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Wersi Pianostar


Pianostar S2000


The Pianostar will come as quite a surprise to the many people who have built Wersi organ kits over the years. Having established a high reputation in the organ world, it is an ambitious new direction for the company to take and in many respects they have succeeded in producing an upright piano that looks and more importantly feels like the traditional acoustic piano. But what is equally important is its innovative extras that take conventional piano principles and stretch the tonal and control possibilities to make the Pianostar suitable for many modern styles as well as classical music.

Back removed showing the electronics.


All this is a lot to expect from one instrument that has refined its electronics (without the use of microprocessors) to fit a remarkably small space. From the photographs, virtually all the electronics can be seen installed on one main rack. Ribbon cables and prewired connectors have done away with all tedious wiring and, apart from the two main dual speaker systems, foot pedals and main amplifier in the base, the whole piano has little to put together.

Except for the keyboard frame, of course, which forms the heaviest and undoubtedly the most critical item for the advanced pianist. A lot of attention has gone into the correct weighting of each key and its smoothness of action. The keys are pleasing to play, although Wersi are planning to update the existing keyboard with a further improved action developed in Italy for production kits. Keys have a firm feel and at first, seem to bounce back too much and prove difficult to manipulate trills. A good playing technique can produce acceptable classical music. It is easy to move from acoustic grand piano to Pianostar and say, "I told you so - not a bit like a 'real' piano". But so much of your decision probably comes from the evaluation of whether or not it's a typical piano 'sound' and Wersi have certainly tried to get this and more. For the player, other factors are important and keyboard sensitivity, harmonic modulation and dynamics should be as critical as tonal excellence.

Dynamic range is certainly as good, if not better (lacking mechanical noise except on very low output volume setting) than an acoustic instrument. Control of keys at pp levels is adequate, although equal sensitivity from one note to the next relies on careful mechanical contact setting-up. This is much improved on the usual 'velocity sensitive' configuration by the use of two 'rest' and 'operate' bus-bars for the key contact instead of two further contacts that often move out of line after a time, producing erratic note volumes.

Circuit Design



The Pianostar sounds are derived from a voltage controllable high frequency oscillator operating at about 1MHz. A correction frequency is fed via a top octave synthesiser IC and 16 to 1 line multiplexer. This frequency is differentiated and rectified, with the resulting DC voltage controlling the final HF pitch output. The multiplexer selects one of the 12 TOS frequencies from the BCD 4-bit code of the Transposer, enabling the whole piano to be tuned instantly to any interval. A Pitch control matches tuning over several semitones to other instruments and Vibrato, Hawaii and Slalom all function by sending appropriate control voltages to the HF oscillator.

Left hand controls.


The HF signal is then passed to a pre-scaler section that divides the basic frequencies for the 12 notes of each octave on Channel 2. It also goes via a programmable fractional divider before another frequency divider produces the notes for Channel 1. This enables Channel 1 to be de-tuned against Channel 2 at calculated intervals up to a perfect 5th. Electronic keying of the fully polyphonic keyboard ensures clean production of all the pitches.

Dynamic volume and envelope shaping are set at this stage, with the latter dependent upon Banjo and Sustain switches and the speed of transition of the key contact from the 'rest' bus-bar to the 'operate' bus-bar.

The critical resistor for sustain time is chosen for each key to match the decay of equivalent piano strings. At this point, too, comes the control logic (through CMOS gates) for switches, sustain and pedals.

Both channels then go through their individual filter sections containing two types of circuitry. The first filter accepts the 'raw' signals produced by the keying circuits and shapes the preset voices. The second filter produces a sine wave from keyed frequencies to make the 'Stage Piano' voice. One active filter is used on octaves 1, 2 and 3 with separate filters on the rest.

Right hand controls.


The channel outputs are finally treated by separate VCFs before going to pre-amps containing volume and tone controls (also noise gates). The S2000 takes these signals to two hybrid amplifier modules and a relay is used to effect switching to headphones.

Performance Features



Playing the Pianostar for the first time at Wersi's superb showrooms in Germany, I was immediately impressed by its stereo image received. The wide spacing of the speakers that are powered by 2 x 100 Watt amplifiers gave a surround sound stereo piano that was truly exciting. The maximum power output seemed overrated but did give enough bass to shake the ceiling at home and would be plenty for regular gigging in restaurants and hotels.

Like the best electric pianos, it uses two-oscillator tuning to achieve its harmonic modulation similar to a piano's vibrating strings. But it uniquely provides de-tuning at set degrees from a single control. Besides giving the very slight pitch differences required for de-tuning to produce the superb stereo 'chorus-like' effect, without which the notes sound dull, it also enables automatic tuning for each preset as well as interval separation of the third, fourth and fifth between the left and right channels. The potential of these larger intervals is great with solo monophonic playing, especially jazz, but its use in polyphonic music is restricted to bell like effects and complex note clusters for the more avant-garde experimentalist.

