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Kurzweil K2600X

Keyboard Workstation
Published April 2000
By Paul Ward

Kurzweil's latest workstation is very much the product of evolution, rather than revolution. Paul Ward finds out whether it's keeping pace with the rest of the synth world...

Kurzweil K2600X header.Kurzweil's K2600 is the latest in a line of workstations that began back in 1992 with the much-vaunted K2000. It utilises Kurzweil's proprietary VAST (Variable-Architecture Synthesis Technology) which, for the uninitiated, is a well-developed system for bringing a powerful set of DSP tools to bear on source waveforms. The K2600 comes in three basic varieties: the K2600R rackmount module, the K2600 76-note semi-weighted keyboard and the K2600X 88-note weighted-action keyboard. The latter is under review here; other than the keyboard itself, the K2600 and K2600X are nearly identical.

New features in the K2600 include completely redesigned audio circuitry with the provision of balanced analogue outputs all round, an upgraded sampling option which provides 20-bit digital I/O, and a physical redesign which makes installing upgrades such as memory expansions much more straightforward. Most of the other principal new features in the 2600 were available as upgrades to the earlier 2500: the most notable is the new effects processor, which was previously available only as part of the KDFX expansion board. Others include the KB3 software-based tonewheel organ emulation and the ability, with the sampling option fitted, to act as a vocoder and RAM-based audio sequencer. Unfortunately, the sampling option was unavailable at the time this review was written.


Physically, the K2600X is large and heavy. The 88-note weighted-action keyboard must be responsible for much of the bulk, but the casing itself is also thick and strong. In general, it's easily robust enough to stand up to life on the road, but the slope of the top panel leaves the end keys exposed, which has some potential for disaster. Generally the design is tasteful and very much in keeping with the instrument's 'professional' status.

Kurzweil K2600X rear panel.The back panel presents a reasonable smattering of connection possibilities. In addition to its mix left/right outputs, the K2600 has four further pairs of separate outputs. All of the analogue outputs can be connected either balanced or unbalanced, and provide a hotter signal than previous Kurzweil instruments, which can only be a good thing. Four switch pedal inputs are provided, along with a pair of control pedal inputs, the second of which shares control duties with a breath controller input — it's nice to see this carried over from the K2500. A pair of SCSI connectors takes care of external data storage, and a small switch allows for control of the SCSI chain termination. An internal SCSI hard drive can also be accommodated. On this unexpanded machine a host of blanking panels hinted tantalisingly at the other connection options available in the form of digital I/O, and analogue sampling inputs. A single set of MIDI In/Out/Thru sockets is present, and the Thru socket can double up as a second, parallel, MIDI output. I'm slightly disappointed that the K2600 hasn't introduced more separately addressable MIDI ports.

Kurzweil K2600X main sliders and ribbon controller.The top panel is very reminiscent of the K2500, with similar physical controllers in evidence. The eight faders sitting to the left of centre can act as simple hardware controls for the internal mixer, or as MIDI volume controllers if required, but also allow access to any number of parameters within the VAST engine. Legending on the K2600 also shows the new use for these faders: as a bank of drawbars for the KB3 tonewheel organ emulation (the mod wheel acts as the 9th drawbar). Above each fader is a programmable button with associated tri-colour LED. These buttons also do duty for KB3, such as switching in percussion, vibrato, or changing rotary speaker speed. Over on the left are a pair of standard mod and sprung pitch wheels, whilst just in front of the wheels is a small (20mm) ribbon, which can generate data from position or pressure. Just behind the wheels are a further two programmable buttons, mostly aimed at performance switching (operating the arpeggiator, for example); behind these is the DOS-compatible floppy disk drive.

A long (600mm) ribbon controller above the keyboard can be zoned to act as three independent control sources. This ribbon is superb to play with, allowing for all kinds of slides, swoops and hammerings that just aren't practical with most other modulation controls. For pitch bending you'd probably want the ribbon value to be sprung so that it returns to zero when you stop using the controller, whilst for filter cutoff it would be preferable for the last ribbon position to latch. Fortunately, Kurzweil allow you to define it either way.

Kurzweil K2600X: using the main ribbon controller.Using the main ribbon controller.Each of the K2600's physical controllers is endowed with its own editable MIDI controller number, scaling, offset, response curve and controller value on entry to, and exit from, a Program. Once you've modified these controls to suit your taste then the settings can be saved. As on the K2500, controller settings must be stored along with a Setup, which I find perplexing. Surely it would be preferable for controller settings to become an object in their own right? This is a complication that seems so avoidable. Kurzweil must have their reasons, I suppose...

