added at the end of this document. The first 12 frequency response curves show the behaviour of the module when stages 1...12 are used as outputs for the final mixer (no feedback, no additional patching). This is the standard phaser application with a different number of phase shift stages. The frequency response curves of the higher stages show the typical comb filters of a phaser. The notches move through the audio spectrum as the manual phase shift control is operated or a control voltage is applied (for a standard phase shifter this is normally the triangle or sine wave from a LFO). The number of notches increases with the number of stages: number of notches = integer of number of stages/2. Odd stage numbers lead to different behaviours in the higher and lower frequencies (low end: high pass behaviour, high end: passage). Even stage numbers show the same response in the higher and lower frequencies (passage for both). Stage 1 is nothing but a high pass filter, stage 2 is the standard notch filter. The second 12 frequency response curves show the behaviour when an inverter is inserted between the stage output in question and the final mixer (one of the polarizers can be used for this job). The result is the inverse frequency response compared to the output without inverter: e.g. low pass for stage 1, band pass for stage 2. The resulting frequency response curve is simply obtained by vertical mirroring the first 12 curves. Additional feedback colors the sound. The third 12 frequency response curves show the behaviour of the filters with one feedback loop. Feedback comes from the stage used as output back to stage 1 (e.g. if stage 11 is used, feedback from stage 11 to stage 1). But it is not imperative to use the same stage for feedback and audio output. Groups 4, 5 and 6 of frequency response curves show the behaviour with different feedback loops. In group 4 the same output 12 is used for all graphs but but the feedback goes from stage 12, 11, 10, 9 ... and so on back to stage 1. Group 5 is nearly the same but output 6 is used for all graphs. In group 6 the output stage is the varying parameter and the feedback goes from stage 8 to 1 for all filters. This is the result from all the response curves:
Different numbers of notches and peaks are possible by using the corresponding patch for output in use and feedback loop ! Last but not least the open structure of the module allows multiple feedback loops (e.g. stage 8 to 3 and stage 6 to 1 simultaneously) and even "forward" loops (e.g. from stage 5 to stage 9). In combination with polarizers additionally the feedback or the output polarity can be normal or inverted. This leads to a multitude of possible filter types. Some examples for multiple and forward loops are shown in the last section of the response curves. Pay attention that for some examples e.g. varying the feedback leads to "moving" peaks. By means of VCAs (A130, A131, A132) or the voltage controlled polarizer A133 the feedbacks can be voltage controlled. For more detailed information please look at the English user's manual A1013_man.pdf 

A1013 Sketch 

Breite/Width: 30TE / 30HP / 152.0 mm Tiefe/Depth: 65 mm (gemessen ab der Rückseite der Frontplatte / measured from the rear side of the front panel) Strombedarf/Current: 50 mA 

Preis/Price: Euro 310.00 The price in US$ depends upon the exchange rate between Euro and US$ at the payment day. Free currency converter: 
Frequency response curves Frequency range is 20Hz ... 20kHz for all graphs 

1. Output stages 12...1 mixed 50:50 with input signal (no feedback, no additional patches) The first 12 frequency response curves show the behaviour of module when stages 1...12 are used as outputs for the final mixer (no feedback, no additional patching). This is the standard phaser application with a different number of phase shift stages. The frequency response curves of the higher stages show the typical comb filters of a phaser. The notches move through the audio spectrum as the manual phase shift control is operated or a control voltage is applied (for a standard phase shifter this is the triangle or sine wave from a LFO). The number of notches increase with the stage number: number of notches = integer of number of stages/2. Odd stage numbers lead to different behaviours in the higher and lower frequencies (low end: high pass behaviour, high end: passage). Even stage numbers show the same response in the higher and lower frequencies (passage for both). Stage 1 is nothing but a high pass filter, stage 2 a notch. 

Stage 12  Stage 11  Stage 10  Stage 9  Stage 8  Stage 7 
Stage 6  Stage 5  Stage 4  Stage 3  Stage 2 (= notch)  Stage 1 (= high pass) 
2. Inverted output stages 12...1 mixed 50:50 with input signal (no feedback, no additional patches) The second 12 frequency response curves show the behaviour if an inverter is inserted between the stage output in question and the final mixer (one of the polarizers can be used for this). The result is the inverse frequency response compared to the output without inverter: e.g. low pass for stage 1, band pass for stage 2. The resulting frequency response curve is simply obtained by vertical mirroring the first 12 curves. 

Stage 12  Stage 11  Stage 10  Stage 9  Stage 8  Stage 7 
Stage 6  Stage 5 
Stage 4 (the famous fast food filter known from A107) 
Stage 3  Stage 2 (= band pass)  Stage 1 (= low pass) 
3. Output stages 12...1 mixed 50:50 with input signal with increasing feedback (the output stage is used for feedback to stage 1 too) blue = min. feedback, red = medium feedback, green = high feedback Additional feedback colors the sound. The third 12 frequency response curves show the behaviour of the filters with one feedback loop. Feedback comes from the stage used as output back to stage 1 (e.g. if stage 11 is used, feedback from stage 11 to stage 1). 

