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Studiologic Sledge

Virtual Analogue Synthesizer By Gordon Reid
Published November 2012

Studiologic's new Waldorf-powered polysynth is here and it's very yellow indeed. Put your sunglasses on and meet the Sledge...

Studiologic Sledge

Studiologic isn't a company in the conventional sense; it's a trading name of Fatar, who are much better known for their keybeds and controller keyboards. But while the Sledge may be built in Italy, its heart pumps German blood because, as the logo in its rear left-hand corner confirms, it's "Powered by Waldorf”. If this suggests something designed for technophiles, prepare to be surprised. Eschewing multitimbrality, splits, layers, programming depth, complex effects, and all of the other gubbins that festoon most digital synths, the Sledge takes us back to an era when men were men, synthesizers were synthesizers, and PA speakers were frightened.

First Impressions

I know that it's not common for one's first impression of a synthesizer to be its colour, but the Sledge isn't just yellow, it's YELLOW. Of course, there's nothing wrong with making your products stand out from the crowd but, if potential customers don't fancy being seen in the company of a yellow lump, it's possible that sales will suffer. When I showed the review unit to a professional keyboard player, he told me that he really liked the design and the sound, but that he would probably never buy one because it might look horrible under lights — garish under white, and brown under reds and greens. I haven't tested it, but I fear that he might be right.

That aside, there's a lot that's good about the design of the Sledge. For one thing, it's very light for a five-octave polysynth. This has been achieved by constructing the whole thing — including the base plate — from plastic. Nonetheless, I was pleased by how robust it felt, notwithstanding that I could lift it off its stand using my little fingers. As for its spacious control surface, I was delighted to find that it uses potentiometers rather than rotary encoders which, on some synths, are almost as likely to decrease a parameter's value when you turn them clockwise as they are to increase it. Just as pleasing are its large, friendly knobs, with even larger ones for the most important functions. These are reminiscent of vintage Moogs: never a bad thing.

At this point, I would usually take a moment to describe the synth's rear-panel connections, but the only hole on the back of the Sledge is the one that accepts the mains lead. Yes! It has an internal power supply, which earns a gold star and a big tick from me. You'll find the rest of its sockets on its left-hand side. These are: quarter-inch audio left and right outputs, a headphone socket, inputs for a sustain pedal and an expression pedal; and MIDI In and Out on five-pin DIN and USB. The positions of the sockets are marked on the top panel in nice, bold lettering, which makes it simple to plug everything in. If space is limited, you may find it awkward having the cables sticking out of the side but, to be fair, I found it to be no problem because the Sledge is only 38 inches wide, whereas having side-facing sockets on 76- or 88-note keyboards can create real difficulties.


The Sledge is unusual in having all of its connections on the left-hand edge — or nearly all: the power input and accompanying switch are found at the rear. The Sledge is unusual in having all of its connections on the left-hand edge — or nearly all: the power input and accompanying switch are found at the rear.

Soundwise, the Sledge is a monotimbral polysynth that claims eight-note polyphony in its marketing materials but actually delivers far more — perhaps the 16 claimed in its manual. With the exception of its wavetable capabilities, its uses traditional subtractive synthesis, with each note based upon (up to) three oscillators, which also offer limited cross-mod (FM) and oscillator sync, plus a separate noise generator. These are followed by a single multi-mode (LP/BP/HP) resonant filter with 12dB/oct and 24dB/oct options, and an audio amplifier, each of which is controlled by a dedicated ADSR contour generator. Three LFOs send modulation to eight destinations, and there's also polyphonic portamento, a choice of mono and poly modes, plus single and multi triggering. Two basic effects sections — chorus, phaser and flanger in one, plus delay and reverb in the other — complete the package.