The machine arrived with a power cable, a good sustain pedal, a small set of accessory disks and a hefty pair of manuals. According to the latter, an instructional video is also supposed to be supplied, but sadly this did not make it along with the review machine.


User sampling on Kurzweil instruments requires the optional expansion, but this is not necessary to be able to play back samples loaded in from external storage, or floppy disk. The K2600 comes with 16Mb of sample RAM as standard, expandable to 128Mb using non-composite 72-pin SIMMs. Program and sequencer memory (P-RAM) is separate from sample memory. As standard the K2600 comes equipped with 486K of P-RAM; this is expandable to 1.5Mb, although at £349 for 1Mb this is a very expensive upgrade!

The K2600 also contains 12Mb of sample ROM waveform data, which includes Kurzweil's excellent 4Mb stereo grand piano, previously available only as an upgrade to K2500 users. Some simple maths tells us that this equates to 8Mb of non-piano sample ROM, which means that this new instrument essentially has the same ROM allocation as was supplied with the K2000 back in 1992! Admittedly the supplied waveforms are excellent, but I can't help feeling that Kurzweil have taken an easy option. How about some loops, oscillator waveforms from classic synths, Mellotrons, bowed guitars, vocal consonants, world instruments, or reverb tails? Provision is made for the addition of up to four 8Mb sample ROM block options to raise the total to 44Mb, but these blocks have to be purchased separately. Currently, Kurzweil have two available in the form of the Contemporary and Orchestral blocks.

In terms of sample compatibility, the K2-series synths are particularly generous and will happily read from many formats, including Roland S700-series (SCSI only), Akai S900, S950, S1000, S3000, Ensoniq EPS, EPS16 and ASR10. Import and export of WAV and AIFF files is also possible. Standard MIDI Song Files are also welcome at the K2600's door, as are any objects created on earlier K2-series machines. K2600 song files can also be exported as Standard MIDI Files. I tried some of these compatibility options and they all seemed to work well, although samples from foreign formats may need a little work to get them into a usable program.

I tried my older K2000 Programs, only to find that the effects settings were all over the place — unsurprisingly, given that the 2600's effects board is completely different to that of its older sibling. I then recalled the K2000 emulation disk I'd seen as I went through the contents of the box! Once I loaded that, my old Programs sounded fine. Although the architecture of the effects processor is completely different from that of earlier K2-series synths, the Kurzweil engineers have done all the hard work of emulating the older effects for you — full marks for that one guys! Anyone transferring programs from a K2500 is likely to be less happy, since there didn't appear to be enough P-RAM in this unexpanded machine to load in the complete K2500 emulation disk — oops! If you need full, instant K2500 compatibility then you may need to budget for an early upgrade. For those who look forward to the next round of A Song For Europe there's a pair of GM-compatibility disks too...


Kurzweil's VAST architecture is based around 31 DSP algorithms, into which may be plugged a variety of DSP building blocks (from a palette of 60) to filter, shape and generally mangle sampled waveform material contained in a Keymap. Each Keymap/Algorithm combination is known as a Layer, and there can be up to 32 Layers within a Program. In normal multitimbral mode you can access up to 16 Programs at a time. A Setup allows for zoning and general cleverness with up to eight Programs simultaneously, which is particularly handy for live performance. I have gone into detail about the intricacies of VAST in previous reviews, and don't intend to repeat it all here; suffice to say that I still feel it is the most flexible, powerful form of S+S synthesis that I have come across. Some of the DSP blocks actually add DSP-generated waveforms to the layer's signal path, and these may be detuned for extremely fat and punchy sounds — with no loss of polyphony. Four oscillators times 32 Layers, times eight Programs makes one heck of a monosynth patch!

As far as VAST is concerned, there's not a lot new in the K2600X. And that in itself is not necessarily a bad thing, though I was hoping that the aliasing noise inherent in the DSP-generated oscillators had been improved. It was not to be — they sounded just the same. The ROM samples still sound as good as they ever did and VAST seems capable of such a breadth and depth of sound that you'd be forgiven for thinking that Kurzweil introduced it yesterday.

The 4Mb of piano waveforms is clearly going to be of considerable interest to certain potential buyers. These sound very good to me, and certainly well up to the expectations of a professional user. I didn't get the same sense of realism that I'd felt with some dedicated electronic pianos, but I doubt that the K2600 pianos would be found wanting in many situations. If a strong piano is of prime importance to you then I'd say you need to try a few machines in any case before parting with any money. The K2600 is far more than a piano box, after all.

