Whilst most analogue sequencers these days offer only 8 steps, Obekorn offers the all important 16 steps required for more serious sequencing. It provides 3 CV channels (2.5, 5, 10V range selection), 5x Gate channels, 8x MIDI to Trigger channels.

Extended information

It has a built in clock, 2 reset options and other controls. It has a reset to step 16 button. This is a crucial feature that those who are familiar to analogue sequencers will realise how important this normally lacking feature is.

It also has the unique ability in that you can control which order it steps in. By either using MIDI notes, or analogue voltages, you can make it miss steps, repeat them go forwards, backwards, or whatever you want!

Case

There are many case styles. Oberkorn has been designed so it can be mounted in a standard Concussor, Integrator or Doepfer modular case. We can offer a 3U, or 6U (to mount 2 Oberkorns!) metal rack mount cases. Or we can supply a low cost plastic housing. If you have your own case or have the ability to build one, we can supply Oberkorn on its own without case/power supply.

For more details read the manual online - note, this does not contain all the important pictures! DOWNLOAD THE MANUAL.







Introduction
Oberkorn is a fully fledged professional analogue sequencer providing plenty of control output and inputs and with some uniquely creative features never before seen.

Overview

Whilst most new analogue sequencers only offer a limiting 8 steps, the Oberkorn offers the all important 16 steps. It is a multi-channel true analogue sequencer with some remarkable features. Below are a list of main features:

3 separate Control Voltage channels. Each has a range switch providing approx. 2.5V, 5V and 10V CV ranges.

5 separate Gate channels. 3 of the gate channel switches are built into the CV pots. The remaining 2 are on a separate row of toggle switches. The switches are 3 position providing the 2 Gate outputs, with centre being off.

Gate channel C is in `Legato mode'. More on this later.

Clear step LEDs. The 16 step LEDs are colour coded so locating whole note steps is easy.

8 channel MIDI to Trigger/Gate converter (with an additional 3 spare channels available internally for those who wish to do modifications.

MIDI Sync cabability, but using a MIDI note instead of MIDI clock. This method has major, important advantages covered later.

MIDI Reset ability - reset to step 1 via MIDI note

MIDI/CV control of the multiplexer (the multiplexer, or Mux, controls which step the sequencer is on). This is a major new and unique facility that allows any of the 16 steps to be played in any order and any direction, missing out or duplicating steps at will. Please read full details about this important creative tool later in the manual. When using this feature, it is possible to activate `legato mode' for all gate channels.

Ability to lock onto your MIDI sequencer to the nearest 16th note, whether stopping, starting, or jumping to another bar in your MIDI sequencer. Will lock on perfectly regardless.

Reset to 16. Just about all other analogue sequencer have an inherant error, in that after reseting the machine (to step 1), when restarting the sequencer, it actually starts on step 2! With our Reset to 16, this problem is overcome.

For more details on all features of Oberkorn , please read the whole manual - don't miss any of it's cool features!


About Analogue Sequencers

Analogue sequencers are devices that allow a sequence (up to 16 steps in the case of Oberkorn) of voltages and gate signals to be `played back' in order from 1 to 16. Each step has its own pot to vary CV and a switch to turn the Gate on or off for that step. As the sequencer advances through each step, the CV and Gate signals for that step are outputed at the CV and Gate sockets. When step 16 is reached, the sequencer resets to step 1 and starts all over again. Oberkorn has 3 CV and 5 Gate channels.

CV is normally used to control an oscillator's pitch, but can be used to control any module that has a CV input, such as filter cut-off. The Gate signal is usually used to trigger an envelope, but can be used to control any module with a gate, trigger or clock input.

There are many controls and features on an analogue sequencer to give more overall control over the way the sequencer opperates.

The major advantage over an analogue sequencer compared to a MIDI/Digital sequencer are:

You have direct access to each note pitch (CV) and note on/off (Gate) as there is a separate control for each step. Software sequencers do not offer this advantage, and very very few hardware MIDI sequencers do either. This makes analogue sequencers more immediate and hands on. With this immediate hands on control, you can experiment by altering the controls as the sequence plays, to evolve and manipulate your patterns in real time. As the signals coming from the sequencer are analogue voltages, they can be added, inverted, slewed, or whatever, and can be used as audio or control signals to feed into other analogue devices.



Quick Start
If you just want to jump straight in and use Oberkorn in it's most basic form - to play an analogue synthesiser - here's how to do it:

Take CV-A out into the CV (VCO pitch) input of your synth.