I started my tests by pressing the (very useful) Panel button, so that the current positions of all the knobs defined the sound, and then programmed a single-oscillator, monophonic brass patch. The result was excellent: perhaps not as commanding as the same patch on an ARP Odyssey (which is my go-to synth for this type of sound), but bright and strident nonetheless. With a lavish application of reverb from the internal effects unit, I was more than happy, so I allocated the patch to a category, named it and saved it. I then set up the aftertouch (which is hardwired to the mod-wheel LFO) to control the vibrato, and noticed my ARP ProSoloist looking over its shoulder to see whether the Enid, circa 1976, had entered the room. Next, I turned my attention to a selection of more than usable lead sounds and then programmed all manner of powerful bass patches, many of which revelled in the speed and snap of the contour generators. I even strayed into VCS3 territory when I recreated some of the bubbly sounds so popular with the space rock fraternity. All the programming and performance controls fell immediately to hand, whereas you have to programme carefully and, in all likelihood, assign modulators to performance controls on modern workstations to obtain the same results. This was a very good start.

Next, I switched Mono off and switched on the chorus. This sent me deep into single osc/voice polysynth territory, and I had soon programmed a range of simple poly-brass patches, pads and carpets. Then, switching on Osc2, I recreated the standard palette of dual-oscillator patches and (to my great surprise) even stumbled across some sounds reminiscent of a very large Yamaha of my acquaintance. Following that, I recreated some of the 'hollow' sounds that were so prevalent in the mid-'80s, as well as popular patches based on the second oscillator tuned upward by a major fifth, discovering in the process that the Sledge has a remarkable capacity for imitating transistor organs. However, this was also when I discovered that the Sledge generates a large amount of intermodulation distortion (loud, spurious, enharmonic pitches) when you play two or more notes at very high pitches. This is not unique to the Sledge, but it's something to be aware of, nonetheless.

The Sledge was proving to be more flexible than I had envisaged, but some of its limitations began to appear when I tried to use oscillator sync. This was because I couldn't sweep the pitches of any of its oscillators using the main contour generators. However, tucked away in the LFO source list and not even mentioned in the manual (!) I found an option called RAMP. This is not an oscillator, low frequency or otherwise. It's a single sweep (upward or downward, depending upon the polarity of the depth control) and it proved to be a vital component in the Sledge's voicing. Directing the Ramp to sweep the pitch of Osc3 and syncing Osc2 to this, I tried to create the aggressive, 'tearing' sounds so beloved of owners of some vintage monosynths but, to my surprise, the Sledge failed to recreate these, instead generating pitch sweeps with a 'sync-y' character. What's more, there's a significant bug in this part of the software because, having played one sync'd note in mono mode, you have to wait a second or two before you can play the next. Ultimately, I found that the best use for sync was to create unusual (but static) waveshapes for polyphonic sounds. While it's useful, this wasn't what I had envisaged.

Likewise, the filter proved to combine flexibility with some unexpected limitations. For example, while the responses of the six filter modes are pleasing, the controls exhibit noticeable quantisation. And, despite what the manual claims, the filter doesn't track the keyboard at precisely 100 percent, so you can't create consistent tones from one end of the keyboard to the other when it's self-oscillating. What's more, this oscillation is very loud when compared with the oscillators' output, which means that some of my favourite sounds from synths such as the Juno 60 are beyond the Sledge.

Yet another area of swings and roundabouts revealed itself when I turned to the velocity sensitivity. I was pleased to find that the Sledge offers three response curves, as well as fixed velocity, but disappointed to discover that the velocity only affects the depths of the amplifier and filter ADSRs. This means that if the filter contour amount is set to zero (as it will be for some patches), velocity has no effect on the brightness of the sound. What's more, the Velocity knob on the review unit had a fault; the parameter value returned to zero unless I held the knob in position.

Finally, I turned my attention to the Sledge's wavetables. At the time of writing, the manual doesn't tell you which tables these are, saying only that "a more complete description ... will be made available separately”. My problem here is that, while Studiologic claim (and I quote again) that the wavetables are "derived directly from the mother of all digital synthesizers, the PPG Wave”, my PPG has 32 wavetables, each containing 64 waves, whereas the Sledge has 66, each with 100 values within them. Consequently, I was unable to compare the Sledge directly to the PPG, nor could I relate its tables to my Waldorf XTk, which is, again, different.