Wheels Keep Turning

Arguably, one of the most important new features to arrive on the K2-series synths is KB3. First introduced in a software update to the K2500 (see Paul D. Lehrman's review of the KDFX expansion board in SOS January 1999), KB is Kurzweil's tonewheel organ emulation mode. And it is clear that an immense amount of work has gone into its design. Kurzweil have analysed several organs to arrive at an emulation capable of not only producing realistic Hammond sounds, but also of taking into account those age-induced qualities that add the grunge and nastiness that you'd expect from a vintage instrument.

By default, KB3 uses DSP-generated waveforms for its lower tonewheels and a sample Keymap for its upper tonewheels, although this assignment can be reversed if you like. The upper Keymap can even include user samples, although the Keymap must use looped samples, since the virtual tonewheels are effectively running all the time — just like the real thing! The number of tonewheels can be specified, along with a volume adjustment to the upper wheels and various transpose options. A number of parameters define the volume of the tonewheels and the relative volume of each key per drawbar, based on measurements taken from organs of varying age and state of repair. The pitch and step amounts of each of the nine drawbars can be altered, and you even have control over which of the drawbars will be 'stolen' to provide the percussion effect. The duration, pitch and volume of percussion and keyclick can be determined, including parameters to introduce random volume changes into the keyclick to more closely simulate the real effect. The options go on to determine the type and volume of leakage from non-playing tonewheels to authentic vibrato and chorus types. All this is before we've gone anywhere near the EQ page and the Leslie emulation, which itself is mind-boggling in its detail!

I hope you get the idea by now that I'm impressed by KB3, because to go on to describe all of the options available would probably fill this entire review! And the results? Simply stunning. It has long been a dream of mine to own a real Hammond, given the space to accommodate it, but the K2600 would certainly see me a very satisfied man. Once I'd got my head around the almost limitless options, I was able to come up with convincing versions of many of the classic organ sounds that have always eluded me. I quickly progressed from sweet jazz combo licks and swirly Genesis-type offerings to all-out assault organs in the Keith Emerson and Jon Lord mould. Brilliant!

In my review of the K2500 (SOS April 1996) I suggested that its 48-note polyphony could become restrictive with the layering possibilities that the machine could offer. The KB3 feature makes this even more of an issue. When trying out a few sequences with a 79-tonewheel organ and a brass section I was suddenly left with only two notes of polyphony with which to play the rest of my arrangement. This is not ideal in a workstation synth.

Effective Changes

Earlier VAST instruments were often criticised for their effects capabilities, which consisted of little more than a basic multi-effects processor hard-wired across the outputs. Kurzweil have obviously taken this to heart and, at the end of 1998, introduced a far more powerful and flexible alternative. The KDFX processor, previously available as a K2500 option but standard in the K2600, is capable of providing up to five simultaneous effects/processors. Four of these are termed 'insert' effects and are allocated to individual effects busses, whilst the fifth handles global effects in the signal path after the insert effects.

Disappointingly, however, an unexpanded K2600 actually offers less than a K2500 with the KDFX board. Adding a KDFX board to the 2500 gave you eight digital outputs in Kurzweil's proprietary KDS format, which could be converted to standard digital formats such as ADAT using the optional stand-alone DMTi format converter. While the 2600 has the KDFX effects processor as standard, however, it does not have the digital outputs. If you want to add multi-channel digital I/O to a K2600, you will need both the DMTi and the DIOS26 8-channel digital interface, at a combined cost of almost £1100. The K2500 also had Kurzweil's basic multi-effects unit as standard, and the KDFX board could happily work alongside this. By contrast, the KDFX processor is the 2600's only source of effects; settings from pre-2600 K-series instrument programs are emulated on the KDFX when those programs are loaded up.

The KDFX effects are impressive in their scope, however, ranging from simple reverbs, delays, distortion and modulation effects to multi-band enhancers, multitap delays, envelope followers, amp/tube simulations, gates, compressors and stereo imaging. There is also a range of combination effects, where two or more effects are available in one algorithm, albeit in a more simplified form than the dedicated single-algorithm versions.

Unfortunately it all gets rather spoiled once the real world of multitimbrality knocks at the KDFX's door. Want to use a chorus, distortion and rotary speaker effect? No problem. Want to add a compressor across your drums? Sorry mate, you've used up your PAUs! These Processor Allocation Units (PAUs) are an index of how much processing power an effect requires to run. In the case of our chorus/distortion/rotary speaker example the requirement is four PAUs, and the K2600 allows a maximum of four PAUs for insert effects. In our example above, the other three effects busses will have to remain dry. Precious few of the KDFX's algorithms require just one PAU, so you can rarely take advantage of the four effects busses in their entirety.

