Magazine Archive

Home -> Magazines -> Issues -> Articles in this issue -> View

Expand Ability

Article from Electronics & Music Maker, July 1985

Two manufacturers follow their already established polysynths with keyboardless voice expanders. Trish McGrath puts the Chase Bit 01 and Siel Expander 80 through their paces.

Thanks to MIDI, you no longer have to surround yourself with keyboards to use a range of different synths. We put two Italian keyless expanders into the ring.

Chase Bit 01 Synth Module

The latest hi-tech product from the rejuvenated Crumar factory - marketed in this country under the name of the UK importer, Chase Musicians - is based heavily on the deservedly successful Bit One polysynth (see review, E&MM October '84). But Chase are at pains to point out that several added features make this more than just a keyboardless Bit One, and on balance, I must say I'd have to agree with them. One thing is clear though - this module's appeal should in no way be confined to existing Bit One owners. Because whereas Yamaha's TX7 expander really needs an experienced DX7 owner to get the best out of it, the Bit 01 uses familiar analogue sound-generating technology. And as digital access synths go, it's surprisingly user-friendly, thanks to no less than four two-digit sets of numeric LEDs and some helpful front panel parameter graphics.

Whether or not it's wise to market the Bit 01 as a 19" rack-mounting module remains to be seen, but I'd imagine that many synth players (not to mention home studio owners) are now geared up for this sort of thing, what with the influx of rackmounting digital delays and MIDI effects units.

Getting down to synth basics, the Bit 01 is a six-voice polyphonic, dual-oscillator touch-sensitive synth module, capable of operating in one of Normal, Double (bitimbral) and Split modes. Double mode sees polyphony reduced accordingly to just three-voice, while the programmable Split divides the six voices evenly to each side. The words 'Lower' and 'Upper' represent familiar terminology that's brought into play in the context of layering two sounds, the volume of two sounds (when layered), the volume of each side of the split point, and the two outputs on the rear panel (for stereo mixing).

The Chase's front panel follows recent synth design fashion by being sparsely populated, though more uncommonly, the controls that are there are logically laid-out and easy to get acclimatised to. To begin with, we find Lower and Upper Volume sliders, plus and minus incrementor buttons with accompanying Value LED, and three buttons that are used to decide which of Address (parameter), Lower program or Upper program the 0-9 selectors will affect. Further to the right are switches for Double and Split, Tape (for saving and loading programs to normal audio cassette), Stereo Out, Park/Write and Compare - all of which come with their own LED indicator. These last two buttons, incidentally, allow you to 'park' your original sound before you begin editing and then 'compare' both versions later on; you can also park a sound while you search the memory for a suitable location in which to store it. With Stereo Out, the Bit 01's designers have supplied the option of bypassing the stereo output when in normal mode. This is a big improvement on the Bit One, where voices were assigned a place in the stereo image using what I can only describe as random logic.

The Expander's onboard memory will happily remember no less than 75 single sounds, while numbers 76-99 are reserved for 'patches' of double or split programs (another good point over the Bit One). And as if just having bitimbral patches wasn't enough, you can program the volume of the Lower and Upper voices, while the Upper part of a Split patch can be transposed in semitones within a range of plus three octaves or minus two, and is also programmable.

Snooping around the rear panel uncovers nothing unusual, namely the Memory Protect On/Off switch, and sockets for Release Pedal, Lower and Upper outputs, MIDI In, Out and Thru, and the mildly necessary IEC power socket.

Graphic Details

While they've undoubtedly incorporated much of the Bit One's sound-generating circuitry into the Bit 01, Crumar have obviously given the Expander's two DCO sections a little more thought. Gone are the parameters to modulate the pitch with EG2 (yes, very useful), and in their place come 'Noise' and 'Detune' (for fine detuning of DCO2). Incidentally, both newcomers (formerly non-programmable slider controls on the Bit One) can be introduced with a good degree of control, the parameters being stepped from 0-63. I only wish other digital access designers would follow the Italians' example here - almost every synth parameter needs a resolution of more than the typical 15 steps...

