Klark Teknik DN 70
A British digital delay with a claimed 90 dB dynamic range and a 50 kHz clock, plus a mains fail-safe that straps the outputs straight to the input.
Overview
The DN 70 is a digital time processor - a rackmount delay line with one input and four outputs. Its numbers would have raised eyebrows in any control room. Klark-Teknik built its own analog-to-digital converter in-house rather than buying one in. The claim was a full 90 dB of dynamic range, with noise performance the company was happy to put in print. Three delay options were offered: 163 ms, 326 ms, and 652 ms. The 652 ms version was a big job. Klark-Teknik's own literature says it uses 28 × 16K-bit random access memories to hold that much delay.
The converter ran at a 50 kHz clock. That is what let the unit hold a 30 Hz to 15 kHz frequency response even at maximum delay. The digital word was described as quasi 15-bit - a 12-bit linear converter with a 2-bit instantaneous flying comma system, meant to push quantizing noise down to negligible levels. You can take or leave the "virtually eliminated" language. The design was clearly aimed at the professional user rather than the hobbyist.
Connectors are all XLR three-pin, one input and four outputs. Outputs A, B, and C are the straight time delays. Each has its own front-panel digital readout in milliseconds, and they are meant for compensating natural time delays in multiple-speaker installations. The fourth, the mixed output, is where the DN 70 becomes an effects unit rather than a delay line. It gives a continuous mix of the delayed signal from A, B, and C. Regeneration and Direct/Delayed Pan controls on the front panel work alongside the individual output levels. Together they give multiple-repeat effects with independent control over each delay's level.
Two features are aimed at permanent installation work. The first is a perpetual memory of delay settings, so a semi-permanent setup survives power cycling without re-dialing. The second is a front-panel lockout control, reached with a common screwdriver, that prevents tampering or accidental re-setting of delay times. The third is the one engineers tend to like: a mains fail-safe that straps the three main outputs directly to the input if the power fails, so the signal path stays alive even when the box doesn't. Any output can also be momentarily set to zero delay without disturbing its stored setting. Input level is handled with a front-panel control and an LED headroom indicator. Internal input and output level presets can be adjusted for level matching and optimum signal-to-noise ratio.
The dating is a bit tangled. The unit was released at the A.P.R.S. '78, and by the following year it was being shown alongside the new DN 71 Controller - a low-cost add-on effects generator built to complement it - and the DN 34 analogue time processor. Studio Sound (August 1978, p.37) carried the launch advertising for the DN 70. It billed the unit as the first of a new generation of digital products from Klark-Teknik, designed for the discerning professional user. The same publication's July 1982 issue (p.85) still listed the DN 70 Digital Delay in the company's roster alongside the DN 22 and DN 27A equalisers, so the model stayed in the catalogue for a good few years. One period listing quotes the delay range as "up to 653 mS". That is a rounding of the 652 ms figure that shows up in dealer and show copy. Treat 652 ms as the specification.
The DN 70 turns up in the gear lists of working British studios of the period, and it was shown at the A.P.R.S. '79 exhibition with the DN 71 and DN 34. Klark-Teknik's reputation at the time rested heavily on the DN 22 and DN 27 graphic equalisers, which the company's own advertising was happy to call an industry standard. The DN 70 was the digital flagship riding on that reputation. The marketing copy was unrestrained: "years ahead of its time," "miles ahead of all its competitors," a performance "which cannot be beaten." That's advertising, not a verdict. What can be verified is the engineering: an in-house converter, a 50 kHz clock, 90 dB of claimed dynamic range, and a fail-safe relay arrangement that suggests someone at Klark-Teknik had been burned by a dead delay line during a show.
For a collector, the DN 70 is an early digital piece from a company better known for analogue equalisers. It shows a respected British signal-processing house going digital, with the odd workaround (12-bit plus flying comma) that implies. The 652 ms version, with its bank of 28 RAM chips, is the one to look for on sheer curiosity value. Condition matters more than usual here. The lockout switch, the internal level presets, and the fail-safe strapping are all things a previous owner may have "adjusted." The operator's manual, provided with each unit originally, is the only reliable guide to getting them back where they belong.
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