Thankfully, the fifth global effect has three PAUs dedicated all to itself, which are not stolen by the insert effects. In addition, since the K2600 is bristling with separate outputs, an external effect processor or two can always be pressed into service.

The other good news is that the effects themselves are of superb quality, with rich reverbs, creamy choruses and phunky phasers. There is a bewildering number of parameters, allowing fine-tuning to a degree that most stand-alone devices would be hard-pushed to match. To take the chorus/distortion/rotary example once again, the description of the algorithm and parameters covers six pages on the display. This includes a thorough overview of the theory behind the algorithm and usage of the various settings for realistic emulation, or special effects. Parameters cover four pages of variables, from individual gain, rate, size, acoustic radiation pattern, resonance and microphone position for both the high and low drivers, to distortion, crossover patterns and six flavours of chorus/vibrato settings. These are not effects that anyone is likely to outgrow in a short time!

Once you have a KDFX configuration that you're happy with the next job is to store it. Kurzweil have introduced a new Object that they term a 'Studio'. The simile here is that of effects and routing options being much like the wiring of a conventional studio, and the analogy works quite well. This means that frequently used KDFX configurations are always on hand, or can be loaded in from previous sessions. This is very useful, and really makes me wonder why this same approach couldn't have been taken for the controller and arpeggiator configurations!


The K2600 has been tweaked in a few other areas, too. I'm a great fan of arpeggiators, and Kurzweil's is certainly now up there with the best of them. Some strange key-latching protocols marred my early experiences with the K2500's arpeggiator, but that's all history now. There are many parameters designed to keep arpeggiator freaks such as myself happy, whilst those with simpler tastes can opt for the click-and-go approach. Arpeggiator settings are stored along with controller Setups, which is a bit of a pain, in my opinion, but I've already covered that.

The K2600's operating system and ROM objects are held in Flash ROM for easy upgradability. I downloaded the latest v1.13 software update from Kurzweil's web page during the course of this review, and can happily report that everything went very smoothly. This is an increasingly important aspect of modern synths and is probably more so in the case of a Kurzweil synth, since they are well known for their continued software support.

Unfortunately, Kurzweil could not supply the K2600 with its sampling option for review. This is a shame, as it didn't give me the chance to try out one of its other new features. Whereas previous incarnations of the K2-series sequencer dealt with MIDI tracks only, the K2600 allows for the addition of RAM tracks, which opens up rudimentary audio recording in sync with the MIDI tracks. The K2600 can actually record its own output to facilitate mixdown and adding of more MIDI tracks over the top. While we're on the subject I must say how good the K2600's sequencer is. If I were ever to give up on a computer-based sequencing package, then I'd be happy to replace it with Kurzweil's offering.

The 64 x 240-pixel backlit display is good as far as it goes, but compared to the large screens manufacturers such as Korg are now using on their high-end machines, it really does look cramped.The 64 x 240-pixel backlit display is good as far as it goes, but compared to the large screens manufacturers such as Korg are now using on their high-end machines, it really does look cramped.The contrast between the K2600 and a computer, however, is most evident in the paltry size of its screen. The 64 x 240-pixel backlit display is good as far as it goes, but compared to the large screens manufacturers such as Korg are now using on their high-end machines, it really does look cramped. Kurzweil still have to resort to some fairly cryptic short names to fit everything in, and waveform editing would be a much more rewarding experience on a larger screen. VAST still has enormous potential, but I feel its presentation needs a makeover for the 21st century, complete with long names, icons and all-round friendly graphics.


There's no doubt that the K2600 oozes quality in both build and sound. The facility to load in your own sample material means that you will never be stuck solely with the ROM samples, excellent though they are, or have to resort to paying extortionate prices for add-on ROM packs. The high level of expandability is welcome, and I'm bowled over by the tonewheel organ emulation. That feature alone has me drooling like one of Pavlov's dogs at a campanology convention. As a committed Kurzweil user I'd love to own this machine in the same way that I'd like a version of the same car I already own, but with a bigger engine.

However, it is now four years since I reviewed the K2500, and since then, Kurzweil seem to have done little more than tack on a couple of previously available options. I am being deliberately contentious here, since I'm aware that a lot of innovation is happening under the bonnet; this is evident in the redesign of the audio circuitry. However, I do feel that Kurzweil should have given us a little more at the factory fitting stage — more P-RAM, in particular. Many of the new features are available only to those who stump up for the sampling option, and this significantly reduces the 'wow' factor.

In short, I can't help feeling that this is one model too many for VAST in its current form. Kurzweil need to dig deeper if they are to regain the cutting-edge credibility they captured with their K2000 workstation. If they had added a larger screen, upped the polyphony, and thrown in an extra MIDI port, the K2600 could have been something much more special.