Each DCO has Triangle, Sawtooth and Variable Pulse waveforms (which can be summed together in any order), with a footage selectable from a range of 32', 16', 8' and 4'. Frequency can be raised in semitone steps up to an interval of a major seventh (11 semitones). Pulse Width regulates the Pulse waveform (from 3% to 97%), while the keyboard dynamics can also be used to control the pulse width, and thus the harmonic content of a sound.

Moving onto the analogue low-pass filtering section, no prizes for guessing it possesses parameters such as Cutoff Frequency, Resonance, Track, ADSR (EG1), and Envelope amount. Less usual perhaps is the way the Bit 01 allows keyboard dynamics to control both the attack of the filter's envelope (soft touch produces a slow attack, and so on) and the modulation depth of EG1. EG2 is tucked away in the VCA section, which also allows both the Attack time and Volume of a sound to be controlled with the ol' fingertips.

"As if just having bitimbral patches wasn't enough, you can program the volume of the Lower and Upper voices..."

Another advance on the Bit One comes in the form of a Program Volume parameter - great for introducing new sounds during a song at an appropriate level.

Identified LFOs

No self-respecting synth would be complete without an LFO section, and the Bit 01 boasts two of them. These can be independently assigned to modulate DCO1, DCO2, the VCF, or the VCA (or all at the same time, if that's what you're into), while the mod wheel can introduce further vibrato to the DCOs. Waveform is selectable between Triangle, Sawtooth or Square, and the LFO section is completed with the addition of Rate (LFO speed), Delay (for delayed modulation), Depth, and Dynamic Rate (hardest key strike for maximum rate) adjustable parameters.

All in all, a comprehensive modulation section, though it would also have been nice to be able to regulate the mod depth with key dynamics.

MIDI Modes

Again, Crumar have been doing their homework. Options to switch Pitchbend, Mod wheel, Release Pedal, and Program Change data in or out of the MIDI datastream are onboard, while the Receive Channel is selectable between Omni mode or channel numbers 01-16. Existing Bit One owners should remember that their synths won't actually transmit pitch, mod, and program change data; maybe the Italians didn't think they'd want an expander...

Seeing that the rich analogue sounds this particular Expander is capable of producing could be especially appealing to some of the DX fraternity, the good news is that E&MM's resident DX7 and review Bit 01 docked beautifully. Also a good match, as far as common features will take it, is the Casio CZ1000, but the Siel DK80, though it passes touch-sensitivity data faultlessly, won't communicate on the pitchbend or mod wheel front. Korg's Poly 800 is also uncooperative on the modulation front, though it doesn't mind disclosing pitchbend info. I guess incompatibility between wheels might not bother some, but it makes you wonder whether some manufacturers (and I don't just mean Crumar) are really taking MIDI seriously.

Siel Expander 80

Not so long ago (E&MM April '85, in fact), we put the Siel DK80 poly-synth under the reviewing microscope, and discovered an amazingly versatile bitimbral synth that cost very little money. And out of all good ideas, an expander is born...

But first the bad news: the Expander 80 is not bitimbral, though in all other respects, you could almost be looking at a DK80 after a spell through a crusher. The good news is that I'm not going to waffle on about the Expander (since I'm sure you couldn't possibly have missed the DK80 review), but I guess for those of you just back from the Arctic...


The Expander 80 is housed in a very compact, grey moulded casing, which Siel have designed to be placed on top of a DK80 (they're supplying the brackets and the power supply is 'built for two'), though there's no reason why it couldn't find a suitable resting place somewhere else.

Programming is by the usual (read 'false economy pain in the neck') digital access method, while the parameter sections comprise Programming Unit, Edit, Sequencer, and Masters. The Expander 80 also has a parameter map for the DCO, VCF, VCAs and so on, so you know where you stand, synthetically speaking.

"Another advance on the Bit One is the Program Volume parameter - ideal for introducing new sounds at an appropriate level."