Take Gate X out into the Gate (or EG trigger) input of your synth.

Press the Reset to 16 button to reset the sequencer. It will reset to step 16. This is correct!

Flick the Run/Stop switch left to `Int' - `Internal'. The sequencer will now run off its internal clock at the speed set by the Tempo control starting at step 1.

Flick the row of Gate switches up (to `X') to produce a Gate pulse to trigger your synth. Return the switch to the centre off position for no Gate.

Alter the CV-A pots to change to pitch CV for each step.

Alter the Tempo control till the sequencer runs at the desired speed.

If you want to restart the sequencer, move the Run/Stop switch to the centre position `Stop'. Press the Reset to 16 switch, then restart the sequencer with the Run/Stop switch.

Basically, just keep playing around till you get a great sequence!




CV + Channels In Details
Oberkorn has 16 steps. (This can be reduced to any number from 1 to 15. More on that later).

Each column of three CV pots and 1 switch is a step. There are 16 columns.

CV Channels

CV-A This sets the voltage for CV channel A from 0V upto the range set by the A Range switch.

CV-B This sets the voltage for CV channel B from 0V upto the range set by the B Range switch.

CV-C This sets the voltage for CV channel C from 0V upto the range set by the C Range switch.



Range Switches

Each CV channel has a separate range switch with 3 positions:

H `High' - The CV range become 0 to 10V

M `Medium' - The CV range becomes 0 to 5V

L `Low' - The CV range becomces 0 to 2.5V
CV A, B & C, and Gate A, B & C Control/Switches
Gate X/Y Switch
Step LED


Gate Channels A, B, C

Each row of CV pots CV-A, CV-B and CV-C, has a built in switch. Turn the switch fully anti-clockwise (you will feel and hear a `click') and the switch is off. Turn to the right (after the click) and the switch is on. The integral switches built into the 3 rows of CV controls provide the Gate signals for channels GT-A, GT-B and GT-C.

As the Gate switch is built into the CV pot, we realise that this means that to have the step produce no gate output means that the CV level will also be zero, but this was the only way to add a Gate channel in such a compact module and also without adding to the cost. We could have left it out leaving nothing to complain about. But it does NOT add to the price, so you are getting 3 extra Gate channels for free! So no complaints about the zero-CV with no-Gate situation.

If you do wish to use CV and Gate together controlling pitch and EG triggering, there are some ways around this problem:

Add some Glide to the CV signal. In some situations this will hide/eliminate the side-effect.

Put the VCA control signal into `Gate' not `EG' amount mode (or have zero release time on the EG). So as soon as the Gate goes to zero, the output of the synth patch will also be zero so you will not hear the pitch drop.



Additional Gate Channels - bottom row of toggle switches

GT-X When the switch is up, the Gate for channel GT-X is set for that sep

GT-Y When the switch is down, the Gate for channel GT-Y is set for that sep

Off When the switch is in the centre position, no Gate is set for either channel X or Y



CV and Gate Output Sockets

The resulting CVs and Gate patterns created from the CV/Gate channels are outputed via the CV/Gate sockets.

The CV sockets are labelled CV-A, CV-B and CV-C. These correspond to the appropriate row of CV pots. The CV signals are normally used to control any control voltage input on a synth or modules, e.g. pitch, filter cut-off, VCA, etc.

The Gate sockets are labelled GT-A, GT-B, GT-C, GT-X and GT-Y. These correspond to the appropriate Gate channels. The Gate signals are normally used to trigger envelope generates, or any thing with a Gate/Trigger input (drum machine/module, monosynth, another analogue sequencer, sample and hold, etc.).

The Gate output level is +7V. This can be changed to any value from 0 to 12V by changing some internal zener diodes.



Gate Output Signals and Gate C Legato Mode

Normally, for each gate switch that is in an `on' position, a gate signal is sent out of its gate socket. If 2 or more gate switches in a row are all on, then the gate signal will go off briefly before going on again for the next consecative gate signal. This way, for instance, an envelope will re-trigger. This is how gate channels X, Y, GT-A and GT-B work.


Gate output for channels X, Y, GT-A and GT-B.

See how each gate switch produces an individual gate signal.



The following section is for advanced users. It describes in more technical detail how gate channels X, Y, GT-A and GT-B work. You only need to tackle this if you wish to fully exploit the direct MUX feature covered later in the manual.