  • 88-note weighted-action keyboard (76-note semi-weighted on K2600).
  • 48-note polyphony.
  • 60 x 640-pixel backlit LCD.
  • 486K P-RAM.
  • 16Mb sample ROM.
  • 12Mb base ROM.
  • Eight analogue outputs plus mix stereo pair.
  • Stereo headphone output.
  • Flash ROM OS for software updates via floppy disk and SCSI.
  • Variable Architecture Synthesis Technology (VAST) with 60 DSP functions.
  • KB3 tonewheel organ emulation.
  • 32-track sequencer.
  • Dual SCSI ports.
  • KDFX effects processing.

Live Vocoders

Since the review model did not contain the sampling option, I was unable to try out Live Mode or the new Vocoder emulation. The former feature was introduced as a software update to the K2500, and was covered by Paul D. Lehrman in his KDFX review in SOS January 1999. It has always been possible to route external audio into sample-option-equipped K2-series synths to take advantage of the internal effects processor. Live Mode, however, adds the facility to use external audio as waveform data in the VAST synthesis engine, in real time, as well as altering the pitch of incoming audio in real time. The K2600 uses an input buffer to effectively 'play ahead' of the incoming audio, although you'll hear gaps in the audio as you release the pitch wheel. With the incredible amount of processing power available in VAST this feature should open up some truly awe-inspiring possibilities. Kurzweil have thoughtfully created some Programs specially designed to show off Live Mode and act as a starting point for your own experiments.

With the optional sampling upgrade, the K2600 is also able to function as a vocoder. Using this feature steals the K2600's polyphony in proportion to the number of filter bands you choose, which may be up to 24 (two notes are used up per filter band). Setting up from scratch seems quite complex from reading the manual, and the use of the output busses is a little fiddly, but examples are provided on the supplied disks to get you started. Usefully, the vocoder may be combined with live mode so that you can mix a VAST-processed version of the audio source in with the vocoded signal.


  • SMP2X sampling option: adds stereo analogue I/O (two balanced low-impedance XLR inputs and one stereo unbalanced analogue high-impedance input on quarter-inch jack) and digital I/O (two channels of AES-EBU and S/PDIF inputs and outputs via optical and co-axial sockets).
  • DIOS26 digital interface: adds eight channels of digital I/O in proprietary KDS format.
  • DMTi Digital Multi Track Interface: adds eight channels of digital input and output via proprietary-format KDS port. Optional Digital Multi Track Interface for data format and sample rate conversion (interfaces with Alesis ADAT and Tascam DA88).
  • P-RAM upgrade kit to 1.5Mb.
  • Up to four 8Mb ROM blocks (two available at present: Orchestral and Contemporary).

K2600-series Prices


  • K2600: 76-note semi-weighted keyboard £2999.
  • K2600S: K2600 with factory-fitted sampling option £tbc.
  • K2600X: 88-note weighted keyboard £3399.
  • K2600XS: K2600X with factory-fitted sampling option £tbc.
  • K2600R: Rackmount £2699.
  • K2600RS: K2600R with factory-fitted sampling option £tbc.


  • Sampling option (for keyboard and rack models) £499.
  • DIOS26 8-channel digital interface £tbc.
  • DMTi 8-channel digital converter £799.
  • Contemporary/Orchestral ROM blocks £249 each.
  • Extension board for ROM blocks £149.
  • P-RAM upgrade £349.
  • Hard drive installation kit (K2600 keyboard) £69.
  • Hard drive installation kit (K2600R rack) £49.

All prices include VAT.


Kurzweil manuals are overflowing with detail, which is good in many ways, but can be overwhelming for the newcomer. Kurzweil really tell it how it is: not content with just describing the vocoder feature, for example, they go on to describe the theory behind vocoder design. Now I am the first to complain when software arrives with nothing more than a PDF on-disk manual, but in this case I think the justification is certainly there for supplying both a hard and disk-based copy.

The guide and reference manuals are each little short of the size of a telephone directory and searching for relevant information can be problematic. I often found during the course of this review that information I needed wasn't listed in the index — try finding 'vocoder', for instance! I checked Kurzweil's web site for a soft version of the manual, but came up empty-handed.

Kurzweil Reviews In SOS

  • K2000: March 1992.
  • K2000 sampling option: August 1993.
  • K2000 v3: February 1995.
  • K2500R: October 1995.
  • K2500/2500X: April 1996.
  • K2000VP: September 1998.
  • KDFX effects board: January 1999.
  • DMTi digital multitrack interface: May 1999.
Published April 2000