An edited version of this text also appears in
Vol.14 No.9. July 1999

Review by Chris Carter


It seems the nearer we get to the 21st century the more we hark back to the 70's and 80's. New and repackaged analogue and wannabe analogue gear from Theramins to drum machines are being announced on an almost weekly basis, and in a retro kinda way it is all pretty exciting wondering what will be resurrected next.

Well, the answer could be LaaLaa but in this case it's a new synth from UK company dsTEC. The OS-1 Original Syn is a rack-mounting, digitally controlled, monophonic analogue synthesiser conforming to the now classic subtractive synthesis VCO-VCF-VCA-ADSR-LFO configuration.

As you can see from the photo the OS-1 is a striking yellow, maybe not to everyone's taste but certainly eye catching and a conversation piece and personally I quite like the colour (an identical shade to the EDP Wasp). Being constructed of welded steel the synth feels solid and built to last and prepared for a hard life on the road and is, unsurprisingly, very heavy for its size. A benefit of the colour scheme is that the smallish legending is still quite easy to read on a darkened stage. It's obvious that a lot of thought has gone into the OS-1 and it hasn't just been cobbled together overnight to jump on the retro band-wagon. Apparently it has been 4 years in development, by the same team that created the Deep Bass Nine and refreshingly is entirely UK designed and built. Now let's move on to the nitty gritty.

Despite the relatively outward minimalist appearance the internal synth and MIDI specification is very comprehensive. The unit has three independent VCO's, a VCF, a VCA, two envelope generators, an LFO, an arpeggiator and a MIDI interface. While the discreet audio circuitry is pure analogue the user interface is decidedly digital. All editing and programming is performed using the increasingly common 'parameter grid' method. In this case a combination of buttons and LED's arranged as a 4 x11 matrix to represent the editable parameters and using a single data knob and two increment buttons to enter parameter values. The only other visual feedback is from three large single digit red LED's. No LCD's or menu's, like I said...minimalist, but also easy to operate and get to grips with. In addition to the parameter grid there are three Mode buttons and a WRITE button to save edited programs into one of the 128 user patch memory locations.

The minimalist theme continues around the back of the case with the usual MIDI trio of IN/OUT/THRU and a standard 3-pin AC socket. There's a single mono output jack and a mono input jack for processing external audio signals (more on this later) but unfortunately there are no CV in/out connectors for those wishing to hook up to existing analogue CV kit.

There are three modes of operation PROGRAM, SYSTEM and EDIT. The OS-1 default mode is Program and when the OS-1 is switched on it performs a little light show that, if nothing else, indicates all the LED's are working. The user patch locations are instantly accessible in this mode using either the data knob, increment buttons or MIDI program changes, all very straight forward. The SYSTEM button is for changing the MIDI channel, turns the patch memory protection off or on (default) and sets the various ADSR trigger modes (see the ADSR section below) and the EDIT button activates the parameter grid.

As could be expected with a comparatively basic user interface the internal architecture is pre-configured, that is to say the VCO's feed into the VCF which in turn feeds into the VCA, Envelope Generator 1 triggers the VCF and Envelope Generator 2 triggers the VCA. The down side of this type of arrangement is that you can't re-patch the internal modules to come up with unusual custom combinations, the benefits are what you see is what you get and no unnecessary multi-page menu's to wade through. The front panel is clearly and logically laid out and assuming you know the basic principles of analogue synthesis most users will find the going straightforward enough, I managed to get into some serious editing within minutes without even glancing at the instruction manual.

Using the front panel as a guide lets take a look at the OS-1 from an analogue perspective.

First in line is the LFO with four editable parameters. RATE (The rate of the LFO is always displayed by a flashing dot in the left LED), SHAPE (Triangular, Square, Saw-Up, Saw-Down, Random). SYNC (off, key down, MIDI clock and MIDI clock+key down) and DELAY. A useful feature available when the LFO is synchronised to an external MIDI clock are the 9 different MIDI sync ratios. These will subdivide/sync the LFO rate over a 1 cycle every 2 bars to 3 cycles per quarter note ratio.

