I must admit that I have never been a huge fan of the 500-series format. I have spent too much time repairing my friends' racking frames, usually due to the voltage regulators frying, and I always found the mechanical aspects very fiddly. For example, unlike the 800, 900, and 9000–series racking systems from Valley People, dbx, and Aphex, the 500-series format utilizes no guiding mechanisms to ensure that the modules line up properly with the mating connectors inside the frame. Also, I found the construction of the 500-series frames themselves rather crude. They are commonly constructed of folded, stamped sheet metal, with screw holes tapped directly into the steel to hold the modules in place, and with fairly large heads of various fasteners protruding from the top and bottom of the chassis — which inevitably cause damage to the items in your rack placed above or below.
As the market for 500-series modules grew, it became like the Wild West out there, with modules that didn't conform to physical and electrical specifications, and with grounding issues too. Despite these problems, the format flourished; and finally, in 2017, it had matured to the extent that I began to take interest in it. In the process of re-organizing some of my outboard gear, I became aware that there were some modules in the 500-series that were unavailable in other formats, so I took the first step investigating what sort of rack enclosures were being made. I produced a chart that listed the features of each of the frames available for purchase — listing positives, negatives, logistical concerns, compatibility, serviceability, etc.
After this first investigatory stage, the list was reduced rather quickly to three possible candidates, though as I began to investigate those three, the list was quickly reduced to one — the ten-slot Rupert Neve Designs R10. I ordered one, and after using it, I realized that there were several important design features in this rack that I had previously neglected or underestimated in my initial chart. It's always a good feeling when your appreciation for something continues to grow after the purchase — which is so infrequently the case.
As with any industrial design, the first thing that you encounter is the physical entity of the device. The R10 is unusually good-looking, with its "British Isles Overcast" light grey enameled panels, shiny round power button, and array of seven LEDs along the front panel. Looking more closely, you will see that, rather than using simple threaded holes in a folded fascia of sheet metal for the module mounting screws, RND has instead opted for two extruded metal rails along the top and bottom of the front panel, with individual hardened-steel captive nuts which have several millimeters of travel side-to-side within the metal rails. This is a fantastic idea.
500-series modules from different manufacturers tend to vary slightly in their width, and the cumulative alignment issues can cause the mounting holes of the modules to be out of alignment with the threaded holes in the chassis; but the captive nuts in the RND frame are able to move side-to-side and even up-and-down — until a module is tightened down onto them — allowing you to position the modules in their most comfortable positions. Moreover, these nuts and their mating screws are very unlikely to seize up or strip due to cross threading; if this happened to any other 500-series frame, it would be irreparably damaged. So again, this is another well-engineered feature that you might not fully appreciate until you encounter a problem, at which point it would be too late.
The rest of the chassis has been designed with similarly thoughtful touches. All fasteners on the top and bottom are countersunk. The metalwork is finished in what feels to be some sort of nonstick finish; it's very slippery, but it's also very unlikely to cause any abrasion with any other gear in your rack. Along the rear panel, there are both XLR and TRS connectors, and the XLR jacks are solidly attached to the rear panel with two screws each, while the TRS ones are mounted with steel coaxial nuts.
One of the primary concerns that I had, based on previous experiences with my friends' 500-series racks, was the power supply design. In analog electronics, the power supply is every bit as important as any other component. We want a power supply that minimizes noise but also has a very low output impedance, which in this case can also prevent crosstalk between modules. Secondarily, we want a power supply that does not radiate electromagnetic fields into the modules in the rack. Several other manufacturers feature an external power supply which connects to the 500-series frame through a long umbilical cable. I do not consider this to afford any particular advantage (beyond easier compliance with region-specific electrical codes for the manufacturer), and because these supplies still have to be placed somewhere, if you have a large configuration of outboard gear, such as I do, these external supplies may induce interference elsewhere in your signal chain, where it may be very difficult to track down. I'd much prefer that the designers take a bit more responsibility on their end by limiting such variables. There also seems to be some division between the use of linear power supplies vs. switch-mode supplies, as well as standard E–I transformers vs. toroidal ones. I was initially concerned that the R10, being made in America — and in Texas, no less — would have taken the brute force ‘Merikan approach of using a super-heavy-duty linear power supply with a massive transformer in the chassis. So, while I was preparing my chart, I contacted RND and asked about the power supply. I was told that the company spent years developing and refining the design of its switch-mode supply, and had placed it in the enclosure with double shielding. This was good news to me.
The power supply is monitored on the front panel by seven LEDs. One LED shows on/off state, while the remaining six indicate total current consumption in increments of 400 mA, from 400–2400 mA, though I was informed that the supply is capable of over 3000 mA. Nearly every other 500-series frame has three LEDs indicating only the presence of voltage along the positive and negative rails, plus phantom power. The R10 omits these LEDs, which initially may seem to be an oversight. But honestly, when the equipment is functioning normally, these are not particularly useful — sort of like the so-called "idiot lights" in the dashboards of automobiles. The power supplies of my other outboard gear don't have rail indicators, so I didn't particularly miss having them on the R10. Instead, I was quite pleased to have current displayed so clearly, and the more I became familiar with the variation in module current consumption, the more I appreciated it was there. When I loaded the rack with six of my 1979-vintage Aphex CX–1 compressors, I could actually see the current LEDs flickering in time with the music! And, after all, as engineers, we like to know what's going on inside the circuitry, so we tend to like meters!
And finally, while calibrating the various modules in my system using a spectrum analyzer, I noticed that the modules placed inside the R10 — and especially those that were replicating vintage electronics that I have in a standard 19'' rack — had incredibly quiet noise floors. Not a trace of 60 Hz or any of its harmonics. And even fully loaded, the RND frame never gets warm to the touch. It just sits there laughing no matter what I throw at it. You can count me in as a satisfied customer of the Rupert Neve Designs R10 500-series frame.