Like the DK80, the Expander comes stocked with 40 preset sounds and 10 user-programmable patches, and it also offers you the option of bringing another 50 or 100 sounds on-line by the use of RAM or ROM packs respectively.

Dissecting the edit map finds the DCO with a waveform selectable between Sawtooth (4', 8' or 16'), Square and Off,, with a separate set of parameters for setting the square wave's output level at each footage of 16', 8', 4' and 2'.

The VCF, meanwhile, comes equipped with Cutoff, Resonance, Keyboard Track (Full, Half or Off), Trigger (Multi or Single), and DEG level controls. The Expander follows DK80 design practice in being a one-filter affair, and personal taste will dictate whether or not you can live with this limitation. To me, playing a polysynth with only one filter is like trying to drive a car with only one wheel (well, maybe not quite - Ed).

The filter's envelope is of the extended ADBSSR variety - the extra characters denoting the inclusion of Break Point and Slope parameters - while the Dynamics (key velocity affecting the sound's timbre) can be either On or Off. One bonus the Expander has been given is that its Noise source can be routed to either the VCF (for tailoring by the Cutoff Frequency and Resonance), or directly to the VCA. Which brings us nicely to another dissimilarity with the DK80...

Whereas the self-contained polysynth was a 12-oscillator, bitimbral creation, the Expander is eight-note polyphonic (one oscillator per voice) in DCO Mode Whole, and four-note polyphonic in (pseudo) Double mode, though with correspondingly increased sonic fatness. However, just to make things more interesting, two VCA sections come on line in Double mode, allowing two different envelopes and dynamic responses for each layer, with each sent to a separate output on the rear (A/Mono and B). Again, both VCAs consist of ADBSSR envelopes, with processing of both Key Dynamics and Damp Pedal data being optional, and Detune allows for both Interval (in semitones up to a max of five octaves) and fine-detuning between the two layers of oscillators.

Remaining parameters include stereo Chorus (either On or Off) and Volume (for setting the relative levels between sounds).

Criticisms? Well, they centre around the level of noise emitted from the internal workings - with the Master Volume set at a reasonable level for a band rehearsal, say, it could well be a real nuisance. Some sluggish processing doesn't go down too well, either. For instance, it takes a couple of seconds (and a few key stabs) for a drastic change to the VCA's attack time to actually register. And this isn't just apparent on the Expander - the DK80 suffers a similar operational reluctance. With the high speed of microprocessors these days, there's really no excuse for this sort of thing. Maybe Siel could do with a Bug-Gun.

Sequencing Sounds

The Expander's modest two-track sequencer is straightforward both in concept (it's a real-time only affair) and in use. Pressing Record 1 and 2 clears anything still in memory, while the Metronome can be selected (or so I'm told - the review model thought differently), using the cursors to vary the tempo. Pressing Start begins recording on Track 1, and you can play back the first track while overdubbing on Track 2.

Not surprisingly, there are limitations aplenty - like the mini-sized memory (about 300 notes), compulsory and independent looping of tracks, and non-storage of pitchbend or modulation, not to mention the four-note polyphony of Double mode. Better is the Sequencer Clock option, which offers three options for triggering sequence playback - MIDI, External (received from the Seq Clock input), and Internal.

Sadly, it's not a realistic possibility to play sequences from both the DK80 and Expander in sync, seeing as they loop in any old fashion; but if you think your reflexes are up to it, have a bash anyway. In any case, the optional multi-footpedal sends Start and Stop commands to both instruments over MIDI, as well as a myriad of commands like Damper Pedal, Program Up, and interrupting key note data to another expander or MIDI keyboard.

"It's not possible to play sequences from both the DK80 and the Expander in sync, as they loop in any old fashion."

The Expander's rear panel boasts the usual trio of MIDI sockets, but MIDI data filtering is confined to just Program Change - either Internal (changes sent over MIDI Out), or External (program changes effected only by controller), or two-way conversation. MIDI Receive Channel can be set to Omni or any channel (Poly) from 01 to 15.

