Klark Teknik DN-30

Two channels of 1/5rd octave graphic EQ in one rack space — and when the power dies, the signal doesn't.

Overview

The DN30/30 — sold in some markets as the DN-30, and known in Klark Teknik's own literature as the DN30/30 Stereo Graphic Equaliser — is the company's bid to put two matched, high-specification graphic channels into a single compact chassis. The manual calls it a breakthrough in equaliser design, and the claim that carries the most weight is the density: two channels of full 1/5rd octave equalisation, in one unit. DB-Magazine (January 1983, p.22) described it as fitting two matched high-specification graphic channels into a single unit, each providing ⅓-octave equalisation over all 30 ISO centre frequencies — the same figure Klark Teknik's own advertising leaned on, and the number that defines the product.

The circuit is where the design earns its keep. Klark Teknik developed all-new circuitry specifically for the DN30/30, built around what the manual describes as ultra-stable N.I.C. minimum-phase combining filter networks — negative impedance convertors rather than the conventional inductor-and-capacitor approach. The measured numbers back the ambition: distortion below 0.01% from 20Hz to 20KHz, and noise better than −90dBm. Those are the figures the manual quotes, and they're the ones that mattered to the working engineers who racked these things.

The scale switching is the ergonomic decision worth understanding. It lets the compact slide potentiometers keep fine resolution for small corrections while still delivering a full 12dB of boost and cut when a room genuinely needs surgery. That's a real trade-off, and it's handled well — you get the fader travel where you need it without giving up range.

Studio Sound (July 1982, p.85) listed the DN 30/30 among Klark Teknik's precision professional audio products, positioning it alongside the widely acclaimed DN 22 and DN 27A graphic equalisers — models that had already become standard tools for correcting room acoustics and complex equalisation problems. The DN30/30 was pitched as the next step: a breakthrough in equaliser design in terms of performance, packaging and cost effectiveness. That's marketing copy, but the packaging claim holds up — getting two full 30-band channels into one unit was the whole trick.

The feature list beyond the EQ is where this thing earns its place in a working rack. A switchable subsonic filter handles the rumble that would otherwise eat headroom. Input and output connections are complementary 3-pin XLR sockets, with full electronic balancing on both ends as standard. The input stage is a differential amplifier with added RF filtering; the output drive circuitry is self-compensating, meaning it will drive balanced or unbalanced loads wired in any pin configuration without instability or damage. As with transformer-balanced outputs, output level remains constant for balanced and unbalanced operation — a detail that matters when you're patching into whatever the venue provides.

The rear p.c.b. houses two relays and an associated drive network that perform two functions worth knowing about. First, the output sockets are isolated from the equaliser until power is switched on and all internal power rails are stable — delayed turn-on that prevents DC or transients from being transmitted to downstream equipment. Second, and more importantly for anyone working live sound: if power is lost during operation, the inputs are connected directly to the outputs, providing total system bypass. Loss of power doesn't mean loss of signal. In a live situation, that could save the show.

Audio levels are monitored simultaneously at four points in the circuitry, driving an overload indicator with a threshold of +19dBm — giving 3dB of headroom before the onset of clipping. If the indicator lights, the manual suggests reducing level on the input control, or if the input stage itself is being over-driven, reducing level at the preceding equipment. An earth-lift switch on the rear panel disconnects signal ground from mains and chassis earth, useful for chasing down earth-loop problems.

The DN30/30 shows up in period studio documentation as a working tool rather than a showpiece. A Recording Engineer equipment summary lists it in the outboard rack at Puk Studios, alongside EMT 251 and Lexicon 224XL reverbs and AMS delays. Another session document shows it patched across multiple console channels — kick, snare top and bottom, lead vocal — often in sequence with dbx gates and limiters. That's the real story of this equaliser: it wasn't a specialty box, it was the utility EQ you reached for when a channel needed shaping, and it was trusted enough to sit in the signal path of a lead vocal.

Klark Teknik's own employee newsletter from the Telex era gives a sense of how the company viewed the DN30's longevity. A US sales manager quoted in the piece noted that you could buy a Klark Teknik DN30 Dual Channel Equaliser for around $1500, tour it for ten years, pull it out of the rack and sell it for $1000. That's a striking claim about retained value, and while it's company copy rather than an independent assessment, it speaks to the reputation these units carried in the touring world.

The DN30/30's place in the Klark Teknik line is clear from the period press: it sat alongside the DN 22 and DN 27A as part of a range built on a reputation for precision. Studio Sound (April 1983, p.55) repeated the pitch in a later issue — the DN30/30 offering much more than a quiet ability to balance channels, with advanced design, tough construction, stringent testing and long burn-in exceeding even Klark Teknik's previously high standards for reliability. Again, that's advertising language, but the burn-in and testing regime is mentioned in the manual as well, so it's not pure puffery.

For collectors and engineers today, the DN30/30 represents a particular moment in British pro audio — hand-built, over-engineered, and designed by people who assumed the unit would be working for decades. The total system bypass on power loss is the kind of feature that only makes sense if you've been in a room when something failed. The N.I.C. filter topology is the kind of design decision that only makes sense if you're chasing distortion figures below 0.01%. Whether you're restoring one for a studio rack or just curious about how the other half equalised, the DN30/30 is a piece worth understanding.