Alesis MIDIverb II (1987)
16-bit rackmount reverb and multi-effects processor with 99 presets, MIDI control, and a distinctive 1987 digital character
Overview
The Alesis MIDIverb II is a 19-inch rackmount digital effects processor introduced in 1987 as a budget professional reverb. It has 99 preset effects: 29 natural reverbs, 10 gated and 10 reverse reverbs, 20 echoes, 10 flanges, 10 choruses, and 10 miscellaneous programs. The "Bloom" effects (Programs 45 and 49) are the famous ones. Alesis claimed other affordable processors couldn't produce them. The unit sounds characterful and slightly hissy, often described as "glued and greasy" with an analog-like feel. It was praised for its near-perfect MIDI implementation, instant recall via MIDI or front panel, and ease of use. It followed the original MIDIVERB and Microverb and was succeeded by the Midiverb 4, though later Alesis FX units did not replicate its sonic character.
Specifications
| Year | 1987 |
| Bit Depth | 16-bit linear PCM |
| Bandwidth | 15kHz |
| Channels | 2 |
| Analog Inputs | 2 |
| Analog Outputs | 2 |
| MIDI Inputs | 1 |
| MIDI Outputs | 1 |
| Preset Effects | 99 presets plus defeat |
| MIDI Patch Locations | 32 |
| Dynamic Range | 85dB |
| Distortion | 0.1% |
| Input Impedance | ~1 Mohm per channel (500k ohms in mono) |
| Input Signal Level Range | -10 to +20dBv |
| Power Requirement | 9V AC adaptor |
| Microprocessor | 8031 |
| Microprocessor Clock Speed | 8 MHz (early units), 12 MHz (later units/factory mod) |
| DSP Chip Clock Oscillator | 16 MHz |
| Internal Chip | Custom-built VLSI chip clocked at 8MHz |
| On-board NVRAM | Xicor X2444P with 32 bytes storage |
| NVRAM Data Retention | 100 years |
| Op-amp Chips | TL084 (early units used LF354) |
| Reset Circuit | 4.7uF capacitor, 10k resistor |
| Format | 19-inch rackmount |
| Electronics | Analog Digital Solid State |
Design
The MIDIverb II uses a 16-bit processor. The front panel is simple: three knobs (Input, Output, Mix), 14 rubber pushbuttons, and an LED display. The rear panel has stereo ¼" input/output jacks, MIDI In/Thru, and a footswitch jack marked Defeat. Power comes from a 9V AC adaptor. Early units use a 3.5mm jack and later ones a DC barrel jack, though it's still AC. Inside are a DSP chip, A/D and D/A converters, small blue film decoupling capacitors, and a power supply board that can be recapped. The reset circuit is a basic RC design (10k resistor, 4.7uF capacitor) and is known to be less reliable. Later Midiverb III units improved on it. The PCB in later versions has separate oscillators for the 8031 microprocessor and the DSP chip. The analog and digital circuits are noted as reliable, but the front-panel potentiometers wear with use, especially the Mix control.
Context
The MIDIverb II followed the original MIDIVERB and Microverb and became a popular inexpensive reverb in the 1990s, especially in home studios. It is associated with the sound of My Bloody Valentine's "Isn't Everything" era and 90s electronica. Later Alesis FX units lacked its character, and the Midiverb 4 is considered its worthy successor. The "Bloom" presets are often cited as a unique reason to own one. It is favorably compared to a Lexicon PCM70 at a fraction of the cost. It pairs well with gear like the Roland SH-101 and shares sonic similarities with the Yamaha REV100.
Market
The MIDIverb II has turned up on the second-hand market for as low as $40 to $100, with one repair unit noted at £30 in 2020. Common problems start with the PSU capacitors, which leak or lose capacitance and cause hiss or erratic behavior. Replacing them often fixes it. Bad tantalum capacitors can overheat and discolor. They can also keep the overload LED on, stop effects from passing, or introduce hum. Small 0.1mfd blue or yellow capacitors are known to short and burn through copper traces. The repair is to replace the cap and bridge the trace. The simple reset circuit can lead to unreliability. Recapping the power supply is a common service. Take care not to pull vias or install capacitors backwards. A hardware reset may be possible by holding buttons during power-on.
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