Mackie Big Knob Passive. Two stereo inputs, two sets of monitor outs, one big volume knob, plus mono, mute and dim.

Entirely passive. No power supply and, in Mackie's own words, zero active electronics in the signal path — just the volume control and switches, which is the whole reason to want one.

I used it to switch between two pairs of monitors in my project studio. Everything works: source select, monitor select, mono, mute and dim. The knob tracks evenly and I hear no channel imbalance, though I have not measured it on a bench.

Clean. Light surface marks on the top, nothing on the face. Serial 204781000BPNI2803.

No box. No cables included — it takes 1/4" TRS.