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K&K Active Cable

Paul White's looking at a gadget to improve impedance mismatch. By Paul White
Published October 1994

Like every good idea, K&K active cable sets out to solve an existing problem — that of impedance mismatch. Electric guitars, for example, have a high output impedance and work best into loads of 1Mohm or more, but even if the amplifier or preamp into which they are plugged has a suitably high input impedance, sound quality can still be compromised by capacitive loading caused by the guitar lead. The classic answer is to use some form of DI box: what K&K have done is to build their miniaturised DI box circuitry into the jack plug at the guitar end of the lead. Not only does this remove the need for a standard DI box, it also eliminates the adverse effects of the cable that normally connects the instrument to the DI box.

Two versions of the cable are available: unbalanced jack and mono jack to XLR balanced, intended to be plugged into the mic input of a mixer. Both types need to get their power from somewhere, and there's no room for a battery inside the plug, so a socket is fitted at the amplifier end of the cable, which accepts power from virtually any external power supply rated between 8 and 20 Volts, AC or DC of either polarity. Alternatively, the balanced XLR version will run from standard phantom power, a rather more elegant solution.

Aside from the chunkier than usual jacks, these 12‑foot leads look fairly normal, though the balanced version has a coiled steel spring outer sheath which resists kinking. The circuitry is designed for low‑noise operation, and claims to have plenty of headroom to prevent clipping; it presents a 1Mohm input impedance to the instrument. The exact output impedance isn't stated other than that it is low impedance.

For live use, these cables should allow long instrument leads to be used without compromising tone, while in the studio they represent a viable alternative to the traditional DI box for guitar recording. There may also be a slight benefit when used with some keyboards and modules, as many of these have a higher output impedance than they should. The cables are not designed to introduce additional gain, purely to provide matching, but this can produce an improvement in signal quality, especially when used with electric guitar or a guitar fitted with a piezo‑electric pickup.

My tests using both a PRS and a Strat were surprising: I achieved the best DI'd clean sound I've ever had, with a lot more top‑end zing and full‑bodied warmth, background noise which was well below the mixer's own mic amp noise, and immunity to interference which seemed to be improved. The only down side I can see is that if you're using the phantom‑powered, balanced model, you can't plug into an amp or overdrive unit unless you take a signal from the desk's insert send or channel direct output. However, for recording any form of clean guitar this product works stunningly well. The prices may initially seem a little high for 'trick leads' but if you forget the packaging and think of them as the ultimate clean guitar preamps, they're worth every penny. Paul White.