ROLAND D-550 (1987)
Linear Module Synthesizer

Rackmount module expander of the famous Roland D-50 based on digital L.A synthesis.

The D50 synthesis engine is still considered today as one of the most interesting ever made LA synthesis, but it is not like a wavetable synthesizer, as no harmonic spectrograms are involved in, instead, it is based on short attack PCM transients for limiting memory usage. Psychoacoustic facts demonstrate that "attack" segment is the most important part for the sound identification by human ear.

RACKMOUNT a 2 standard units expander.
Main panel features a blue display and 36 buttons for sound edit

Back panel terminal connectors:
- Midi interface
- main signal out

Front panel terminal connectors:
- headphones out
- data card slot.

TECH main core is a 8-bits CPU CMOS UPD78312 manages 16 voices polyphony - relative DAC is a Burr-Brown model HP54HP. LA synthesis WG Wave Generator is a mix of 2 syntheses:

- 2 Digitally generated basic waveforms sawtooth & square wave, a kind of primitive VA - PCM wavetable

L.A STRUCTURE HIERARCHY L.A minimal part is the PARTIAL composed by 2 UPPER tones + 2 LOWER tones then 4 combined tones make a PATCH; TONE has value for relation between both partials and each partial is like an oscillator with various synthesis chain elements.

WG (voice) + TVF (filter) + TVA (amplitude)

WAVE GENERATOR is a 128 kb ROM (at IC29-30) PCM wavetable + a digital waveform generator. In total there are 101 sound waves available:

- 47 Transient PCM acoustic - 29 Transient PCM spectral loops - 23 Transient PCM normal loops - 2 digitally generated sawtooth and square wave

ALGORITHMS the WG combines partial synthesis elements with a digital ring modulator in 7 possible pathways or algorithms: (p= pcm sample / s= digitally generated wave)

ALG P.1 P.2 2 partials Combination diagram 1 S S mix partial 1-2 2 S S mix partial 1 + Ring modulator 3 P S mix partial 1-2 4 P S mix partial 1 + ring modulator 5 S P mix partial 1 + ring modulator 6 P P mix partial 1-2 7 P P mix partial 1 + ring modulator

PERFORMANCE parameter CHASE is a delay mode between the tones with 3 directions modes:

- Upper -> Lower - Upper -> Lower -> Lower - Upper -> Lower -> Upper PATCH can be played also with a legato with variable portamento time.

 

FILTER structure is based on the TVF -time variant filter- which is a digital 4-poles resonant lowpass filter.

TECH filter has a restriction: TVF does not act on a PCM element, later possible on V-synth D50 emulation. Hear Filter assigned to aftertouch

LFO 3 delayed modulators (shapes: saw, triangle, random and square) and 3 destinations:

- LFO to amplitude - LFO to pulse width - LFO to filter cutoff Hear LFo

ENVELOPE 2 main EGs, all partials have their own EG for both amplitude + filter, for a total of 4 TVF EGs and 4 TVA EGs:
- EG1 amplitude : 5 segments + 5 times
- EG2 filter : 5 segments + 5 times.

EFFECTS 2 dedicaed chips (87136+87137) handles 32 reverbs echoes + 7 chorus modulations + 1 simple serial -12 dB EQ with HIGH settings boost (250 Hz) or a LOW boost (63 Hz) + Q-emphasis.
Effect can be balanced with dry / wet parameter to different tones in 3 modes:

- mono tones with stereo reverb - stereo tones with stereo reverb - stereo Tones with reverb to upper or lower tone. Hear Reverb delay

MIDI quite basic but full MIDI exclusives is implemented with full support of edit and data dump.

MAINTENANCE after many year the display inverter usually fails resulting the LCD dark-grey; now there are some backlight replacement.

MEMORY
- 64 RAM internal patches
RAM is doubled if using cards m-256E or m-256D.
Battery replacement: a CR-2032 lithium battery in holder.

LEFT - Two different D550 boards, on the left an early version 1.0 with MKS550 script, not appearing the other, some PCM IC are piggybacked. - click for bigger pic comparison -

 

OS eprom, lastest is V.1.02

DOWNLOAD BIN FOR FREE AND F$$$ EBAY SCAMMERS

Related MODELS:

D-50 is the 61-keys keyboard version.	PG-1000 dedicated D50 programmer	VC-1 card is an emulation for V-synth
D-10 another member of the LA family.	MT-32 a kind of D-10 consumer version o	MEX EXPANSION board enhances D50 functions

 

 

EDITOR many computer-based softwares are available:

- D50 librarian (PC donationware) PIC - Soundquest (MAC/PC $$) - EMC D50 editor manager (Atari ST) PIC - Roland D50 parameter editor (Commodore Amiga) PIC - DR.T editor (Atari ST) - Synth works (Atari ST) PIC - D50 manager (Atari ST) PIC - CTRLR (PC/MAC free) PIC - D50v (VST editor) PIC - coffeeshopped (IOS editor) PIC

 

VST PLUGIN / SAMPLED VERSION there is no OFFICIAL D550 VST PLUGIN for computer, but some free and commercial samples set:

KR AUDIO

200 MB free SAMPLES

 

DEMO: advertising : 1 Famous: 1 - Demo: 1 Pad: 1 - 2 - 3 - 4 - 5 bell : 1 - 2 organ: 1 - 2 - Synth: 1 - 2 - 3 - 4 - 5 - 6 - 7 Bass: 1 - 2 Ambient: 1 Noise: 1

hires pic

MANUAL

SERVICE MANUAL

FACTORY SET + 5000 patch DOWNLOAD

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