• Korg Poly 61
  • Korg Poly 61

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Korg Poly 61



There is no doubt that Korg synthesisers from the Japanese Keio Corporation have reached a turning point which is marked by the appearance of the Poly-61. Nearly two years have elapsed since the production of the Polysix, although it is still a comparatively new instrument to the U.K.. and the change has been from this analogue machine to virtually total digital control on the new Poly-61.

The Poly-61 is a 6-voice programmable polyphonic synthesiser that stores 64 program settings and uses 2 oscillators for each voice. It also features fast 8 second tape interface for creating your 'sound library', chord memory, arpeggiator and a new style of 'digital access control' that is easy to use and dramatically reduces the number of controls required. At first glance, the Poly-61 may look rather limited, but it does in fact offer as much control as its analogue counterpart — with all programs and parameters set from three dual-digit displays using up/down and numbered pushbuttons.

Before proceeding, it is worth noting the low cost of this instrument as a result of the transition and reduced number of controls — the Poly-61 is £995 inc VAT, a saving of more than £200 over the Polysix, and a comparison of its facilities with other polyphonies will show it's very competitively priced indeed.

Presentation



Here's another change to the Korg line, with an overall light blue/grey satin-toned appearance. The cabinet is of wooden construction with plastic material covering ends and base. To the left of the standard 61-note (C to C) keyboard is a dark grey plastic panel housing the joystick. A slight rough edge at the front was noticeable here compared with the good finish elsewhere. The joystick is a new type for Korg — smaller than usual but perfectly usable.

The sloping rear panel in medium satin grey contains rear sockets (labelled conveniently on front panel top), power switch and cable winder. The rear panel and main front panel are made in one folded metal piece.

On the front panel, controls are neatly sectioned from left to right, with the current Korg knobs in grey/off-white two-tone finish and new momentary 'click' pushbutton switches (apart from 3 ordinary 2/3 way slide switches at far right), as follows: Volume, Joystick, Tune, Indicator Value, Programmer, Key Assign Mode, and Arpeggiator.

Above these sections are 'Program No.', 'Parameter No.' (both 2 digit ½" red LED displays), and 'Value' i.e. Indicator Value for parameter selected (2 digit ½" green display). To the right of these displays is printed the information for selecting the different parameters available (in red) and the value settings available (in green). The main legending is in soft blue with 'Tron' style square grids around the controls.

The instrument measures 110 (H) x 350 (D) x 985 (W) and weighs 12Kg. Supplied accessories are data cassette (64 factory-programmed sounds) and connection cord for tape recorder. Optional extras are hard case, stand, volume pedal, footswitch and stereo headphones.

Rear connections.


Rear Panel



From the performer's viewpoint, these are from left to right: Mono Output (with high or low switch), Stereo phones (8 ohms), Arpeggio Trigger In (for external control from drum machine, computer or sequencers etc — Korg's negative going pulse-to-ground required, although the E&MM Trigger Interface box or Korg MS-02 interface unit will match up any trigger), Release (gives release parameter only when inserted momentary foot-switch is pressed to add piano-like sustain pedal effect), Program Up (advances program number one step via momentary footswitch). Tape Interface switches are also located here for 'Tape Enable' and 'Write Enable', along with Tape 'To' and 'From' sockets. All sockets are standard jack types.

Circuitry



The main panel swings back for quick servicing, although full access to the PCB's requires removal of keyboard section. There are 3 main PCB's on the base, with left board containing dual 8049 micro processors, 8255 x 3 peripheral interface, 8253 x 4 etc. plus battery back-up. The centre voice board features 6 SSM 2056 IC's and the right board contains +/-5V, +15V power supply. Extra boards are provided for joystick and modulation as well as the 3 panel-mounted PCB's holding pots and switches. Rear panel jacks are sealed PCB mounted types.

Programming



Once you've connected the Poly-61 output to your mixer/amplifier set-up and powered up, the display reads PS61 (!) followed by Program No. 11, Parameter 11 and an arbitrary Value No. A volume control lets you match output level to your system, and both Write and Tape rear switches are set to 'disable'.

The Programmer section allows 64 different sounds to be stored in the instrument's memory and at any time these can be saved as a complete set on standard mono cassette recorder. Programs are dialled up using 8 switches numbered 1-8. Since the instrument controls are either for changes to programs or parameters, two switches to the right of these select either Program or Parameter, followed by a red Write switch which enters new programs you've created.

So to get Program 21 you press 2, then 1 and this will be displayed in the Program No. display. If you get it wrong, you can easily change the number around. Programs are grouped in 8's, so you'll only get 11-18, 21-28, through to 81-88 for the total 64 programs. The Poly-61 comes with factory-loaded sounds that are fully listed in the large instruction manual. These contain a good selection of sounds and you'll hear samples on E&MM Demo Cassette 9. In performance the instrument offers quick switching from one program to the next and, since you can arrange sounds in the required order for each piece easily (without losing any existing programs), a touch of a button (or footswitch in Program Up socket) will call these up instantly. Changeover is very smooth and can be done whilst playing.

Joystick and left hand panel.


Editing



To create a new sound of your own, you select a program near to the sound you want (or any suitable program number). All editing is 'temporary' until you actually 'Write' it into a program. The actual number you select this to be does not have to be the location you're working at, e.g. Program 21 can be edited and then stored in Program 31, leaving the original Program 21 intact. This is a very useful procedure in practice.

Editing is carried out by selecting 'Parameter' mode and choosing one of the 20 parameters available using the 8 numbered buttons (in the same way as locating a Program number). The Indicator Value Display will then show your setting as you use the down or up buttons below it. An interesting feature here is the red 'Edit' LED that glows only when you've changed an existing value, so it's easy to find original settings. Pressing both Up and Down buttons together restores the original parameter value.