Stage 12, feedback from 12 to 1  Stage 11, feedback from 11 to 1  Stage 10, feedback from 10 to 1  Stage 9, feedback from 9 to 1  Stage 8, feedback from 8 to 1  Stage 7, feedback from 7 to 1 
Stage 6, feedback from 6 to 1  Stage 5, feedback from 5 to 1  Stage 4, feedback from 4 to 1  Stage 3, feedback from 3 to 1  Stage 2 , feedback from 2 to 1  Stage 1, feedback from 1 (out) to 1 (in) 
4. Output stage 12 mixed 50:50 with input signal with increasing feedback (feedback from stage 12...1 to 1) blue = min. feedback, red = medium feedback, green = high feedback But it is not imperative to use the same stage for feedback and audio output. The fourth and fifth group of frequency response show the behaviour with different feedback loops. Always the same output is used (output 12 for group 4, resp. output 6 for group 5) but the feedback goes from stage 12, 11, 10, 9 ... and so on back to stage 1. 

Stage 12, feedback from 12 to 1  Stage 12, feedback from 11 to 1  Stage 12, feedback from 10 to 1  Stage 12, feedback from 9 to 1  Stage 12, feedback from 8 to 1  Stage 12, feedback from 7 to 1 
Stage 12, feedback from 6 to 1  Stage 12, feedback from 5 to 1  Stage 12, feedback from 4 to 1  Stage 12, feedback from 3 to 1  Stage 12 , feedback from 2 to 1  Stage 12, feedback from 1 (out) to 1 (in) 
5. Output stage 6 mixed 50:50 with input signal with increasing feedback (feedback from stage 12...1 to stage 1 for all filters) blue = min. feedback, red = medium feedback, green = high feedback 

Stage 6, feedback from 12 to 1  Stage 12, feedback from 11 to 1  Stage 12, feedback from 10 to 1  Stage 12, feedback from 9 to 1  Stage 12, feedback from 8 to 1  Stage 12, feedback from 7 to 1 
Stage 12, feedback from 6 to 1  Stage 12, feedback from 5 to 1  Stage 12, feedback from 4 to 1  Stage 12, feedback from 3 to 1  Stage 12 , feedback from 2 to 1  Stage 12, feedback from 1 (out) to 1 (in) 
6. Output stages 12...1 mixed 50:50 with input signal with increasing feedback (feedback from stage 8 to stage 1 for all filters) blue = min. feedback, red = medium feedback, green = high feedback 

Stage 12, feedback from 8 to 1  Stage 11, feedback from 8 to 1  Stage 10, feedback from 8 to 1  Stage 9, feedback from 8 to 1  Stage 8, feedback from 8 to 1  Stage 7, feedback from 8 to 1 
Stage 6, feedback from 8 to 1  Stage 5, feedback from 8 to 1  Stage 4, feedback from 8 to 1  Stage 3, feedback from 8 to 1  Stage 2, feedback from 8 to 1  Stage 1, feedback from 8 to 1 
7. Some Examples with two feedback loops blue = min. feedback, red = medium feedback, green = high feedback Last but not least the open structure of the module allows multiple feedback loops (e.g. stage 8 to 3 and stage 6 to 1) and even "forward" loops (e.g. from stage 5 to stage 9). In combination with polarizers additionally the feedback can be normal or inverted. This leads to a multitude of possible filter types. Some examples for multiple and forward loops are shown in the last section of the response curves. 

Output: stage 10 feedback 1: 8 to 3 feedback 2: 6 to 1 Main peak moves from middle resonance (red) to high resonance (green) to new position 
Output: stage 10 (inverted) feedback 1: 6 to 1 feedback 2: 12 to 10 
Output: stage 10 feedback 1: 6 to 1 feedback 2: 12 to 10 (inverted) 
Output: stage 10 feedback 1: 6 to 1 feedback 2: 12 to 10 
Output: stage 10 feedback 1: 4 to 1 feedback 2: 10 to 1 (inverted) 
Output: stage 10 feedback 1: 2 to 1 feedback 2: 10 to 4 (inverted) 
Output: stage 10 feedback 1: 2 to 1 feedback 2: 10 to 3 
Output: stage 6 feedback 1:9 to 1 feedback 2: 4 to 9 
Output: stage 6 (inverted) feedback 1: 9 to 1 feedback 2: 4 to 9 
Output: stage 6 feedback 1: 9 to 1 (inverted) feedback 2: 5 to 9 (inverted) 
Output: stage 6 (inverted) feedback 1: 9 to 1 (inverted) feedback 2: 5 to 9 (inverted) 
Output: stage 6 (inverted) feedback 1: 5 to 1 feedback 2: 9 to 1 
Output: stage 5 feedback 1: 8 to 1 (inverted) feedback 2: 12 to 6 
Output: stage 1 (inverted) feedback 1: 8 to 1 (inverted) feedback 2: 12 to 6 (inverted) 