Next are the three independent VCO's. These are well specified oscillators and cover approximately 6 octaves, not bad for analogue VCO's. To find three VCO's in any kind of analogue synth would be a bonus but to find so many in a compact unit such as this is pretty amazing.

Each VCO has editable parameters for: Coarse Frequency, Fine Frequency, VCO shape (see below), LFO depth, Env 1 depth and Output level. VCO's 2 & 3 have an additional X-Mod feature which allows variable cross modulation and waveform sync with the other VCO's. VCO's 1 and 2 can output saw, inverted saw, variable pulse (including square) and modulated pulse (called CHORUS here). It's worth noting that the Pulse (CHORUS) waveforms are modulated by an additional (and uneditable) 16-speed LFO that that doesn't tie up the main LFO and allows for some animated full-bodied effects when all three VCO's are in action. VCO 3 has all the above waveforms but also includes white noise and a setting for enabling the external audio input. The external signal is then available alongside the other VCO's for processing by the VCF and VCA. All the VCO's will respond to MIDI pitch bend and modulation.

Something that certainly inspires confidence in the OS-1 is the stability of the VCO's, which amazingly require no warm-up period. They also showed no signs of tuning drift at the extreme ends of the keyboard, a common problem with many analogue VCO's. Apparently this stability is down to some very clever 90's designing of the oscillator circuits, well done team !

The VCF is a 24dB low-pass type and can be pushed into self-oscillation to act as a fourth (sine wave) VCO. There are half a dozen parameters available: Frequency, Resonance, LFO depth, Envelope 1 depth, Keyboard tracking and Keyboard Velocity. The frequency of the VCF can also be controlled from a MIDI modulation wheel.

I know I've said this before but trying to make comparisons on the sound of one VCF against another is asking for trouble, people take this stuff far too seriously. I'll just say that to MY ears it sounds perfectly fine, better than some I've come across but maybe not as 'sweet' as a few I've used, and I'm not naming names so there !

There are two envelope generators, Env 1 for control of the VCO's and VCF and Env 2 dedicated to the VCA. These are standard ADSR types with Attack, Decay and Release times variable from 0-10 secs and a 0-100% Sustain parameter. The minimum ADR settings aren't the shortest I've come across and trying to adjust the lower values was frustrating as there is a noticeable increase in the timing (particularly in the Attack time) when the display moves from zero to the first digit, and this is over a scale of 0-127. These parameters seem to be hindered by the resolution of the control system, but this is a side effect of digital control and something you wouldn't usually get using a regular analogue control pot. Four different keyboard trigger and re-trigger modes are available (using the SYSTEM button) and these settings are saved with each patch.

Love them or hate them there's no denying that when used sparingly arpeggiators can be a useful and creative tool. The OS-1 arpeggiator allows you to hold down between one and eight notes. The basic modes are: Off, Up, Down, Up/Down, Down/Up and Random, with a further 40 or so variations covering eighth and sixteen note triggering over a three octave range. The arpeggiator has its own Rate function, which is also displayed by a flashing dot in the middle LED, and it can also be synced to a MIDI clock. As both the arpeggiator and LFO can be synced to MIDI some fun rhythmic effects can be programmed using different time base subdivisions for each.

The MIDI specification is impressive with all editable parameters controllable over MIDI (a controller no. chart is included). This allows for some extraordinary and some may say overkill manipulations of the sounds via a MIDI sequencer, or in real-time using something like the Doepfer Drehbank, Kenton Control Freak or Phatt Boy MIDI controllers. Other recognised MIDI parameters are MIDI clock start/stop, hold, portamento, pitch bend and volume.

The 128 user patch memories can be saved and reloaded as individual MIDI SysEx dumps. This involves the truly unpleasant process of writing raw SysEx code into your sequencer to instruct the OS-1 to start dumping or loading, something not all sequencers can do (particularly non-computer types) and something I feel a lot of users aren't going to bother with. Also there is no way to perform a bulk dump or load of all the patches in one procedure. Not very user friendly considering how easy the rest of the OS-1 is to use.

