Building Passive High-Pass Filter Sidechain Cables for a Dangerous Compressor

The Dangerous Compressor has two built-in sidechain options: a bass cut at 6dB/octave with a -3dB point at 60Hz, and a sibilance boost with a 1kHz corner frequency and +2dB shelving at 5kHz. Both are useful. The 60Hz high-pass, though, has always felt a little low for my purposes. I tend to want something closer to 120Hz.

The compressor also has an external sidechain input, which means you can route a separate signal to control the gain reduction. I tried running a stereo equalizer through it for a while, which gave me full flexibility, but in practice I always came back to 120Hz. At some point the flexibility stopped being useful and started being noise.

The Cable Solution

Bob Katz had shared a simpler approach on a mastering engineering forum. I contacted him and he described it directly: XLR cables with two 100nF capacitors wired in series on the signal leads, built inside the connector shell. That passive RC network creates a high-pass filter with a -3dB point at approximately 120Hz. No external gear, no power required. The sidechain cable is the filter.

The wiring diagram is below.

One thing worth noting: you can use the external sidechain cables in combination with the internal bass cut sidechain to get a third frequency option at approximately 160Hz. That gives you three distinct high-pass values plus the sibilance boost, all without any additional outboard.

Component Tolerancing

If you build these, match your capacitors carefully. I tested around 25 caps to find four that were within 0.5% tolerance of each other. Mismatched caps will produce a different filter frequency on each channel, which defeats the purpose. Measure before you solder.

You can experiment with different capacitor values to shift the corner frequency. The relationship is straightforward: larger capacitance moves the corner frequency down, smaller capacitance moves it up. Test and measure any substitutions before using them on a session.

It’s not pretty, but it gets the job done.

BK Mod Note

The stock Dangerous Compressor ships with timing capacitors at relatively low values, which makes the attack and release times noticeably shorter than what the front panel markings suggest. If you want the attack and release to match the panel values, an 805-sized SMT 2.2uF capacitor can be soldered across C61 and C78. Details and the Digikey part number are in the footnote below.

After the BK Mod, the compressor becomes significantly more versatile. At conservative settings, 5 to 10dB of gain reduction can be applied with very little audible character, useful in a mastering context where the goal is usually cohesion rather than obvious compression.