Happily, using the wavetables is a doddle. You select the desired table using the large, dedicated knob in the Osc1 panel, and the waves within it using the PW knob, which is repurposed when the wavetable function is selected. You can then move within the table using the LFOs but, more importantly, you can sweep through it using the (unsung but vitally important) ramp generator in the LFO section. I started programming some sounds, and the results were startling. Within minutes, I had saved one of the best electric pianos I have ever created on a non-physically-modelled synthesizer, and it took me no time at all to program a huge range of organs, as well as some of the glassy pads and percussive sounds that made the PPG such a revelation when it appeared. This was not because the Sledge is a hyper-powerful wavetable synth, because it isn't. In fact, it's much more limited than the PPGs and the various flavours of Waldorf that succeeded it. But it's much quicker and simpler to program than previous wavetable synths, making it almost inevitable that something interesting will emerge. The Sledge actually makes wavetable synthesis fun!

Room For Improvement

It's not quite one-knob-per-function, but it's not far off... It's not quite one-knob-per-function, but it's not far off...

Despite all the good stuff, there are other areas in which the Sledge falls short of ideal. For example, there are odd bugs such as the sudden truncation of heavily reverberated sounds when you turn the master control knob toward zero. More annoying are things such as the loud thump that it sends to your speakers when switching it on and off, and the fact that — when plugged into my MacBook Pro via USB — it chattered away quietly to itself. Then there are voicing shortcomings, including the crude filter overdrive, which does little more than clip the signal. (You can confirm this by trying, and failing, to overdrive a square wave!) Then there's its unweighted keyboard. This is adequate when compared with some of the less sophisticated actions of vintage synths, but the Sledge would benefit from the installation of something more robust and more suitable for polyphonic playing. Of course, this would add to the cost of the final product and, in all likelihood, to its weight, but I can't help feeling that the Sledge deserves something better.

Given its hands-on editing and tiny menus (just 20 parameters in total, including the arpeggiator), it isn't surprising that the Sledge requires no support software. However, the lack of any information in the manual regarding its use as a MIDI controller (which merely promises that "a complete information chart ... will be published in official Studiologic sites”) was frustrating. So I took a leap in the dark, launched a suitable soft synth on my Mac, and started to play. No drivers were needed; the soft synth immediately responded to note on/off, velocity, pitch-bend, mod, aftertouch, and the sustain pedal, although the Sledge's control panel did nothing. Mea culpa... the Send Ctrl and Receive Ctrl parameters were set to 'off'. Switching these on allowed the Sledge's knobs and buttons to send MIDI CCs, although not always the ones that I expected. This isn't a huge problem; MIDI CCs can be learned or remapped, so I have no doubt that the Sledge will perform well as a controller. Unfortunately, next time I switched the Sledge on, the LFO depth defined in the Wheel section was permanently applied in its full amount. Having tried to eliminate this by power cycling (ineffectual) and sending appropriate MIDI messages (also ineffectual), I fixed it by removing the USB cable and power-cycling the synth with the Receive Ctrl parameter set to 'off'. I was then unable to recreate the problem, so hopefully it was just a glitch.


While claims that the Sledge offers a separate knob or button for each function aren't quite true, it's as simple to use as its control panel suggests. This is great news, because there's definitely a place in the world for a polysynth that dispenses with all the frippery of today's multitimbral synths, workstations and soft synths, and allows you to program a great sound using just the knobs and switches on a spacious and very nicely laid-out control panel. This philosophy was good enough in the era of the Prophet 5 and OBX, and as far as I'm concerned, it still holds good today. The trick, as with all synths, is to look to what it can do, rather than worry about what it can't.

Sure, there are many players who will prefer a wider range of facilities but, back in the '70s, manufacturers understood that the relationship between the sound, the control panel and the player could inspire the performance. By focusing on this, the engineers at Studiologic have reminded me of something that I once understood intimately, but seemed to have forgotten: synthesis can be both rewarding and Fun. Despite some initial reservations, I thoroughly enjoyed programming and playing the Sledge. It deserves to be a success.  


