DigiTech RDS-1900
A rack delay from the DOD era that traded bandwidth for time.
Overview
The RDS-1900 is one of those pieces that tells you exactly what it is the moment you look at the spec sheet. Fifteen kilohertz of bandwidth, roughly two seconds of delay, and a price that sat in the middle of DigiTech's early RDS line. It was a mid-range model in a family that also included the RDS 900 and the RDS 3600, and the way the three were positioned says a lot about how DOD Electronics thought about the digital delay market in the mid-1980s.
DigiTech's own advertising described the RDS series as "the finest in state-of-the-art digital technology" and promised "the ultimate in digital delay systems at completely affordable prices," inviting direct comparison with the competition (Modern Recording, February 1986, p.15). That's marketing copy. The prices are the better evidence, though manufacturer documents conflict. They list the RDS-1900 at either $299.95 or $599.00, the RDS 900 at either $259.95 or $539.00, and the RDS 3600 at either $399.95 or $769.00.
The RDS-1900 forced a trade-off. The 15 kHz bandwidth was respectable for the era, and it let the delay handle full-range material without the dull, muffled sound of cheaper digital delays. You paid for that bandwidth in delay time. Two seconds was the ceiling. The RDS 3600 could stretch to over seven seconds, but only by dropping all the way down to 4 kHz. Digital delay memory in the 1980s was expensive, so you picked your compromise. The RDS-1900 was for players who wanted their echoes to sound like echoes rather than lo-fi artifacts.
Studio Sound (October 1986, p.86) ran a user report on the DOD digital delay line that touched on the practical realities of operating these units. The reviewer, Dave Foister, noted that timing was crucial when working with the delay, and singled out a "Delay Kill" function that did exactly what its name promised. He also observed that the function would have been more useful duplicated on the front panel — a fair criticism of an era when rack units often buried their most useful controls behind footswitch jacks. That kind of detail is worth noting because it speaks to how these units actually behaved in use, not just how they looked on a spec sheet.
DOD Electronics, the parent company, was building a full line of digital delays at multiple price points and delay times. The RDS 900 offered 8 kHz bandwidth and roughly one second of delay, priced at either $539.00 or $259.95 depending on the manufacturer document. The RDS 3600 offered the same 15 kHz bandwidth as the 1900 for two seconds, but could also drop to 8 kHz for four seconds or 4 kHz for over seven seconds. It was priced at either $769.00 or $399.95 depending on the manufacturer document. The RDS-1900 sat in the middle with full bandwidth, moderate delay time and a mid-range price. It suited someone who needed clean repeats and didn't need walls of ambient wash.
By the late 1980s, the RDS series was showing up in dealer listings alongside much more expensive studio gear. A 1985 Studio Sound classified section listed a used RDS 1900 at £245, in the same column as Lexicon reverbs and AMS units costing thousands. It was a working tool, not a prestige piece, and the price put it within reach of musicians who couldn't afford the high-end studio delays.
A later DB Magazine listing from July 1987 describes the RDS 3.6, a related model, as offering up to 3.6 seconds of delay at half bandwidth. It also lists chorusing, vibrato, doubling, echoes, multiple echo, and flanging. The RDS-1900 shared the same basic design philosophy, even if it didn't have all those modulation options.
For collectors today, the RDS-1900 is a curiosity more than a grail. It dates from when digital delay was becoming affordable for working musicians but hadn't yet been commoditized into the pedalboard stompboxes that would dominate the 1990s. The 15 kHz bandwidth still holds up for most applications, and the two-second delay time is enough for slapback, doubling, and moderate ambient effects.
The caveats are the usual ones for gear of this vintage. These units are now decades old, and the digital memory and conversion circuitry of the mid-1980s was not built to last forever. The Studio Sound review noted that the Delay Kill function has no front-panel access, which is still a minor annoyance. The two-second maximum delay time is limiting by modern standards.
The RDS-1900 wasn't designed to compete with modern delay units. It was designed to give musicians clean digital delay at an affordable price. The 15 kHz bandwidth was the headline and the two-second delay was the compromise. The price was $299.95 or $599.00 depending on the document.
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