Behringer Abacus Analog Music Computer for Eurorack

Quick Start Guide

Safety Instructions

1. Read these instructions.

2. Keep these instructions.

3. Heed all warnings.

4. Follow all instructions.

5. Do not use this apparatus near water.

6. Clean only with dry cloth.

7. Do not block any ventilation openings. Install in accordance with the manufacturer's instructions.

8. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat.

9. Use only attachments/accessories specified by the manufacturer.

10. Use only with the cart, stand, tripod, bracket, or table specified by the manufacturer, or sold with the apparatus. When a cart is used, use caution when moving the cart/apparatus combination to avoid injury from tip-over.

11. Correct disposal of this product: This symbol indicates that this product must not be disposed of with household waste, according to the WEEE Directive (2012/19/EU) and your national law. This product should be taken to a collection center licensed for the recycling of waste electrical and electronic equipment (EEE). The mishandling of this type of waste could have a possible negative impact on the environment and human health due to potentially hazardous substances that are generally associated with EEE. At the same time, your cooperation in the correct disposal of this product will contribute to the efficient use of natural resources. For more information about where you can take your waste equipment for recycling, please contact your local city office, or your household waste collection service.

12. Do not install in a confined space, such as a book case or similar unit.

13. Do not place naked flame sources, such as lighted candles, on the apparatus.

Abacus Controls

The Behringer Abacus is an analog music computer for Eurorack systems. It features a complex architecture designed for sound design and manipulation.

The controls are divided into several sections, primarily focusing on the four channels, each with CV inputs, trigger inputs, rise/fall time controls, and various output options.

Channel 1 Controls:

1. CHANNEL 1 CV INPUT: Accepts variable voltages (+/- 10 V) for processing by Channel 1. If no voltage is present, a self-generated voltage of approximately +10 V is used.
2. CHANNEL 1 TRIGGER INPUT: Accepts positive-going gate or trigger signals above +2.5 V to activate the Rise/Fall function.
7. CHANNEL 1 RISE CV INPUT: Allows CV control of the Rise function, in conjunction with control 8. Accepts voltages in the range +/- 8 V. Positive voltages increase Rise time, negative voltages decrease it.
8. CHANNEL 1 RISE TIME: Sets the Rise time. Can be modulated by feeding a CV to socket 7.
15. CHANNEL 1 FALL CV INPUT: Allows CV control of the Fall function, in conjunction with control 16. Accepts voltages in the range +/- 8 V. Positive voltages increase Fall time, negative voltages decrease it.
16. CHANNEL 1 FALL TIME: Sets the Fall time. Can be modulated by feeding a CV to socket 15.
19. CHANNEL 1 CYCLE TRIGGER: Allows an external positive-going gate or trigger (+2.5 V or more) to trigger Channel 1's Cycle function.
20. CHANNEL 1 ATTENUVERTER: Attenuates (CW) or inverts (CCW) the output of Channel 1 after Rise/Fall processing.
23. CHANNEL 1 RESPONSE: Varies the response of Channel 1 from logarithmic to exponential.
25. CHANNEL 1 CYCLE: Initiates cycling of Rise and Fall until the button is pressed again to stop. The button illuminates when cycling.
26. CHANNEL 1 OUTPUT: Outputs the processed voltage from Channel 1.
31. CHANNEL 1 END OF RISE OUTPUT: Outputs a +9 V voltage at the end of the Rise function, indicated by an LED.
32. CHANNEL 1 UNITY OUTPUT: Outputs a 0-+10 V voltage following Rise/Fall functions when Channel 1 is cycling; otherwise follows the channel input unaffected by the attenuverter. LED shows green for positive voltage, red for negative.

Channel 4 Controls:

4. CHANNEL 4 CV INPUT: Accepts variable voltages (+/- 10 V) for processing by Channel 4. If no voltage is present, a self-generated voltage of approximately +10 V is used.
5. CHANNEL 4 TRIGGER INPUT: Accepts positive-going gate or trigger signals above +2.5 V to activate the Rise/Fall function.
9. CHANNEL 4 RISE TIME: Sets the Rise time. Can be modulated by feeding a CV to socket 10.
10. CHANNEL 4 RISE CV INPUT: Allows CV control of the Rise function, in conjunction with control 9. Accepts voltages in the range +/- 8 V. Positive voltages increase Rise time, negative voltages decrease it.
17. CHANNEL 4 FALL TIME: Sets the Fall time. Can be modulated by feeding a CV to socket 18.
18. CHANNEL 4 FALL CV INPUT: Allows CV control of the Fall function, in conjunction with control 17. Accepts voltages in the range +/- 8 V. Positive voltages increase Fall time, negative voltages decrease it.
22. CHANNEL 4 CYCLE TRIGGER: Allows an external positive-going gate or trigger (+2.5 V or more) to trigger Channel 4's Cycle function.
21. CHANNEL 4 ATTENUVERTER: Attenuates (CW) or inverts (CCW) the output of Channel 4 after Rise/Fall processing.
24. CHANNEL 4 RESPONSE: Varies the response of Channel 4 from logarithmic to exponential.
30. CHANNEL 4 CYCLE: Initiates cycling of Rise and Fall until the button is pressed again to stop. The button illuminates when cycling.
29. CHANNEL 4 OUTPUT: Outputs the processed voltage from Channel 4.
37. CHANNEL 4 END OF CYCLE OUTPUT: Outputs a +9 V voltage at the end of the Cycle function.

Shared Controls and Outputs:

3. CHANNEL 2 CV INPUT: Accepts voltages in the range +/- 10 V for attenuverting by control 20.
12. CHANNEL 2 ATTENUVERTER: Attenuates (CW) or inverts (CCW) voltages fed to Channel 2 input on socket 3 or the internally generated voltage (-10 V to +10 V).
13. CHANNEL 3 CV INPUT: Accepts voltages in the range +/- 10 V for attenuverting by control 21.
14. CHANNEL 4 BOTH CV INPUT: Accepts a voltage (+/- 8 V). A positive voltage exponentially decreases total Rise/Fall time; a negative voltage exponentially increases it.
11. CHANNEL 1 BOTH CV INPUT: Accepts a voltage (+/- 8 V). A positive voltage exponentially decreases total Rise/Fall time; a negative voltage exponentially increases it.
33. OR OUTPUT: Outputs the result of an analog OR function based on attenuverter settings for Channels 1-4. Channels 1 and 4 require external voltage.
34. SUM OUTPUT: Outputs a summed voltage (+/- 10 V) based on attenuverter settings for Channels 1-4. LED shows green for positive, red for negative. Channels 1 and 4 require external voltage.
35. INVERTED SUM OUTPUT: Outputs the inversion of the Sum output 34.

Hints and Tips

Channels 1 and 4 can be used to modulate each other's Rise, Fall, or Both functions.
Channel 4's EOC trigger can be used to trigger an external Sample & Hold generator, which can then be used as a modulation source.
Channel 1's EOR output can be used as a modifier to any CV input on channels 1 and 4, or as an external voltage input to any channel.
Channels 2 and 3 can be used to provide an offset voltage for the CV inputs of Channel 1 and 4.
Experiment with the inverted sum voltage as a control source.

Function Times Table

	Rise Time	Rise Peak	Fall Time	Fall Min	Cycle Time
Log	9 m 0 s	9.48 v	25 m 15 s	0.03 v	42 m 45 s
Lin	55 s	9.48 v	50 s	0.03 v	1 m 45 s
Exp	7 s	4.5 v	5 s	0.03 v	10 s

Power Connection

The module comes with the required power cable for connecting to a standard Eurorack power supply system. Follow these steps to connect power to the module. It is easier to make these connections before the module has been mounted into a rack case.

Turn the power supply or rack case power off and disconnect the power cable.
Insert the 16-pin connector on the power cable into the socket on the power supply or rack case. The connector has a tab that will align with the gap in the socket, so it cannot be inserted incorrectly. If the power supply does not have a keyed socket, be sure to orient pin 1 (-12 V) with the red stripe on the cable.
Insert the 10-pin connector into the socket on the back of the module. The connector has a tab that will align with the socket for correct orientation.
After both ends of the power cable have been securely attached, you may mount the module in a case and turn on the power supply.

Installation

The necessary screws are included with the module for mounting in a Eurorack case. Connect the power cable before mounting.

Depending on the rack case, there may be a series of fixed holes spaced 2 HP apart along the length of the case, or a track that allows individual threaded plates to slide along the length of the case. The free-moving threaded plates allow precise positioning of the module, but each plate should be positioned in the approximate relation to the mounting holes in your module before attaching the screws.

Hold the module against the Eurorack rails so that each of the mounting holes are aligned with a threaded rail or threaded plate. Attach the screws part way to start, which will allow small adjustments to the positioning while you get them all aligned. After the final position has been established, tighten the screws down.

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