There are no problems when it comes to pitchbend and modulation data flow from the DK80 to Expander, but pitchbend is limited to the preset tone or so up and down. However, using another controller synth with a wider range gets over this snag, though on some counts, other synths don't fare so well.

Korg's Poly 800 transfers pitch wheel data but no modulation (again), the DX7 behaves in a similar fashion (though it isn't coy about key velocity data), while the Casio CZ also sends pitchbend on cue. As we've said before, there's no beating testing a new purchase with your current line-up. Better to be safe than incompatible...


In spite of sharing the same country of origin, the same intended musical function and some elements of paper specification, these two expanders aren't strictly comparable. So I'm not going to come down on one side or the other, just draw a few separate conclusions.

Although it's a pity Crumar haven't seen fit to implement such niceties as allowing Lower and Upper sounds to be received on different MIDI channels and retaining the Bit One's Unison mode, the Bit 01 represents as good value for money as you're likely to find.

Plus-points include the number of innovative ways you can control the 01's parameters with touch (it'd be a terrible waste to team up the machine with a non-touch-sensitive synth), the programmable double and split patches, the parking facility, and last but not least, the sound.

Factory programs offer a wide range of good, warm strings, piano, and brass voices, with percussive and effects sounds coming away with marginally fewer flying colours. But with a programming system as straightforward as this, some presets won't last long.

Siel have certainly come up with a cost-effective package in the Expander 80. In fact, it's the cheapest MIDI voice expander currently available - by quite some margin. But as with anything that cuts corners, there'll be many who feel that it's the corners that are worth dishing out good money for.

The inclusion of a Double mode goes some way to beefing up the sound of the EXP80, but human nature dictates that you'd prefer it to have gone the whole hog of separate filter section, LFO and complimentary waveforms. The Sequencer might be a novelty to the relative synth newcomer, but its drawbacks are unlikely to impress a seasoned player.

And so to the sounds. The presets are identical (rather than complimentary) to those on the DK80, so the same sort of comments apply. You won't like them all, you may not even like any, but bear in mind that this is more a reflection on Siel's programmers than on the 80-series circuitry's capabilities. Personally, I'd like to hear Siel come up with the sound quality to match the versatility of their synths. Cost-effectiveness isn't everything, after all.

If you find the Siel sound is to your liking and cash is at a premium, the Expander 80 should be well worth a look. But if the latter criterion doesn't apply, you might find your aural senses more satisfied by the machine from the company up the road.

RRP of the Siel Expander 80 is £399 including VAT.

Further information from Siel (UK), (Contact Details).

The Chase Bit 01 sells for £699. Further info from Chase Musicians, (Contact Details).

Also featuring gear in this article

Featuring related gear

Previous Article in this issue

Ensoniq Mirage

Next article in this issue

Sequential Tom

Publisher: Electronics & Music Maker - Music Maker Publications (UK), Future Publishing.

The current copyright owner/s of this content may differ from the originally published copyright notice.
More details on copyright ownership...


Electronics & Music Maker - Jul 1985

Review by Trish McGrath

Previous article in this issue:

> Ensoniq Mirage

Next article in this issue:

> Sequential Tom

Help Support The Things You Love

mu:zines is the result of thousands of hours of effort, and will require many thousands more going forward to reach our goals of getting all this content online.

If you value this resource, you can support this project - it really helps!

Donations for July 2024
Issues donated this month: 14

New issues that have been donated or scanned for us this month.

Funds donated this month: £20.00

All donations and support are gratefully appreciated - thank you.

Magazines Needed - Can You Help?

Do you have any of these magazine issues?

> See all issues we need

If so, and you can donate, lend or scan them to help complete our archive, please get in touch via the Contribute page - thanks!

If you're enjoying the site, please consider supporting me to help build this archive...

...with a one time Donation, or a recurring Donation of just £2 a month. It really helps - thank you!

Small Print

Terms of usePrivacy