The gate signal output is actually produced by ANDing (a boolean term) the state of the gate switch with the clock.



Gate Switch Clock Gate Signal output

off off off

on off off

off on off

on on on

From the above table, you can see a gate signal is only created when the gate switch is on and there is a clock voltage present. As soon as the clock signal goes low (0v) or the gate switch is off, then there is no gate output.


For Gate channel GT-C the output is different. It is in Legato mode. This means that when consecutive gate switches are all on, then the output will stay on, adding the output of the on gate switches together creating a longer gate signal. This way, for instance, an envelope will not re-trigger, but stay on for consecative on switches, only going off when it meets the first off gate switch. This is because the GT-C gate switch condition is not ANDed with the clock signal.


CLOCK
Gate output for channels GT-C.

See how the 2 consecative on gate switches produce a gate signal that is on for the duration of the switches.



Varying Gate Note Length

All the gate outputs (except GT-C) will have a gate length that is equal the the clock pulse width. You can see this by looking at figure 1. So to alter the gate pulse width you simply have to alter the clock pulse width. Most VCOs have square wave outputs whose pulse width can be altered. This output can then be used to clock the sequencer. The Concussor VCO-RM is one such module.


Example showing the effect a clock signal with varying pulse width has on the gate signal. This does not apply to channel GT-C.




Splitting CV and Gate outputs

All CV and Gate channel outputs are buffered. This means their signals can be split many times with a multiple without losing any level.



Step Indicator LED

Each Step has an LED indicator to show which step the sequencer is on. The LEDs are just to the right of each step.

LEDs 1, 5, 9 and 13 are red to indicate quickly the whole notes in a 4/4 pattern.

LEDs 2, 3, 4, 6, 7, 8 are yellow to indicate the notes in the 1st half of the sequencer.

LEDs 10, 11, 12, 14, 15, 16 are green to indicate the notes in the 2nd half of the sequence.
When the sequencer is not running, the voltage represented by the relevant CV control is continuously available at the relevant CV output. It will not change till the sequencer is either manual stepped or clocked to the next step. The CV controls can be altered in real time to alter the CV output whilst the sequencer is stopped.





MIDI to Trigger Converter


Oberkorn features a 16 channel MIDI to Trigger/Gate converter.
It allows a number of devices to be triggered directly from a MIDI note, independently from the sequencer. Some of the MIDI-Trigger channels have special functions described later.

The MIDI-Trigger outputs can be used to trigger drum voices, EGs, analogue sequencers, or anything else with a clock/trigger/gate input.



Channel Overview

Channels 1-8 (1-8) These triggers are freely available to use on the front panel via 8 jack sockets. These allow devices such as envelope modules or drum modules to be triggered independently of the sequencer by a MIDI note.

Trigger 9 (SYN) This is hard wired to the Clock input of the sequencer, so a MIDI note can be used to synchronise Oberkorn to a MIDI sequencer. More on this later.

Triggers 10-13 (A/B/C/D) These are hard wired to the Mux. More on channels 10 to 13 later.



Trigger 14 (INternal1) This is hard to Reset. When this trigger is activated the sequencer will reset to step 1. This will work whether the sequencer is running or stopped.



Triggers 15-16 (IN2/3) These are spare and internal and effectively unused. They can be utilised via modifications. E.g. they could be wired to additional jack sockets on the rear panel.




Connecting

Connect the MIDI sequencer or other MIDI device to the MIDI input of Oberkorn . Connect the trigger outputs to device you wish to trigger.



Programming

• Programming the MIDI channel is a very simple proceedure.

• Press the PROG button. The 1st LED will flash, and triggers will be sent out of output 1.

• Oberkorn will now be in MIDI omni-on mode, so it will receive information on all MIDI channels.

• Press the MIDI key you wish output 1 to be assigned to. Output 1 will be assingned to that note number. Oberkorn will set its MIDI receive channel (which will be the same for all outputs) to the MIDI channel the keyboard is transmitting on.

• Continue to program the following 15 outputs by pressing each key your wish to assign them to in turn.

• As each key is pressed, the next LED flashes and triggers are sent out of the respective output.

• After all 16 outputs are assigned the unit returns to normal mode.

• If you wish to skip programming any individual output, simply press the PROG button to skip outputs.

Set-up information is stored in non-volatile memory. Information is retained when the power is switched off or module disconnected from power board. No battery back-up is required!