After voicing my concerns it transpires that an editor/librarian program is being written that will handle the general day to day process of saving and loading patches to computer. This should be available to download from the dsTEC web site by the time you read this. An on-line user group is also being set-up for exchanging custom patches and tips. Assuming of course that you have a computer and access to the web...mmm !

As I've already said a side effect of using digital editing control with an analogue system is the relatively coarse resolution of the controllers and occasionally you can hear a stepping effect when adjusting or sweeping some parameters. I wasn't entirely happy with the data knob and would have preferred to have seen a continuous 180% rotary controller included, not the standard end-stop type, but I can live with it.

Also I would like to have seen a more adventurous implementation of the VCA, as there's no amplitude modulation available from the LFO waveform, and a choice between logarithmic or linear ADSR control would be useful, as would an LFO controlled panning stereo output. Not including a ring modulator is a real disappointment and although similar effects can be achieved using the VCO X-Mod feature nothing beats the real thing for really extreme modulations and FM effects.

The OS-1 is a breeze to use with no hidden menu's or arcane operating systems to hinder you and is a great example of plug and play. Using the parameter grid and 3 digit display to edit isn't as restrictive as you might imagine. This is partly due to the (relatively) limited number of parameters available, but that's the nature of monophonic subtractive analogue synthesis. Let your ears rather than your eyes to be the best judge of what sounds right.

The 'yellow pages' instruction manual is informative and well laid out, a refreshing change. The factory pre-sets are, on the whole, very good and showcase the abilities of the OS-1 well. There are some genuinely cone busting basses, screaming lead sounds, zany effects, perky arpeggiator patches and plenty of contemporary (and over used) TB303 type resonant basses. But I must say had the most fun programming my own sounds.

The audio quality is top notch and for an analogue instrument the noise floor is relatively low. As with many analogue instruments the upper and lower audio ranges can produce some frighteningly extreme frequencies approaching sub and ultra sonic, so beware !

Funnily enough even in an increasingly crowded analogue market there aren't many truly analogue/digitally controlled synths that I'm aware of. The closest relative to the OS-1 is probably the very non-programmable (but infinitely tweakable) Doepfer MS404 Synth, which includes a built-in MIDI-CV interface but only one VCO and while it's a fine synth is frankly not in the same league.

And don't be fooled by the dayglo colour scheme, the OS-1 is definitely a professional instrument. It's well specified, easy to program, very stable in use and capable of some outstanding analogue sounds. Admittedly the single knob approach is unusual for an instrument proclaiming its analogue heritage and analogue diehards may find this a bridge too far. But the OS-1 has been designed as a hybrid programmable analogue MIDI performance synth and is happy to leave the dirty work of CV's, gates and patch-cords to the modular big boys. The price may appear to be slightly on the high side of reasonable but this synth is going to be an investment and destined to become much sought after in years to come.

Maybe the Original Syn doesn't break any new ground in synthesiser design using as it does proven analogue and MIDI technologies but nevertheless dsTEC have succeeded in breeding an excellent and professional hybrid instrument.

Analogue yet programmable.

Powerful three VCO sound and impressive VCF

Easy to use, easy to program

Impressive MIDI specification

External audio input

Solid, heavy duty construction


Minimalist user interface

No Ring Modulator

No CV in/out

Basic VCA control

Awkward MIDI patch dump/load implementation

Not as 'hands on' as a regular analogue synth


The general feel of the Original Syn is that of a slightly spartan 'get the job done with the minimum of fuss' approach but with a nudge and a wink that also says 'I've got a programmable analogue powerhouse under the bonnet waiting to be unleashed'. The OS-1 is ideal for anyone wanting a great sounding pro analogue instrument without dirtying their hands with CV's and patch cords.

PRICE: £699 incl. VAT


dsTEC Ltd

PO BOX 1218

Stone, Staffordshire

ST15 8GX

tel: +44 (0)1785 616466

fax: +44(0)1785 615656

email: sales@dstec.co.uk

web: www.dstec.co.uk

Copyright © 1999 Chris Carter / SOS Publications.