In the DIY community, mainly at the groupDIY, there have always been dreams for some sort of modular format. Loads of discussions have occured in the past. Loads of great ideas developed, but nobody has ever moved beyond the discussion and created a "standard" or started on a project for this.

With the overwhelming popularity of API's 500 series racks, and the many upcoming DIY projects for this format, a new discussion been started.

Can we do a DIY friendly 500-style rack?
Can we add some more advanced features?
(Most people in the DIY community always want to modify or add features)
Yes, we certainly can.

While there was some discussion about the most desired features, Collin from Audiomaintenance came up with a great idea... use an 18-pin card edge connector instead of a 15-pin connector that the original 500 series rack uses. What a great idea!

Moving all of the other desired features aside, since you can never implement all, I began the design of the new GroupDIY 51X PCB backplane. (With the consent of Colin of course!)
The first 15 pins of the 18-pin connector are used in the exact method as the original 500 series rack. This is a major advantage. It allows you to use any standard 500 series compliant module in a 51X rack.

So, what are the additional connection points used for? They are used for +/- 24 Volt power rails. Why you ask? With this voltage available, you can easily design and build DIY modules requiring +24V, like NEVE, Neumann or Telefunken style circuits. Or take full advantage of both higher power rails for Forsell, John Hardy or APP studio ing. DOAs.

Now, why is this format called 51X?
Well... you always need a name... and the PCB backplanes and enclosures have been designed to allow the DIY builder to choose from multiple applications.

First, we have the GDIY511. The enclosure can be a standard 19" rack mount. This backplane can be fitted with either of the following: