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Analogue Solutions Oberkorn

Analogue Sequencer
By Gordon Reid

ANALOGUE SOLUTIONS OBERKORN

Analogue sequencers may seem simple devices, especially when compared to their computer-based counterparts, but they can be put to fantastically complex uses in the right hands. We plumb the hidden depths of the new Oberkorn...

To say that there's a glut of analogue sequencers on the market is, perhaps, to overstate the case. But things are very different from the situation approximately six years ago when UK company Analogue Systems (as opposed to the similarly named but unrelated Analogue Solutions) launched their 16-step TH48 sequencer into a market then occupied only by vintage units from the likes of ARP, Moog, Korg and Roland (see review in SOS April 1995). Today, anybody entering the field needs something that marketing gurus call a 'USP' — a Unique Selling Point. Without one of these, the product is doomed to obscurity, fighting to hold onto a small niche in an already overcrowded market. Enter the Oberkorn... a 16-step analogue sequencer that is far more than simply a 16-step analogue sequencer.

The Oberkorn [named after an obscure, heavily step-sequenced Depeche Mode track from the early '80s — Ed] is a three-channel, 16-step sequencer with extensive sequence-control capabilities. The SOS review unit was delivered in a 3U case without rackmounting wings, and is powered by an external AC/AC adaptor. However, Analogue Solutions do supply three other case options, all of which incorporate internal power supplies, and take a standard IEC mains lead. Alternatively, you might wish to buy the Oberkorn naked for insertion into your own case, or for use within one of Analogue Solutions' 3U or 6U cases, as used for their Concussor modules.

The front panel is divided into four sections; the first is the basic 16-step sequencer, and the second is the MIDI controller, while the third contains the sequencer outputs on 3.5mm sockets. The fourth panel contains the sequence control inputs and outputs.

Sequencer Rows & Channels

Each of the 16 steps comprises four controls and a Step LED (shown below). These LEDs are colour-coded Red (every fourth step), Yellow (non-fourth notes in the first half of the sequence) and Green (non-fourth notes in the second half of the sequence). Personally, I find the Yellow/Green distinction unnecessary, but this doesn't matter too much, as Analogue Solutions will fit your choice of LEDs (including blue ones on request) if you specify these with your order.

The four controls at each step comprise the CV control knobs for each of the three channels, plus a three-position switch called Gate X/Y. The range of the CV control knobs is determined by a single switch found at the end of each row (see left). Marked M, H, and L (Mid, High and Low) these switches set the range of each row to 0V to +5V, +10V and +2.5V respectively.

When used with analogue synths adhering to the 1V-per-octave CV standard, the Low setting provides a 2.5-octave range with reasonable pitch accuracy. Unfortunately, the CV knobs (shown right) are rather small, and even on this minimum range it proves very difficult to program the notes to accurate semitones. The five-octave range offers a greater range of notes but with even less accuracy, while the full 10-octave range is all but impossible to set up for use with pitch. Nonetheless, this still has uses when the CV is directed to other inputs such as the filter cutoff frequency on the receiving instrument. Of course, mapping 10V to a single-turn knob will always be difficult unless a voltage quantiser is incorporated, but I still find the Oberkorn's pots a little too inaccurate, and would have preferred a continuous Range control to allow me to choose the best compromise between range and accuracy.

The CV knobs have an interesting extra function which you can use to create sequences in which not all the steps are 'on'. Turn the knobs fully anticlockwise and they click 'off'. In this position, no Gate is output for that step. Unfortunately, this means that the output CV is also 0V, so you can't use this feature to create minims, semibreves and so forth. Nevertheless, if you want to use one of the rows just for its Gate signal, ignoring the output CVs, you can, and this can be very useful.

What's more, Analogue Solutions have understood the need for extended (legato) notes. So, whereas Gate channels A and B produce a Gate on every step (thus making the output a Trigger rather than a true Gate), Gate channel C only produces a Gate on the first of a series of 'on' steps (thus making it a true Gate rather than a Trigger). This means that you can produce sequences of notes with different durations (provided that the total length does not exceed 16 steps).

This brings us to the 'Gate X/Y' switch. In its centre position, this switch has no function, but when switched 'up' it generates a Gate pulse at the 'GT-X' output on the right of the Oberkorn, and when 'down' it generates a pulse at the 'GT-Y' output (see right). This means that the Oberkorn can generate no fewer than five Gate/Trigger sequences simultaneously (three from the outputs from channels A to C, and one each from the GT-X and GT-Y outputs, as determined by the settings of the Gate X/Y switch). This is a high specification for the price.

Sadly, there is no facility to chain the multiple rows into a single 32-step or 48-step sequence. I have always found this a powerful (if vanishingly rare) facility, but none of the modern batch of sequencers offers it. No matter... the Oberkorn offers something much more interesting than this, which I'll discuss later when when I come to the MIDI Step and MIDI Sync facilities. My other concern is that the Gate level of +7V is strangely chosen. Some synths will not respond to this, requiring a full +10V to operate correctly. However, should it prove a problem for you, Analogue Solutions can and will customise your Oberkorn if requested, because it only requires a few component changes to raise the Gate as high as +12V.

The Sequence Controllers

There are eight inputs in the slightly overcrowded Sequence Control section (shown on the next page), plus three buttons, two switches, and a knob, and these provide the auxiliary controls to make best use of the sequencer itself.

Let's dispense with the knob first, because this is easy: it's the Tempo control that determines the sequence speed when you're using the internal clock. The clock is also directed to the 'Int Clk' output, thus allowing you to sync other analogue gear with the Oberkorn.

Alternatively, you may wish to drive the Oberkorn from a pulse generator in an external device, in which case you switch the 'Int/Stop/Ext' switch to 'Ext' and connect the external clock to the 'Ext Clk' input. You may find this input hard to locate for a moment (because the Tempo knob sits in the position where it would otherwise be annotated) but it's the uppermost of the sockets in the Control section (left). While on the subject of external clock control, it would have been nice if there had also been a 'Clk CV' input (thus allowing you to adjust the speed of the internal clock using a CV), but there isn't.

Below these inputs, you'll find the 'Step 1' output, which produces a Gate pulse each time the Oberkorn reaches sequencer Step 1. This is very useful for clocking external units, and for triggering once-per-sequence events such as crash cymbals or the like. The mirror to this function lies at the bottom of this column of sockets. It's the 'Reset' input, which resets the sequencer to Step 1 when it receives a +5V pulse. When used together with either the GT-X or GT-Y outputs, this has a particularly important function; it allows you to create sequences of fewer than 16 steps. For example, imagine connecting the GT-X output to the Reset input, and setting all the GT-X switches to 'off' until step 13, which you set 'on'. When the sequence reaches step 13, it will output a GT-X pulse which causes Reset to send the sequence back to step 1, thus changing the length of the sequence to 12 steps. What's more, you can change the states of the GT-X switches as the sequence plays, dynamically altering the sequence length in real time. Neat.

You can achieve the same effect manually (if less accurately) by pressing the 'Reset 1' button, which has equally obvious applications in live or real-time use. Similarly, you can reset to step 16 by pressing the Reset 16 button. This is handy when the Oberkorn is stationary, ensuring that step 1 is the first one played when you reactivate the sequencer. The third of the buttons is called 'Step', and this allows you to progress through the sequence a step at a time for programming.

The remaining four sockets in the Sequence Control panel — the A, B, C and D inputs/outputs, and the MIDI Sync switch — have more complex uses that require an understanding of the MIDI Control section, so let's have a look at this first.

MIDI Control

To the immediate right of the sequence rows, you'll find the MIDI In and Thru sockets, 16 LEDs, eight outputs, and a 'Prog' button (shown right). The function of the In and Thru sockets is obvious. The rest of the section is not, but it allows you to trigger a number of analogue devices from the Note On messages contained in one channel of a MIDI signal.

Setting up the MIDI Control section uses a method I have encountered a couple of times before; the first note received tells the Oberkorn which MIDI channel to monitor, and this will then be the only channel that affects the triggers it generates.

So, for example, if you press the Prog button and then play a middle 'C' on channel 10 on the external MIDI device connected to the MIDI In, channel 10 becomes the active channel, and the Note Ons for middle 'C' are converted to the triggers produced at trigger output #1. By playing 15 subsequent notes, you can then program the sources for the other 15 trigger channels. So, if you play a chromatic run from middle 'C', the next seven notes ('C#' to 'G') produce the triggers output by the sockets marked 2 to 8.

Channel 9 (which, in this example, would be 'G#') is a particularly important one... its triggers appear internally at the same place as the external clock input. Therefore, if you flip the 'Int/Stop/Ext' switch to 'Ext' you can drive the Oberkorn from an external MIDI sequencer, moving one step to the right each time you play G# on MIDI channel 10.

The next four trigger channels (10 to 13) are directed to a multiplexer within the Oberkorn (of which more in a moment), while trigger channel 14 is wired to the MIDI Reset function. The last two (15 and 16) are unused, but can be custom-wired to your requirements.

The reason for the 16 LEDs in this section now becomes obvious. Named 1 to 8, 'Syn' (for external synchronisation), A, B, C, D, and 'In1', 'In2' and 'In3' (which stand for Internal 1, 2 and 3) these show when a trigger is produced on any given trigger channel.

This system may sound arcane (and reading this again, it I think that it does), but it is not. It simply allows you to create triggers or clock pulses from a MIDI keyboard or MIDI sequencer. Furthermore, unlike connecting the Oberkorn to MIDI Clock, it allows you to start and stop the sequence in time with information contained in the external MIDI sequence. The uses for this are manifold, and maximise the integration between MIDI and analogue CV/Gate systems. Furthermore, the setup memory is not volatile, so the Oberkorn remembers the assigned MIDI channel and notes even when switched off; a nice touch.

MIDI Sync & MIDI Step

Having explained the finer points of MIDI operation with the Oberkorn, I can now return to discussing the A, B, C and D inputs/outputs and the MIDI Sync switch that I previously skipped. As you can now see, Trigger channels 10 to 13 produce triggers derived from four MIDI notes (which, in my previous example, would be 'A' to 'C'). If you now consider these four notes as a chord, you can — by playing any combination of the notes within the chord — generate any of 16 possible combinations. Are you still with me? No? Well, think of it like this: Imagine that the trigger channels named D, C, B and A are the four bits in a four-bit binary word. Therefore, if you play no notes, the output is a '0000'; if you play all four notes in the chord the output is '1111' (the binary representation of '15' in decimal); and, for example, trigger D and B alone give '1010' (the binary representation of '10' in decimal). OK, I'll admit that this is extremely weird, and it took me a while to get the hang of it, but it's really quite smart once you get the hang of it. The output values from D, C, B and A are allocated to the sequence steps, so '0000' equates to step 1, '0001' equates to step 2, '0010' equates to step 3... and so on, up to '1111', which represents step 16. This means that, with the MIDI Sync switch set to 'Mux' (ie. multiplexer), you can use the four allocated notes on your external MIDI keyboard or sequencer to trigger the Oberkorn to play any of its 16 steps. Furthermore, when used with Trigger #9 (the external clock trigger, as explained above), you can determine not only which step plays when, but also for how long it does so.

