UK Resolution Mag has a 'Modular Processing Supplement' in the current issue that mainly deals with the API 500 format.
The first product line mentioned is from 'Classicapi' aka Jeff Steiger. The GDIY 51X format is described in that context.
Quote:
The product is also GroupDIY 51X Appliance compatible, this being a DIY-friendly extension of API's 500-Series rack specs
to include an 18-pin card edge connector instead of a 15-pin connector, the extra connection points being used for +/-24V
power rails to allow designers to build DIY modules requiring +24V, including Neve, Neumann, or Telefunken-style circuits.
Unquote.
Cool...
The first product line mentioned is from 'Classicapi' aka Jeff Steiger. The GDIY 51X format is described in that context.
Quote:
The product is also GroupDIY 51X Appliance compatible, this being a DIY-friendly extension of API's 500-Series rack specs
to include an 18-pin card edge connector instead of a 15-pin connector, the extra connection points being used for +/-24V
power rails to allow designers to build DIY modules requiring +24V, including Neve, Neumann, or Telefunken-style circuits.
Unquote.
Cool...