Kludge Audio 509 500-Series Rotating Limiter

Kludge Audio

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Product Code: 3539
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Kludge Audio 509 500-Series Rotating Limiter combines a very fast broadcast-style limiter with their phase rotator for superior limiting, utilizing waveform symmetry.

For many years, Kludge Audio made the 508 Phase Rotator. This device didn't make anything any louder, but it made a limiter more effective by making waveforms more symmetric and easier to limit. It was a great tool for asymmetric signal sources like vocals, horns, or close-miked strings. Customers liked it but found it cumbersome to use, so Kludge Audio integrated a very fast broadcast-style limiter into the same module along with a phase rotator for complete processing in a single space. This is the new Kludge Audio 509 Rotating Limiter!

The rotator is an all-pass filter that alters the phase of each component the signal differently depending on its frequency. If a 50 Hz signal is passed through, it will come out with identical polarity on the output. But, if an 800 Hz signal is passed through it will come out with the polarity completely reversed. A side effect of this adjustment is to make the waveform more symmetric.

This is what it does. The top waveform is a typical female vocal recorded with Neumann U87. It's asymmetric, with peaks in one direction greater than in the other, because the human vocal cavity is just that way. The bottom waveform has been processed by the phase rotator. It's more symmetric, with peaks more evenly distributed between the top and bottom of the waveform. This means when you limit it, the limiting will be more even between the top and bottom, and you can limit it more aggressively without distorting it. It is especially useful on severely asymmetric waveforms like brass instruments and vocals. After the phase rotator we have included a high speed opto limiter with a simple threshold control, incredibly fast attack, and controlled decay that depends on how hard it limiting. This is not your like an old 1176, it lets you limit harder than that! It uses a modern opto element with a very sharp knee and very fast operation.

Going Forward. You can use the limiter alone without the rotation, you can use the phase rotator alone with an external compressor or limiter, but you'll find you like using them together because they work as a team. There's no magic to it, but in the modern day when everyone is trying to eke out every little bit of loudness in their tracks, the phase rotator can help you bring vocal levels up a tiny bit and keep vocals front and center in your mix. It's a great help in getting the radio-ready sound.

Kludge Audio 509 500-Series Rotating Limiter Features

  • It replaces the old 508 Phase Rotator with a combination rotator and limiter
  • The limiter is very fast, like a broadcast limiter, with a very sharp knee.
  • It is based on an opto element, but the opto is much faster and harder than a traditional 1176 or the like.
  • The limiter attack was as fast as we could make it and the decay depends on how aggressively you limit; more aggressive limiting gives you longer decay time.
  • The limiter overshoot is almost zero because the attack is so fast and it is so well-controlled.
  • The phase rotator takes asymmetric waveforms and makes them symmetric, so you can limit them more without hearing distortion.
  • Voices and brass instruments are especially asymmetric, but drums and bass guitars can be too.
  • Phase rotation has been in use for broadcast processing for decades but is difficult to use unless it's integrated with the limiter like with the Model 509.
  • The rotator and limiter parts are individually bypassable so you can use just one or the other.

Kludge Audio 509 500-Series Rotating Limiter Includes

  • Kludge Audio 509 500-Series Rotating Limiter
  • Manufacturer Warranty

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What We Think


The Kludge Audio 509 Rotating Limiter is an impressive and easy to use limiter in an affordable 500-series format. It features one knob for your threshold and a phase rotator switch which allows you to limit the dynamics more aggressively without hearing distortion artifacts. If you need some aggression on a track, simply leave the rotator switch off and crank the knob up. With the rotator switch engaged, I find it’s a great final touch on a lead vocal. The 509 is not a brick wall limiter but it’s so fast, sources are very well controlled, and the limiter overshoot is almost zero. The fast attack also allows you to get amazing decay out of tracks depending on how hard you limit them. Check out the Kludge Audio 509 Rotating Limiter, I think you’ll love it!

Wes DeLoach, Pro Audio Sales

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