You think that this is complex? Nah, this is complex... The step accessed by the binary word is dependent upon the step at which the Oberkorn lies when the external MIDI input first appears. Furthermore, you can mess with manual resets and even the GT-X and GT-Y resets while the external MIDI sequence is running. You can even use the A, B, C and D sockets as inputs to modify the step value being calculated by the A, B, C and D trigger channels. This means that you can create a data loop by sending one of the sequence Gate channels to one of the inputs, thus modifying the sequence using the sequence. Finally, any of the A, B, C and D sockets not used as inputs will function as outputs, transmitting the internal triggers generated by the trigger channels. Ouch! I don't know about yours, but my head hurts!

A Problem

If all the above reads as an almost unqualified 'thumbs-up', it probably is. Indeed, the review Oberkorn had only one serious problem... but it was a biggie. When I tried to program a melodic sequence in, for example, sequence channel A, with a filter CV sequence in Channel B, I noticed that the pitch CVs seemed to drift considerably. I then realised that value of channel B was affecting the CV generated by channel A, and vice versa. I suspected that the Oberkorn's power supply couldn't handle the current drain, because turning the Channel B knob from minimum to maximum on a given step flattened channel A by a full semitone. Switching B and C from 'off' to 'on' and turning them fully clockwise flattened A by a minor third! This rendered the Oberkorn useless for real-time melodic work. After all, how could I change one sequence while it was running, if doing so destroyed another?

I contacted Analogue Solutions to discuss this, and they agreed that it was a problem with the power supply. The company claim that this issue will be resolved by the time you read this, but given the nature of the problem, I would advise that you check any Oberkorn before purchasing it.

Conclusions

I have never encountered another product with the same list of features and capabilities as the Oberkorn. This made it quite difficult for me to come to grips with it, if only because previous experience was not much help. But once I understood the MIDI section and MIDI Step, I found that I had a very interesting box in my studio.

However... although the review Oberkorn otherwise worked faultlessly for the time I had it, the interaction it exhibited between Sequence channels A, B and C would render it all but useless for many players. On the other hand, if Analogue Solutions resolve this problem as they have suggested, I can imagine that the Oberkorn would be very useful for all forms of dance music, and ideal for trance, in which its ability to 'compose' new sequences from just 16 steps could be superb. Nevertheless, don't let me place any limitations upon its usefulness... I'm sure that you will find applications for the Oberkorn that I never considered.

Stop Press — Upgrades

Following completion of my review, Analogue Solutions contacted SOS to update a couple of points. Most significant of these is that they claim to have rectified the voltage drag-down problem I noted towards the end of the review. Note, however, that at time of going to press, I hadn't had an opportunity to test this for myself, so the cautionary point I make at the end of this article about trying an Oberkorn for yourself should stand.

Of the other improvements, I was pleased to hear that a new, stronger ABS case has also been adopted. That's not to say that there's anything wrong with the case you see in the photographs accompanying this review; I'm sure that it would last forever in my studio. However, if you were thinking of taking it out on the road, I wouldn't be quite so confident, so the new case is welcome. The case also has a pair of quarter-inch jack sockets plus a CV input with an associated gain control, all of which you can wire up yourself (or ask Analogue Solutions to wire up) to suit your particular requirements.

Pros

  • A very powerful three-row, 16-step analogue sequencer.
  • Very powerful integration between MIDI and CV/Gate technologies.
  • Up to five simultaneous Gate channels.

Cons

  • The voltages output by the sequencer rows affected one another on the review unit, although this may now have been corrected.
  • Unusual +7V Gate/Trigger level does not trigger all synths.
  • No facility to chain the three rows.
  • No internal clock CV input.

Summary

Far more than a simple analogue sequencer, the Oberkorn is a unique product offering a method of integration between MIDI and CV/Gate technologies. If you're looking to extend your use of analogue sequencing beyond the norm, this is probably the box to consider, provided the voltage drag-down problem I noticed on the review unit is taken care of.

information

£599 including VAT.

Analogue Solutions +44 (0)1384 353694.

www.analoguesolutions.com

Published July 2002