The PRX 150-Pro is housed in a black anodized-aluminum case with an amp-style strap handle, and it looks all business. When I unpacked my review unit, the vented front, side, and rear panels caught my eye. They are, of course, for cooling, but they give the box a striking, industrial vibe. A passive device, the PRX 150-Pro requires no AC power for operation.
Two front panel knobs—Step Attenuation and Variable—let you control your amp’s output level. Step Attenuation has six discrete settings labeled A-F. Settings A-E reduce the level in 3 dB increments. Switching to position F engages the Variable knob, which lets you further attenuate the output by as much as 16 dB. The unit can handle a 150-watt input signal and our review model provided an overall cut of 30 dB (which effectively takes a 100-watt amp down to 0.5 watts—3% of the amp’s power rating). However, Aracom informs us that the latest PRX 150-Pros can attenuate up to 40 dB— which can take a 150-watt amp down to .015 of a watt.
The PRX 150-Pro’s magic really happens at the back panel. The input—where you plug in your amp’s speaker output—offers 2-, 4-, 8,- and 16-ohm settings, and that’s what sets the PRX apart from most other attenuation devices. Having a variable input selector lets you use the PRX with different amps with various fixed output impedances. You don’t have to purchase separate units to accommodate, say, a Fender Super Reverb and a Marshall JCM900. And if your amp offers selectable output impedance, you can explore the different taps on the output section, which can alter the amp’s tone and feel.
The Aracom’s own output impedance is also variable, and you can set this independently of the unit’s input impedance. You can switch the PRX 150-Pro’s parallel output jacks to 2, 4, 6, 8, and 16 ohms, which gives you complete flexibility to mix and match amps and speaker cabs with dissimilar impedance ratings. Very flexible. Further, a true-bypass switch on the back panel allows you to bring the PRX in and out of the circuit.