I saw an ad for this Australian-made monitor controller in Recording this month, and bought one for $149. It's good enough and useful enough, I think, to report on. First of all, its a half-rack size passive attenuator with three stereo inputs (on XLR/TRS combo jacks, RCA, & mini TRS), mute and mono sum switches, two balanced outputs (on XLR), and separate attenuators for main (stereo) output and Aux input. I'm using it after a Lucid DA9624 DAC to switch between a powered pair of Dynaudio BM15As, and two pair of smaller speakers connected to an amp. I use ProTools for editing, and there being no mono sum feature on the Master Fader, I was mainly looking for a device that would enable me to easily check mixes and stereo tracks in mono (to help detect phase and comb filtering problems, and had a convenient half-space next to the Lucid for it in the rack. Devices from Coleman, Grace, et al are all full space and larger, (though Cranesong have announced a half-space Avocet, which should be superb, but isn't available yet, I think); and there's a not-so-superb Samson C Control (which I returned to zzounds after trying it and discovering a significant loss of HF with it in the path). Anyway, listening with the M-Patch physically in and out of the chain, I detected very little (nearly infintesimal) signal degradation. It has large aluminum knobs, that don't wobble, sturdy selector switches, and a durable looking all-metal chassis, including a blue, brushed aluminum faceplate (for those who care). Another advantage of using it is that I can run my DAC hotter, which sounds better to me than being forced to keep the DAC output low into the powered monitors.
The manual doesn't give any real technical specifications, and I'm not a technician of any kind, so I can't delve into any theoretical detail here. Just thought this sorta thing could be useful to a lot of DAW users like myself.
If interested, I got mine through Kay Sound in New York, though indirectly through the SM Pro Audio distributor in Canada. I think it's actually made by a company called Violet Audio, but there's no mention of that company in the manual. The box, manual, and faceplate all have the "SM Pro Audio" logo. I'm an academic professional and have no association with any company.