If the set-up is altered for any unpredictable reason (for example power disconnected during programming), the factory default program will be loaded at start-up. Factory default is MIDI channel 1, Output 1 set to C60, the next 15 outputs set to the next 15 keys.





Sequencer Control Section
EXT jack socket in

If you wish to use an external clock or other gate signal to control the speed of the sequencer, feed a clock signal into the EXT socket. When the Run/Stop switch is set to EXT, the sequencer will run at the external clock rate.

INT jack socket out

The internal clock signal is constantly available from this socket to allow other devices to be sync'ed to Oberkorn

Step 1 jack socket out

Each time step 1 is reached, a gate signal is output from the Step 1 socket. This allows control of other devices, e.g. it allows the FS01 fill-in module to count whole bars. It can also be used to trigger drum voices or envelopes once per bar. It can be used to clock another sequencer 1 step each time Oberkorn makes a complete pass.

Reset jack socket in

When a 5V signal is input to the Reset socket, the sequencer will reset to step 1. One of the gate outputs can be patched into here to change the sequence length.

Tempo control

This control sets the tempo speed of the internal clock.

Run/Stop

When the switch is to the left (INT) the sequencer will run (play). It will use the internal clock as a tempo control. When to the right (EXT) the sequencer will run at the tempo set by any external clock signal fed into the EXT clock jack socket. The clock signal from the internal MIDI-Trigger unit is also wired to the external socket. When in the center position the sequencer will not run (stop).

Reset to 1

When this button is pressed, the sequencer will jump straight to step 1. This button will work even when the sequence is running. The sequencer can also be reset via the Reset in jack socket (see below), or using the IN1 MIDI to Trigger Channel (See MIDI section).

Reset to Step 16

When this button is pressed, the sequencer will jump straigh to step 16. This button will work even when the sequence is running. More on the need for this below.

Step

When this button is pressed, the sequencer will advance one step. This button is best used when the sequencer is not running. By pressing the Step button, you can set the controls for each step in turn in your own time. If the sequencer is on Step 16 (or whatever the last step is if set up to have less than 16 steps), pressing the Step button will return the sequencer to step 1. This button will work even when the sequence is running.

A, B, C, D in

Details about the Multiplexer control inputs A, B, C, and D and the MIDI Sync switch are covered later.

MIDI Sync

For normal use it does not matter on this switch's position. But it will be described in more detail later.



Reset In Socket: Changing the Pattern Length of the Sequencer

To change the pattern length to anything lower than 16, you must feed one of the Gate channel outputs into the Reset input socket. As the sequencer plays, as soon the first gate on signal is reach for the Gate channel you are using, the sequencer will reset to step 1.

For example you want an 8 step pattern. Feed the GT-X gate channel output into the Reset input. Position all the GT-X gate switches to Off (or in `Y' position), except switch 9. As soon as 9 is reach, the seqeucner will reset. The pattern will be 8 steps long. Note, step 9 is never actually reached or played. Another example, for a 12 step sequence, you would have switch 13 on (but none before step 13).

In short, patch a gate output to the reset input. The sequencer will reset to step 1 and continue running as soon as it reaches a gate on switch for the gate channel you are using.

This features, like all others on Oberkorn, can be operated in real time to allow you to change the pattern length in real time as the sequencer is running.

The sequencer can also be reset to step 1 using the Reset1 button, or the IN1 MIDI to Trigger channel.



Reset to 16 Button

Pressing this button will reset the sequencer to step 16, not the usual step 1 like other sequencers (although this feature has been included with the Reset to 1 button).

With just about all other sequencers the sequencer must manually be stepped to the last step, otherwise when the clock is started (whether an internal or external clock is used), step 2 is in fact the first step to be played (the CV and Gate settings for step 2 are the first to appear at the sockets, not step 1). In a few situations this might not be a problem, but as soon as you try syncing another analogue sequencer, or use a MIDI sequencer as a master (along with some sort of MIDI to clock converter) it becomes a problem. The analogue sequencer will always be 1 step ahead of the other.

In these situations you would normally have to manually step the sequencer to the last step each time the sequencer is started. Oberkorn is as far as I know the only sequencer to automatically go to the last step eliminating this problem, speeding up operation and making you life that much easier!


MIDI Synchronisation
MIDI Clock Sync with MIDI Trigger #9

MIDI Trigger #9 is hard wired to the external clock input of Oberkorn . Each time the MIDI key programmed for MIDI-Trigger 9 is pressed, the sequencer will advance 1 step. This means by programming a string of notes in the MIDI sequencer, Oberkorn can be made to keep perfect time with the MIDI sequencer. Now the string of notes need not be a continuous string of 16th notes, if could be some sort of synchopated pattem. Note, it works best if the internal clock is in STOP mode.