At around £750$1600 in the shops, the Sledge sits somewhere in the middle of the price spectrum for a virtual analogue synth. So, given the simplicity of its wavetable synthesis (which precludes comparison with more powerful systems), I think that that's how we should approach it.

More affordable than the Sledge, the Roland SH01 Gaia is a more powerful VA synthesizer, combining three synth engines with five simultaneous effects and 64-note polyphony. However, its three-octave keyboard might remove it from your shopping list. Somewhat more expensive, the respected Nord Lead 2X — which seems to have been around forever, but is still a current product — is deeper, less immediate, and it has a different character that you may or may not prefer. Strangely, the synth that I think might have been the Sledge's closest rival was the Oberheim OB12. This misunderstood Italian synth was superb value when it was discontinued after just three years in production, and I hope that a kinder destiny awaits the Sledge.

What Is Wavetable Synthesis?

Many people use the term 'wavetable' to describe any ROM that contains a selection of waveforms. In this context, however, it should be used to describe a selection of related waveforms that can be output in a given order to obtain a particular sound. Consider sampling a piano note for 10 milliseconds every 100 milliseconds as it decays over the course of, say, five seconds. This would create a table of 50 sequential samples that occupied just 10 percent of the memory of a complete recording of the note. Starting at the first sample and then sweeping through the rest in the correct direction and at the correct rate (and, preferably, interpolating between the samples as you did so) would then rebuild the original note with remarkable accuracy. Sweeping through it in the wrong direction, selecting discontinuous samples, or travelling in some fashion around the samples in the middle of the table would, as you might imagine, produce different sounds. Of course, it's not necessary to limit wavetables to decaying notes played on acoustic instruments, and many are built using additive synthesis, leading to all manner of unusual new timbres. It's a powerful synthesis method, which is one reason why vintage instruments based upon it remain so desirable.


While experimenting with the Sledge, I stumbled across an undocumented unison function. Unfortunately, this has no detune capability, so it just makes sounds louder and slightly flangy when the phase relationships of the notes leads to cancelling. What's more, I couldn't invoke it reliably, so it's either a bug or an unfinished feature. Either way, it should be sorted out.

The Arpeggiator

In keeping with its vintage synth philosophy, the Sledge offers a monophonic arpeggiator. Many of its controls are as you would expect: on, off and latching, with up, down and alternate modes over a healthy maximum range of five octaves. It also provides MIDI Sync, note duration, and four sort modes to determine the order in which notes are played within each octave. You have to program it using a menu, but this is simple, and the results are stored on a per-patch basis. I quickly obtained some pleasing results with it, including a surprisingly accurate recreation of Vangelis's note-ordered arpeggios from Blade Runner. On the other hand, there's no latch on/off button on the panel and, if you've programmed a latched arpeggio, you have to enter the menus to stop it, which is daft.


The Sledge offers 999 patch memories, of which 100 contain factory programs. Many of these are surprisingly useful because, rather than stuff the thing full of monster patches that might sound impressive in a music shop but ultimately prove to be useless in a mix, the programmers have included sensible sounds such as strings, brass, pads, lead sounds, basses and organs alongside the inevitable sound effects. With 899 empty memories, and perhaps the easiest programming surface of any current digital synth, what's to stop you programming your own sounds? Nothing. Start twiddling.


  • It has character and flexibility, and can sound excellent.
  • Its large panel makes programming simple and fun for all standards of users.
  • A 61-note velocity- and aftertouch-sensitive keyboard is unusual at this price.
  • It's light and manageable.


  • Its limitations may frustrate some potential users.
  • There are still some bugs to be hunted down and squashed.
  • Its colour may be a problem for some potential purchasers.
  • The documentation should be revised and extended.


There's definitely a place in the world for a polysynth that's simple to program and produces some great sounds with minimal effort. When you're in the mood for a bit of virtual analogue synthesis, try the Sledge. I had not expected to like it this much, and I had to revise my opinion considerably during the course of this review. You too might be surprised.


£759 including VAT.

Synthax Audio +44 (0)1727 821 870.