Electronic keyboards, the start of it all. Right from the beginning of modern concert sound, DI boxes have played an essential role in getting the sound from the stage to the PA system.
Probably the most iconic “direct” instrument of all was the Fender Rhodes. Harold Rhodes started developing the idea as far back as the 1950s, but it was in 1970 that the Rhodes Stage piano took the concert stage bringing the first “portable” keyboard to market.
The original Rhodes piano tone was created by a piano-like hammer striking a “tine” that would vibrate up and down in front of a magnet to create the tone—very much the same way an electric guitar string vibrates atop a magnetic pickup. One would adjust the tone by changing the “tine-to-magnet” relationship.
And like an electric guitar, the output from the suitcase was not amplified (or buffered) in any way. So the output from the piano was generally sent to a guitar amp where it was mic’d.
Some years later, the first active DI boxes came round. They didn’t load the Rhodes pickups, which made it practical to send the “direct” sound to the PA system and monitors.
But something happened. That something was Keith Emerson and Rick Wakeman, and the Moog synthesizer, which found its way out of the electronic music department to the stage. These guys no longer had one or two keyboards—they had racks of them!
An early Fender Rhodes, the one that started it all.
The Arp 2600 and String Ensemble, Oberheim, Korg, the venerable Sequential Circuits Prophet 5 - it was an analog explosion. Everyone had a Rhodes (or Wurlitzer) and a bunch of synths.
Fast forward to 1981, and Yamaha introduced the DX7, which would go on to become one of the most successful keyboards ever. It brought along something totally new: frequency modulated digital technology. Now you could get a bell-like Rhodes sound without the weight.
The world then changed again with the E-MU and the Akai S900 digital sampler. All of a sudden, we had complete orchestration, real sounding piano samples, and digitally sampled drum tracks were everywhere. There was no going back.
Today, pretty much all keyboards and drum machines are digital, and can basically be thought of as keyboard controlled CD players. And like a CD player, the output from a digital synthesizer is relatively powerful when compared to an electric guitar or an old Rhodes piano.
Because they’re so “loud,” they needed headroom to operate, meaning that the old active DI box that may have been a boon to the low-output Rhodes piano can no longer keep up.