CAPI 511-VPR XLR Filtered Rack Bundle
At $369.21 new, this 3RU kit promised pro-grade 500-series expansion without breaking the bank - if you were willing to solder.
Overview
The CAPI 511-VPR XLR Filtered Rack Bundle is a build-it-yourself kit from Classic Audio Products, Inc. (CAPI). It's aimed at the DIY audio crowd who want a fully VPR-compliant 500-series rack without the boutique price tag. It's marketed as a "complete kit solution," and it ships unassembled. A PDF guide and bill of materials get emailed after purchase. Owners report it lands between professional capability and accessible cost - "rock-solid yet affordable," in the manufacturer's own words. It takes time and basic electronics skills to build, and the result is a custom 11-slot home for 500-series modules wired entirely through XLRs.
Eleven slots in a 3RU height keeps the rack manageable in a standard rack. It runs on an outboard switch mode PSU, which CAPI engineered to handle global voltages. That supply delivers bipolar ±16V and 48V phantom power, meeting full VPR spec, with a total output of 2,000 mA. That's over 180 mA per slot on paper. The VPR standard calls for 130 mA per module per rail, so there's some headroom. Audio I/O is all XLR, which avoids the fragility of 1/4" jacks in a permanent install. The 15-pin card edge connectors for the modules are included, as is the 5-pin male XLR for DC power input.
Specifications
| Manufacturer | Classic Audio Products, Inc. (CAPI) |
| Product Type | 500 series rackmount enclosure/kit/bundle |
| Slot Count | 11 |
| Rack Unit Height | 3RU |
| Power Requirement | requires an outboard power supply for operation |
| Power Supply Output | 2,000 mA for all 11 slots |
| Power Supply Spec (VPR) | running on +/-16V at full VPR spec (130mA per module, per rail) |
| Power Supply Type | switch mode PSU |
| Power Supply Compatibility | can accept just about every voltage mains from all over the world |
| DC Voltages Provided | bipolar 16V as well as 48V for phantom |
| Connectors Included | includes all 15-pin card edge connectors as well as a PC mount 5-pin male XLR connector for the DC power inlet |
| Audio Connections | All audio in and outs are via XLR connectors |
| Compliance | fully VPR compliant, 500 series rack |
Key Features
LC Filtering on the 9-11 Backplane
The "Filtered" in the name is a specific response to the switch mode power supply. This version has LC filtering mounted on the rear of the backplane for slots 9 through 11. According to builder discussions, the filtering exists mainly to clean up noise from the cost-effective switch mode supply. Earlier DIY racks might have used linear supplies. CAPI's switcher keeps the kit affordable and globally compatible, but it introduces potential high-frequency noise. The LC filter helps suppress that, especially on the last few slots.
Complete Kit with VPR-Compliant Power
Unlike bare enclosures, this bundle includes everything needed for a functional, standards-compliant system. The kit provides the 3RU chassis, all 15-pin card edge connectors, XLRs for audio I/O, and the DC power inlet. The bundled switch mode PSU is designed to meet VPR specifications, delivering stable ±16V and 48V phantom across all 11 slots. Its universal voltage input means it can be used worldwide. Builders note that the documentation, while sufficient, is delivered by email after purchase, which can delay the start of the project.
Eleven-Slot XLR-Wired Enclosure
Eleven slots leave room for preamps, EQs or compressors. Unlike many racks that mix XLR and 1/4" jacks, this bundle routes all audio in and out through XLR connectors. That favors balanced lines and sturdy connectors over convenience. It suggests the target user is building a permanent setup, not a portable rig. The use of XLRs throughout reduces the risk of ground loops and noise, especially in complex signal chains, and lines up with high-end console practices. The metal case isn't described in detail.
Collectibility & Value
New units were listed at US$369.21 for the filtered version, with a slightly lower price of US$353.21 for a non-filtered variant. That suggests the filtering upgrade carried a small premium. By 2024, a used unit in "Excellent" condition sold for $746.84, more than double its original price. Other new listings have appeared around $625, indicating strong demand among DIY enthusiasts. The appreciation isn't driven by nostalgia or scarcity, but by the ongoing relevance of the 500-series format and the difficulty of sourcing a complete, filtered, VPR-compliant kit. No data exists on common failures or long-term reliability, but the modular nature means individual components can be serviced. As a build-it-yourself product, its value hinges on completion and integration into a larger system.
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