Steve Chick's MIDI Bass

Started by Elantric-fgn, March 06, 2010, 11:37:53 PM

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Midi Bass Performance

The Midi Bass consistently provides highly accurate, low latency MIDI tracking, at approximately 5mS for fixed velocity tracking; and typically 8mS for dynamic velocity tracking on all notes. When we refer to the latency of the Midi Bass here, we are specifically referring to the time it takes for the Midi Bass to analyse and output MIDI data. To gain some perspective, consider that sound travels through air at one foot per millisecond, so an additional 8 milliseconds of latency is akin to standing 8 feet further away from your speaker cabinet.

The performance of the Industrial Radio Midi Bass is made possible by the unique, wired-fret approach to MIDI tracking. This system utilises multiple sensors integrated into the bass which include the wired-fret neck construction, tension sensing bridge pieces, and piezo bridge saddle pickups.
Sensor Overview

When you play the Midi Bass, the onboard electronic sensors detect that you are playing, and generate a parallel stream of MIDI data that mirrors your actual bass performance. The fret-sensing fingerboard tells the Midi Bass what note you are playing, strain gauges in the bridge measure string bends, and the piezo bridge saddle pickups measure the dynamics of the string. The Midi Bass continually monitors all these sensors and translates your playing to MIDI.

Basic MIDI messages are comprised of note on, note off, note number, velocity/dynamics and pitch wheel. The Midi Bass' computer constructs the midi output messages from its sensors in the following manner:

    * Wired Frets = MIDI note number
    * Bridge Strain Gauge = Midi Pitch wheel
    * Piezo pickups = MIDI note on, MIDI note off  and velocity/dynamics

Fret Sensing Fingerboard

Each fret is split / electrically isolated into 4 seperate fret segments and is wired with an array of resistors. The fret segments tell the bass where you are fretting the string.

Tension Sensing Bridge

The Midi Bass bridge is comprisied of 4 individual pieces. These bridges are constructed of a spring steel that allows for a small amount of flex. An electronic sensor called a strain gauge is fitted on the back of the bridge pieces. These sensors measure the tension in the bass strings. From this tension information the pitch bend of the string can be accurately calculated.

Piezo Bridge Saddles

The Midi Bass uses Graph Tech "Ghost" piezo saddles. The output of the piezos are then processed by special, low frequency pre-amps. This results in a very distinct transient voltage output. The dynamic pressure of your fingers on the strings is actually monitored.

Stringed instrument midi controllers live or die by their latency, so how does the Midi Bass stack up?

Despite the release of several different designs of stringed guitar style midi controllers over the last twenty or so years, development of the Midi Bass has continued to be pushed forward because none of these alternate systems has delivered a real bass that solves the latency challenge.
What is Latency?

The definition of latency is "the period of apparent inactivity between the time the stimulus is presented and the moment a response occurs." In relation to midi controllers, latency is the period of time that elapses between the performer playing a note (stimulus) and the target midi instrument playing a sound (response), Basically we're talking about an unwanted delay between your playing and hearing a note.

Before we go any further, please consider the instrument we're dealing with here - Bass. One of two elements integral to the rhythmic components of most music genres. The natural enemy of rhythm is unwanted delay / latency. Low latency is absolutely essential in a bass instrument. In tests, the Midi Bass has exhibited a low and (importantly) consistent latency.

A Midi Bass / Nord Micro Modular setup shows latency in the order of 6 milliseconds for fixed midi velocity messages and 9 milliseconds for dynamic midi velocity messages. Note that the Micro Modular synth contributes about 1 millisecond of the latency.

To gain some perspective, consider that sound travels through air at around 1 foot per millisecond, and an additional 9ms of latency is akin to standing 9 feet further away from your speaker cabinet.

Here are 3 pictures we captured from a PicoScope digital scope connected directly to the magnetic output of the bass and the output of the Nord synth. The Blue trace is the magnetic pickups of the Midi Bass. The grey trace is the audio output of the Nord Micro Modular synth.

First the low E on the Midi Bass using fingers

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