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Wireless MIDI Piggyback

Tired of being tied down by MIDI cables? With the aid of a radio mic system, MIDIman's unique TransMIDI lets you transmit MIDI data over the airwaves. Paul Ireson gets a taste of freedom.

MIDIman's TransMIDI system is, I think, unique in being the only means of transmitting MIDI data via a wireless audio link. Though forcing MIDI data through such a system imposes certain limitations, it brings the single major benefit of freedom — used with a suitable sling-on keyboard, a keyboard player will have the same on-stage freedom of movement that has previously been the domain of wireless-equipped guitarists. Prince has a TransMIDI built into his custom remote keyboard controller, and if it's good enough for Him, then it looks a good bet for the rest of us mere mortals.

There are two components to the MIDIman hardware: a cigarette packet-sized transmitter, powered by a 9V cell, and an adapter-powered receiver. The former converts the MIDI datastream, received at its MIDI In socket, to an audio signal which is output via a quarter-inch jack socket. That's all there is to the transmitter, apart from an on/off switch: the only other thing you need to know about it is that you can expect about eight hours of continuous operation from a regular battery. The receiver is responsible for converting the audio back into MIDI data — it features a Data In jack socket for audio hook-up, plus a MIDI Out and a MIDI In which is merged internally with the reconstituted MIDI data. With a wireless transmitter/receiver system to carry the audio from one half of the TransMIDI system to the other, you're in business.

Given that the audio source from the TransMIDI 'transmitter' (a misnomer really, as it's an encoder rather than a transmitter) is fed through a jack socket, a guitar transceiver setup is ideal. I tested TransMIDI with a Sennheiser SK2012 transmitter and a Mikroport EM2003 receiver, which proved totally reliable, and eminently suitable. You should be able to use a wide range of wireless equipment with TransMIDI, the main requirement being an audio bandwidth of 15kHz or so (TransMIDI's carrier signal is around 12kHz). MIDIman recommend that you avoid any system using dbx or other noise reduction, as this may phase shift and corrupt the data. The range of the whole system will be determined by the range of the wireless system that TransMIDI is hooked up to, so if the wireless system has a range of 100 metres in regular use, then it will have a range of 100 metres with TransMIDI.


In a word, yes. I plugged my 2-octave Novation portable keyboard into the TransMIDI transmitter, plugged that into the Sennheiser transmitter, and secured both of them to a guitar strap (the Novation has lugs for attaching one). I then plugged the radio receiver into the TransMIDI receiver's Data socket, and replugged the MIDI lead that usually comes from my master keyboard's MIDI Out to the TransMIDI MIDI Out. I turned everything on, adjusted the audio level from the Sennheiser receiver to ensure optimum 'intelligibility', and that was it. I might as well have had a direct MIDI connection from the Novation; there was no noticeable delay with note triggering, and modulation, pitch bend, and patch change data were all handled by the system with ease, as I strolled around my flat indulging in half-hearted Jan Hammer impersonations.

Relying on a 12kHz audio carrier does impose some limitations, however. Although you can transmit SysEx data over TransMIDI, dumps can be no longer than 128 bytes in length (in layman's terms, that's equivalent to 'pretty damn short'). TransMIDI cannot cope with a 'full' MIDI datastream for sustained periods, and may need to spread events out in time in order to get them through TransMIDI's own compression tricks. So if, for example, you are transmitting performance data which includes complex chords on several channels, all playing on the same beat (or as near as makes no odds, given that MIDI is a serial protocol, and the notes will therefore be slightly 'smeared' in time), the notes may be slightly 'arpeggiated'.

In order to minimise any problems that this might cause, you can first ensure that no unnecessary data is being carried and therefore clogging up the system. MIDI clocks can be a major culprit, and extraneous controller and aftertouch data should also go. (You can also prioritise parts by MIDI channels, and put time-critical parts on 'priority channels'. Normally, that means shifting drums and bass onto channels 1 and 2, because if a sequencer is told to transmit notes on all 16 channels simultaneously, it will transmit the channel 1 notes, then channel 2, and so on in numerical order. TransMIDI, however, takes account of sequencing convention and prioritises channel 10 over channel 1, so you can leave your drums on 10.)


Having said all that, I'm hard-pressed to think of a real world situation where you would want to transmit very dense MIDI data over a wireless link. The only point in replacing something as simple as a single MIDI lead with something as complicated as a wireless MIDI piggyback system is so that you can prance about on stage. TransMIDI is more than up to the task of handling as much complex soloing as you can. Although I can't imagine wanting to send the output of a sequencer over the airwaves, I daresay somebody out there can, and MIDIman are to be commended for accommodating their demands.

To return to the connections on the TransMIDI receiver for a moment, specifically the MIDI In — the point of this connection is that you can use TransMIDI in parallel with another, probably fixed, controller. So, when incorporating TransMIDI into your live rig, you don't need an additional MIDI merger. Instead you just connect the TransMIDI receiver between your regular master keyboard and your rack/MIDI patchbay (master keyboard Out to TransMIDI In, TransMIDI Out to rack/patchbay In), and you're in business, with both controllers merged.

A niche product if ever there was one, TransMIDI carries out its one specific task with ease. Whilst its profile has been low — there is, after all, a very small demand for gear such as this — you'll certainly know whether or not you have a need for TransMIDI. If you do, it won't disappoint.

Further information

MIDIman TransMIDI £419 inc VAT.

Zone Distribution, (Contact Details).

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ART SGX-LT Multi-Effects

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Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Sep 1992

Gear in this article:

MIDI Utility > Midiman > TransMIDI

Review by Paul Ireson

Previous article in this issue:

> ART SGX-LT Multi-Effects

Next article in this issue:

> Sample Shop

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