In the previous issue, I discussed how I had successfully employed a $25 car-audio EQ as a sidechain EQ for stereo bus compression. It was a cheap and highly effective solution, but it had its downsides, so I went back onto Amazon and started searching for tone-control circuits to assemble my own EQs. I found dozens — some based on analog-processing ICs and others with standard components. I purchased six different circuits that looked promising and put each one on my test rig. One of them, a $17 board sold under the pseudo-descriptive title NE5532 Preamp Volume Control Board 10 Times Pre-amp A51, met every one of my requirements: an easy modification allows it to handle +4 dBu input levels; its output can drive +4 dBu levels with plenty of headroom; it doesn't invert its output relative to its input; its controls are easy to use and easy to recall; and its EQ curves work effectively in a sidechain for bus compression. Moreover, the low-distortion, low-noise circuit actually sounds good enough to use as a primary EQ! I haven't traced the circuit to determine its topology, but it sure sounds like (and reacts like) the Baxandall tone controls on a home hi-fi receiver. It has bass and treble pots with ±15 dB boost/cut, and a midrange pot with +9 dB boost and −10 dB cut. The curves are wide and gently sloped, in frequency and in phase response, as you'd expect from a "Bax" EQ. The whole tone stack is "centered" around 600 Hz, which is about an octave below most hi-fi tone-control sets. This lower-frequency center-point actually works great for sidechaining. For example, I'm able to "tilt" how a bus compressor reacts to kick drum and bass guitar, versus guitars and vocals, versus cymbals and sibilance.