This 'digital access control' can be carried out for all 20 parameters one at a time and takes only a second or so to make a parameter edit — there lies the big difference between analogue and digital control and may take some time to get used to. You'll also have to wait for the up/down switches to reach the required value. Like Korg's new digital delay, they run slow at first then more quickly when held on.

Since all parameters, except one, cover a maximum 15 values, it's quickly done. The exception is Frequency Cutoff, which takes some 5 seconds to go from 0 to 63!

Writing a program to memory is probably as quick and easy as you'll get. With rear Write switch enabled, pressing the Write button and selecting a program number is all you have to do.

Even though battery back-up (with power off) can hold your 64 programs (provided you use the instrument for a few hours each year), another most useful feature is to be able to store your sounds on cassette. Tape transfer is a very fast 8 seconds with little possibility of error. The displays show TAPE, LOAD, SAVE and VRFY to indicate load, save and verify functions. An error is shown by ERR and correct transfer by GOOD.

Parameter and Program section.


Parameters



Using the digital access control system as explained, the following parameter sections allow you to synthesise your sound (or make changes to existing programs): DCO1, DCO2, VCF, EG, VCA, and MG.

Unlike the Polysix and Mono/Poly, the Poly-61 uses new digital controlled oscillators (DCOs). These are very stable in use and the circuitry does not give any pitch drift. Since 12 DCOs are used (2 for each note played normally), any detuning between oscillators is held constant, unlike other VCO type instruments (Memorymoog, Chroma, etc).

Incidentally, parameters are logically numbered in tens, from 11, 21, to 61 for each section. As sections have one or more parameters available, you can't dial a wrong number — the system ignores you! It'll take a few hours to get to know the numbers, but after that VCA is always 51 and soon! Korg have scored here by putting clearly marked parameter labelling in full on the panel in case you forget.

DCO1 has 3 parameters available: Octave 4', 8', or 16'; Waveform — Sawtooth, Square and variable pulsewidth; PW/PWM which alters square wave to pulse or depth of pulsewidth modulation from 0 to 7 values.

DCO2 has Octave 4', 8', 16'; Waveform — off, sawtooth and square; Interval — this offsets DCO2 pitch from DCO1 to give minor 3rd, Major 3rd, perfect 4th and 5th intervals as well as unison; Detune — gives fine pitch adjustment between the 2 oscillators (that you play on each note) for honky-tonk, chorus-like fat sounds. Incidentally, no zero setting is given (there's always phase shift present) and the range is up to 50 cents (¼ tone).

The VCF uses new voltage controlled filters that are 24 dB/oct low pass types. Controllable parameters are Cutoff (0-63); Resonance (0-7) which does not go into oscillation; Keyboard track (on/off); and EG Intensity (or depth).

Only one EG is available to modify filter and amplifier sections. This has the standard ADSR parameters (0-15 value setting). Maximum times are Attack 10 seconds, Decay 23 seconds and Release 20 seconds which are adequate for most synthesis.

The VCA section has a value change for either EG or on/off (organ touch) selection. Finally the MG (Modulation Generator/LFO) has frequency (0-15) from 1 cycle every 3 seconds to 20Hz approx., and Delay (0-3) settings that modulate DCO pitch, DCO1 PWM and VCF Cutoff Frequency (with DCO and VCF (0-7) depth values). Pitch vibrato and tonal wah-wah etc. can be obtained with the MG.

Poly-61 opened up.


Performance Controls



The Poly-61 has plenty of polysynth features to make your performance more enjoyable. The joystick is an established favourite with Korg and offers four way control for pitch +/-7 semitones (horizontally) and vibrato depth or filter depth (vertically). Joystick rotary pots set Bend limit and Frequency rate (independent of MG) with LED indication from 1 cycle every 8 seconds to 10Hz approx. A Tune control sets overall pitch +/- 1 semitone. Three Key Assign modes are available: Poly, Chord Memory/Unison, and Hold. In Poly mode, six independent notes can be played on the keyboard, with last note priority as you play more notes. Chord memory unison lets up to 6 notes be 'memorised' and then played from any one key at the correct transposition — great for parallel tones jazz or drawbar style. Unison makes big fat 'six voices to one note' playing (mono). The Hold switch keeps notes playing after release — particularly useful in Arpeggio mode.

The Arpeggiator is now a standard feature on poly machines and this one triggers notes held (either chords or unison) once every 26 seconds to fast 6 notes runs every ¾ second or so. The range of the Arpeggio will be the same as the keyboard span for the current DCO pitch setting, so 'C' has 6 notes to use — others have what's left! Arpeggios run up, up/down or down over full keyboard, 2 octaves or 1 octave. You can add notes to your arpeggio provided you don't make a 'fresh' key press, and use external triggers as mentioned.

Conclusions



If you make comparisons between the Poly-61 and the Polysix (and other polysynths), you'll find it's a winner for its price. Sound making possibilities are plentiful, especially through the use of two oscillators per note, although you'll have to decide whether one EG is enough. There is no noise generator — an important omission if this is going to be your first polysynth, but its light weight, good looks, wide-ranging sounds plus unlimited program storage and low cost should make it a very popular 'new look' instrument.


Also featuring gear in this article

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Browse category: Synthesizer > Korg



Previous Article in this issue

Tokai Flying V

Next article in this issue

Concert Review


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

 

Electronics & Music Maker - Mar 1983

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Synthesizer > Korg > Poly 61


Gear Tags:

Analog Synth
Polysynth

Review by Mike Beecher

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