Coupled with instant pitch transposition for putting a piece into any key - ideal for accompanying trumpets, clarinets and saxophones with music all in the same pitch - the 'Slalom' slider gives polyphonic glide down an octave and 'Hawaii', at the touch of the left foot pedal, gives that well-known semitone glide up to the note. In addition, this pedal can operate Vibrato (slow/fast, heavy or light) while the right pedal gives the expected sustain.

Envelope shape board taken from mounting rack.


An interesting feature, situated with these controls at the left end of the keyboard, is filter control. A low pass filter can be modulated using its Speed control to give a continuously changing tonal effect set by Resonance, Frequency Cut-off and Amplitude (depth of modulation) controls. At slow speeds this creates deep swirling qualities associated with polyphonic synthesisers and at higher speeds produces tremolo and wah-wah, that can be made to 'bubble' at maximum Resonance and Speed. A button also selects 'Keyboard follow' for the filter, opening it up on progressively higher notes and interesting on a sequence of low to high chords for its sudden tonal changes. A combination of vibrato and filter modulation on piano tones gives some pleasant vibraphone effects.

There are eight presets that produce distinctive percussive tones: the Rock Piano is bright on top but thinner on bass; the Stage Piano is the most mellow and nearest to classical piano except in the lowest registers which tend to be lacking in bright harmonics; the Kinura has boosted high harmonics to give a great punchy and penetrating sound; Banjo is really banjo - even the action of the piano seems different (through envelope keying) - but you'll have to do strumming yourself by rapid reiteration (hard work!); Harpsichord and Cembalo (the latter couples two octaves of Harpsichord) are very authentic; Honky-Tonk puts the de-tuning to maximum use (incidentally, all detuning is set appropriately for each preset on normal 'automatic' setting) for all pub piano enthusiasts; and Piano gives a brighter overall sound compared with Stage Piano.

During playing, it's better to stick to one preset for classical music choosing Stage Piano or Harpsichord more frequently than the rest, but for modern music the choice of tones (including mixed combinations of presets) make the instrument very satisfying to play.

Each preset button has an LED indicator built in and a similar set of buttons control Octave coupling as well as Hawaii, Vibrato and VCF.

Pianostar T2000


Finally, the right hand controls provide total Volume setting for the built-in amp/speaker system or stereo headphones, Bass boost and Tape playback level, with on/off switch, 5-pin Din record/playback for stereo tape and headphone jack socket close by. The tape facility is ideal for electronic music recording and also allows you to play along with any accompaniment.

The cabinet is factory made with a well polished wood veneer finish and tasteful speaker cloth. No castors though - you have to slide its quite heavy weight on glide buttons. You'll never open the lid to see inside, for the whole of the back's thick hardboard panel unscrews instead. The electronics construction has been well thought out, with the main rack section and the keyboard sliding out for easy access. Circuit boards with clear legends take components supplied in labelled packs and the assembly manuals have enough information for all but the most inexperienced constructor.

A portable version, the Pianostar T2000, is also available without amps and speakers. The keyboard range is reduced from seven octaves to six and the cabinet is finished in black rexine and a heavy moulded plastic material. This version measures 26 x 52 x 112 cms and comes with stand and separate pedal unit, whilst the upright model is 102 x 58 x 145 cms.

Conclusion



Probably the best way to make a final assessment is to try the Pianostar yourself at one of Wersi's showrooms or listen to it being played by their expert German demonstrator, Hady Wolff on E&MM's Demo Cassette No. 3.

My criticisms are few - low notes tend to be a little woolly on Stage Piano, which is generally a very usable rich sound; the lowest octave with non-piano presets like Cembalo (using added low octave) is best avoided and, in any case, would not be part of the range of its original instrument. Slight transformer buzz was completely solved by reseating it in its case and the only playing problem was in avoiding transient clicks from preset buttons by switching them when keys are released (and sustain off).

The upright piano model S2000 kit represents best value at £1,273.00 (inc. VAT) with complete cabinet and built-in amplification. The portable T2000 is £1,225.00 (inc. VAT) with 5 Watt stereo monitor, headphone, and preamp outputs. Ready made prices are £2,102.00 and £2,038.00 respectively.

The instrument gives a lot of pleasure by virtue of its variety of sounds and will be an ideal compliment for any lounge, be it a family living room or hotel, and a versatile electronic instrument for professional or home recording studios.



Previous Article in this issue

Working with Video

Next article in this issue

Organ Talk


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

 

Electronics & Music Maker - Jul 1981

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Piano > Wersi > Pianostar

Review by Mike Beecher

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