Roland MT-32

The Roland MT -32 is a MIDI synthesizer module, which was first sold in 1987 by the Roland Corporation.

  • 3.1 clipping
  • 3.2 Differential Linearity Error
  • 3.3 buffer overflows

Features

As with the Roland D -50 Linear Arithmetic synthesis, a form of sample-based synthesis combined with subtractive synthesis with the MT -32 ( Multi-Timbre ), used for sound production. Samples are used for drums and for the Attack phase, while the sustain phase is produced in the traditional way.

The MT -32 contains a library of 128 synth and rhythm sounds 30, which can be played on eight melodic and rhythm channel. He also has a digital reverb effect. Successor models (see below) expand the sample library by 33 sound effects. Since no piano -Attack Sample is available, the MT -32 can not produce a convincing piano sound.

As a full-fledged synthesizer is the MT -32, in contrast to simple wavetable devices, very programmable. A sound consists of four partials that can be combined in various ways (including ring- modulation). It can be a total of 32 partials available, the polyphony depends on the tonal complexity of the music, so that sound simultaneously between 8 and 32 notes.

The MT 32 does not play standard on the other popular MIDI channel 1 (and hence do so as little MIDI files, which have been written for the MT-32 ), but can be programmed in such a way as to have some degree of general to achieve MIDI compatibility.

Models

The MT -32 technology can be divided into three generations divide:

First generation

The first generation has no headphone jack. LA32 sound generator chip is a 80 - legged Pin Grid Array. Control CPU is an Intel C8095 -90. Digital -to-analog converter is a Burr-Brown PCM54 without optional setting potentiometer; its input signal has a resolution of 15 bits ( see below).

  • MT -32 Platinum Revision 0, used in devices up to serial number 851,399th

The PGA - LA32 - chip is later replaced by a flat 100 -legged type.

  • MT -32 with "old " board revision 1, used in devices with serial number 851400-950499.
  • Roland MT -100: A combination of the MT- 32 with the Roland PR -100 hardware sequencer.

Second generation

A headphone jack is added. Control CPU is an Intel P8098. The same digital-analog converter, however, the input signal has a resolution of 16 bits ( see below).

  • MT -32 with " new " Platinum Revision 1, used in devices from serial number 950,500th

After all compatible modules have 33 additional sound effect samples.

  • Roland CM- 32L: sound module for use with a computer (" CM " stands for " Computer Music "); only has a volume control, a MIDI message will disappear - and a power indicator lamp as external controls. Published in 1989.
  • Roland CM -64: A combination of the CM- 32L with the sample-based Roland CM- 32P, the " Computer Music " version of the Roland U- 110. Of CM- 32P - part playing on the unused part of the CM- 32L MIDI channels.
  • Roland LAPC- I: ISA -bus expansion card for IBM PCs and compatibles. If the MPU -401 interface.
  • Roland RA -50: Accompanying machine with integrated MT -32 sound module ( ROM module of the CM- 32L ).

Third Generation

The digital -to-analog converter is now a Burr- Brown PCM55, which factory is set ( see below). The vibrato is considerably stronger than previous models.

  • Roland CM- 32LN: sound module for notebook computers, the NEC PC-98 series; contains a special connector for direct operation on the 110 -wire extension jack on the computer. Released only in Japan.
  • Roland CM -500: A combination of the CM- 32LN with the Roland GS compatible Roland CM -300, the " Computer Music " version of the Roland SC -55. Published by 1992.
  • Roland LAPC -N: C-bus expansion card for the computer NEC PC -88 and NEC PC-98 series. Released only in Japan.

Problems with sound quality and compatibility

Clipping

The MT 32, and all the compatible modules using a parallel 16-bit digital-to- analog converter with a sampling rate of 32 kHz. To improve the signal to noise ratio without having to invest in higher quality components, the amplitude of the digital input signal is doubled:

  • In modules of the first generation by omitting Bit 14 ( the most significant bit ) and left shift the remaining bits to the left, thus reducing the effective resolution of 15 bits;
  • In later modules in that the LA32 sound generator chip itself generates digital waveforms of higher amplitude.

In both cases, this produces a loud noise distortion when sounds are played at high volume

Differential Linearity Error

The modules used in the first and second generation digital -to-analog converter, a Burr-Brown PCM54, requires an external adjuster ( though allegedly factory adjusted ) so as to correct the differential linearity error.

For cost reasons, built Roland no such circuit; for this reason, soft sounds a slightly metallic sound. This distortion is much more pronounced in the MT 32 of the first generation, possibly because bit 0 due to the bit shift (see above) is not connected; However, the effect is to listen to a lesser extent on models of the second generation.

In the third generation modules used Roland instead the factory adjusted Burr -Brown PCM55, which has almost no audible linearity errors.

Buffer overflows

The first generation with firmware versions below 2.00 units require a delay of 40 milliseconds between system exclusive messages. Some computer games, which have been programmed for compatible or later check - ROM versions do not work with such early devices and produce wrong notes or lead to a crash of the firmware.

Music for PC Games

The MT -32 has been extensively used in PC games in the late 1980s and early 1990s as a quality alternative to AdLib and Sound Blaster cards for the production of music and sound effects. Sierra On-Line was the first company, who supported him in their 1988's game King 's Quest IV; they also sold the module.

With the increasing popularity of the General MIDI standard and its reference implementation in the Roland Sound Canvas modules waned since 1993, support for the MT -32 in favor of the General MIDI standard, which has been used by many wavetable based sound cards. Instead of their own, especially to use for the MT -32 optimized sound and music data, programmed later games simply the sound library of the MT- 32 so that these coarse the General MIDI Level 1 specification, whenever the was MT -32 at all yet supported.

Emulation

Because of the popularity of the MT- 32 for music playback from PC games, many modern sound cards provide a simple " MT -32 emulation mode ", usually realized either through a SoundFont consisting of General MIDI instruments, which are arranged according to the standard MT -32 sound sequence, or by recordings of the original MT -32 sound. The result is often perceived as bad, because the sampling technology can not replicate the pitch - and time-varying characteristics of the original synthesizer technology; the programming of own sounds (see above) is also not supported at all.

An exception is the Orchid Soundwave 32 card, which was published in 1994 by Orchid Technology; their DSP enabled a more faithful reproduction of the original sound quality.

More recently, attempts to LA technology in software to emulate using the original PCM and control ROM. Significant is the open source project Munt, which tries to emulate the MT -32 hardware using a WDM driver for Windows XP; further, it is part of ScummVM. Munt is based on the previous MT -32 Emulation Project, which was the occasion for a brief legal dispute with Roland, the manufacturer of the MT -32, on the distribution rights of the original ROMs.

Polyphony and monophony in instruments Industry Standard Architecture MPU-401 Texas Instruments Ad Lib, Inc. Wavetable synthesis
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