Note for this to work, the MIDI Sync switch must be selected to `SYNC'.

`Why not just use a standard MIDI clock to analogue clock converter?' I hear you say. Simple reason. When using standard MIDI clock converters, you cannot start and stop the analogue sequencer at any point while the MIDI sequencer is running. This is because MIDI clock runs continuously while the MIDI sequence runs. These means you cannot get the analogue sequencer to pause for a number of bars mid way through the MIDI sequencer. By using a MIDI note and a MIDI note to analogue Trigger converter (as with Oberkorn ) this problem is overcome, as to pause Oberkorn mid-MIDI sequencer, you simply just mute the track that has you MIDI note sync pattern programmed in. Also there is no reason why the MIDI notes have to be a stream giving a steady clock signal. Some sort of syncopated pattern can be written to get Oberkorn to step how you want. Also effects like shuffle or triplets could be programmed.





Controlling Step Order
MUX Control Input Sockets A, B , C, D

One common feature of all analogue sequencers is that they always run from left to right, i.e. from 1 to 8 or 1 to 16, (depending on how many steps it has). OK, some let you skip steps, but it is still essentially running in numerical order.

Oberkorn is the first analogue sequencer that allows you to overcome this problem. Oberkorn can be programmed to run through the steps in ANY ORDER you wish. Steps can be repeated or even missed out altogether. In order to describe how this function opperates, it is best to briefly explain how analogue sequencers work.
4 bit control bus



The clock is basically a square wave LFO.

The counter counts the clock pulses. The counter produces a 4 bit binary output (an address) to represent step positions 1 to 16 (see conversion table below). This is transmitted via a 4 bit address bus to the multiplexer. Each address line can have a high or low output.

The multiplexer is an electronic analogue switch. It can have a number of inputs and outputs, in this case 16 inputs and 1 output. The 16 inputs are the voltage output from each CV control. The output is routed to the CV output socket. The 4 bit binary address signal (representing the numbers 1 to 16) selects which of the 16 inputs to the multiplexer is switch to the output, i.e. which voltage from the 16 CV controls is routed to the CV output.

As the counter counts clock pulses, it counts up from 1 to 16. When it reaches 16 it resets to 1. It is in this way that the 16 different CV controls are routed to the CV output socket in turn.



How Oberkorn Can Access Any Step

Counters always count in upwards and in order from 1 to a higher number. (There are counters that count down, but you never see these incorporated into sequencers). The way in which Oberkorn can be made to step in any order is by completely bypassing the counter, feeding your own signals into the 4 bit address bus of the multiplexer. The multiplexer address bus can be programmed via the control input sockets on the front panel, or by using the built in MIDI to Trigger converter on Oberkorn.



Using MIDI to Trigger to control the Mux

MIDI Triggers 10 to 13 are hard wired to the multiplexer control inputs. That means different combinations of the 4 note on/off conditions allows you to create you own 4 bit pattern to select any of the 16 steps. You can build up a library of MIDI note patterns to give you different stepping orders.

When using the MUX control inputs, the Run/Stopswitch must be in the STOP position, and the Reset to 1 button must be pressed to reset the sequencer to step 1. Note, you can experiment with having the sequencer running, but for generally use it needs to be at step 1 with no clock signal.



Using the Control Input sockets on the front panel.

As mentioned above, it is best note to use the 4 control inputs at the same time as the internal clock is running or that the sequencer is not at step 1, but it can for experimentation. Just 1, 2, 3 or all sockets can be used. There is no need to use all 4 sockets together. Use any 0/5V signal to control these inputs, e.g. LFO, Gate, etc.

Technical specifications

MIDI In, MIDI Thru

External Clock Input

4x Mux control Inputs

Internal Clock Output

Step 1 Pulse Output

MIDI Triggers x10 (2 internal) Outputs

CV x3 Outputs

Gate x5 Outputs

16 CV pots /Gate Switches x3

16 Gate switches (3 position)

CV Range switch x3

Tempo pot

Reset Button

Int/Stop/Ext Run/Stop switch

MIDI Sync switch

MIDI Program button

MIDI activity LEDs x16

Blue Tempo LEDColoured Step LEDs x16

Reset to 1 button

Reset to 16 button

Step button