I added this box to my rack for a two-month testing period and was impressed right from the start. It's pretty much a 2U channel strip with preamp, compressor, gate, and EQ sections. At first I was struck by the unit's simplicity. No need to flip through the manual, everything was clearly marked, front and back. Also, each section of the unit is a breeze to operate. The input section has a four-position selector for mic, mic +48, line, and instrument. I liked that a lot. I have a strong favor for gear that is quick and easy to dive into. The compressor is laid out nicely-clear indicators on a light colored background. Some might find that the four preset attack and release times are a little constricting, but I never found that to be the case. (The times are actually semi-automatic; very quick transients will make the time constants signal-dependent.) I didn't use the Gate, so I cannot comment further.
EQ? Four band with useful frequency points and +/- 12 dB gain-all very nice, usable, and smooth. Although I twisted the knobs all over the place, I only ended up tracking with a coupla dB either way. The output section has a meter with a variety of settings, an Output gain knob, and a switch that put the EQ before or after the compressor. I liked this a lot, too. I really wish more manufacturers would take a cue and err on the side of simplicity and readability. I never once felt like I was fighting the box to find out what was going on. The inside of the unit is immaculate. Good, tidy construction all around. As its name states, the 5051 is a valve (tube) unit. It houses three twin triodes (12AX7A's): one stage for the preamp, one for the compressor's gain stage, and four for the EQ.
I was booked for tracking and mixing some ska sessions, and this unit saw a lot of duty. I tried it on overheads, vocals, horns, guitars amps, and as a DI for bass. It certainly added its own color to whatever mic I tried. And while I didn't end up using it on everything, many applications made it to tape. It always sounded good, with a nice, noticeable "bloom" that I associate with tubes (though it wasn't right for every track on this project). My particular favorite use was for trombone and tenor horn section. We were going for a 60s-ish sound, and the 5051 was perfect-nothing harsh about it. I had the box in place for the mixing sessions, too. Our mixer liked it and used it almost exclusively on bass guitar. The settings weren't extreme in any way, but it added a good, mellow thickening that fit the songs well.
Priced at $749, it's a bargain. If you tried to put together a similar chain out of stand-alone components, you'd end up paying a whole lot more.