I would recommend the Lindell Audio 510 Power MkII ten-slot chassis and power supply to anyone looking for a rackmount 500-series frame. It has several features that make it very functional and versatile. Firstly, it has both XLR and DB25 connectors (wired in parallel) for the first eight slots. This makes connecting to a patchbay equipped with DB25 connectors much easier and more affordable. I also really like this feature as it makes the rack really easy to interface to most multichannel converters if you're doing a remote recording, which is one of my main uses for 500-series gear. Secondly, it has feed switches between slots, so you can tie the output of a mic preamp in slot 1 to the input of an EQ in slot two without using cables, for instance. This is another great feature for doing remote recordings, as it allows you to effectively build channel strips within the rack. Thirdly, unlike all my other 500-series frames (except my API eight-space one), this has a sturdy, metal-boxed, external power supply instead of an oversized line-lump that will eventually fail when its cabling has too much strain put on it — something that happens a lot on remote gigs.
The Lindell supply has a standard IEC input jack for AC power (100–250 V, 50/60 Hz), and an XLR5 output for DC power to the frame. Therefore, both cables can be disconnected from the power supply and are easily replaced if there is ever a failure. The power supply can deliver a maximum of 5 A, and if your modules together draw too much current, a protection circuit steps in and shuts the power supply down. If you exceed 1 A per slot, PTC fuses choke the current. There are two PTCs per slot (twenty in total), one for the +16 V rail and one for −16 V, and they reset automatically when conditions fall back to normal.
Our 510 Power MkII is fully loaded with discrete, Class A mic preamps and EQs, which need solid power. I've never had any issues with the frame, power supply, or any of the modules mounted inside. The frame also had no problem physically accepting any module I tried inserting into it. The only check against this unit is that there is no power switch, but this is the case with every 500-series chassis I own, except the aforementioned API rack, which has a switch on the external power supply. If you're in the market for a rackmount chassis for your 500-series gear, the Lindell Audio 510 Power MkII is a serious contender.